Unclassified

NEA/CSNI/R(2009)6

Organisation de Coopération et de Développement Économiques
Organisation for Economic Co-operation and Development

24-Sep-2009___________________________________________________________________________________________English text only
NUCLEAR ENERGY AGENCYCOMMITTEE ON THE SAFETY OF NUCLEAR INSTALLATIONSNEA/CSNI/R(2009)6
Unclassified

Cancels & replaces the same document of 28 July 2009

FIRE Project Report: "Collection and Analysis of Fire Events (2002-2008) First Applications and Expected Further Developments"

June 2009

The complete version is only available in PDF format.

English text only

JT03270251
Document complet disponible sur OLIS dans son format d'origine
Complete document available on OLIS in its original format

NEA/CSNI/R(2009)6

ORGANISATION FOR ECONOMIC CO-OPERATION AND DEVELOPMENTThe OECD is a unique forum where the governments of 30 democracies work together to address the economic, social andenvironmental challenges of globalisation. The OECD is also at the forefront of efforts to understand and to help governments respond to
new developments and concerns, such as corporate governance, the information economy and the challenges of an ageing population. The
Organisation provides a setting where governments can compare policy experiences, seek answers to common problems, identify goodpractice and work to co-ordinate domestic and international policies.
The OECD member countries are: Australia, Austria, Belgium, Canada, the Czech Republic, Denmark, Finland, France, Germany,
Greece, Hungary, Iceland, Ireland, Italy, Japan, Korea, Luxembourg, Mexico, the Netherlands, New Zealand, Norway, Poland, Portugal, theSlovak Republic, Spain, Sweden, Switzerland, Turkey, the United Kingdom and the United States. The Commission of the European
Communities takes part in the work of the OECD.
OECD Publishing disseminates widely the results of the Organisation’s statistics gathering and research on economic, social andenvironmental issues, as well as the conventions, guidelines and standards agreed by its members.

This work is published on the responsibility of the Secretary-General of the OECD. The
opinions expressed and arguments employed herein do not necessarily reflect the official
views of the Organisation or of the governments of its member countries.

NUCLEAR ENERGY AGENCYThe OECD Nuclear Energy Agency (NEA) was established on 1st February 1958 under the name of the OEEC European Nuclear
Energy Agency. It received its present designation on 20th April 1972, when Japan became its first non-European full member. NEA
membership today consists of 28 OECD member countries: Australia, Austria, Belgium, Canada, the Czech Republic, Denmark, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Japan, Luxembourg, Mexico, the Netherlands, Norway, Portugal, Republic ofKorea, the Slovak Republic, Spain, Sweden, Switzerland, Turkey, the United Kingdom and the United States. The Commission of theEuropean Communities also takes part in the work of the Agency.
The mission of the NEA is:– to assist its member countries in maintaining and further developing, through international co-operation, the scientific,
technological and legal bases required for a safe, environmentally friendly and economical use of nuclear energy for peacefulpurposes, as well as– to provide authoritative assessments and to forge common understandings on key issues, as input to government decisions on
nuclear energy policy and to broader OECD policy analyses in areas such as energy and sustainable development.
Specific areas of competence of the NEA include safety and regulation of nuclear activities, radioactive waste management,
radiological protection, nuclear science, economic and technical analyses of the nuclear fuel cycle, nuclear law and liability, and public
information.
The NEA Data Bank provides nuclear data and computer program services for participating countries. In these and related tasks, theNEA works in close collaboration with the International Atomic Energy Agency in Vienna, with which it has a Co-operation Agreement, as
well as with other international organisations in the nuclear field.

© OECD 2009
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NEA/CSNI/R(2009)6

COMMITTEE ON THE SAFETY OF NUCLEAR INSTALLATIONSThe NEA Committee on the Safety of Nuclear Installations (CSNI) is an international committee
made up of senior scientists and engineers, with broad responsibilities for safety technology and research
programmes, and representatives from regulatory authorities. It was set up in 1973 to develop andco-ordinate the activities of the NEA concerning the technical aspects of the design, construction andoperation of nuclear installations insofar as they affect the safety of such installations.
The committee’s purpose is to foster international co-operation in nuclear safety amongst the OECDmember countries. The CSNI’s main tasks are to exchange technical information and to promotecollaboration between research, development, engineering and regulatory organisations; to review
operating experience and the state of knowledge on selected topics of nuclear safety technology and safetyassessment; to initiate and conduct programmes to overcome discrepancies, develop improvements andresearch consensus on technical issues; to promote the coordination of work that serve maintaining
competence in the nuclear safety matters, including the establishment of joint undertakings.
The committee shall focus primarily on existing power reactors and other nuclear installations; it shallalso consider the safety implications of scientific and technical developments of new reactor designs.
In implementing its programme, the CSNI establishes co-operative mechanisms with NEA’s
Committee on Nuclear Regulatory Activities (CNRA) responsible for the program of the Agency
concerning the regulation, licensing and inspection of nuclear installations with regard to safety. It also cooperates with NEA’s Committee on Radiation Protection and Public Health (CRPPH), NEA’s Radioactive
Waste Management Committee (RWMC) and NEA’s Nuclear Science Committee (NSC) on matters ofcommon interest.

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NEA/CSNI/R(2009)6

PREFACE

After the CSNI State-of-the-Art Report on level-1 PSA methodology [CSNI/R(92)18] was published,a study on fire risk assessment was started by PWG5 (now WGRISK), which resulted in the international
workshop on fire risk assessment held from 29 June to 2 July 1999 in Helsinki, Finland and in a State of
the Art report on “Fire risk analysis, fire simulation, fire spreading and impact of smoke and heat on
instrumentation electronics” [CSNI/R(99)27] issued in March 2000. In 2000, the Committee on the Safetyof Nuclear Installations (CSNI) of the Nuclear Energy Agency of the Organisation for Economic Cooperation and Development (hereinafter referred to as the “OECD/NEA”) approved the establishment of an
OECD/NEA Fire Incident Records Exchange Project on collection of data on fire events at nuclear power
plants. This Project was finally established in 2002.
The objectives of the OECD-FIRE Project are to:(a) Collect fire event experience (by international exchange) in an appropriate format in a qualityassured and consistent database (the “OECD-FIRE database”);(b) Collect and analyse fire events over the long term so as to better understand suchtheir causes, and to encourage their prevention;

