Fire Protection Regulations for the Safe
Shutdown Phase – Deterministic and
Probabilistic Approach
Marina Röwekamp
Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) gGmbH
Köln, Germany
Heinz-Peter Berg
Federal Office for Radiation Protection (BfS)
Salzgitter, Germany
Technical Meeting on Fire Protection Approaches and Experiences
IAEA, Vienna, May 27-29, 2015
1
Contents
 Introduction and historic background
 Regulatory approach in Germany
•
Safety Requirements for NPPs
•
Nuclear KTA fire protection standards
•
Probabilistic guidance documents
 Conclusions and outlook
Technical Meeting on Fire Protection Approaches and Experiences
IAEA, Vienna, May 27-29, 2015
2
Introduction and Historic Background (1)
 Operating experience from nuclear installations has demonstrated a
non-negligible contribution of fires to the overall risk during the entire
life cycle (from construction up to decommissioning
 As a result, the German nuclear regulatory requirements are
continuously updated and enhanced
 High level overall “Safety Requirements for NPPs” came into effect in
2013, affecting also fire safety
• They cover all plant operational phases including post-commercial
safe shutdown
• The scope includes all external and internal hazards including fires
• As a result from post-Fukushima lessons learned, event
combinations of causally related events including fires as well as
independently occurring events simultaneously are systematically
addressed
Technical Meeting on Fire Protection Approaches and Experiences
IAEA, Vienna, May 27-29, 2015
3
Introduction and Historic Background (2)
 High level “Safety Requirements for NPPs” cover deterministic safety
assessment as well as supplementary probabilistic risk assessment
(PRA)
 Nuclear KTA fire protection standards have
been updated accordingly in the recent
past
 Probabilistic guidance is based on German
Guide “Probabilistic Safety Assessment
(PSA) for Nuclear Power Plants” and its
supplementary technical documents on
PSA Methods and Data (from 2005)
 An additional technical document
supplementing the others with an
extended scope and new/enhanced
methods and data will be published in 2015
Technical Meeting on Fire Protection Approaches and Experiences
IAEA, Vienna, May 27-29, 2015
4
Regulatory Approach for Fire Protection in NPPs (1)
 Fire hazard analysis (FHA) and Fire PSA are good practice in Germany
for non-nuclear as well as nuclear installations for > 20years
 FHA approach has already been applied when developing the “Fire
Protection Concept” (internationally, e.g. by IAEA, often called “Fire
Safety Program”) for a plant or a new building to be added
•
FHA is kept up to date
•
FHA requires systematic analysis
 Fire PSA is state-of-the-art analytical tool applying
•
Verified and validated methods
•
Data from national as well as international operating experience
from nuclear installations
Technical Meeting on Fire Protection Approaches and Experiences
IAEA, Vienna, May 27-29, 2015
5
Regulatory Approach for Fire Protection in NPPs (2)
Enhanced nuclear standards “Fire Safety in NPPs” – KTA 2101 (1)
 Actual enhancements in German regulation on NPP fire safety mainly
focus on systematically addressing individual fire events as well as
event combinations of fires and other anticipated events
 Such combined events may occur independently of each other,
but one of the events during the mission time of the other or in causal
relationship (consequential events)
 In the plant design the following event combinations of fires and
consequential events have to be considered:
• Fire and consequential component failure (including high energetic
faults) of electrical or mechanical components as well as of
pressurized pipework and vessels
• Fire and consequential plant internal explosion including gas
explosions from radiolysis gases in systems and components
Technical Meeting on Fire Protection Approaches and Experiences
IAEA, Vienna, May 27-29, 2015
6
Regulatory Approach for Fire Protection in NPPs (3)
Enhanced nuclear standards “Fire Safety in NPPs” – KTA 2101 (2)
 The following event combinations of anticipated events and
consequential fires have to be considered:
• Component failures and consequential fire including high
energetic faults of electric and mechanic components as
well as of pressurized pipework and vessels
• Plant internal explosion and consequential fire
(with additional requirements in KTA 2103 standard on
explosion protection)
• Earthquake and consequential fire
(with additional requirements in KTA 2201 standard series on
seismic protection)
• Lightning and consequential fire
(with additional requirements in KTA 2206 standard on lightning
protection)
Technical Meeting on Fire Protection Approaches and Experiences
IAEA, Vienna, May 27-29, 2015
7
Regulatory Approach for Fire Protection in NPPs (4)
Enhanced nuclear standards “Fire Safety in NPPs” – KTA 2101 (3)
 Independently, but simultaneously occurring fires and other
anticipated events have to be considered as follows:
•
“Directly” (i.e. 1 week) after an anticipated event fire protection means
needed to ensure the required function of those items important to safety
after such an event have to be made operable again or replaced by
suitable other means
•
For the following anticipated events these requirements are assumed to
be met: plant internal flooding, internal or external electromagnetic
interference (EMI), seismic (including consequences), extreme site-specific
hazards (e.g. weather, external flooding)
