6 th Review Meeting of the
Convention on Nuclear Safety
Country Group 3
24 March 2014, Vienna
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Basic information on the national programme
Changes in the legislation since the last Review
Meeting
Significant events since the last Review Meeting
Action on challenges and planned measures from the last Review Meeting
Current Challenges
Questions Raised from Peer Review of National
Report
Updates to National Report to 6th Review Meeting
Conclusions

Basic information on the national programme

Mine
TRIGA
NPP Krško

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Westinghouse PWR, 2 loop
700 MWe
Commercial operation since
1983
Ownership 50:50 Slovenia-
Croatia
Without major problems
Life time extension after
2023 is foreseen
Intensive post Fukushima improvements

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TRIGA research reactor
Central Interim RW Storage
Former Uranium Mine
Looking for the LLIW Repository
>1000 sources of ionizing radiation

We have everything the big country has …
… but we have to manage it with less resources!

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Krško NPP operation was without major problems, however ...
 ... 11. March 2011 has drastically changed the focus of nuclear safety related activities

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New mobile equipment’s
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Mobile DG’s - various power (from 3 KW up to 2 MW)
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Mobile Air Compressors
Mobile FP pumps
 Stress tests and National Action Plan
 Long term improvements:
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Comprehensive Safety Upgrade Programme:
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Filtered Containment venting – implemented
Passive Autocatalitic Recombiners – implemented
Additional SI and FW pumps – by 2018
Additional heat sink – by 2018
External control room
– by 2018
Dry spent fuel storage – by 2018

Fire truck with a hydraulic fire-fighting arm
Tanks: 8500 l of water & 1500 l of fire-extinguishing foam

30 m 3 /hr, 32 bar
2 discharge connections
Testing the spraying of the “imaginary SFP”

Fuel (diesel, gasoline) stored on-site
Mobile and portable diesel generators

 3 rd safety related diesel generator
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Reduces risk primarily from the Station Blackout
Sequence and from seismic events
 Upgrade of flood protection dikes.
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Protects against more demanding Probable
Maximum Flood
 Reactor pressure vessel head replacement
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In response to industry events involving Alloy 600 penetrations and 82/182 weld material

 Aging management programme approved
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It makes operation after 2023 possible
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One more Periodic Safety Review have to be done before first 10 year life extension
 Second Periodic Safety Review is concluded, to be approved by June 2014
 KI iodide tablets distributed in 10 km radius around the Krško NPP.

 Replaced main generator rotor
 Upgraded of 400 kV buses and undervoltage protection
 Replaced main feedwater isolation valves actuators
 Upgraded fire protection detection system,
 Refurbished residual heat removal and essential service water systems.

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Operator immediately started with improvements
The SNSA issued three decisions to the Krško NPP:
 to perform an extraordinary PSR in line with specifications for European Stress Tests
 to reassess the severe accident management strategy and implement safety improvements for prevention of severe accidents and mitigation of its consequences
 to review bases for emergency planning and response including emergency planning zones

 Evaluation of seismic and flooding margins,
 Additional station blackout analyses,
 Drain cycle of the 1E batteries,
 Water heatup and evaporation rate in the spent fuel pool,
 Evaluation of spent fuel pool criticality.

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Krško NPP was well designed and constructed,
Potential external events were taken into account during preparation of protective and mitigating measures.
A single recommendation after Peer Review:
“The regulator should consider requesting to update the seismic design basis for future design modifications and consequently the associated PSA model.”

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Its core is the Krško NPP’s Safety Upgrade
Program
Implementation of upgrades foreseen already in
2009
Implementation of Short-Term Improvements
(accelerated B.5.b Requirements Actions):
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Procurement of AC diesel generators, pumps and compressors, implementation of quick connection points for this equipment, additional fire protection equipments, including high capability fire truck
Amendments to the emergency operating procedures and severe management accident guidelines

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Safety upgrade of AC power,
Additional FW pump,
Additional heat sink (AHS),
Additional SI pumps with a dedicated water supply,
Containment filter vent system and passive autocatalytic recombiners,
Emergency control room,
Fixed spray system around the spent fuel pit,

 Mobile heat exchanger with provisions to quick connect,
 Flood protection upgrade,
 New technical support center,
 Upgrade of existing operational support center.

