Title of publication
New nuclear reactors: Generic Design Assessment
Guidance to Requesting Parties
ONR-GDA-GD-001 Revision 1
August 2014
Office for Nuclear Regulation
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Generic Design Assessment of New Nuclear Reactor Designs – Guidance to Requesting Parties
© Office for Nuclear Regulation, 2014 ONR Document ONR‐GDA‐GD‐001 Revision 1 You may use and reuse this information free of charge in any format or medium, under the terms of the Open Government Licence v2.0. ONR logos cannot be reproduced without the prior written permission of the Office for Nuclear Regulation. Some images and illustrations may not be owned by ONR and cannot be reproduced without permission of the copyright owner. Any enquiries should be sent to onr@onr.gsi.gov.uk, or to psi@nationalarchives.gsi.gov.uk for the use and reuse of Crown material. Published 08/14 For published documents, the electronic copy on the ONR website remains the most current publicly available version and copying or printing renders this document uncontrolled. Office for Nuclear Regulation
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Contents Section 1: Introduction .................................................................................................................. 3
The Purpose of this Guidance................................................................................................... 3
Background .............................................................................................................................. 3
Objectives of the Generic Design Assessment Process............................................................. 4
Requesting Party...................................................................................................................... 4
Overall Process and Timescales ............................................................................................... 5
Security .................................................................................................................................... 6
Section 2 ‐ The Generic Design Assessment Steps ........................................................................... 8
Step 1: Preparation of the Design, Safety Case and Security Submissions............................... 8
Step 2: Fundamental Design, Safety Case and Security Claims Overview................................ 9
Step 3: Overall Design, Safety Case and Security Arguments Review .................................... 11
Step 4: Detailed Design, Safety Case and Security Evidence Assessment .............................. 14
GDA Conclusions and Close‐out ............................................................................................. 16
Design Acceptance Confirmation........................................................................................... 16
Interim DAC and GDA Issue Close‐out (if required)................................................................ 16
No Design Acceptance Confirmation ..................................................................................... 17
Section 3 ‐ Requesting Party GDA Safety and Security Cases ........................................................ 17
Scope of GDA ......................................................................................................................... 17
GDA Submissions, RP Readiness Review and Internal Challenge........................................... 18
GDA Safety and Security Document Submissions .................................................................. 18
Generic Pre Construction Safety and Security Reports........................................................... 18
GDA Design Reference and Design Reference Point .............................................................. 19
Design Reference Change Control.......................................................................................... 19
Master Document Submission List......................................................................................... 20
GDA Submission Quality Assurance Arrangements ............................................................... 20
GDA Cut‐Off Dates and Submission Consolidation ................................................................ 20
Generic Site Characteristics ................................................................................................... 20
Use of Documentation Not Specific to Great Britain ............................................................. 21
Protective Markings............................................................................................................... 21
Fault Analysis and PSA ........................................................................................................... 21
Life Cycle ‐ Construction to Decommissioning and Spent Fuel Management ........................ 22
Safety Management .............................................................................................................. 22
Processes for Development of the Safety Case ...................................................................... 23
Section 4 – Outputs from GDA ..................................................................................................... 23
Openness, Transparency, Progress Reporting and Public Involvement ................................. 23
Generic Design Assessment Reporting by ONR...................................................................... 23
Regulatory Observations and Regulatory Issues.................................................................... 24
Design Acceptance Confirmation........................................................................................... 24
Interim Design Acceptance Confirmation .............................................................................. 24
GDA Issues ............................................................................................................................. 25
Requesting Party Resolution Plans......................................................................................... 25
Legal Status of DAC and Period of Validity ............................................................................ 26
Assessment Findings .............................................................................................................. 26
Section 5 ‐ Supporting Information for ONR's Generic Design Assessment Process........................ 27
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Meaningful GDA..................................................................................................................... 27
Assessment Topics ................................................................................................................. 28
Progress Decision ‘Gates’....................................................................................................... 28
Legal Duties............................................................................................................................ 28
ALARP..................................................................................................................................... 28
Safety Assessment Principles ................................................................................................. 29
Technical Assessment and Inspection Guides ........................................................................ 30
Taking Account of Overseas Regulator Assessments............................................................. 30
International Guidance .......................................................................................................... 31
Utilities Requirements Documents......................................................................................... 31
Regulatory Uncertainty.......................................................................................................... 31
Safety Case Ownership and Involvement of Future Licensees in GDA ................................... 32
Age of Design ......................................................................................................................... 32
Technical Support Contractors............................................................................................... 33
Research................................................................................................................................. 33
Review of Decision ................................................................................................................. 33
Section 6 ‐ Project Management and Administration ................................................................... 33
Joint Programme Office ......................................................................................................... 33
ONR‐Requesting Party Interface Arrangements .................................................................... 34
Requesting Party Project Office ............................................................................................. 34
Regulatory Questions............................................................................................................. 34
Recovery of ONR Costs........................................................................................................... 34
Section 7 ‐ Interface Between GDA and Nuclear Site Licensing ..................................................... 34
Nuclear Site Licence Assessment............................................................................................ 34
Site Specific Security Plan....................................................................................................... 35
Design Variants...................................................................................................................... 35
Transfer of Knowledge from Vendor to Licensee ................................................................... 35
Relationship of Generic Design Assessment and Site Specific Detailed Design, Construction and Commissioning................................................................................................................ 36
Appendix 1: Generic Design Assessment Approach ...................................................................... 37
Appendix 2: Typical Assessment Topics........................................................................................ 38
Appendix 3: The Generic Site Envelope ........................................................................................ 42
References .................................................................................................................................. 43
Glossary and Abbreviations......................................................................................................... 45
Contacts...................................................................................................................................... 47
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Section 1: Introduction The Purpose of this Guidance
1
This document provides guidance on the Office for Nuclear Regulation’s (ONR) Generic Design Assessment (GDA) process for the safety and security assessment of nuclear power stations intended for construction and operation in Great Britain. This process will be applied where ONR is asked to assess a reactor design in advance of an application for a nuclear site licence being made. This document is primarily intended to inform those parties who request such an assessment (the 'Requesting Parties' (RP)). 2
The objective of this guidance document is to provide RPs with: 3

a description of the safety and security submissions required; 
a clear explanation of ONR deliverables; 
indicative timescales for those deliverables; and 
information on the principles that ONR will apply when judging the adequacy of the safety and security submissions. This guidance has been developed in conjunction with the Environment Agency, with who ONR will work closely in GDA. The Environment Agency has published separate guidance to RPs on its GDA process (Ref. 8). There is also a separate 'top‐tier' guide (Ref. 1) which provides an overview of the processes followed by both regulators and how those processes are integrated. Background
4
ONR was established on 1 April 2011 as an agency of the Health and Safety Executive (HSE), pending planned legislation to establish it as a separate, independent statutory body. It brings together the relevant functions in respect of nuclear safety, security and transport regulation and the international safeguards regime, superseding the former Nuclear Installations Inspectorate, Office for Civil Nuclear Security, Department for Transport Radioactive Materials Transport Division, and UK Safeguards Office. 5
In its expert report to the Government's 2006 Energy Review, The health and safety risks and regulatory strategy related to energy development (Ref. 2), ONR concluded that important lessons had been learnt from previous experience with new nuclear power stations. In particular, the use of a standardised design where the design and safety case are well developed much earlier in the project, would facilitate a reduction in both the time for regulatory assessment as well as the regulatory uncertainty for licence applicants during the construction phase. 6
ONR therefore proposed a new two‐phase process: Phase One would involve the assessment of potential new nuclear reactor designs on a generic basis, in advance of any site‐specific proposals. This became known as GDA. Phase Two would involve an applicant seeking a nuclear site licence to construct such a reactor based on the GDA design at a specific site. Office for Nuclear Regulation
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7
Guidance on GDA was first published in 2007 and has since been updated and supplemented. This current update draws on the experience from the first round of GDA, which started in 2007 when ONR and the Environment Agency began assessment of four reactor designs. Two designs were withdrawn by the vendors part way through assessment. The Westinghouse AP1000® assessment was paused at Westinghouse’s request after ONR granted an Interim Design Acceptance Confirmation (iDAC) and identified the GDA Issues remaining. The EDF and AREVA UK EPR™ design was taken through to the end of GDA and in December 2012 ONR issued a Design Acceptance Confirmation (DAC) (and the Environment Agency granted a Statement of Design Acceptability (SODA)). Objectives of the Generic Design Assessment Process
8
9
Compared with the previous regulatory approach to proposals for new reactors, GDA is designed to have a number of advantages: 
it allows ONR to get involved with designers at an early stage, where it can have maximum influence. Design changes required to address ONR concerns are more easily implemented while designs are still on paper, rather than when construction has begun, or expensive plant items have been manufactured; 
it is a step‐wise process, with the assessments getting increasingly detailed. This allows ONR to identify key design issues early in the process and, thus, reduce the financial and regulatory risks for intending power station developers; 
it can separate design issues from specific site related issues; and 
it is open and transparent. The public can view detailed design information on the Internet and comment on it. ONR also gives regular feedback on how its assessments are progressing and publishes reports at the end of key steps. Other key features of the GDA process are that it: 
gives RPs the opportunity to demonstrate at an early stage that the legal requirements of Great Britain are capable of being met by the design; 
facilitates a rigorous ONR assessment; 
will, where possible, be completed within reasonable and predictable timescales; 
facilitates joint working between ONR and the Environment Agency; 
gives clarity to ONR's requirements, processes and timescales; 
has clear outcomes; 
allows for submission of an international standard design and use of international safety case information (with potential benefits of standardisation); and 
leads to generic Pre‐Construction Safety and Security Reports and (if the design is considered acceptable) to a DAC, which can both be used in subsequent nuclear site licence applications. Requesting Party
10
Requests for ONR to undertake GDA, with a view to gaining a DAC, will normally originate from a reactor vendor, however, this may also be done as a vendor / operator partnership. Consequently, the term RP is used throughout this document to identify the organisation seeking the DAC and to distinguish it from a nuclear site licence applicant. Office for Nuclear Regulation
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Overall Process and Timescales
11
GDA is not a mandatory process, but because of its advantages for both reactor vendors and developers, it is expected that it will normally be requested for new nuclear power stations intended for construction in Great Britain. 12
If GDA is to be applied, the proposals for building new power reactors will be subject to two regulatory phases, which may overlap: 13

Phase One, GDA, is ONR's assessment of the safety and security case for a generic design, and may lead to issue of a DAC if the design is considered acceptable; 
Phase Two, nuclear site licensing, is ONR’s assessment of a site‐specific proposal to construct and operate a power station based on a design which has been through GDA. This includes ONR’s assessment of the site licence application, as well as the subsequent regulation of the construction and commissioning of the power station. This process is presented in Table 1 with indicative timescales. The planned assessment in Phase One is divided into four steps, which are described in detail in this document, and illustrated in Appendix 1. Specific assessment timetables will be drawn up and agreed by ONR and the GDA RP during Step 1. Table 1: GDA and licensing process
Phase
Phase One: GDA
Step
Process
Approximate timescale
1
Preparation of the design, safety case and
security submissions
RP is responsible
2
Fundamental design, safety case and
security claims overview
~6-8 months
3
Overall design, safety case and security
arguments review
~12 months
4
Detailed design, safety case and security
evidence assessment
~28 months
After Step 4 there may be a period of GDA Issue close-out, the scope and time of which will depend on the
nature of any outstanding issues and the RP’s resolution plans for those GDA Issues.