events and(c) Generate qualitative insights into the root causes of fire events in order to derive approaches ormechanisms for their prevention and to mitigate their consequences;(d) Establish a mechanism for efficient operation feedback on fire event experience including thedevelopment of policies of prevention, such as indicators for risk- informed and performancebased inspections; and(e) Record characteristics of fire events in order to facilitate fire risk analysis, including
quantification of fire frequencies.
After more than six years of event data collection (343 events at the date of the publication of thisreport) it is now possible to derive relevant information for fire safety analysis, which is presented in thisreport. Although first applications with respect to Fire PSA are possible on a more general level, it will be
important to collect as many events as possible in the future to enlarge the data base and to encourage
additional participation of organisations from other OECD Member States to support the OECD FIRE
Database Project.

ACKNOWLEDGEMENTS

The preparation of this reports benefited from the contributions of each National Co-ordinators of theOECD FIRE Project. Special acknowledgements are due to W. Werner for the statistical analysis and to
M. Röwekamp, Chair of the FIRE Project Review Group, for the entire review of the report.

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NEA/CSNI/R(2009)6

TABLE OF CONTENTSEXECUTIVE SUMMARY ............................................................................................................................. 7
1.

PROJECT BACKGROUND .................................................................................................................... 92.

PURPOSE AND SCOPE OF THE PROJECT ....................................................................................... 11

3.

STRUCTURE OF THE DATABASE .................................................................................................... 13
3.1
3.2
3.3
3.4
3.5

4.

Reported events ........................................................................................................................... 13
Description of OECD FIRE events ............................................................................................. 13
Relevance indices ........................................................................................................................ 13
Fire event analysis support data................................................................................................... 13
Further improvements to the database ......................................................................................... 14

CONTENTS AND BASIC STATISTICS .............................................................................................. 15
4.1 Database contents ........................................................................................................................ 15
4.2 Statistics ....................................................................................................................................... 15
4.3 Conclusions on the statistic analysis ........................................................................................... 24

5.

NATIONAL APPLICATIONS OF THE DATABASE........................................................................... 25
5.1
5.2
5.3
5.4
5.5
5.6
5.7

6.

Fires and explosions (Germany) .................................................................................................. 25
Filter fires (Germany) .................................................................................................................. 25
Comparison of the OECD FIRE database with national databases (France, U.S.A.).................. 25
Pre-incident planning (Sweden) .................................................................................................. 26
Use of "Type Fire” in pre-incident planning (Sweden) ............................................................... 26
Fire event tree (Sweden) .............................................................................................................. 26
Ignition mechanism analysis (Japan) ........................................................................................... 26

FUTURE DATABASE APPLICATIONS (DETERMINISTIC AND PROBABILISTICAPPLICATIONS) .................................................................................................................................. 27
6.1 Support to fire frequency estimation ........................................................................................... 27
6.2 Support to fire scenario quantification ........................................................................................ 27
6.3 Fire suppression human performance analysis ............................................................................ 28
6.4 Support to screening of fire scenarios ......................................................................................... 28
6.5 Information on causes of fires and related phenomena ............................................................... 28
6.6 Conspicuous data ......................................................................................................................... 28
6.7 Analysis of homogenous groups .................................................................................................. 29
6.8 Support to analytical approaches from the database (fire development, HRR) ........................... 30
6.9 Application of the database for fire brigade response time estimation ........................................ 30
6.10 How do fires spread to other compartments ................................................................................ 30
6.11 Analysis of high energy electric (arcing) faults (HEAF) ............................................................. 31

7.

PERSPECTIVES ................................................................................................................................... 32

8.

CONCLUSIONS / RECOMMENDATIONS ........................................................................................ 33

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NEA/CSNI/R(2009)6

8.1 Feedback to CSNI (WGRISK) ..................................................................................................... 33
8.2 Feedback to CNRA (WGIP, WGOE)............................................................................................ 33
8.3 Need for improving the database structure in the next term ......................................................... 34
8.4 Interest in extending the database to other OECD member countries for the next term .............. 34
REFERENCES .............................................................................................................................................. 35
APPENDIX A - OECD FIRE CODING GUIDELINES ............................................................................... 37
1. Introduction .................................................................................................................................. 40
2. Fire event analysis support data.................................................................................................... 40
3. Description of an OECD FIRE event ........................................................................................... 41
APPENDIX B - STRUCTURE OF THE NARRATIVE PART AND THE CODED FIELDS IN THE
OECD FIRE DATABASE ................................................................................................. 79
APPENDIX C - NATIONAL APPLICATIONS OF THE DATABASE ........................................................ 80
C-1 Fire And Explosion ...................................................................................................................... 80
C-2 Filter Fires ................................................................................................................................... 84
C-3 Fire Event Tree ............................................................................................................................ 86
C-4 Swedish Test Application for Deterministic Database Use ......................................................... 87
C-5 Comparison of The Oecd Fire Database with National Databases (Validity Check) .................. 88
C-6 Swedish Use of "Type Fire" ...................................................................................................... 102
C-7 Examples of Important Fires and their Consequences Including Eventswith Potentially Severe Consequences ..................................................................................... 103
C-8 Jnes Application to Ignition Mechanism Analysis..................................................................... 105
APPENDIX D - DETAILS OF FUTURE APPLICATIONS OF THE OECD FIRE DATABASE ............. 111
D-1 Initiator Frequencies .................................................................................................................. 111
D-2 Example for Initiator Frequencies, Based on Data in the Oecd Fire Databaseand on Preliminary Assumptions .............................................................................................. 113
D-3 Branch Point Probabilities for Fire Event Trees ........................................................................ 117
D-4 Identification of Scenarios Typical of Fires Leading to Severe Consequences ......................... 125
D-5 How Do Fire Effects Spread to Other Compartments ............................................................... 125
D-6 Outlook on Further Statistical and Operation Experience Use.................................................. 127
APPENDIX E – OECD FIRE DATABASE MEMBERS ............................................................................ 128