 New Act on Liability for Nuclear Damage issued
 Amendments of the Act on Ionising Radiation
Protection and Nuclear Safety comprising:
 requirements of Nuclear Safety Directive,
 the restriction of the right to go on strike,
 provisions on physical protection,
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 duplications in the area of radiation practices, availability of inspectors and professional officers, etc.
 Resolution on Nuclear Safety

Significant events since the last
Review Meeting

 Activation of false alarms in the seismic monitoring system,
 Inoperability of the service water system,
 Trip of auxiliary feedwater pump,
 Inoperability of Chilled Water System,
 Reactor vessel head cable bridge incident,
 Extensive fuel damage

 Reactor trip and safety injection actuation system due to the loss of external load
 Main steam isolation valve stem failure
 Shutdown due to large amounts of debris in the Sava river
 Malfunctioning of primary temperature measurement system

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23 March 2011 (during Fukushima!)
Spurious activation of bus protection in the
NPP’s 400 kV switchyard,
Rapid pressure decrease in the main steam line,
Safety injection (SI) signal on low steam line pressure,
Diesel generators started automatically,
No other problems

 25 February 2013
 Sudden closure of main steam isolation valve
(MSIV) – valve stem break,
 Increased steam flow in another line resulted in pressure drop actuating the safety injection system and the reactor trip,
 Similar event occurred 1997,
 Replacement and redesign of MSIV.

Broken MSIV stem

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28 October 2012
The flow of the river Sava rose very rapidly
High river washed down materials from river banks,
The inlet of the condenser cooling system was clogged,
Condenser cooling water flow was reduced,
Temperature and pressure in the condenser increased and vacuum in the condenser deteriorated.
Operators carried out manual preventive shutdown of the reactor.

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Trip due to the malfunctioning of the primary temperature measurement system
 Extensive fuel damage
See last part of this presentation with updates to the
National Report

Action on challenges and planned measures from the last Review
Meeting

Problems of domestic TSOs – Reliance on foreign TSO
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Not all technical aspects could be covered by domestic Technical Support Organizations
(TSOs)
Operator is seeking expertise from anywhere
Reducing number of domestic experts
No systematic support to nuclear fission related research, experts are growing older ...
 Challenge remains!

Financial and Human Resources for the SNSA
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SNSA is financed only by the state budget,
Due to the crisis funds are decreasing,
No new employments!
SNSA had to abandon ISO9001 certification
SNSA is fulfilling its mission, but ...
... has already publicly announced what risks are increasing due to restrictions
 Challenge remains and is growing bigger!

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Between 25 September – 4 October 2011
The SNSA Strengths
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Adequate legal framework
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SNSA has in place an effective process for carrying out this responsibility,
Response to the accident at the TEPCO Fukushima Daiichi power plant has been prompt and effective.
Good practices
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SNSA
’ s quality management system,
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An inter-ministerial committee chaired by SNSA for coordination of emergency planning
Communications system used during emergency situations

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A need to develop a national policy and strategy for nuclear safety - done
Possible alternative methods of financing SNSA – decided not to go for independent agency!
SNSA needs competencies and resources – see previous challenge
Necessary steps to be taken for the Low and
Intermediate Level Waste Repository – SNSA has actively pushed for it, some progress
Transition between the emergency phase to long term recovery operations and the post-accident phase,
... and some others.

Done in 2012!

Upgrade of Flood Protection and
Installation of New Diesel Generator
 Done in 2011-12!
 Flood protection
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Upgrade by up to 1.8 meters of flood protection dikes along the river Sava.
Seismic criteria the same as for the Krško NPP
Safety margin of 0.75 m.
 Third Diesel Generator
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Class 1E 3.5 MW diesel generator
Increases safety in case of a seismic event and loss of offsite power.