Phase Two: nuclear
site licensing
-
ONR engagement with intending licence
applicant on preparation of site licence
application and development of applicant
organisation
~ 18-24 months
~12-18 months
Nuclear site licence application
assessment by ONR, with subsequent
granting of a nuclear site licence if the
application is judged to be acceptable
14
The timescales set out in Table 1 for GDA are indicative and assume that ONR is only called upon to assess a single reactor design at any one time. The actual timescales will depend on factors such as: 
the number of designs and site licence applications being assessed simultaneously by ONR; 
the content, quality and timeliness of the submissions provided; 
the completeness of the design; Office for Nuclear Regulation
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
the significance of any issues arising during ONR’s assessment; 
the responsiveness of the RPs to ONR challenges and questions; 
the availability of resource to ONR; 
the ability to draw on information from overseas nuclear regulators; and 
ONR's experience with similar reactor designs. 15
For the nuclear site licensing assessment, the timescales will be dependent on the time taken for the applicant to develop its organisation and Licence Condition arrangements, and on the extent of early and positive engagement with ONR on these matters. 16
A crucial assumption is that all relevant submission documents are available at the start of each assessment step, and are of suitable and sufficient content. If documentation is submitted late or piecemeal, this may have a detrimental effect on the assessment schedule. 17
It should be noted that: 
Phase One and Phase Two are separate assessment processes; 
there is no guarantee that the Phase One process will lead to a DAC ‐ this will depend on whether the design, safety case and security submissions meet ONR requirements; 
similarly, a DAC does not guarantee that a subsequent Phase Two licensing application will be successful, as the latter phase covers wider issues; and 
the nuclear safety of plants is the responsibility of the licensee, and the issue of a DAC or a nuclear site licence does not transfer any of this responsibility to ONR. 18
The GDA process was developed in collaboration with the Environment Agency and it drew on interactions between ONR and various stakeholders including the Department of Energy and Climate Change (DECC), vendors, nuclear site licensees, potential operators and non‐
governmental organisations. It has been updated in the light of the experience gained with the first tranche of designs, particularly the UK EPR™ and the AP1000®. 19
Although they are significant milestones, the issue of a DAC and the granting of a nuclear site licence do not themselves provide ONR’s permission for the start of nuclear power station construction. This is because it is ONR’s policy to require, under the conditions attached to the nuclear site licence, that its specific regulatory permission is given before nuclear safety related construction can be commenced. Security
20
The requirements for security at nuclear premises are laid down in the Nuclear Industries Security Regulations 2003, as amended. 21
Under the Regulations (Regulation 22), any person who holds sensitive nuclear information and is proposing to become involved in activities in, or in relation to, a civil licensed nuclear site in Great Britain is subject to these Regulations. 22
The Regulations require a ‘responsible person’, in the case of a nuclear power station the holder of the nuclear site licence, to submit a site security plan for approval by the Secretary of State for Energy and Climate Change; in practice ONR would approve this on the Secretary of State’s behalf. The details of the scope of the plan are set down in the Regulations. 23
In GDA, ONR will conduct a security assessment alongside the safety assessment. The key focus of this assessment will be to understand the areas of the installation that require protection and the measures that will be designed into the facility to form an integral part of Office for Nuclear Regulation
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the overall security infrastructure if the facility was to be built. A robust process for identification of potential 'vital areas' underpins this process. 24
Some of the above information may be “sensitive nuclear information” which is required to be protected in accordance with the Regulations. Guidance on this aspect is contained in a separate document by ONR’s Civil Nuclear Security (ONR (CNS)), The Management of Sensitive Nuclear Information during the Generic Design Assessment of Nuclear Technologies (Ref. 19). 25
The overall aim will be for the RP to develop an acceptable generic Conceptual Security Arrangements (CSA) suite of documents for the design in question. If this design of reactor is subsequently constructed, ONR would require these arrangements to be incorporated into the licensee’s site specific security plan, approval of which will be required before construction commences. This plan would need to identify the arrangements that will be in place for the completed project and for the security status during different project stages. An example of a stage would be when nuclear fuel is first brought into the site. 26
The task of defining worst‐case malicious activity scenarios is a matter for ONR, which has sole responsibility for establishing and documenting the design basis threat (DBT). The DBT defines a range of threats that could be faced by civil nuclear facilities. The RP will need to discuss with ONR how the plant will be designed and operated to address the DBT. 27
Where sensitive security information of a reactor design has to be shared across international borders the RP will need to obtain the appropriate cross‐border arrangements, export control licenses and security clearances, etc. Office for Nuclear Regulation
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Section 2 ‐ The Generic Design Assessment Steps Step 1: Preparation of the Design, Safety Case and Security Submissions Step 1: Description and aims Step 1 is the preparatory part of the design assessment process. The bulk of the work will be undertaken by the RP in setting up its project management and technical teams and arrangements for GDA, and in writing and preparing submissions for Step 2, including the Preliminary Safety and Security Reports. It also involves discussions between the RP and ONR to ensure a full understanding of the requirements and processes that will be applied and to arrive at formal agreements for cost recovery. Step 1: The RP is required to: 1.1 Formally ask ONR to perform a GDA of the proposed nuclear power station design. 1.2 Discuss with ONR the proposed schedule for submission of safety and security documentation and the format of the documentation including the Preliminary Safety and Security Reports. 1.3 Enter into agreements with ONR as appropriate, covering: (a) the scope of ONR assessment; (b) project management arrangements and quality management system; (c) the design change control process to be applied; (d) timescales for responses to ONR assessment questions / issues etc; (e) arrangements for the public input process; (f) arrangements for ONR to recover its costs; (g) arrangements for ensuring that the designers and safety case producers are suitably qualified and experienced persons; (h) the safety case developer's quality control, including peer review arrangements; (i) a work programme and bespoke timetable for assessments (which will be kept under review). 1.4 Ensure that ONR will have full access to any commercial information necessary for it to complete its assessments at each step. This documentation is to be made available for inspection in ONR’s offices. 1.5 Prepare sufficient safety and security documentation to enable ONR to undertake at least the Step 2 assessment. 1.6 Prepare the template for the Master Document Submission List and any required arrangements for handling it. 1.7 Identify and suitably mark those elements of the documentation that are commercially sensitive. 1.8 Undertake discussions with ONR and classify the documentation in accordance Office for Nuclear Regulation
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Step 1: Preparation of the Design, Safety Case and Security Submissions with security requirements, identifying sensitive nuclear information against ONR guidance. 1.9 Publish the safety submission on their website (removing commercial and security sensitive information) to allow comments to be made by the public during GDA. Step 1: ONR will: 1.9 Confirm that it has received the request for a GDA. 1.10 Agree with the RP the proposed schedule for submission of safety and security documentation and its format, and inform the RP of the implications of this for ONR's assessment programme. 1.11 Review the scope of the safety and security submissions for the Step 2 assessment and inform the RP: 

if this is sufficient for ONR to begin Step 2 assessment; or of any shortfalls in the documentation and consequential delay to the completion of the Step 2 assessment. Step 1: ONR output ONR will publish statements saying that: 
it has received a request to perform a GDA; and 
Step 1 has been completed and that the information submitted is sufficient to allow the start of Step 2. Step 2: Fundamental Design, Safety Case and Security Claims Overview Step 2: Description and aims Step 2 is an overview of the acceptability, in accordance with the regulatory regime of Great Britain, of the design fundamentals, including review of key safety and security claims. This step may take around 6 to 8 months, assuming the ONR GDA team is engaged on a single reactor design assessment. The aim of this step is to assess the key claims and identify any fundamental safety or security shortfalls that could prevent the proposed design from being licensed in Great Britain. A related aim is that the RP will come to fully understand the regulatory approach used in Great Britain and thus ensure that adequate safety and security documentation will be developed for Steps 3 and 4. It will also introduce ONR inspectors to the fundamentals of the design and provide a basis for planning subsequent, more detailed, assessment. Step 2: The RP is required to: Provide safety documentation in the form of a Preliminary Safety Report (PSR), that includes sufficient information for ONR’s Step 2 assessment, in particular: 2.1 A statement of the design philosophy and a description of the resultant conceptual Office for Nuclear Regulation
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Step 2: Fundamental Design, Safety Case and Security Claims Overview 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19 design sufficient to allow identification of the main nuclear safety claims including identification of hazards, control measures and protection systems. A description of the process being adopted by the RP to demonstrate compliance with the legal duty in Great Britain to ensure risks to workers and the public arising from the operation of a power station based on the proposed design are reduced ‘So Far As Is Reasonably Practicable’ (SFAIRP). It should be noted that for ONR's assessment purposes the terms ALARP (As Low As Reasonably Practicable) and SFAIRP are interchangeable and require the same tests to be applied (refer to Section 5 below for further information). Details of the safety principles and criteria that have been applied by the RP in its own assessment processes, including the control of risks to workers and the public. A broad demonstration that the RP’s safety principles and criteria are likely to be achieved by the design. An overview of the approach, scope, criteria and output of the deterministic safety analyses. An overview of the approach, scope, criteria and output of the probabilistic safety analyses. Specification of the site characteristics to be used as the basis for the safety analysis (the 'generic site envelope'). Explicit references to standards and design codes used, justification of their applicability, and that they represent relevant good practice, and a broad demonstration that they have been met (or exceptions justified). Information on the quality management arrangements for the design, including design controls, control of standards, verification and validation, and the interface between design and safety. Details of the safety case development process, including peer review arrangements, and how this gives assurance that nuclear risks are identified and managed. Information on the quality management system for the safety case production. Identification and explanation of any novel or complex features, including their importance to safety. Identification and explanation of any deviations from modern, international good practices. Sufficient detail for ONR to satisfy itself that its Safety Assessment Principles (SAP) are likely to be satisfied. Where appropriate, information about all relevant assessments completed by overseas regulators. Identification of outstanding information that remains to be developed and its significance. Information about any long‐lead items intended for incorporation into a plant constructed in Great Britain that may be ordered or manufactured during the GDA process. Information on radioactive waste management and decommissioning. Information on the reference design, safety and security submission freeze that will be applied. Office for Nuclear Regulation
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Step 2: Fundamental Design, Safety Case and Security Claims Overview 2.20 Security related information covering the reactor technology concept, physical layout proposals, computer system security requirements and proposals for identification of Vital Areas. The RP will also be required to provide the first Master Document Submission List. The RP will also be required to respond to questions and points of clarification raised by ONR during its assessment, and to issues arising from public comments. Step 2: ONR will: Undertake an assessment directed at reviewing design concepts and claims. This will include: 2.21 The design safety philosophy, standards and criteria used. 2.22 The approach to ALARP. 2.23 The fault study approach including Design Basis Analysis (DBA) and Severe Accident management. 2.24 The probabilistic safety analysis (PSA) approach. 2.25 The overall safety case scope and extent. 2.26 An overview of the claims in a wide range of areas of the safety analysis. 2.27 The generic site envelope and its relevance to the safety case. 2.28 The proposals for nuclear security. 2.29 The proposals for the reference design and safety submission freeze (for the purposes of GDA), including proposals for management of design changes 2.30 Identification of any matters that might be in conflict with Government policy. 2.31 Identification of any significant issues that may prevent ONR from issuing a DAC. 2.32 Consideration of outstanding relevant issues raised through the public involvement process. Step 2: ONR output 
A public statement from ONR on whether any fundamental safety or security issues had been identified that might prevent the issue of a DAC or that would need to be addressed in order to acquire one. 
Publication of a summary report to support this statement. 
The relevant internal ONR assessment reports will be published, along with any other reports relevant to Step 2. 