•
For the following anticipated events the occurrence frequencies of
independent event combinations of these with a fire have to be estimated:

For PWR: Leakages in the secondary RHR

For BWR: Loss of coolant outside the containment
Technical Meeting on Fire Protection Approaches and Experiences
IAEA, Vienna, May 27-29, 2015
8
Regulatory Approach for Fire Protection in NPPs (5)
Enhanced nuclear standards “Fire Safety in NPPs” – KTA 2101 (4)
 Systematic consideration of nuclear specific requirements on escape
and rescue routes during all plant operational states
 Enhancements in the updated regulation fully considering lessons
learned from:
• National as well as international operating experience with fires in
nuclear installations, such as prevention from smoke intrusion from
fires outside buildings
• Post-Fukushima investigations and emergency preparedness,
e.g. accessibility of buildings and fire compartments
photo by GL Bautechnik GmbH, Germany
internet photo
Technical Meeting on Fire Protection Approaches and Experiences
IAEA, Vienna, May 27-29, 2015
9
Specific Post-Fukushima Situation for German NPPs (1)
 After the reactor accidents of Fukushima 8 of 17 NPP units in Germany
have stopped commercial plant operation due to political decision
 The remaining 9 units will phase out in the near future with the
last units by end-2022
 A majority of the German reactors will remain in the so called
“post-commercial safe shutdown” plant operational phase for
several years
 The safe shutdown phase for the German NPPs at the time being is
characterized as follows:
• Plant is no longer operating commercially
• License for decommissioning has not yet been granted
• Fuel is still on-site, fuel elements are typically in the spent fuel pool
 The risk of fuel damage and releases has to be considered
Technical Meeting on Fire Protection Approaches and Experiences
IAEA, Vienna, May 27-29, 2015
10
Specific Post-Fukushima Situation for German NPPs (2)
 Same as for all low power and shutdown plant operational states,
fire risk is non-negligible for long duration safe shutdown phase
according to:
• More frequent incipient fire occurrences resulting from human
actions, e.g. hot work
• Several barriers being open to enable work, e.g. for preparing
decommissioning
• Combinations of fires with other events also cannot be excluded
 Spent fuel pool (SFP) safety becomes more important
 Specific considerations for fire protection under safe shutdown
conditions
• Fire protection concept has to be adapted
• On-site fire brigade is highly important and cannot be reduced
Technical Meeting on Fire Protection Approaches and Experiences
IAEA, Vienna, May 27-29, 2015
11
Consideration of Fires During Safe Shutdown in PSA (1)
 German “Safety Requirements for NPPs” require PSA as supplement
to deterministic analyses in case of any plant modification or change in
procedures assumed to change the plant specific PSA result(s)
 German “Safety Requirements for NPPs” as well as valid PSA Guide
require PSA also for low power and shutdown (LPSD) phases
 PSA scope recently covers also the post-commercial safe shutdown
phase and PSA for SFP (fuel damage frequency, FDF)
 As a result, the technical guidance document to be published in 2015
supplementing the documents on PSA methods and data specifically
provides guidance on:
• Level 1 PSA for external hazards
• Extensions of Level 1 PSA, particularly for LPSD, including fires
• Enhancements and extensions of internal events Level 2 PSA
for FP as well as LPSD
Technical Meeting on Fire Protection Approaches and Experiences
IAEA, Vienna, May 27-29, 2015
12
Consideration of Fires During Safe Shutdown in PSA (2)
 Contributions to of hazards, in particular fires, to fuel damage during
safe shutdown phase are non-negligible, e.g.
•
Fire occurrence frequency is non-negligible
•
Fires affecting fuel outside reactor are more important
 As a result, the technical guidance document to be published in 2015
supplementing the documents on PSA methods and data provides
guidance for LPSD Fire PSA:
• Systematic and consistent approach for all plant operational states
including safe shutdown (from screening up to detailed analysis)
• Adapting assumptions, boundary conditions and data to safe
shutdown
• Considering plant modifications, changes in accessibility and
human factor
Technical Meeting on Fire Protection Approaches and Experiences
IAEA, Vienna, May 27-29, 2015
13
Conclusion and Outlook
 Lessons learned from post-Fukushima investigations are being
considered, e.g.:
• Accessibility of buildings and fire compartments in case of fires
as consequential events from external hazards
• Need for precautions against fires resulting from external hazards
induced internal hazards (HEAF, explosion, etc.)
•
Prevention of internal flooding s inadmissibly impairing items
important to safety as a result of fire
 Need for more exemplary applications of new “Safety Requirements
for NPPs” and in-depth investigations, in particular for modifications
during safe shutdown phase
 Need for addressing human reliability in area events (from external
and internal hazards including event combinations)
Technical Meeting on Fire Protection Approaches and Experiences
IAEA, Vienna, May 27-29, 2015
14
Thank you
for your attention!
For questions please contact the authors:
Marina Röwekamp:
Marina.Roewekamp@grs.de or
Heinz-Peter Berg:
hberg@bfs.de
Technical Meeting on Fire Protection Approaches and Experiences
IAEA, Vienna, May 27-29, 2015
15