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NEA/CSNI/R(2009)6

EXECUTIVE SUMMARY

Background
Fire Hazard Analyses (FHA) and Probabilistic Fire Safety Analyses (Fire PSA) have shown thatfire may be an important contributor to core damage and plant damage states. Yet, realistic modellingof fire scenarios is difficult due to the scarcity of reliable data for fire analysis. In an attempt toimprove the situation, the CSNI issued a State-of-the-Art Report on level-1 PSA methodology[CSNI/R(92)18] and a study on fire risk assessment was started by the CSNI/WGRISK (formerly
PWG5). In 1996, a Task Group was established to review the status and maturity of methods used infire risk assessment for operating nuclear power plants. This group concluded in 2000 that “Theshortage of fire analysis data is one of the major deficiencies in the present fire risk assessment.”
Based on these conclusions, several OECD member countries have agreed to establish theInternational Fire Data Exchange Project (OECD FIRE) under the umbrella of the CSNI to encourage
multilateral co-operation in the collection and analysis of data related to fire events in nuclear power
plants. The Project was formally launched in January 2003 for a three-year period with nine countries,
which was followed by a four years term with the addition of three further countries. It is anticipatedthat a new term for the project will start in 2010.
Objective of the work
The objectives of the OECD FIRE Project include the establishment of a framework for multinational co-operation in sharing event information useful to fire risk assessment. The primary activity
was to define the format for collecting fire event experience in a quality assured and consistent
database. In the course of the Project improvement of fire record event attributes was made to facilitate
quantification of fire frequencies and fire risk analysis. The permanent activity is to collect andanalyse fire events over the long term so as to better understand such events, their causes, and theirprevention. The Database thus obtained allows generating qualitative insights into the root causes offire events which can then be used to derive approaches or mechanisms for their prevention or for
mitigating their consequences. Amongst the applications of the Database is the possibility for member
countries to establish a mechanism for the efficient feedback of experience gained in connection withfire events, including the development of defenses against their occurrence, such as improvements ofthe existing national as well as international reporting systems and indicators for risk based
inspections.
Description of the work
Applicable to commercial nuclear power plants only, the OECD FIRE Project exchanges fire
events data covering all plant operational modes including construction and decommissioning phases.
Currently, the Database contains 344 fire events, most of them quality assured. The events are fromthe period from the early 1980ies to 2008, with the bulk of the events in the period of the mid 1990ies
to end of 2007. Although the reporting of events is not exhaustive, the Database provides a good
platform for starting the analytical phase7

NEA/CSNI/R(2009)6

Results and their significanceImportant observations from the statistical evaluation can be summarised as follows: Fires aremost likely to occur in process rooms, the origin of approximately one third of the events in the
Database was the turbine building. The latter is in accordance with observations from international
event databases such as IRS and INES.
With regard to fire detection and suppression, the availability of an adequate amount of suitablefire detectors and appropriate manual fire fighting capabilities is essential. A large majority of the fires
could be confirmed within a very short time period (minutes). Only a minority of fires was suppressedby automatically actuated fixed extinguishing systems; in more than 75 % of the events, manual firefighting means were involved in the successful fire suppression. The share of self-extinguished fires
and of fires terminated by fire source isolation is also significant. Finally it could be concluded thatevents associated with long suppression times are more likely to cause severe fire effects than thosewith short suppression times, and they are correlated with the need for several attacks by different
means of fire suppression.
Conclusions and recommendations
Although the data are inhomogeneous due to the differing reporting thresholds and criteria in the
Project member states, the OECD FIRE Database provides qualitative insights into the root causes ofincipient fires and the time dependent fire development. First national applications of the Database
have shown the importance of detailed fire event descriptions providing broader insights beyond theinformation in the coded fields.
Although first applications with respect to Fire PSA are possible on a more general level, it will
be important to collect as many events as possible in the future to enlarge the database by a continuousand consistent reporting of events by the Project members and to encourage additional OECD Member
States to support the OECD FIRE Database Project for achieving better corroborated data for PSA use.
The human factor in the fire event sequence has to be investigated in more detail. Indications of thepositive effects of human intervention on fire extinguishing can already be found in the existing
Database.
The database is becoming large enough to use it how to estimate room based fire initiatorfrequencies from information contained in the OECD FIRE database. Appendix D contains a detailed
proposal how to estimate room based fire initiator frequencies from information contained in theOECD FIRE database.
One of the main questions which could be answered by the Database is how fires can propagate
from the initial fire compartment to other compartments, even if there are protective means available
for prevention of fire spreading.
The coding of events has to reflect as far as feasible the needs of the analysts. Therefore theCoding Guidelines are continuously improved and enhanced to meet these requirements.
Improvements in the Database structure and a more consistent and exhaustive reporting to the
Database will give the possibility to provide a high lev4el of information.
Data collection is continuing. Data flow of approx. 30 events per year is expected, as can beextrapolated from operating experience (about two thirds during power operation and one third during
non-full power operating conditions).
Project members express the hope that this report will encourage additional participation oforganisations from other OECD Member States to support the OECD FIRE Database Project.