Confirmation that the design can move to Step 3. It should be noted that ONR’s judgement on acceptance in principle will be subject to the proposed design concept and RP's design criteria being realised in the detailed design, and the safety case claims being supported by appropriate arguments and evidence. Step 3: Overall Design, Safety Case and Security Arguments Review Step 3: Description and aims Step 3 is a review by ONR of the safety case arguments of the proposed reactor design and the related security aspects. This step may take around 12 months, assuming that ONR GDA assessors are Office for Nuclear Regulation
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Step 3: Overall Design, Safety Case and Security Arguments Review engaged in the assessment of a single reactor design. The intention in this Step is to move from the fundamentals of the previous step to an analysis of the design, primarily by examination at the system level and by analysis of the RP's arguments that support the safety claims. The specific aims of this step are to: 
improve ONR knowledge of the design; 



assesses the safety arguments; identify significant issues; identify whether any significant design or safety case changes may be needed; identify major issues that may prevent ONR issuing a DAC and attempt to resolve them;  achieve a significant reduction in regulatory uncertainty. The exact scope and focus will depend on the design and on the outcome of Step 2. Step 3: The RP is required to: Provide, at the start of Step 3, safety and security documentation, usually a Pre Construction Safety Report (PCSR) that include the following: 3.1 Explanation of how the decisions regarding the achievement of safety functions ensure that the overall risk to workers and public will be ALARP. 3.2 Responses to any issues outstanding from Step 2. 3.3 Sufficient information to substantiate the claims made in the PSR. 3.4 Sufficient information to enable ONR to assess the design against all relevant SAPs. 3.5 A demonstration that the detailed design proposal will meet the safety objectives before construction or installation commences, and that sufficient analysis and engineering substantiation has been performed to prove that the plant will be adequately safe. 3.6 Detailed descriptions of system architectures, their safety functions and reliability and availability requirements. 3.7 Confirmation and justification of the design codes and standards that have been used and where they have been applied, non‐compliances and their justification. 3.8 Fault analyses including DBA, Severe Accident Analysis and PSA. 3.9 The safety function categorisation, and the safety classification of structures, systems and components (SSC), with a demonstration of how this is reflected in the design. 3.10 Justification of the safety of the design throughout the plant's life cycle, from construction through operation to decommissioning, and including on‐site spent fuel and radioactive waste management features. 3.11 Identification of potentially significant safety issues that have been raised in assessments of the design by overseas regulators, and explanations of how they have been (or will be) resolved. Office for Nuclear Regulation
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Step 3: Overall Design, Safety Case and Security Arguments Review 3.12 Identification of the safe operating envelope and the operating regime that maintains the integrity of that envelope. 3.13 Definition of the technical and documentary scope of GDA, including definition of the safety and security submission, definition of a Design Reference, and Design Reference Point, and implementation of GDA submission configuration control arrangements. This should also include confirmation of: (a) which aspects of the design, safety case and supporting documentation are complete and are intended to be covered by the DAC; and (b) any aspects that are still under development, and identification of outstanding confirmatory work that will be addressed during Step 4. 3.14 Confirmation of the proposals for updating the Master Document Submission List, for the reference design, and for the safety submission freeze (for the purposes of GDA), including proposals for management of design changes. Where necessary, the RP should update the safety case on their website (removing commercial information, and security sensitive information) to reflect the above additional details, and to allow comments to be made by the public. The RP will also be required to respond to questions and points of clarification raised by ONR during its assessment, and to relevant issues arising from public comments. Step 3: ONR will: Undertake an assessment, on a sampling basis, primarily directed at the system level and by analysis of the RP's supporting arguments. The scope will be partly defined by experience in Step 2 and the issues arising in that step, and also by experience in previous GDAs. This will include: 3.15 Consideration of whether the design is likely to meet the RP's design safety criteria and reduce risks ALARP. 3.16 Undertaking an initial assessment of the scope and extent of the arguments in each of the technical areas, including the generic site envelope. 3.17 Assessing the safety case development process scope and extent. 3.18 Reviewing what overseas regulators have done and how ONR can make use of it. 3.19 Deciding on scope and plan for further assessment. 3.20 Assessment of the quality assurance (QA) arrangements, including: (a) QA arrangements for the early manufacture of long lead time items important to safety; (b) safety case and design change control arrangements. 3.21 Identification of any research needs and setting up of longer‐term research or contract support to complement Step 4. 3.22 Assessment of the RP's independent verification. 3.23 Identification of needs for additional regulatory verification / analysis. Office for Nuclear Regulation
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Step 3: Overall Design, Safety Case and Security Arguments Review 3.24 Judging whether the design is balanced in terms of the different contributors to the overall risk from the plant. 3.25 A review of the proposals for spent fuel management, radioactive waste management and decommissioning. 3.26 Issues raised through the public involvement process. 3.27 Consideration of security proposals and a detailed review of the security architecture of the plant. Step 3: ONR output 
A public ONR statement on the progress of the assessment of the design, safety case and security arguments. 
A report to support this statement. This will describe any safety issues identified thus far that have the potential to lead to significant design or safety case changes, or which may prevent ONR issuing a DAC.  Confirmation that the design can move to Step 4. It should be noted that ONR’s judgement to accept system design and safety arguments at Step 3 would be subject to provision of evidence that the system performance and reliability requirements will be met in practice through the detailed design, and to the resolution of any outstanding issues in Step 4. Step 4: Detailed Design, Safety Case and Security Evidence Assessment Step 4: Description and aims Step 4 is an in‐depth ONR assessment of the safety case evidence, generic site envelope submitted and the related security aspects. This step may take about two years, assuming ONR GDA assessors are engaged on only a single reactor design assessment. The general intention of this step is to move from the safety arguments and system level assessment of Step 3 to a fully detailed examination of the available evidence, on a sampling basis, given in the safety and security submissions. The aim of this step is: 
to confirm that the higher level claims and arguments are properly justified; 
to complete sufficient detailed assessment to allow ONR to come to a judgment of whether a DAC can be issued. The exact scope and focus will depend on the design and on the outcome of Step 3. Step 4: The RP is required to: Provide, at the start of Step 4, any outstanding information, safety case material and research results that provide evidence to support the PCSR and the security submission. In addition, the RP is required to submit: 4.1 A demonstration that construction, manufacture and installation activities Office for Nuclear Regulation
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Step 4: Detailed Design, Safety Case and Security Evidence Assessment will result in a plant of appropriate quality. 4.2 A demonstration that the constructed plant will be capable of being operated within safe limits. 4.3 Arrangements for moving the safety case to an operating regime; i.e. the arrangements to ensure that the requirements of, and assumptions in, the safety case have been clearly identified and can readily be captured in: (a) technical specifications; (b) maintenance schedule; (c) procedures (normal operation, emergency, accident management); (d) training programmes; (e) emergency preparedness; (f) operating limits; (g) radiation protection arrangements for operators; (h) lifetime records; (i) commissioning requirements, etc. 4.4 Confirmation of the Design Reference and safety submission definition and provision of updates to the Master Document Submission List. 4.5 Arrangements for supporting licensees to put in place a Design Authority. 4.6 Arrangements to support licensees manage any site‐specific changes against the generic design, within an agreed change control process. 4.7 Responses to any issues outstanding from Step 3. The RP will also be required to respond to questions and points of clarification raised by ONR during its assessment, and to respond to relevant issues arising from public comments. Step 4: ONR will: Undertake a detailed assessment on a sampling basis of the safety case evidence and security proposals. This will include: 4.8 Consideration of issues identified in Step 3. 4.9 Judging the design against the SAPs and whether the proposed design reduces risks ALARP. 4.10 Inspections of the RP's procedures and records. 4.11 Independent verification analyses. 4.12 Reviewing details of the design controls, procurement and quality control arrangements to secure compliance with the design intent. 4.13 Establishing whether the system performance, safety classification, and reliability requirements are substantiated by the detailed engineering design. 4.14 Assessing arrangements for moving the safety case to an operating regime. 4.15 Assessing arrangements for ensuring and assuring that safety claims and assumptions are realised in the final as‐built design. 4.16 Judging whether significant site parameters are appropriately defined in the generic site envelope. 4.17 Reviewing the security submission. 4.18 Reviewing overseas assessment progress on similar designs and issues raised by overseas regulators. 4.19 Considering relevant unresolved issues raised through the public involvement process. Office for Nuclear Regulation
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Step 4: Detailed Design, Safety Case and Security Evidence Assessment 4.20 Resolution of identified nuclear safety and security issues, or identifying paths for resolution. Step 4: ONR output  A public ONR statement providing the conclusions of the planned assessment.  A decision on whether or not to grant a DAC or an iDAC. 

A report to support this statement. The relevant internal ONR assessment reports will be published, along with any other reports relevant to Step 4. GDA Conclusions and Close‐out There could be three potential outcomes at the end of Step 4: 1) Provision of a DAC which would mark the end of GDA for that generic design. 2) Provision of an iDAC that identifies outstanding GDA Issues. 3) Provision of no DAC. These three potential outcomes are discussed below. Design Acceptance Confirmation If ONR are fully content with the generic safety and security aspects then it would provide the RP with a DAC which would mark the end of GDA for that generic design. Provision of a DAC will mean that this generic reactor design is capable of being built and operated in Great Britain, on a site bounded by the generic site envelope, in a way that is acceptably safe and secure (subject to site specific assessment and licensing). Interim DAC and GDA Issue Close‐out (if required) If ONR are largely content with the generic safety and security aspects then it would consider the provision of an iDAC. Provision of an iDAC means that Step 4 has been completed, ONR has completed its planned assessment, and that ONR is largely content that the design is capable of being built and operated in Great Britain, but that there are some GDA Issues remaining. The provision of an iDAC would only be considered when the RP is able to submit and publish credible resolution plans that identify how it will address each of the GDA Issues. All the GDA Issues would need to be addressed to ONR’s satisfaction before a final DAC could be provided or before ONR could consider granting permission for the start of nuclear island safety‐related construction1 for a power station based on that design. 1
This relates to construction of the main nuclear island, which includes the main reactor building and nuclear auxiliary buildings (such as diesel generator buildings), but does not include, for example, sea defences or the cooling water pump houses that are located away from the nuclear island. Office for Nuclear Regulation
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Interim DAC and GDA Issue Close‐out (if required) The GDA Issue close‐out stage will be an in‐depth ONR assessment of the additional design and safety or security case evidence submitted in response to the GDA Issues. Scope and timescales for this stage will depend on the programmes identified in the resolution plans provided by the RP. The RP will have to submit evidence in accordance with the programmes identified in the resolution plans. The final submissions will need to include updates to the:  Generic PCSR;  GDA Design Reference;  CSA document; and  Master Document Submission List. The RP will also be required to respond to questions and points of clarification raised by ONR during its assessment, and to respond to relevant issues arising from public comments. ONR will complete sufficient assessment to be able to judge whether the additional information submitted by the RP is adequate to address all the GDA Issues. ONR will then publish:  A statement providing the conclusions of the GDA Issue close‐out assessment. 

A report to support this statement. A DAC if the design, safety case and security submissions are judged to be acceptable. 