 Plant site would remain dry
Upgrade of dikes upstream of the plant to protect the plant to the flood flows beyond the P robable
M aximum
F lood
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 WENRA Reference Levels are fully transposed into Slovenian legislation,
 Slovenian legislation is harmonized with the
EU Nuclear Safety Directive and EU Nuclear
Waste Directive

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The latest revision of Quality Assurance Plan in 2011.
In line with Slovenian Rules JV5 and IAEA GS-R-3 requirements
Covers Safety Culture, Self-Assessment, Human
Performance, Industrial Safety
The bases for the revision were:
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Changes of the Slovenian regulatory requirements and licensing documents,
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SNSA inspection requirements,
Changes of international standards,
Conclusions of the first PSR,

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PSR2 was completed
There were no major issues which would prevent further safe operation
15 safety factors were reviewed
An action plan is being developed and will be implemented in the next 5 years.
Some issues from the action plan:
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Procedures periodic review
Root cause analysis
Temporary modification survey
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Generation of solid radioactive waste
Potential tube wear from secondary side loose parts
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Cyber Security Threats and Airplane
Crashes
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Krško NPP has prepared and implemented Cyber
Security programme
SNSA has trained its people
 Airplane Crashes
 Noflight zone in place around the NPP Krško
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NEI 06-12 B.5.b requirements was one of the inputs to post
Fukushima action plan and those consider also airplane crash
Bunkerized structures for DG3 and future safety equipment
Alternative Spent Fuel Pool cooling system,
Fire fighting of airplane fuel fires capabilities
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Improved SAMGs.

 Most of those measures are within the Safety
Upgrade Programme (see post-Fukushima related slides)
 Upflow conversion in the reactor vessel
 Improvements in off-site emergency planning together with Croatia
 Inviting peer review missions:
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WANO, IRRS-FU, OSART, EPREV
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 Individual actions of the Safety Upgrade
Program as well as other National post-
Fukushima Action Plan (NAcP), including Design
Extension Codition (DEC) implementation
 Reassessment of alternative spent fuel strategy
(part of NAcP)
 Preservation of knowledge and competencies:
 Financial and Human Resources of SNSA
 Domestic TSOs

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The complete set of answers to the questions raised by other CP is available at the SNSA site: http://www.ursjv.gov.si/fileadmin/ujv.gov.si/pageuploads/si/Porocila/
NacionalnaPorocila/KJV_6th_answers.pdf
Questions were evenly distributed among articles, with the exception two:
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“regulatory body”: the decreasing SNSA budget, challenge to keep competency due to small nuclear programme, ageing of the
SNSA staff, sharing information to the public of the SNSA activities
“assessment and verification of safety”: PSA, PSR, SAMG, response to Fukushima, performance indicators,

 The other questions referred to.
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Post-Fukushima upgrades (plan and status)
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Management system of the licensee
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Emergency preparedness in Slovenia and Croatia and review of emergency plans in the light of Fukushima
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Incident reporting system by the operator
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Assessing safety culture
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Transparency and communication to the public by the licensee

 Discovered during outage in October 2013,
 Six fuel assemblies were leaking,
 50 cm long segment of the fuel rod found in the fuel transfer channel

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Open defects in 8 fuel rods of three fuel assemblies,
Primary cause debris fretting, baffle jetting and gridto-rod fretting
Extensive inspection of fuel assemblies and the core baffle plate
Corrective action: armoring of fuel assemblies with dummy stainless steel rods at exposed positions
Prior to the start of operation an extended Failed
Fuel Action Plan was prepared

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Resistance Temperature Detectors Bypass was eliminated during outage 2013
After the outage signal “spiking” caused reactor trip due to creation of OP ΔT (for a split second)
Corrective actions:
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Installation of “surge suppressors”
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Some equipment was tagged out until the problem was resolved
The vendor will analyze lead/lag filters used in processing the signals and redesign appropriate circuits

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The only NPP operating safely
Slovenia has Legislative System harmonized with best practices
Regulatory Supervision is efficient and effective, although the risks due to lack of resources are increasing
Slovenia and its Nuclear Facilities fulfill requirements of the
Convention on Nuclear Safety