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NEA/CSNI/R(2009)6

1. PROJECT BACKGROUNDThe OECD FIRE Database is one of the five nuclear power plants (NPP) operational events
databases currently developed under the umbrella of the OECD/NEA. The need for such database has
emerged in the late 1990s when it became evident that the International Recording System (IRS) could
not allow for specific analysis and use in risk assessment. In this respect only dedicated databases
allow for “topic focused” lessons learned as well as for quantitative analysis and eventually
determination of initiator frequencies.
Fire Hazard Analyses (FHA) and Probabilistic Fire Safety Analyses (Fire PSA) have shown thatfire may be an important contributor to core damage and plant damage states, particularly for older
NPP. Yet, realistic modelling of fire scenarios is difficult due to the scarcity of reliable data for fire
analysis.
In an attempt to improve the situation, the CSNI issued a State-of-the-Art Report on level-1 PSA
methodology [CSNI/R(92)18] and a study on fire risk assessment was started by the CSNI/WGRISK(formerly PWG5). In 1996, a Task Group was established to review the status and maturity of methods
used in fire risk assessment for operating nuclear power plants. The Task Group issued a questionnairein May 1997 to all nuclear power generating OECD countries. The Summary Report [1] of thisactivity was published in March 2000. One of its concluding remarks was as follows:“The shortage of fire analysis data is one of the major deficiencies in the present fire risk
assessment. In order to facilitate the situation, it would be highly important to establish aninternational fire analysis data bank, similar to that set up by OECD for the CCF data collection andprocessing system (ICDE/CCF data bank at OECD). Such a data bank would provide fire event dataon real fire cases, incipient fires (e.g. smoldering) detected/extinguished before development,
dangerous or threatening situations, reliability data on fire protection measures, and theunavailability of fire fighting systems, for example, due to component failures or operational errors.”
Based on the above concluding remarks, several OECD member countries have agreed toestablish the International Fire Data Exchange Project (OECD FIRE) to encourage multilateral cooperation in the collection and analysis of data related to fire events in nuclear power plants. During its
2000 annual meeting, CSNI formally approved the carrying out of this Project. The Project wasformally launched in January 2003, initially joined by 9 countries. At the end of the first term
(December 2005), a second term was agreed on, ending after December 2009. Currently, twelve
OECD member countries have signed the OECD FIRE agreement (Canada, Czech Republic, Finland,
France, Germany, Japan, Korea, The Netherlands, Spain, Sweden, Switzerland and United States).
The operation of the project is described in detail in the Operating Procedures [2]. In particular,
the responsibilities of the participants, the funding and the distribution of the Database are addressed.
The Project is managed by a Project Review Group composed of National Coordinators (NC) of theparticipating countries, who have full responsibilities to take decisions for the Project. Funding isprovided by each country and the Operating Agent (OA) ensures the quality assurance (QA) and theoperation of the Database.

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NEA/CSNI/R(2009)6

Applicable to commercial nuclear power plants only, the OECD FIRE Project exchanges fire
events data covering all plant operational modes including construction and decommissioning phases.
Currently, the Database contains 344 fire events, the majority of these being quality assured, forthe others quality assurance (QA) pending. The events are from the period from the early 1980ies to2008, with the bulk of the events in the period of the mid 1990ies to end of 2007. Although thereporting of events is not exhaustive, the Database provides a good platform for starting the analyticalphase.
Data collection is continuing. Data flow approx. 30 events per year is expected, as can beextrapolated from operating experience (about two thirds during power operation and one third during
non-full power operating conditions).

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NEA/CSNI/R(2009)6

2. PURPOSE AND SCOPE OF THE PROJECT

Improving the safety of nuclear power plants by better accounting for feedback from operating
experience and by providing common resources for analytical work in the frame of deterministic andprobabilistic assessments is the main objective of the OECD FIRE Project. To fulfill this objective, theProject includes the establishment of a framework for a multi-national co-operation in fire datacollection and analysis. The objectives of the OECD FIRE project are:•to collect fire event experience by international exchange in an appropriate format in aquality assured and consistent database (the “OECD FIRE Database”);•

to collect and analyse fire events over the long-term so as to better understand such eventsand their causes, and to encourage their prevention;•

to generate qualitative insights into the root causes of fire events in order to examine:- approaches or mechanisms for their prevention and mitigation of theirconsequences- fire causes- new dependencies as a result of fires having occurred•to establish statistics based on the Database contents for e.g. identifying repeating causes,
fire mechanisms, etc.;•

to support member countries to establish more effective national fire event reporting
practices;•to establish a mechanism for the efficient operational feedback on fire event experience
including the development of policies of prevention, such as indicators for risk informed andperformance based inspections; and•to record characteristics of fire events in order to facilitate fire risk analysis, including
quantification of fire frequencies.

The Database is envisioned to be used to•support model development, validation, etc.;•

identify all types of events and scenarios for inclusion in PSA models ensure that allmechanisms are accounted for;•support fire PSAs by real data;•compare fire event data from member states with the accumulated international datacollected within the OECD FIRE Database.

With emphasis on data validity and data quality, OECD FIRE Coding Guidelines [3] have beendeveloped (see also Appendix A) for collecting and classifying fire event data to ensure consistent11

NEA/CSNI/R(2009)6

interpretations and applications. The Operating Procedures [2] and the Quality Assurance Manual [4]complete the Project documentation. This task of document elaboration has been an important part of
the first phase of the Project (2003 - 2005).
Fire data have been continuously delivered to the OECD FIRE Project since January 2003. The
first data collection concerned the observation period from 1 January 2001 to 31 December 2002. The
first data collection had several objectives:•to confirm and, if necessary, improve the design and attributes of the OECD FIRE Database;•to confirm and, if necessary, improve the Coding Guidelines against data;•

to test routines for further data collection.

Since 2004, and based on the feedback from the first years stable routines for reporting and quality
assurance [4] are in place.
One challenge in setting up an international database is to ensure a consistent reporting level
between countries in order to capture all events fulfilling the objectives of the project. Regulatory andutilities' reporting levels are different between member countries (e.g., did the fire or did it not affectsafety equipment, different duration thresholds, etc.), and, in addition, the reporting criteria may havechanged with time. For events from the past, the Database includes for reference the evolution withtime of reporting levels. For future events, one objective of the first three years phase was to define a
project reporting level, which will account for the countries' policies while correctly addressing thetechnical objectives of the project.
Fire events considered in the OECD FIRE Database are defined as follows [3]:•Any process of combustion characterised by the emission of heat accompanied by (open)
flame or smoke or both, or•Rapid combustion spreading in an uncontrolled manner in time and space.

Note:
This includes incipient fires as well as fully developed fires. Fires shall be included in the
Database if they are relevant to safety and also if the same type of fire has the potential to be
relevant/significant for safety under different boundary conditions (such as different ventilation
conditions, other plant operating states (POS), same components affected in other locations, etc.).
Explosions not resulting in an open flame shall be excluded.