The relevant internal ONR assessment reports. No Design Acceptance Confirmation If ONR is not content with the generic safety and security aspects then no DAC would be issued. ONR will then publish a statement providing the conclusions of its assessment. This would be the case where ONR judged that there is a significant, unacceptable shortfall in the design, safety or security submissions. It would be a matter for the RP to decide whether to propose additional work to address the shortfalls, which may allow a DAC or iDAC to be provided at some future date. Section 3 ‐ Requesting Party GDA Safety and Security Cases Scope of GDA
28
Although ONR requires a certain minimum level of detail to complete GDA, it recognises that full engineering details of the design will not be available at the GDA stage, as it is normal to finalise some of these as part of the procurement and construction programme. 29
The scope of what is included within GDA is dependent on the information supplied by the RP (remembering that GDA is a voluntary process, undertaken at the request of the RP). However, the required information for GDA needs to be sufficient in scope and detail to underpin the generic safety and security case for the design. If there are omissions in that information, then this may jeopardise the completion of a meaningful assessment under the GDA process. In this case ONR will require the scope of the GDA submissions to be expanded in order to include such essential information. 30
The final GDA scope should be agreed before the end of Step 3. Office for Nuclear Regulation
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GDA Submissions, RP Readiness Review and Internal Challenge
31
Before each of the assessment Steps, the RP is required to conduct a readiness review to confirm that it can fulfil all the requirements for that Step (as defined in the tables above that describe Steps 1 – 4). This should include an internal challenge process within the RP organisation. The results of the readiness review should be provided to ONR together with the request to start the assessment Step. 32
The process of preparing documents for submission to ONR should also include internal challenge within the RP organisation. This should be applied, on a graded approach commensurate with safety, to the safety and security submissions, and to responses to ONR questions etc, throughout GDA. (See also ‘Processes for development of the safety case’ below). GDA Safety and Security Document Submissions
33
The GDA submissions should include the: 
Generic PCSR; 
CSA document / suite of documents; 
GDA Design Reference; and 
Supporting references as identified in a Master Document Submission List. The DAC will refer to these in order to define the basis of what has been included within the scope of GDA. These documents and their control arrangements are described below. Generic Pre Construction Safety and Security Reports
34
RPs are required to provide a comprehensive, generic PCSR and a security document plus relevant supporting reference documents. 35
The SAPs include a section on the regulatory assessment of safety cases. This is supported by the ONR Technical Assessment Guide (TAG) on the purpose, scope and content of nuclear safety cases (T/AST/051 – Ref. 16) which identifies the principal safety reports associated with key stages in a nuclear facility’s life cycle. Table 2 below shows how these relate to the GDA process. 36
ONR expects a facility safety case to describe the basis for the safety of that facility by following the ‘claims’, ’arguments’ and ‘evidence’ chain of reasoning. This means that the safety case should set out the technical claims that show that the risk is ALARP; supported by sound arguments for which experimental or other detailed evidence is presented. It is important that the information provided in the safety case is suitable and sufficient to demonstrate, in the opinion of ONR, that risks have been reduced so far as is reasonably practicable (SFAIRP). 37
For a PCSR ONR accepts that it may not be possible to provide all the evidence justifying the safety of the facility. Much of the evidence and associated confirmatory analysis cannot be gathered until the SSCs have undergone final detailed design by a manufacturer / supplier or have been constructed and are in the process of being tested. Since the choice of supplier and the construction and commissioning are matters for the operator, this level of information is generally not included within GDA. However, for GDA, ONR expects the RP to provide its arrangements that will ensure that the safety claims and assumptions will be realised in the as‐built design (see Step 4 table in Section 2). Office for Nuclear Regulation
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Table 2: Safety reports identified in T/AST/051 (Ref. 16)
Report
Input to
PSR
Assessment in Phase One Step 2
Generic PCSR
Assessment in Phase One Steps 3 and 4
Updated Generic PCSR
Assessment of GDA Issue responses (if required)
Site-specific PCSR
Phase Two Site specific and Licensing
assessment
Pre-Commissioning Safety Report
Prior to (inactive and active) commissioning
Pre-Operational Safety Report
Prior to reactor operation
38
If the RP desires, it may submit the generic PCSR along with the PSR during Step 1 of the GDA process. 39
The generic PCSR should include information that defines the characteristics assumed for the generic site envelope. 40
ONR will require the RPs to enable the public to view and comment on the safety cases on the Internet, with the exception of any commercially confidential and security sensitive information. 41
The security reports will comprise the CSA document and supporting references. Guidance on the content of this is provided in Ref. 20. GDA Design Reference and Design Reference Point
42
RPs are also required to submit a Design Reference which lists all the documents that describe the design of the reactor and associated plant that the GDA submissions refer to. ONR will expect this to be ‘frozen’ at a specific date known as the Design Reference Point. 43
The Design Reference and its Design Reference Point will be agreed on a case‐by‐case basis with each RP. However, if the Design Reference is not in place at the start GDA Step 3, this will cause uncertainty, inefficiency and possibly delays to the assessment, as it will not be clear to ONR exactly what the design definition is. 44
The pre construction safety and security reports must align exactly with the plant described in the Design Reference. Design Reference Change Control
45
It is recognised that the RP may wish to develop the design beyond the Design Reference Point. There may also be changes to the design that are necessary to respond to ONR Assessment Findings. It is therefore important that a GDA design change process is implemented by the RP, in agreement with ONR. 46
The details of the change control system are for the RP to propose and ONR to agree. However, ONR will expect this to be based on a robust system such as those required to satisfy nuclear site Licence Condition 20 (modification to design of plant under construction). 47
Features that ONR will expect to see include: a categorisation system reflecting the potential safety and security impact of the change; change control committees to oversee the categorisation of the proposed changes and the overall running of the process; and a route for Office for Nuclear Regulation
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alerting ONR to the more significant changes to the safety case. ONR will inspect these arrangements as part of GDA. 48
Changes proposed at an advanced stage in GDA may jeopardize the ability of ONR to complete a timely and meaningful assessment. Consequently, ONR will take a view on whether the proposed changes should be brought within the scope of GDA. Master Document Submission List
49
As GDA progresses ONR will request submission of a selection of the PCSR supporting references so that more detailed information can be examined. There will also be developments in the safety case, design modifications, and responses to ONR assessment questions that all need to be captured in the GDA submissions. The GDA information submitted by the RPs can therefore become a complicated mix of documents. 50
In order to keep appropriate control of this mix of documents, project management arrangements are required to keep track of the documents submitted, of subsequent changes to these documents, and of documents withdrawn, etc. Key to these arrangements is a Master Document Submission List, which is a ‘live’ document that allows ONR to understand and reference precisely what constitutes the latest versions of the GDA submissions. GDA Submission Quality Assurance Arrangements
51
As well as ensuring that each RP’s safety case submission is well defined, ONR requires that it is produced under robust QA arrangements. The RPs’ arrangements will be required to ensure that this is achieved, and examination of these arrangements forms part of ONR’s assessment during GDA. GDA Cut-Off Dates and Submission Consolidation
52
It is important that ONR’s assessment is based on an agreed set of documentation during each GDA Step. To be able to assess new information and include this within ONR’s reports at the end of each Step there need to be agreed cut‐off dates for submission of new information into each Step. These will be agreed between ONR and the RP. 53
In addition, towards the end of GDA, there will be a need for the RP to re‐consolidate the Design Reference and generic Pre Construction Safety and Security Reports and supporting documentation to take into account: 
all the additional information that has been provided in response to ONR technical questions; and 
any RP proposed GDA submission changes that ONR has agreed can be included in the GDA scope. It is the information contained within this final consolidated GDA submission that ONR will refer to in its concluding reports on GDA. Generic Site Characteristics
54
The RP may specify generic siting characteristics suitable for a range of sites in Great Britain against which ONR will assess the acceptability of the design safety case. These characteristics, such as the density and distribution of the assumed local population, seismic hazard, extreme weather events and other external hazards, should, as far as possible, Office for Nuclear Regulation
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envelop or bound the characteristics of any potential site in Great Britain so that reactors of this type could potentially be built at a number of suitable locations. An alternative would be for the RP to propose a specific site for consideration in GDA; if afterwards the design was proposed for implementation at any other site, the licence applicant would need to consider site specific variations from the site used in GDA. 55
Guidance on ONR's expectations on generic site characterisation is contained in Appendix 3. 56
For the Phase Two nuclear site licensing assessment, a licence applicant would need to demonstrate that its chosen site fell within the generic site envelope so that the GDA can be taken fully into account during ONR’s licensing assessment. Use of Documentation Not Specific to Great Britain
57
ONR recognises that the RP may choose to use existing design and safety documents that were not written explicitly for Great Britain. While this may be efficient for the RP in providing documentation, it is unlikely that on its own, it will be sufficient for GDA. ONR needs to receive additional and specific submissions that demonstrate how the requirements of Great Britain have been, or will be, met. 58
ONR requires that plants are designed and will be built and operated in SI (International System) Units and that documents submitted are written in English. Protective Markings
59
As far as possible safety case information provided to ONR should be made available to the public. Nevertheless, where the RP considers that it should be protected on the grounds that it is sensitive nuclear information or commercially confidential, the RP should clearly mark it accordingly. The RP should also give its reasons for designating the information in this manner. 60
The RP should use a protective marking scheme consistent with HMG’s (Her Majesty’s Government) protective marking scheme. For sensitive nuclear material the RP should follow ONR(CNS)’s guidelines in Ref. 19. 61
Finally, the RP should be aware that over‐protecting information, ie, marking documents with protective markings more restrictive than those required by the nature of the information contained, can cause unnecessary difficulties handling the documentation and possible delays. Fault Analysis and PSA
62
Fault analysis should be carried out comprising DBA, PSA, and Severe Accident analysis. 63
ONR expects that the submission for design acceptance should include a full scope Level 1 and Level 2 PSA. The PSA should be used to help show that the design satisfies the ALARP requirement. A Level 3 PSA relevant to the generic site will also be expected. 64
The regulatory regime enforced by ONR is, in general, non‐prescriptive and there are therefore few numerical legal requirements. However it is guided in its safety case assessments by certain numerical targets in the SAPs. In assessing against these, ONR will seek sufficient information for it to be able to judge that the targets are likely to be achieved and that the overall risk is ALARP. Further guidance on ONR expectations relevant to PSA and to fault analysis can be found in the SAPs and in the TAGs on accident analysis (Ref. 16). Office for Nuclear Regulation
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Life Cycle - Construction to Decommissioning and Spent Fuel Management
65
ONR will expect the safety submissions to cover all through‐life aspects including design, construction, maintenance, operation, spent fuel and radioactive waste management and decommissioning of the power station. The level of detail of the information required may vary according to the significance of each aspect to the GDA. 66
RPs should identify the management arrangements for the spent fuel and radioactive waste arising from operation of the reactors for their projected life. This should include: 
the strategies for the management of spent fuel, all radioactive wastes and substances that might become wastes; 
the safe storage of radioactive wastes pending disposal; 
the disposability of radioactive wastes; 
a demonstration of how the design and its proposed operation will avoid or minimise the generation of radioactive waste; and 
the strategies for decommissioning the facility. 67
This information may be captured in a Radioactive Waste Management Case, which can form part of the generic PCSR. This should show how the safe management and disposal of waste produced over the life of the power station can be achieved. When providing this case, the RP should take into account the radioactive waste facilities expected to be available in Great Britain. There should also be consideration of the need to transport waste and spent fuel and the implications of this for its long term management. 68
The Government has set out its framework for managing higher‐activity wastes through geological disposal in Managing Radioactive Waste Safely (Ref. 9). This process is based on the current radioactive waste inventory in Great Britain (Ref. 10) but it is intended to be able to accommodate waste and spent fuel arising from any new build programme. RPs will be expected to seek assurance that the anticipated waste streams will be acceptable for disposal in such a facility; the Nuclear Decommissioning Authority (NDA) has published a protocol to facilitate the necessary assessments, Disposability Assessment of Solid Waste Arisings from New Build (Ref. 11). Safety Management
69
The GDA process requires RPs to provide information on the quality management arrangements for the design and safety case production. 70
In addition, the arrangements for RPs to support licensees to put in place a Design Authority should be described in Step 4. For guidance on Design Authority aspects, see Maintaining the design integrity of nuclear installations throughout their operating life (Ref. 12). 71
If key safety‐related plant, intended or potentially for use in Great Britain, has already been or is in the process of being manufactured, the RP should specify what quality management arrangements have been or will be used during all stages of the manufacturing process. 72
Safety management requirements for the Phase Two licensing process will be more onerous (see Section 7 below on the Phase Two assessment). 73
Existing guidance on some aspects of ONR's assessment of the design process, Design Authority, change control, design QA and intelligent customer capability is given in ONR's TAG T/AST/057 Design safety assurance (Ref. 16). Office for Nuclear Regulation
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Processes for Development of the Safety Case
74
The process used to produce safety cases needs to consistently deliver good‐quality, fit‐for‐
purpose cases. For a safety case to claim that the plant under consideration is very reliable or highly unlikely to fail, the process used to derive such claims needs to have commensurate reliability. The RP will therefore need to demonstrate that the process that has been used in the safety case production has included, for example, appropriate verification controls, a formal approval procedure, and an independent review, the rigour of which should be demonstrated to be consistent with the safety importance of the subject matter. 75
In view of this, ONR's assessment may involve inspection of the originating organisation's processes as well as assessment of the safety cases themselves. Further information on ONR's expectations regarding safety case due process is given in the SAPs, and in TAG T/AST/051 (Ref. 16). Section 4 – Outputs from GDA Openness, Transparency, Progress Reporting and Public Involvement
76
ONR is committed to high standards of openness and transparency in its GDA process. As part of this commitment, regular progress reports will be issued throughout GDA and published on the Joint Regulators website. These will include metrics to indicate the performance of ONR and the RP and progress against programme. In addition, ONR will publish its assessment reports and a range of other documentation associated with the GDA process. 77
Arrangements will be agreed between ONR and the RP to enable the public to view the safety case on the Internet, with the exception of commercially confidential and security sensitive information. An opportunity will then be given for the public to comment to the RP on that information, who will be asked to respond to any relevant issues raised. The regulators will oversee and administer this public involvement process and at key stages ONR will publish its views on the main issues raised and responded to. 78
Throughout GDA ONR will remain responsible for all decisions made on the acceptability or otherwise of the design put forward by the RP. Thus, while the issues raised in the public involvement process, and the RP's responses, will be given due consideration and the decision‐making process will be made as transparent as possible, regulatory decisions in relation to safety and security will remain vested in ONR. 79
ONR also has duties to provide information to the public when requested to do so under the Freedom of Information Act 2000 and the Environmental Information Regulations 2004. Even if the information is protectively marked, ONR would still be obliged to consider whether it is in the public interest for it to be released. Generic Design Assessment Reporting by ONR
80
On completion of each of the GDA Steps, ONR will come to a decision on the acceptability of the RP's submission, make a public statement, and publish a summary report to support the decision. This will be supported by relevant technical assessment reports at the end of Steps 2 & 4. The summary reports will summarise the assessments undertaken and reasons why ONR's decision was reached. If a submission is unsuccessful, ONR will identify the safety issues that are regarded as either unacceptable or requiring further elaboration. ONR's judgements and public statements may be deferred if the RP wishes to make further information available for ONR to take into account before reaching a decision. In this event, ONR may make a public statement explaining that this was the reason for the delay. The GDA reports will identify, where appropriate, outstanding issues or requirements for subsequent phases / steps. Office for Nuclear Regulation
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Regulatory Observations and Regulatory Issues
81
In addition to the open reporting described above, the regulators will publish all the Regulatory Observations (RO) and Regulatory Issues (RI) (see Section 6 for definitions) that are raised throughout GDA, together with the RP resolution plans (see below). Design Acceptance Confirmation
82
If ONR provides a DAC to an RP it will mean it is confident that, based on the GDA submissions, the design is capable of being built and operated in Great Britain, on a site bounded by the generic site envelope, in a way that is acceptably safe and secure. This is of course subject to site specific assessment and licensing. 83
Where a design has been subject to GDA, a DAC will need to have been issued before ONR would consider granting permission for the start of nuclear island safety‐related construction for a power station based on that design. ONR would take the DAC into consideration in assessing the adequacy of the licensee’s case for starting such construction. 84
In the case where an iDAC has been issued, ONR will need to be satisfied that all of the GDA Issues have been addressed satisfactorily before a final DAC will be given. 85
One outcome from GDA, following provision of a DAC, is a commitment from ONR not to further assess at the site‐specific stage of the project aspects of the safety and security case already assessed and accepted at the generic design stage. However, should the RP or operator (licensee) later make either generic or site‐specific safety or security significant changes that affect the basis of the GDA outcome, then those aspects of the GDA submission may require re‐assessment by ONR. Interim Design Acceptance Confirmation
86
Provision of an iDAC means that ONR is confident that the design is capable of being built and operated in Great Britain, on a site bounded by the generic site envelope, in a way that is safe and secure. However, it also means that there are some GDA Issues remaining that need to be addressed to ONR’s satisfaction before nuclear island safety‐related construction of a reactor based on that generic design could commence. 87
Before providing an iDAC, ONR will need to be content that all the GDA Issues are amenable to timely resolution. This confidence is based on resolution plans (see below), submitted by the RP, which set out the work it needs to do to address each issue and identify how long this work would take. 88
Provision of an iDAC would mark the end of ONR’s planned assessment of the submitted safety case (and security provisions) for the generic design, with any further GDA work being focused on resolution of GDA Issues. 89
Once all the resolution plans are completed and GDA Issues addressed satisfactorily, and the safety case has been updated, ONR would consider whether a final DAC could be issued. Office for Nuclear Regulation
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GDA Issues
90
At the end of GDA Step 4 there may remain significant regulatory issues that, while not so serious as to prevent ONR from issuing an iDAC, would need to be resolved before the issue of a DAC. These are called GDA Issues and are defined as follows: Unresolved issues considered by regulators to be significant, but resolvable, and which require resolution before nuclear island safety‐related construction of such a reactor could be considered. 91
Example cases that could result in GDA Issues are as follows: a)
there is uncertainty whether the proposed civil structure is suitable, i.e. either there may be concerns over the civil design itself, or there is a potential for modifications that cannot be accommodated by the proposed foundations or within the building shell and structural components. b)
a fundamental gap has been revealed in the safety case, i.e. an omission of an important fault sequence, uncertainty over the suitability of a key safety system, or concern that the risks may not be ALARP. 92
The GDA Issues will be uniquely numbered and listed in the iDAC. 93
The subjects covered in GDA Issues will be known in advance to the RP, as the subject areas in which they arise will have been discussed with ONR during the GDA assessment process. 94
The successful closing out of the GDA Issues will mark the end of GDA. The timescales for each Issue close‐out will be dependent on the Issues themselves and the timely provision of technically acceptable responses by the RP. 95
When GDA Issues have been addressed satisfactorily, the RP will need to update the GDA submissions to reflect this (including Design Reference and generic PCSR) so that these can be referenced in the final DAC. The need for this activity should be included within each resolution plan. ONR may identify the submission update as a GDA Issue in itself, particularly if there are, for example, numerous new modifications that the RP wants to roll into the final DAC. Requesting Party Resolution Plans
96
Resolution plans will be submitted by the RP in response to ROs, RIs and GDA Issues. The resolution plans set out the work the RP needs to do to address the matters raised by ONR and identify how long this work would take. The plans should include the work required to update the GDA submissions (including Design Reference and generic PCSR) 97
Resolution plan contents will vary depending on the topic in question but will need to have sufficient detail to convince ONR that all relevant aspects can be addressed within the timeframe identified. They will be published on the Joint Regulators website. 98
Where GDA Issues are identified at the end of Step 4, ONR will use the information provided by the RP to come to a judgement on the credibility of the resolution plans so that a decision can be made on whether to issue an iDAC or not. 99
It is important to note that the resolution plans are indicative. Subsequent to the publication of a resolution plan, the RP could adopt an alternative approach to clearing an issue so long as that will give an equally acceptable safety / security outcome. Office for Nuclear Regulation
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Legal Status of DAC and Period of Validity
100
A DAC will represent ONR’s expert judgement at the time it is provided. Being based on a generic design and the associated generic safety case submissions, the DAC does not guarantee that ONR will grant any site‐specific permissions for a station based on that design. 101
A DAC has no legal status and is not a legal requirement of Great Britain’s nuclear licensing regime for new nuclear power stations. However, ONR expects the GDA process to be followed by most applicants as this is likely to be a more business efficient approach. 102
Any DAC or iDAC would apply for that generic design for a period of ten years from the date of issue. This would be subject to no significant new information arising during that period which might call into question the basis of ONR's original assessment of the design. This period of validity is commensurate with the requirement for licensees in Great Britain to undertake periodic safety reviews of their existing nuclear facilities every ten years. 103
If an RP wishes to seek renewal of a DAC at the end of this ten‐year period, ONR will require them to review the safety case in the manner of a periodic safety review and report to ONR. It is envisaged that DAC renewal would be much less resource intensive than the original assessment, but some design improvements might be needed to gain renewal if these were found to be reasonably practicable at that time, e.g. in the light of emerging international practices. Assessment Findings
104
GDA is designed to assess the generic safety case for future reactor designs; it is not intended to provide a complete assessment of the final reactor design, as there will be other factors, operator specific or site‐related, that ONR would expect to consider during the site‐specific stages. Also, in some instances, final validation of the safety case can only be completed when the final detailed design of equipment is developed by a manufacturer / supplier, or when the facility is being constructed and is in the process of being tested. This validation process is normal regulatory business and will be subject to appropriate regulatory controls. 105
Part of the link from GDA to site‐specific assessment is assured by identification of GDA Assessment Findings. These findings are primarily concerned with the provision of additional safety case evidence, after GDA, to confirm certain safety aspects as the project progresses through the detailed design, construction and commissioning stages. The Assessment Findings will be identified in the detailed assessment reports for each technical topic area. 106
Typical cases that could result in GDA Assessment Findings are: a) Areas in the safety submission where ONR requires additional confirmatory analysis, but is content that the work can be undertaken during the detailed design, construction and commissioning stages. b) Important conditions linked to major verification and validation commitments given by the RP in its safety submission that cannot be completed until the construction / commissioning phase. 107
It will be the responsibility of the future operator / licensee to ensure that Assessment Findings are addressed as appropriate, during the detailed design, procurement, construction or commissioning phase of the new build project. However, depending on the timing of site‐
specific projects, it is also possible that certain Assessment Findings could be cleared by the RP in parallel with GDA Issues being addressed. 108
After GDA, the Assessment Findings will be subject to appropriate control as part of normal regulatory oversight of new nuclear power station projects. For each GDA Assessment Finding, the relevant ONR assessment report will identify an indicative generic target milestone for Office for Nuclear Regulation
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when resolution would be expected. At a later date ONR would expect the operator / licensee to address each GDA Assessment Finding in more detail within its own site‐specific plans. The operator / licensee will be able to bring forward alternative target milestone proposals so long as these are credible. 109
Assessment Findings are mostly matters that ONR would raise anyway during site‐specific assessments. Identifying them in GDA will maximise the time available for future licensees and operators to address them. Thus, early identification of Assessment Findings in this way represents one of the key benefits of the GDA process and provides for further reduction in regulatory uncertainty. 110
Assessment Findings will help form a starting point for ONR’s site‐specific assessment but they must not be considered by the site licensee to be an exhaustive list of regulatory matters. Other regulatory matters will arise as ONR’s site specific assessment progresses. The licensee will be responsible for the completeness and correctness of its safety case, and addressing regulatory findings is only one element in the delivery of an acceptable safety case. Section 5 ‐ Supporting Information for ONR's Generic Design Assessment Process Meaningful GDA
111
Before ONR can conclude that a DAC can be provided, it must have completed a meaningful assessment. A meaningful GDA will be one where ONR has: 
received sufficient information on the generic reactor design in the safety and security submissions to allow assessment in all relevant technical topic areas; and 
completed a sufficiently thorough and detailed assessment of the information in the generic safety and security submissions. 112
In the above, 'thorough and detailed assessment' means that ONR has looked in detail at the generic design submissions and judged them against the SAPs, including the need to demonstrate that risks are reduced, or are capable of being reduced, ALARP. The assessment relates only to the safety case information provided on the generic design and does not mean that ONR has received and assessed all the information necessary to permit construction and operation of a plant, based on that design, at a specific site in Great Britain. 113
The depth and scope of ONR’s assessment is unlikely to be the same in all technical areas, reflecting likely variation in the information available, and also its specific relevance to the safety case. However, ONR will need to be satisfied that its sampling of the information that is available, together with any work programmes to resolve technical issues arising during the assessment, has allowed it to come to a balanced judgement on the overall acceptability of the safety and security case for the proposed generic design. 114
If the supply of information on the design and the safety and security submissions are inadequate, then it follows that ONR will not be able to provide a DAC. 115
It is vital, therefore, that the RPs provide design safety case submissions of high quality, to an agreed timetable. Crucial to the delivery of a meaningful GDA is complete clarity on what documents constitute the RPs’ GDA submissions, and how the information they contain addresses the requirements in this guidance document. Office for Nuclear Regulation
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Assessment Topics
116
The scope of ONR’s technical assessment will depend on a number of factors including the details of the reactor design under consideration. Typically, however, the topic areas listed in Appendix 2 would be covered. Progress Decision ‘Gates’
117
It should be noted that progress to a GDA Step is not automatic on completion of the previous Step. Progress to the next Step will depend on the provision of sufficient and suitable submissions by the RP. ONR will review the information supplied, and planned to be supplied, by the RP and take a decision on the adequacy of the timeliness, scope, content and quality, before starting an assessment Step. Legal Duties
118
The GDA process is undertaken within the existing nuclear regulatory framework for Great Britain, which is fully described in Licensing Nuclear Installations (Ref. 3). The main element of this is the Nuclear Installations Act 1965, which sets down the requirement to obtain a nuclear site licence from ONR before installing a nuclear reactor on a site. It is underpinned by the more general Health and Safety at Work Act 1974, which places a fundamental responsibility on duty holders to reduce risk SFAIRP. 119
When assessing GDA submissions, ONR will also take into account other relevant health and safety legislation in Great Britain (as described in Licensing Nuclear Installations, Ref. 3), including The Ionising Radiations Regulations 1999 (Ref. 4). ALARP
120
For ONR's assessment purposes the terms ALARP and SFAIRP are interchangeable and require the same tests to be applied. ALARP is also equivalent to the phrase 'as low as reasonably achievable' (ALARA) used by other bodies in radiation protection nationally and internationally. 121
ONR's decision‐making process is based on the approach described in Reducing risks, protecting people (Ref. 5). This includes an explanation of the concept of ALARP and describes the legal requirement in Great Britain to demonstrate that risks are reduced ALARP, such that any further measures to reduce the risk would entail a gross disproportion between the sacrifice (time, trouble and money) and the risk averted by their adoption. The way in which ONR assesses claims from licensees, or RPs, that they have reduced risks ALARP is set out in detail in its TAG T/AST/005 (Ref. 16). 122
The development of standards defining relevant good practice often includes ALARP considerations, so in many cases meeting these standards may be sufficient to demonstrate that the design would satisfy legal requirements in Great Britain. In other cases, e.g. where standards and relevant good practice are less evident or not fully applicable, or the demonstration of safety is complex, the onus will be on the RP to implement risk reduction measures to the point where it can demonstrate to ONR that the costs of any further measures would be grossly disproportionate to the risk averted. 123