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3. STRUCTURE OF THE DATABASE

3.1 Reported events
The reporting of fires is limited to nuclear power plants. Fires at research reactors, nuclear waste
storage facilities, etc. are excluded. The reporting includes all plant internal fires on-site (inside andoutside buildings) as well as plant external fires if these have the potential to impact nuclear safety.
The reporting shall include fires in all operation modes, also fires during construction anddecommissioning.
3.2 Description of OECD FIRE eventsThe OECD FIRE event is described by the narrative event description and a number of coded
descriptive fields with attributes selectable from predefined menus. The source of information
normally is the narrative event description; the entries in the coded fields are derived from thenarrative event description. The classification of the fire event through coded attributes provides thepossibility to search for and identify specific fire events of interest in the OECD FIRE Database for awide range of applications. Details are provided in Appendix B.
3.3 Relevance indices
Relevance indices are implemented to characterise the quality of fire event reports collected in
the OECD FIRE Project. The rationale to introduce relevance indices is twofold:•

The Operating Agent wants to have a mechanism that allows filtering out issues in thereports for which more information must be sought.

•

The user desires to have knowledge of the completeness of the information in the Databaseand of the degree of confidence he can put in the information in the Database if he wants toanalyse data for various purposes.

The relevance indices essentially are “completeness indices”, i.e. they measure how complete anddetailed the reported information is and by what kind of references it is supported.
3.4 Fire event analysis support data
Fire event analysis requires supporting data that are stored in two database support modules.
These are:•

The Reporting Threshold Module defines thresholds for reporting fire events to authorities
by the utilities. If collected fire data are to be used for statistical purposes it is essential toknow the reporting routines applied in the various countries. Essentially, there are twodifferent reporting threshold levels:

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NEA/CSNI/R(2009)6•-

LER level fires:
The Licensee Event Report (LER) level is normally defined in the technicalspecifications. Several different definitions exist, depending on member country anddate of the fire event. In some member countries a fire event will be reported as a LER
if it had affected a safety component. Other LER definitions are based on the durationof the fire.

-

All fires:
Some OECD FIRE member countries have access to all fire reports. This fact also has
to be documented in the reporting threshold module.

The Fire Brigade Organisation Module contains the general description of on-site and offsite fire brigade organisation. Distance between plant and off-site fire brigade stations aswell as off-site fire brigade response time are provided. Changes over time in theorganisation can be addressed in the Database.

3.5 Further improvements to the database
Experience with the OECD FIRE Database in its current form suggests improvements that would
enable more detailed analyses of fire events. This would entail revisions of the Coding Guidelines andcorresponding changes of the Database coding and structure, as well as substantial re-coding work.
Such improvements are envisaged to be implemented in the next phase of the project. They aredescribed in Section 8 Conclusions.

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4. CONTENTS AND BASIC STATISTICS

4.1 Database contents
Fire data have been continuously delivered to the OECD FIRE Project. Today, data collection is acontinuing process and stable routines for reporting and quality assurance are in place.
Currently, the Database contains 344 fire events, the majority of these being quality assured, forthe remaining ones QA pending. The events are from the period early 1980ies to 2008, with the bulkof the events in the period from the mid 1990ies to 2007. Although the reporting of events is not
exhaustive, the OECD FIRE Database provides already a good platform for starting with analysis
work.
One challenge in setting up an international database is to ensure a consistent reporting level
between countries in order to capture all events fulfilling the objectives of the project. Regulatory andutilities' reporting levels are different between member countries. The respective information iscollected in the Reporting Threshold Module of the Database (see section 3.4).
4.2 Statistics
This Section presents statistics on selected important features of all the data collected up to theend of 2008 in the OECD FIRE Database. The statistics are mostly not exhaustive, i.e. the presented
numbers do not add up to 100 % because only the more important features are included in thepresentation of statistical results, or because relevant information is missing for some events, or
because the thresholds for reporting events to the Database vary between member countries.
Figure 1 shows the statistics of time from first alarm to confirmation of the fire, i.e. verificationof the occurrence of a fire and identification of its location. As can be seen 70 % of the fires wereconfirmed within two minutes after the alarm, most of them within one minute. On the other hand
15 % of the fires needed more than five minutes to be confirmed. For 10 out of 344 events the time toconfirmation is unknown. There is no conspicuous correlation between time to confirmation and theseverity of consequences of fires.

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NEA/CSNI/R(2009)6

250
225

no. of events

200

150

100

48

40

50
12
0
T < 1 minFigure 1:

1 min < T < 2 min 2 min < T < 5 min

5min < TTime T to fire confirmation of for all reported events

Figure 2 shows the time from the first alarm to the suppression of the fires for all events withknown suppression time. There is a steady decrease of the times to suppression. Only 11 % of the fires
needed suppression times in excess of one hour. Some of these were transformer fires that needed longextinguishing times because of the large amounts of hot metal. The number of reports with unknown
suppression time is large.
no. of events

80
70
60

70
58

50

40

40

38

30

20

20

10

10

7

0
1 min < T < 5 min 5 min < T < 15 min 15 min < T < 30 min 30 min < T < 1 hFigure 2:

1 h <T < 2 h

2h <T <3 hTime to fire suppression for all reported events16

3 h <TNEA/CSNI/R(2009)6

Figure 3 shows that a completely different distribution of suppression times is observed for the
11 events with known suppression times that led to severe structural impact as defined in this report(“Structural influence or collapse”, “Adjacent rooms affected”, “Total loss of one room”, “More than
one fire compartment affected”). For all events (see Figure 2) the suppression times decrease steadily
from the peak at the lowest suppression time, but for events leading to severe structural impact thepeak of suppression times is at the time interval of 30 min < T < 60 min, and the bulk of the
distribution is at suppression times 30 min < T 45 % of the events leading to severe structural impact
needed suppression times of more than one hour, in contrast to Figure 2, all events, where thecontribution of this range of suppression time periods is only 11 %. This supports the forgone
conclusion that fires leading to severe structural impact are more difficult to suppress. This is further
corroborated by the observation that 40 % of the events leading to severe structural impact needed
several attacks to be completely suppressed, whereas only 11 % of “all events” needed several attacks.
For fires leading to severe structural impact a strong correlation between the need for several attacks
and the time required to suppress the fire seems to exist.
There are five events leading to severe impact on safety trains as defined in this report (codings “Allsafety trains of one system affected”, “More than 1 safety train (but not all) affected”). One of these
events affected more than one fire compartment and is therefore included in Figure3. Its suppression
time was in the 120 min < T < 180 min range. The distribution of suppression times (See Figure 4) issimilar to that in Figure 2. Furthermore, none of the events required several attacks. Thus, regarding
suppression times and number of attacks needed, there is nothing conspicuous about events affecting
safety trains, unless they are accompanied by severe structural impact.