While meeting good practice is a fundamental requirement for safety cases, this is expected to be supported by a demonstration of how risk assessments have been used to identify any potential weaknesses in the design and operation of the proposed facility, showing where improvements have been considered and to demonstrate that safety is not unduly reliant on a Office for Nuclear Regulation
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small set of particular safety features. ONR will expect the application of ALARP to have been carried out comprehensively and to show that further risk reduction measures are grossly disproportionate to the risk averted. 124
Additional guidance on ALARP is given in ONR's TAG T/AST/005, Demonstration of ALARP (Ref. 16). 125
For new reactor designs, elements of what may be regarded as good practice and of what is reasonably practicable might be found in the design of modern reactors currently operating or under construction or licensing in Great Britain or elsewhere in the world. However, other approaches to achieving the levels of safety embodied in aspects of these designs are also acceptable. Also, the WENRA documents that set out safety reference levels, safety objectives and common positions for new reactors (Ref 7) can be considered to be relevant good practice and so showing that these have been met would be one way of contributing to the demonstration that risks have been reduced ALARP. 126
It is important that the information provided by the RP in the safety case is suitable and sufficient to demonstrate to ONR that risks have been reduced ALARP. As part of this demonstration, the RP will be required to show that the technical standards it has used result in a design for which risk has been reduced ALARP. This will need to include consideration of any updates to those technical standards since the original design and safety analysis were completed. Safety Assessment Principles
127
ONR assessors are guided in their judgement by ONR's SAPs (Ref. 6), which set out relevant good practice for a wide range of nuclear facilities. To ensure consistency with international requirements, the SAPs have been benchmarked against the nuclear safety standards of the International Atomic Energy Agency (IAEA). 128
ONR assessors will use SAPs when reaching a judgement on the acceptability of the safety case for the proposed design. The SAPs are not criteria but are an aid to judgement. Priority is given to achieving an overall balance of safety rather than satisfying each principle or making an ALARP judgement against each principle. The principles themselves are applied in a reasonably practicable manner and the judgement made is always subject to consideration of ALARP. 129
The SAPs will also provide RPs with information on the regulatory principles against which their safety provisions will be assessed and judged by ONR. However, the SAPs have been developed as guidance for assessing safety cases and as such they are not intended, nor are they sufficient, to be used as design or operational standards. Similarly, the SAPs are not sufficient to be used as an outline for, or as the determinant of, the scope and depth of any safety case. 130
The RP may choose to enhance their understanding of the basis for regulatory decision making by undertaking their own comparison of their design safety principles against the SAPs. This may allow the RP to anticipate any issues or shortfalls, and to include in their submissions explanations as to how the safety goals underlying the SAPs are met, or by providing evidence that equivalent safety is achieved by other means. It is ONR's expectation that any comparison of a safety submission against the SAPs that an RP wishes to present should not form part of a safety submission itself, but would be a separate document. Where comparisons have been undertaken, these will be of interest to ONR assessors and may be requested. 131
RPs should note that not all SAPs are intended for use in nuclear power station assessments, nor are all the SAPs relevant for the GDA process. ONR assessors will therefore use their Office for Nuclear Regulation
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judgement to evaluate the various aspects of the RP’s submission against those SAPs that are relevant. Additional guidance to ONR assessors on interpretation of the SAPs is given in TAGs (see below). It should be noted that ONR assessment will always be based on the latest versions of SAPs and TAGs. Technical Assessment and Inspection Guides
132
ONR provides guidance for its inspectors, including those undertaking GDA assessments, in its TAGs and Technical Inspection Guides (TIG). These give detailed interpretation of the SAPs and guidance in their application. The SAPs and the TAGs are an integrated suite of guidance to ONR's nuclear inspectors carrying out assessment of safety cases and these will be used for GDA. Most of the TAGs and TIGs are published on ONR's website (see Refs 16 and 17), except for a small number that are withheld for security reasons. 133
TIGs are mainly aimed at nuclear site inspectors carrying out Licence Condition compliance inspections. However, the GDA process will involve inspection of the RPs' processes, and some of these guides are therefore relevant, in particular NS‐INSP‐GD‐017 Management Systems (Ref. 17) which also deals with quality assurance (QA). Taking Account of Overseas Regulator Assessments
134
Where a reactor design has been subject to assessment by overseas nuclear regulators, ONR sees great value in being able to draw on that experience, and to share its own experience with them This is in fact an extension of the normal information exchanges that take place between international nuclear regulators through bilateral arrangements and via organisations such as the IAEA, the International Nuclear Regulators Association (INRA), the Nuclear Energy Agency (NEA) of the Organisation for Economic Cooperation and Development (OECD), in particular through its Committee on Nuclear Regulatory Activities (CNRA). In addition, ONR is participating in the work of the Multinational Design Evaluation Program (MDEP – see www.oecd‐nea.org/mdep). 135
Throughout the GDA process ONR will seek to take advantage of assessments of the proposed design undertaken previously by overseas nuclear safety regulators. For example, where detailed independent analyses of nuclear safety issues or validation of computer codes are available, ONR will seek to make use of them. ONR assesses on a sampling basis and therefore the availability of additional information will help to target resources to best effect. ONR's attention could then, for example, be concentrated on areas of the design specific to Great Britain. 136
However, it should be noted that it is the responsibility of the RP to demonstrate the safety of its design, including highlighting and directing ONR to previous outputs and assessments made by overseas regulators, not for ONR to seek out and assemble information on regulatory issues raised or resolved overseas. 137
IAEA guidance states that even if a similar design has been authorised in another State, the national regulatory body should still perform its own independent review and assessment (Review and Assessment of Nuclear Facilities by the Regulatory Body (Ref. 13), paragraph 3.37). The Convention on Nuclear Safety, to which the UK is a signatory, states that each country must undertake safety assessment of its own nuclear facilities and make its own regulatory decisions about the safety of those facilities. In line with these international expectations, ONR will therefore be undertaking its own assessment of the generic safety case and coming to its own judgements. ONR will not necessarily accept that a regulatory issue of concern to it has been resolved simply because an overseas regulator has considered a similar issue and agreed its resolution. ONR may, as it considers necessary, test the robustness of Office for Nuclear Regulation
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such claims. ONR's position on this international context is given in New nuclear power stations: Safety assessment in an international context (Ref. 14). 138
The extent to which overseas assessments can be taken into account will depend on a number of factors including: 
the date of the assessment and its continuing validity; 
the level of detail and the purpose of the assessment; 
the local conditions of use in the country where the assessment was undertaken; 
the depth of information provided by the RP including the evidence of issue resolution; 
whether overseas assumptions (e.g. on plant operating regime) will remain valid if the technology is adopted in Great Britain; 
whether a demonstration can be made satisfying the UK legal requirement that the risks have been reduced to a level that is ALARP; 
the scope of ONR's formal information exchange agreements with the overseas regulator; 
the overseas regulatory system and ONR's knowledge of it; and 
the willingness of the overseas regulator to engage with ONR on issues of primary interest to Great Britain, including providing access to detailed information. International Guidance
139
As they prepare their submissions, RPs may wish to take account of the requirements of IAEA safety standards and guides. ONR's SAPs have been benchmarked against these standards to ensure that ONR requirements fully reflect international nuclear safety standards. Utilities Requirements Documents
140
Reactor vendors often claim that their designs are compliant with Utilities Requirements Documents (e.g. US or European). ONR regards these documents as being guidance for the designers. ONR will not endorse the utilities' standards or use them for assessment purposes. ONR will assess the safety of the design using the SAPs. Regulatory Uncertainty
141
GDA is intended to be a predictable process against a reasonably certain timescale, but the outcome and timing depends on a number of factors which are out of ONR's control, including the quality of the RP's submissions and their answers to ONR’s questions. The assessment timetable given in Table 1 can therefore only be indicative. 142
By allowing the completion of elements of the design safety assessment process before major investment in site selection, equipment ordering, manufacture and construction, the GDA process provides a mechanism for reducing regulatory uncertainty for the RP and potential licence applicants, while maintaining the rigour of ONR's regulatory assessment. The process is also designed to promote increased public involvement and enhance confidence, both in the regulatory process itself and, ultimately, in any decisions regarding the safety of the proposed design. 143
To help provide certainty in the regulatory processes, ONR will establish agreements with the RP setting out in detail what it expects from them, as well as the scope of the assessment etc. Office for Nuclear Regulation
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The arrangements will also set down what may be expected of ONR and how the working interface between the RP and ONR will be organised. The detailed working arrangements are set out in an Interface Arrangements document, as described in the Section 'Project Management and Administration' below. ONR will engage with the RP throughout the assessment process, and will provide progress statements. ONR will require that the RP responds to assessment questions within an agreed timeframe. 144
While ONR believes that the GDA process offers the potential for a stepwise reduction in regulatory uncertainty, it cannot completely eliminate the possibility that ONR will request design changes as a result of its assessments during the site specific detailed design and construction. Safety Case Ownership and Involvement of Future Licensees in GDA
145
In law in Great Britain, the licensee has the ultimate responsibility for ensuring the safety of the plant. Therefore, the safety case produced in GDA must be developed with a potential operator’s legal duties in mind, not as a means to satisfy the regulator. In the GDA Phase, ONR will expect the safety case to be fit for use by a site operator, and in Phase Two, nuclear site licensing, ONR will assess the degree to which the prospective site licensee understands and takes responsibility for the safety case. 146
ONR expects that the GDA request will have support from a prospective site operator / licensee in Great Britain from the outset. But, as GDA may take place well before a future licensee has made its final technology choice, the involvement of future licensees in GDA cannot be mandatory. Nevertheless, ONR encourages future licensees to be involved in GDA wherever possible as this will be of significant benefit to them in demonstrating, during the nuclear site licence application: 147

an understanding of the safety case; 
knowledge of the hazards from its activities and how to control them; 
that it can be an intelligent customer for any work it commissions externally; and 
that it understands the nuclear regulatory framework in Great Britain. Although the vendor has the detailed knowledge of the design, prospective operator involvement will demonstrate that there is intent to transfer knowledge to the operator throughout the GDA process. ONR will look for evidence that this knowledge transfer is occurring and that any prospective licensee has plans for incorporation of the GDA information within its site specific safety and security submissions. Age of Design
148
If the original reactor design has been frozen or 'fixed' for several years, evidence should be provided by the RP that adequate consideration has been given to: 
developments in nuclear technology since the design was frozen; 
operating experience in similar plants elsewhere; 
relevant new research findings; and 
any other factors arising that may have an impact on the safety of the design. These will be taken into account in ONR's regulatory assessment. Office for Nuclear Regulation
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Technical Support Contractors
149
ONR may choose to place work packages with contractors, including organisations outside Great Britain, to help it carry out its detailed technical assessment. It is common practice for ONR to engage specialist contractors in this manner to give technical and scientific support and advice to its regulatory assessment. However, all regulatory decisions are made by the nuclear regulators – not by contractors. The costs of such contracts will be charged to the RP. 150
Throughout GDA ONR will make relevant RP documentation available to ONR’s technical support contractors, as appropriate, to allow the required scrutiny to be undertaken. Research
151
152
ONR's expectation is that adequate research and technical studies will have already been completed and will be made available by the RP where necessary to ONR. Factors affecting research requirements include: 
departure from proven technology; 
uncertainties in performance; and 
degree of defence‐in‐depth. ONR may carry out additional confirmatory research, using external contractors, to support its regulatory decisions. The costs of such research will be charged to the RP. Factors affecting the need for such research include: 
familiarity of the technology in Great Britain; 
issues arising from early steps of the safety case assessment; 
other research and development programmes, including research information from overseas regulators who have reviewed the design. Review of Decision
153
Where an RP is dissatisfied with a decision by ONR it may make representations to the appropriate inspector and their line management in ONR, and ultimately to the Chief Inspector of Nuclear Installations. If the RP remains dissatisfied it may seek a review by ONR of the process by which the decision has been reached. This decision review process is set out in reference 21. Section 6 ‐ Project Management and Administration Joint Programme Office
154
There is co‐ordination of the processes between the two nuclear regulators (ONR and the Environment Agency), which is described in a top‐tier guidance document New nuclear power stations Generic Design Assessment: A guide to the regulatory process (Ref. 1). To help administer the GDA process, a Joint Programme Office (JPO) has been set up to provide a single point of contact between the RP and the two regulators. Office for Nuclear Regulation
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ONR-Requesting Party Interface Arrangements
155
The RP will be required to agree to an Interface document which will describe the working arrangements with the two regulators. This will set out the agreed system for transmission and tracking of safety and security submissions, correspondence, meetings, and issue tracking. 156
The Interface document will also identify that a system of metrics will be used to indicate the performance of ONR and the RP against the programme, and this will be published as part of ONR’s regular progress reporting. The Interface document will be agreed with the RP in Step 1. 157
The RP will also be required to agree, in Step 1, to a Regulatory Nuclear Interface Protocol that addresses the essential values and behaviours associated with the interactions between the RP and the regulators that are expected to apply throughout GDA and which facilitate the achievement of effective ways of working. Requesting Party Project Office
158
If based outside Great Britain, the RP will be expected to set up an office in Great Britain for the day‐to‐day management of its GDA project, and for interfacing with ONR. The majority of project and technical meetings should take place in Great Britain. All the GDA documentation, including any protectively marked documents, needs to be made available to ONR (and its technical support contractors, as required), via the JPO in Bootle, Merseyside, Great Britain. Regulatory Questions
159
160
As part of the Interface arrangements, a management system for handling regulatory questions will be agreed with the RP. This will use a tiered approach as follows: 
Regulatory Query (RQ) – these are requests by ONR for clarification and additional information and are not necessarily indicative of any perceived shortfall. 
Regulatory Observation – an RO is raised when ONR identifies a potential regulatory shortfall and requires action and new work for it to be addressed. Each RO can have several associated Actions. ROs will be published on the Joint Regulators website. 
Regulatory Issue – an RI is raised when ONR identifies a serious regulatory shortfall which is potentially significant enough to prevent provision of a DAC, and requires action and new work for it to be addressed. Each RI can have several associated Actions. RIs will be published on the Joint Regulators website. It is possible that a question raised as an RQ could escalate to an RO or to an RI. Recovery of ONR Costs
161
The RP will pay all ONR costs in connection with the GDA. The detailed arrangements for cost recovery will be agreed with the RP at the beginning of Step 1. Section 7 ‐ Interface Between GDA and Nuclear Site Licensing Nuclear Site Licence Assessment
162
The GDA process is not mandatory and potential licensees are free to submit licence applications for designs that have not been subject to GDA. However, ONR expects the GDA Office for Nuclear Regulation
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process to be followed by most applicants as this is likely to be a more business efficient approach. In either case, ONR would undertake a rigorous assessment of the proposed design. 163
Where GDA has been followed, Phase Two of the new nuclear power station regulation process includes ONR's assessment of an application for a nuclear site licence. This will consider the site‐specific plant (taking account of the assessments undertaken throughout GDA), the specific site, and the operating organisation which will become the licence holder. 164
It is likely that there will need to be a significant period of discussion between the intending licence applicant and ONR during which the applicant will prepare the licence application documents and will develop its organisational capabilities and competences. Such a period could typically be between 18 months and two years. If the applicant subsequently provides detailed and adequate submissions, ONR's assessment of that application could take between 12 to 18 months. 165
Guidance on applying for a nuclear site licence is given in Licensing Nuclear Installations (Ref. 3). Potential site licence applicants are encouraged to contact ONR early to discuss the process. 166
The safety case submissions for licensing assessment may reference the DAC with additional site‐specific information. Also: 
any site‐specific aspects not covered by the generic site envelope will have to be assessed; and 
any proposed changes to the design would also need reassessment on a case‐by‐case basis within a formal design change control system. Site Specific Security Plan
167
For security aspects, the overall aim of GDA will be for the RP to develop an acceptable generic CSA document. These generic arrangements would then form the basis of the site specific security plan, approval of which will be required before construction commences. A further approved site security plan would be needed before any radioactive material is brought onto site. Design Variants
168
The future operator may wish to vary a design that has received a DAC to meet its particular needs. Such design changes would need reassessment on a case by case basis, but ONR’s preference is that significant changes to the GDA design are avoided for reasons of standardisation except where the changes would give safety benefits. ONR also considers that ALARP considerations are likely to lead to a high degree of standardisation for a series of reactors. Transfer of Knowledge from Vendor to Licensee
169
The nuclear site licence requires that the licensee is fully in control of activities on its site, understands the hazards of its activities and how to control them, and is an intelligent customer for any work it commissions externally. This requires the licensee to have suitably qualified, and experienced staff undertaking all activities that could affect safety on the site. 170
The licensee will need to have a Design Authority, and a process for transfer of knowledge from the designer to the operator. For guidance on design authority aspects, see Maintaining the design integrity of nuclear installations throughout their operating life (Ref. 12). Office for Nuclear Regulation
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171
For most potential reactor designs the expert knowledge will initially rest with the RP and appropriate strategies to transfer knowledge and information to potential operators / site licensees will need to have been developed before nuclear site licensing. The GDA process provides an opportunity for prospective licensees to develop their competence on the reactor design, build up qualified and experienced staff, and transfer knowledge to them from the RP organisation. 172
ONR will expect this development of knowledge to be well advanced by the time the applicant makes the nuclear site licence application (i.e. by the start of Phase Two), and the licence applicant must be able to demonstrate that it is ready to take safe and secure control of all activities on the site before the licence is granted. Relationship of Generic Design Assessment and Site Specific Detailed Design,
Construction and Commissioning
173
A successful GDA outcome does not guarantee that ONR will permit the construction of a nuclear power station based on that design. That will depend on ONR being satisfied with site‐specific safety case and security submissions. However, the final DAC will be required before regulatory consideration is given to granting consent, under a nuclear site licence, for nuclear island safety‐related construction. 174
In the site‐specific phase of a project based on a reactor design that has been through GDA, ONR will expect the final GDA submission documentation to be incorporated largely unchanged within the potential operator’s site‐specific Pre‐construction Safety and Security Reports, supplemented as necessary with detailed site‐specific information. To improve the efficiency of ONR’s site‐specific assessment work, it is essential that the potential operator ensures that the use of the GDA information is clearly identified in its submissions. 175
Similarly, the potential operator must ensure that there is a programme in place to address the Assessment Findings from GDA during the ongoing design, procurement, construction, testing and commissioning programme. 176
At the site‐specific stage of the project, ONR does not anticipate the need for any further assessment of aspects of the safety and security case already assessed and accepted in GDA. This is subject to no significant new information arising which might call into question the basis of ONR's original assessment of the design. Also, if the RP or licensee make generic or site‐specific safety significant changes that affect the basis of the GDA outcome, then those aspects of the GDA safety and security submission may require re‐assessment by ONR. 177
It is anticipated that a GDA DAC will be used to underpin the regulatory permissions needed by one or more operators to construct a fleet of reactors based on a common design. This is a key advantage of the GDA process. Office for Nuclear Regulation
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Level of scrutiny
APPENDIX 1: GENERIC DESIGN ASSESSMENT APPROACH
Step 1
Step 4
Step 3
Overall Design
Overall
Step 2
Safety
Review of
“Arguments”
Fundamental
Fundamental
Review
Detailed
Detailed
Design
DAC
Assessment
“Evidence”
SoDA
Assessment of
Overview of the
“Safety
Claims”
Overview
Preparation
Preparation
Time
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Appendix 2: Typical Assessment Topics The scope of ONR’s technical assessment will depend on a number of factors including the details of the reactor design under consideration. Not every topic may need to be examined in all 4 GDA Steps, but overall ONR would normally expect the GDA submissions provided by the RP, and the ONR assessment, to cover the following topic areas. Internal Hazards ONR’s safety assessment within this topic would typically include hazards such as fire, explosion, flood, dropped loads, pressure part failure, and steam release etc. within the reactor buildings. ONR would consider the adequacy of: the identification of hazards; prevention of hazards; and the protective barriers, segregation, separation, and active protection systems that are included within the design to provide mitigation in the event that such internal hazards should occur. Civil Engineering and External Hazards ONR’s assessment of civil structures would normally include consideration of the integrity of structural components such as steel‐framed buildings, concrete structures such as walls and the containment, and the reactor building foundations. ONR’s assessment of external hazards would typically include those natural or man‐made hazards that originate externally to both the site and the process and over which the operator has little control. External hazards include earthquake, aircraft impact, extreme weather, and flooding, and the effects of climate change. Terrorist or other malicious acts are also assessed as external hazards. Probabilistic Safety Analysis ONR would examine in detail the PSA. PSA is an integrated, structured, logical safety analysis that combines engineering and operational features in a consistent overall framework. It is a quantitative analysis that provides indications of the overall risk to the public that might result from a range of faults (for example, failure of equipment to operate, human errors, or hazards such as fires). PSA enables complex interactions, for example between different systems across the reactor, to be identified and examined and it provides a logical basis for identifying any relative weak points in the proposed reactor system design. Fault Studies, Transient Analysis and Severe Accidents Fault Studies ONR’s assessment would include the transient analysis and fault studies, which are the safety analyses of nuclear reactors on matters such as reactor core physics, thermal hydraulics, heat transfer and a wide range of other physical phenomena under steady state, transient and fault conditions. Fault analysis involves a detailed study of the reactor system, its characteristics and mode of operation, with the aim of identifying possible faults that might occur and lead to the release of radioactive material. This is followed by a thorough examination of the conditions brought about by those faults. In particular, for those conditions that might affect the integrity of the nuclear fuel, the aim is to demonstrate the adequacy of the engineered protection systems in preventing a release of radioactive material. Severe Accidents Office for Nuclear Regulation
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Included within the fault studies area is the topic of severe accident analysis. Here ONR would typically look at safety arguments for challenges to the containment from high pressure or temperature in accident conditions and design features that are provided to cope with events such as core melt. Control and Instrumentation (C&I) Control systems are typically those that are used to operate the plant under normal conditions and reactor protection systems are those safety systems that are used to maintain control of the plant if it goes outside normal conditions. ONR’s assessment in this topic area would include reviews of both hardware and software aspects of these systems. Electrical Engineering Many of the important systems on a nuclear power station require electrical power for their operation (pumps, valves etc). Therefore, the safety assessment in this topic area typically would cover the engineering of the essential electrical power supply systems, examine these under a wide range of transient and fault conditions, and consider their likely reliability, and the performance of protection devices. Fuel Design Within this topic ONR would typically look at the performance of the reactor fuel under a wide range of in‐reactor and storage conditions, both in normal operation and in fault conditions. Reactor Chemistry ONR’s assessment of the chemistry of new nuclear reactors would normally include the effects of coolant chemistry on pressure boundary integrity, fuel and core component integrity, fuel storage in cooling ponds, radioactive waste (accumulation, treatment and storage), and radiological doses to workers. Radiation Protection ONR’s assessment would consider the justification for radiation doses to workers and the public, the adequacy of engineering controls (such as material selection or radiation shielding), measures to control radioactive contamination, and criticality safety. Mechanical Engineering ONR assessment would typically include the safety assessment of essential mechanical items important to safety such as pumps, valves, lifting equipment including cranes, fuel handling equipment, ventilation systems etc. It also includes the layout and routing of the mechanical equipment and systems to ensure that appropriate maintenance regimes can be developed, and that equipment is protected from hazards and degradation. ONR’s mechanical engineering assessment would also consider the capability of the systems to deliver their functions. Office for Nuclear Regulation
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Structural Integrity This topic includes ONR’s assessment of nuclear safety‐related metal pressure vessels, piping, other structural components and their supports, including material selection, design, fabrication, in‐
manufacture examination and testing, the analysis of structural integrity under normal load and faulted conditions (including fracture mechanics based analyses), and lifetime ageing of materials assessment (including effects of neutron irradiation). Human Factors ONR’s assessment of the human factors (HF) aspects would examine the feasibility and acceptability of the claims for human actions that are needed to contribute to safety, the vulnerability to human errors, the adequacy of the (generic) Human Reliability Analysis, and the engineering systems’ maintenance reliability from a HF perspective. This would be complemented by a broader holistic assessment across a range of important HF aspects. Management of Safety and Quality Assurance (MSQA) ONR’s assessment would examine the RP’s QA and Management of Safety organisational and procedural arrangements to deliver the GDA safety and security submissions. This would also include examination of the control and updating of the GDA submissions, including the arrangements for freezing and updating the Design Reference. Radioactive Waste and Spent Fuel Management ONR’s assessment would examine the proposals for the safe minimisation, handling, storage and disposal of radioactive waste arising from all parts of the power station, and would include the proposals for decommissioning. Cross‐cutting Topics Certain safety aspects cut across a number of different technical topic areas and so these are managed in a transverse manner. Examples might include: 

Definition of the Design Reference. 