no. of events

5
4

4

3
2

2

1

1

2

1

1

0
1 min < T < 5 min 5 min < T < 30 min 30 min < T < 1 hFigure 3:

1h < T< 2 h

2h < T< 3 hTime to suppression of fires with severe structural impact

17

3h < T< 4 h

NEA/CSNI/R(2009)6

no. of events

5
4
3

3
2

1

1
0

0

1 min < T < 5 min

5 min < T < 30 min

Figure 4:

30 min < T < 1 h

0

0

0

1 h<T < 2 h

2 h <T < 3 h

3h <T < 4 hTime to suppression of fires with severe impact on safety trains

The contribution to fires from buildings is dominated by the turbine building (See Figure 5). For
all events, this contribution is 27 %, for events with severe fire effects it is 40 %. Fires in the turbine
building are more likely to lead to severe fire effects than those originating in other buildings.

95

100

no. of fires

80
60

47

39

40

37

20

9

0
turbine buiding
100
80

Auxiliary building

reactor building

electrical building

13.7

11.3

10.8

reactor building

electrical building

switchyard

contribution (%)

60
40

27.6

20

2.6

0
turbine buiding
Figure 5:

Auxiliary building

Contribution of buildings where fires mainly occurred

18

switchyard

NEA/CSNI/R(2009)6

Regarding the types of rooms where fires have occurred, the highest contribution is found inprocess rooms (35 %, see Figure 6), approx. 60 % of these being located in the turbine building. For
events with severe fire effects the contribution of fires in process rooms is 40 %. This indicates thatfires in process rooms are more likely to result in severe effects than fires originating in other types ofrooms.
The ignition mechanisms are dominated by “electrical” with approx. 47 % (see Figure 7).
However, the ignition sources “hot component” and “hot work” also represent significant contributors.
With regard to fire extinguishing, the dominant method for fighting fire is “manual fire fighting
alone” with a contribution of nearly 50 % (see Figure 10) Fixed automatically actuated fire
extinguishing systems were demanded in case of 8 % of the events, for 2 % of the events the fires
were extinguished solely by automatically actuated systems. In the remaining cases combinations ofseveral methods, which all included manual fire fighting, were applied. The category “selfextinguished, fire source isolation, controlled burn out” also contains manual actions. Thus, for mostof the fire events collected in the Database the fire suppression involved manual actions.

140
120

no. of fires

119

100
80
60
40

30

22

20

7

3

cable rooms

main control rooms

2

0.9

cable rooms

main control rooms

0
process rooms
100
90
80
70
60
50
40
30
20
10
0

rooms for electrical switchgear rooms
control equipment

contribution (%)

34.6

8.7
process rooms

Figure 6:

6.4

rooms for electrical switchgear rooms
control equipment

Contribution of room types where fires mainly occurred

19

NEA/CSNI/R(2009)6200

no. of fires

160
150
100

58

54

50

25

19

mechanicalself-ignition

7.3

5.5

mechanicalself-ignition

0electrical
100
80
60

hot component

hot work

16.9

15.7

hot component

hot work

contribution (%)
46.5

40
20
0
electricalFigure 7:

Contributions of the different ignition mechanisms

contribution of events (%)

The ignition mechanisms are dominated by “electrical” with approx. 46% (see Figure 7).
However the ignition sources “hot component” and “hot work” also represent significant contributors.
For the consequence category “Two or more safety trains lost” the contributions from the ignition
mechanisms are significantly different (See Figure 8).

100
90
80
70
60
50
40
30
20
10
0

80

46
20

17

5 events with more than 1 safety train lostall 344 events in the DB

Ignition source :electrical hot component
Figure 8:Comparison of percentage of significant contributions from ignition sources for eventsfrom consequence category "Two or more safety trains lost" and all events.

20

NEA/CSNI/R(2009)6

Similar differences are observed for the contributions from root causes (See Figure 9).
100contribution of events (%)

90

80

80
70

56

60
50
40
30

26

20

20
10
0

5 events with more than 1 safety train lostall 344 events in the DB
root cause:electricalFigure 9:

hot component

Percentage of important contributions from root causes for events from consequence
category "Two or more safety trains lost" versus all events.

Comparison of the events from the consequence category “Two or more safety trains lost" to thecomplete OECD FIRE Database leads to the following findings:•

Ignition sources and root causes
For the consequence category “Two or more safety trains lost”, the contributions from theignition source “electrical” and from the root cause “equipment” ( approx. 80 %) by far
exceed the average values (46 % and 56 %) for all events. In many cases where electricaldevices are the source of ignition, these devices are no longer functionally available from the
beginning of the fire event. Hereby at least one safety train may be lost. Additional trains
may be lost due to fire spread, or due to inadequate response to the initial fire event.

•Fire fighting performance
The fire fighting performance was coded “normal” in all cases. However, 40 % of the
14 events from the consequence categories “more than one fire compartment affected”,“adjacent rooms affected”,” total loss of one room”, or “structural impact or collapse”
needed several attacks to finally extinguish the fire. For all events, only 11 % needed several
attacks to extinguish the fire, see Figure 12. This comparison indicates that fires which are
difficult to fight potentially lead to more severe effects as mentioned above. For the more
severe events more detailed information on the fire fighting process is principally available.