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Safety Function Categorisation and Safety Classification of SSCs. 
Lessons learnt from the Fukushima accident. Design changes. Operating Limits and Conditions and Examination, Maintenance, Inspection, and Testing. ALARP Security Under this topic ONR would consider whether the security protection provided on the nuclear power station is adequate to protect against the theft of nuclear materials or sensitive nuclear information or the sabotage of facilities. Office for Nuclear Regulation
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Conventional Safety and Fire ONR’s assessment would consider aspects of the design that might impact on conventional (i.e. non‐
nuclear) safety during construction and operation of the power station, on COMAH (Control of Major Accident Hazards regulations) and compliance with fire safety regulations (includes compliance with the general requirements of the Health and safety at Work etc Act 1974, the Construction (Design and Management) Regulations 2007, and the Regulatory Reform (Fire Safety) Order 2005). Office for Nuclear Regulation
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Appendix 3: The Generic Site Envelope Although much of a power station design will be independent of the location chosen for its construction, some assumptions about the characteristics of the plant's environment must be considered in developing the design of certain safety‐related features. ONR expects that designs submitted for GDA will be suitable for being built on a variety of sites within Great Britain. To this end, ONR will expect the RP to specify the 'site envelope' within which the plant is designed to operate safely. The definition of the site envelope can be as broad or narrow as the RP wishes. However, it should be unambiguous and specify any site‐related characteristics which have been explicitly included within or excluded from that definition. If a subsequent site licence application is made for a site in Great Britain which has characteristics bounded by the generic site envelope then the time taken for ONR's licensing assessment will be minimised. If the proposed site has characteristics which lie outside the generic site envelope, the applicant will need to demonstrate by some other means that the proposed plant is acceptable at the proposed site. This may involve additional safety analysis and / or plant redesign. This note provides a brief overview of ONR's expectations for a generic site envelope. Heat Sink The type and capacity of potential heat sinks should be specified. Grid Connections Assumptions about the type and reliability of grid connections should be identified. Density and Distribution of Local Population When considering the generic site envelope, account should be taken of factors that might affect the protection of individuals and populations from radiological risk. Key factors here include assumptions about the local population distribution and density, and the provision for effective emergency preparedness and accident management. Assumptions regarding the density and distribution of the local population should also take account of existing Government policies on strategic siting suitability. The current Government policy is given in the National Policy Statement for Nuclear Power Generation (Ref. 15) External Hazards External hazards that could affect the safety of the facility should be identified and treated as events that can give rise to possible initiating faults. The RP should demonstrate that an effective process has been applied to identify typical external hazards and potential environmental changes such as climate change (e.g. a change in sea level) which may affect sites in Great Britain. Any foreseeable variations in these factors during the expected lifetime of the site should be identified and taken into account. Further guidance is available in ONR's SAPs. For a generic list of external hazards that may influence the plant design see WENRA report Safety of new NPP designs (Ref. 7). Also, refer to TAG T/AST/013 (Ref. 16). The generic site envelope should encompass a range of external hazards for sites typical of Great Britain. The sensitivity of the design to the magnitude of external hazards should be well understood. This will be particularly important at the site‐specific application stage, where a rigorous comparison of the generic site envelope against site‐specific criteria will be undertaken. Office for Nuclear Regulation
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References 1 New nuclear power stations Generic Design Assessment: A guide to the regulatory processes ONR & Environment Agency Report NGN01 Version 3. June 2013. www.hse.gov.uk/newreactors/ngn01.pdf 2 The health and safety risks and regulatory strategy related to energy developments: An expert report by the Health and Safety Executive contributing to the Government's Energy Review, 2006 HSE June 2006 www.hse.gov.uk/consult/condocs/energyreview/energyreport.pdf 3 Licensing Nuclear Installations ONR June 2012. www.hse.gov.uk/nuclear/licensing‐nuclear‐
installations.pdf 4 Ionising Radiations Regulations 1999 SI 1999/3232 www.legislation.gov.uk/uksi/1999/3232/contents/made 5 Reducing risks, protecting people: HSE's decision making process HSE 2001 ISBN 978071762151 4 http://www.hse.gov.uk/risk/theory/r2p2.pdf 6 Safety Assessment Principles for Nuclear Facilities HSE 2006 (First edition, Revision 1) (Previous edition 1992) www.hse.gov.uk/nuclear/saps/saps2006.pdf 7 WENRA Reactor Safety Reference Levels WENRA January 2008, WENRA Statement on Safety objectives for new nuclear power plants WENRA November 2010, Waste and Spent Fuel Storage Safety Reference Levels 2011, Decommissioning Safety Reference Levels 2012, Safety of new NPP designs WENRA March 2013 http://www.wenra.org/
8 Process and Information Document for Generic Assessment of Candidate Nuclear Power Plants Version 2 Environment Agency March 2013 https://brand.environment‐
agency.gov.uk/mb/Ndy3V 9 Managing Radioactive Waste Safely: A framework for Implementing Geological Disposal Cm 7386 Defra, BERR and devolved administrations for Wales and Northern Ireland June 2008 www.gov.uk/government/uploads/system/uploads/attachment_data/file/68927/7386.pdf 10 UK Radioactive Waste Inventory NDA And DECC April 2010 www.nda.gov.uk/ukinventory 11 Radioactive Waste Management Directorate: Disposability Assessment of Solid Waste Arisings from New Build NDA April 2008 www.nda.gov.uk/documents/upload/Disposability‐
Assessment‐of‐Solid‐Waste‐Arisings‐from‐New‐Build‐April‐2008.pdf 12 Maintaining the design integrity of nuclear installations throughout their operating life: A report by the International Nuclear Safety Advisory Group INSAG‐19 IAEA 2003 www‐
pub.iaea.org/MTCD/publications/PDF/Pub1178_web.pdf 13 Review and Assessment of Nuclear Facilities by the Regulatory Body Safety Standards Series GS‐G‐1.2 IAEA 2002 www‐pub.iaea.org/MTCD/publications/PDF/Pub1128_scr.pdf 14 New nuclear power stations: Safety assessment in an international context HSE June 2008 www.hse.gov.uk/newreactors/international.pdf 15 The National Policy Statement for Nuclear Power Generation DECC July 2011. www.decc.gov.uk/en/content/cms/meeting_energy/consents_planning/nps_en_infra/nps_en
_infra.aspx 16 Technical Assessment Guides ONR www.hse.gov.uk/nuclear/operational/tech_asst_guides/index.htm. 17 Technical Inspection Guides ONR Office for Nuclear Regulation
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18 www.hse.gov.uk/nuclear/operational/tech_insp_guides/index.htm.
Nuclear power station Generic Design Assessment. Interface between Office for Nuclear Regulation / Environment Agency and Requesting Parties JPO/004 HSE March 2013 www.hse.gov.uk 19 The Management of Sensitive Nuclear Information during the Generic Design Assessment of Nuclear Technologies. ONR’s CNS February 2008 www.hse.gov.uk/nuclear/ocns/ocnsinfomanage.pdf 20 Guidance on the Security Assessment of Generic New Nuclear Reactor Designs ONR (CNS) Technical Assessment Guide CNS‐TAST‐GD‐007 Revision 0 2013 (pending publication) 21 Decision Review Process, ONR‐PER‐IN‐006, revision 2, July 2013 http://www.hse.gov.uk/nuclear/operational/assessment/ns‐per‐in‐006.pdf While every effort has been made to ensure the accuracy of the references listed in this report, their future availability cannot be guaranteed. Office for Nuclear Regulation
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Glossary and Abbreviations ALARP As Low As Reasonably Practicable C&I Control and Instrumentation CNRA Committee on Nuclear Regulatory Activities (of the OECD‐NEA) CSA Conceptual Security Arrangements DAC Design Acceptance Confirmation DBA Design Basis Analysis DBT Design Basis Threat DECC Department of Energy and Climate Change EDF and AREVA Electricité de France SA and AREVA NP SAS ENSREG European Nuclear Safety Regulators Group GDA Generic Design Assessment HMG Her Majesty’s Government HSE Health and Safety Executive HSWA74 Health and Safety at Work etc. Act 1974 IAEA International Atomic Energy Agency iDAC Interim Design Acceptance Confirmation ILW Intermediate Level Waste INRA International Nuclear Regulators Association IRRS Integrated Regulatory Review Service (IAEA) JPO Joint Programme Office LLW Low Level Waste MDEP Multinational Design Evaluation Programme MSL Master Submission List NDA Nuclear Decommissioning Authority NEA Nuclear Energy Agency (of the OECD) OCNS Office for Civil Nuclear Security (now Civil Nuclear Security, part of the Office for Nuclear Regulation) OECD Organisation for Economic Cooperation and Development OJEU Official Journal of the European Union ONR Office for Nuclear Regulation ONR (CNS) Civil Nuclear Security (part of the Office for Nuclear Regulation) PCSR Pre‐construction Safety Report PRA Probabilistic Risk Analysis PS Protection System PSA Probabilistic Safety Analysis PSR Preliminary Safety Report QA Quality Assurance Office for Nuclear Regulation
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QMS Quality Management System REPPIR2001 Radiation (Emergency Preparedness and Public Information) Regulations 2001 RI Regulatory Issue RO Regulatory Observation RP Requesting Party RQ Regulatory Query SAP Safety Assessment Principles SFAIRP So far As Is Reasonably Practicable SML Submission Master List SoDA Statement of Design Acceptability (Environment Agency) SSC Structures, Systems and Components TAG Technical Assessment Guide (ONR) TSC Technical Support Contractor WENRA Western European Nuclear Regulators’ Association Office for Nuclear Regulation
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CONTACTS
Deputy Chief Inspector Civil Nuclear Reactor programme Office for Nuclear Regulation Redgrave Court Merton Road Bootle Merseyside L20 7HS www.hse.gov.uk/nuclear email: new.reactor.build@hse.gsi.gov.uk For information about health and safety visit www.hse.gov.uk. You can view HSE guidance online and order priced publications from the website. HSE priced publications are also available from bookshops. This document is issued by the Office for Nuclear Regulation (ONR). For further information about ONR, or to report inconsistencies or inaccuracies in this publication please visit www.hse.gov.uk/nuclear. Office for Nuclear Regulation
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