21

NEA/CSNI/R(2009)6

180
160

161

100

no. of fires

contribution (%)
80

140
120

60

100

46.8
72

80
60

40

42

40

19

20
0

12.2

5.5

0
A

Legend:
A:
B:
C:
D:

20.9

20

B

C

D

A

B

manual fire fighting alone
fixed system manually actuated and manual fire fighting
fixed system automatically actuated, or manual fire fighting and fixed system automatically
self-extinguished, or fire source isolation, or controlled burn out

CD

actuated

Figure 10: Types of fire extinguishing
The OECD FIRE Database demonstrates the importance of the on-site fire brigade and otherplant personnel trained in fire fighting (See Figure 11). About two thirds of the fires wereextinguished by plant personnel (including the on-site fire brigade) alone. In 12% of the cases plant
personnel was assisted by an external fire brigade, only 2% of the fire events were extinguished byautomatically actuated systems alone.
250
207

100

no. of fires

contribution (%)

200

80

150

60

100

40

41

50

20

16

11.9

8

4.7

2.3

C

D

0

0
A
Legend:
A:
B:
C:
D:

60.2

B

C

A

D

B

on-site plant fire brigade, shift personnel, people available in the fire area
on-site plant fire brigade or shift personnel with participation of an
external fire brigade
fixed fire extinguishing system; on-site plant fire brigade
automatically actuated fixed extinguishing system alone

Figure 11: Who extinguished the fire22

NEA/CSNI/R(2009)6

contribution of events (%) several attacks needed

50
45

42

40
35
30
25
20
15

11

10
5
0
several attacks needed, structural impact and fire
propagation

several attacks needed (all events)

Figure 12: Percentage of several attacks needed for events from consequence categories” more than
one fire compartment affected”, “adjacent rooms affected”, “total loss of one room”, or“structural damage or collapse” versus all events.

23

NEA/CSNI/R(2009)6

4.3 Conclusions from the statistic analysis
The following conclusions can be drawn from the statistical evaluation of the information
gathered to date in the actual version of the OECD FIRE Database with in total 344 events:•

Confirmation of fires:
Approx. 70 % of the fires were confirmed within two minutes after the alarm, most of themwithin one minute. Only for 14 %, more than five minutes were needed for confirmation. On
the plant wide basis, there is no statistically significant evidence that longer times toconfirmation lead to more severe effects.

•

Times to suppression of fires:
There is a strong positive correlation between long suppression times and the severity ofconsequences of fire events, i.e. events associated with longer suppression times are more
likely to result in severe effects than those with short suppression times. Furthermore, eventswith long suppression times are likely to require several fire fighting attacks, partly withdifferent types/means of extinguishing.

•

Origin of fires:
Regarding the buildings of fire occurrence, fires are most likely to occur in the turbine
building (approx. 30 %). With respect to the types of rooms of fire origin, process rooms (asdefined in Appendix A), particularly in the turbine building, have the highest fire occurrence
rate. Furthermore, fires in the turbine building and in process rooms are more likely to cause
severe consequences (structural damage as well as significant impact on safety trains) thanfires anywhere else.
Note: Severe consequences on safety trains in turbine buildings can only occur in thoseplants where safety significant trains are located there.

••

Types of fire extinguishing:
The majority of events involved manual fire fighting actions. 11 % of the fires required
several and partly different fire fighting attacks for successful suppression. Self-extinguishedfires, fires terminated by isolation of the fire source or by controlled burn out also represent
significant contributions. Fixed automatically actuated fire extinguishing systems were
demanded in 8 % of the events, 2 % of the fire events were extinguished by automaticallyactuated extinguishing systems alone.

•

Who extinguished the fire:
About two thirds of the fires were extinguished by the on-site plant fire brigade, shift
personnel, and other people available in the fire area, most of these by manual fire fighting
alone, and fewer by a combination of manual fire fighting and fixed systems. Another 12 %of the fires were extinguished by the on-site plant fire brigade and shift personnel withparticipation of an external brigade. Only 2 % of the fires (mainly transformer fires) were
suppressed solely by stationary fire extinguishing systems automatically actuated by the fire
detection systems.

Fire fighting performance:
The fire fighting performance was “normal”, meaning successful, in all cases. Only 11 % of all
events in the Database needed several attacks for fire suppression, However, 40 % of the eventsin the consequence categories “more than one fire compartment affected”, “adjacent rooms
affected”,” total loss of one room”, or “structural damage or collapse” needed several attacks.
This indicates that there is a correlation between the number of attacks and duration of
suppression and the severity of the consequences.

24

NEA/CSNI/R(2009)6•

5. NATIONAL APPLICATIONS OF THE DATABASE

Information from the OECD FIRE Database has been used by participating countries in the studyof the following issues and more detailed descriptions are provided in Appendix C.
5.1 Fires and explosions (Germany)
A query in the OECD FIRE Database on the potential combinations of fire and explosion events
has indicated a significant number of explosion induced fires. Most of such event combinations
occurred at transformers on-site, but outside of the NPP buildings or in compartments with electricalequipment. Approximately 50 % of the fires were extinguished in the early fire phase before flashover.
As a consequence of these indications, improvements concerning the fire protection of transformers
are intended in Germany.
5.2 Filter fires (Germany)
Since reportable filter fire have occurred in German NPP, there is an interest of the regulators tofind out more details on the potential ignition sources, fire duration and possibilities. The OECD FIRE
Database surprisingly contains only a quite low number of filter fires. Most of these occurred in theauxiliary building. Unfortunately, only in few cases information on the type of the combustibles filter
materials is available, indicating the necessity for improving the Database for statistical use.
5.3 Comparison of the OECD FIRE database with national databases (France, U.S.A.)
Section C-5 of Annex C provides the methodology implemented by IRSN for the estimation of
the fire frequency using the French operating experience feedback, revealing a good consistency
between the French and the OECD FIRE Databases. The same methodology has been applied using
the OECD FIRE Database. This exercise has shown that the statistical use of the Database is easy andwell adapted to define the reference numbers needed for the fire frequency estimation. Notably, theOECD FIRE Database is very useful for those countries whose operating experience feedback isinsufficient for a statistical use of national fire events. In addition, even if the national operating
experience is sufficient, for equipment for which no fire event occurred, the use of OECD FIRE data
may be very helpful.
Currently, NRC is using two fire events databases based on U.S. NPP experience. The first
database is essentially the EPRI fire events database [5] which has had a few additional features added
due to the NUREG/CR-6850 project, and the second database containing LER and some smaller fire
event data that is used in the OECD FIRE Project. In the near future, the NRC will be integrating thebest features of each database. Upon completion of that work, the NRC plans to examine theinternational OECD FIRE Database for insights which will improve the overall NRC database. The
NRC currently views the OECD FIRE Database program as a very effective program to better
understand international NPP fire events.

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NEA/CSNI/R(2009)6

5.4 Pre-incident planning (Sweden)
After a switchgear room fire in 2005 the need of making the existing pre-incident planning more
effective became apparent. A support to plan the missions is the information on different types of fires.
“Type fire” is a short description of how a certain type of fire may develop, what its risks possibly are,and what choices of extinguishing agents and methods have to be used for different fires and plant
locations, how to do pre-planning, to update instructions for the fire brigades on how to extinguish afire and to perform drills and exercises on those types of fire dominating the risk (see [6] and also thenext application on “Type Fire”).
5.5 Use of "Type Fire” in pre-incident planning (Sweden)
The idea with respect to the emergency planning is to plan the efforts and working steps in orderto give the operational and emergency staff good and up-to-date support to make decisions and to start
the mission without delay (cf. [7]). The planning is to a large extent created on the basis of theidentified and most common types of fires and their relevance checked against “real fire events” stored
in the OECD FIRE Database.
5.6 Fire event tree (Sweden)
One idea of a recently ongoing activity [8] in Sweden is to develop fire event trees. By studying
the OECD FIRE Database with all the events included fire event trees may be derived based on the
documented fire types, causes, and consequences. One goal of this project is to possibly identify somecommon features for those fire scenarios that result in the most severe consequences in the event trees.
The activity is explained in detail in Appendix C-3.
5.7 Ignition mechanism analysis (Japan):
Ignition mechanisms have been analysed (cf. [9]) in order to understand the ignition mechanism
and to identify potential fire sources for Fire PSA. The OECD FIRE Database and the fire database[10] being developed in Japan have been analysed and the fire events have been categorised into sevenclasses with the result that the contribution of electric components from the perspective of ignition issignificant. The activity is explained in detail in Appendix C-9.

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NEA/CSNI/R(2009)6

6. FUTURE DATABASE APPLICATIONS (DETERMINISTICAND PROBABILISTIC APPLICATIONS)

Currently, 344 fire event records from 12 countries are collected in the OECD FIRE Database.
This constitutes a rich source of qualitative and quantitative information that can be used to support
deterministic and probabilistic fire analyses. Below is a short description of fire analysis issues thatcan benefit from the data collected in the OECD FIRE Database. For some issues a more detailed
explanation is provided in Appendix D.
6.1 Support to fire frequency estimation
Several different approaches are used to estimate fire frequencies in fire PSAs, such as room
based frequency estimation, component based frequency estimation and frequency estimation by useof influence factors. The information collected in the OECD FIRE Database represents the reality offire events observed. This provides the basis for estimating “real” initiator frequencies that can be used
to corroborate or eventually update the frequencies currently used in Fire PSA (after member
countries´ own quality assurance and verification process).
Appendix D-2 presents a detailed example of estimates of fire frequencies for process rooms,
switchgear rooms and cable rooms/ducts, which typically are considered important in fire PSAs. The
estimation performed shows an overall fire frequency of about 1.0 E-01/ry and, with the assumed
number of rooms of a given type, fire initiator frequencies per room and reactor year in the range of E04. (The numbers of rooms still have to be validated). This is significantly lower than the E-03 range
used in some Fire PSAs as initiator frequencies for process rooms, switchgear rooms and cablerooms/ducts.
Fires in process rooms, switchgear rooms and cable rooms/ducts typically dominate the fire induced
core damage contribution in most fire PSAs. As the calculated core damage frequencies are directly
proportional to the fire initiator frequencies, the presented example suggests (with all mentioned
reservations) that the results of some fire PSAs are too conservative. Differences between the member
countries can be found in Appendix D with some detailed information provided in Table 2 of thisAppendix.
6.2 Support to fire scenario quantification
Fire event history contained in the OECD FIRE Database can be used to examine thecompleteness of Fire PSA event trees. It is also possible to generate statistical support to thequantification of branch point probabilities in fire event trees. Section D-3 in Appendix D presents an
example of a fire event tree whose structure and branch point probabilities are based on informationfrom the OECD FIRE Database. A comparison with the event trees used in the frame of Fire PSA
studies, including the conclusions to be drawn, is still pending.

27

NEA/CSNI/R(2009)6

6.3 Fire suppression human performance analysis
Fast manual suppression is essential in many scenarios. To better understand human performance,
influence factors should be identified and evaluated. Possible influence factors are the distance of thefire to fire fighting personnel, alarm routines, possibilities to reach the fire, etc.
6.4 Support to screening of fire scenarios
The OECD FIRE Database can be used to generate screening thresholds for support andfacilitation of fire PSAs. An example for using the frequency estimates derived from the Database forscreening purposes is provided in Section D-2 of Appendix D.
6.5 Information on causes of fires and related phenomena
The fire data experience stored in the Database can provide answers to several interestingquestions and insights on phenomena, such as:•

Examples of frequent fire initiators and their root causes:
One example of frequent initiators has been older electrical coils. Other types of frequent
initiators can be identified by use of the Database.

•

Examples of electrical equipment failure modes:
In the fire analysis, modelling of “hot shorts” has been frequently discussed. Does the
Database contain any example of “hot shorts”? Is it possible to use the Database to support the“hot short” discussion?

•

Examples of fire protection equipment malfunctions :Fire events including some kind of failure in the extinguishing phase should be highlighted orwhen several attacks were needed.

•

Examples of fire barriers impaired:
Examples of impaired or destroyed fire barriers are rare, nevertheless it is important to study
them. Fire barriers impaired can result in simultaneous failure of redundant equipment. These
effects have up to now only been coarsely analysed.

6.6 Conspicuous data
The data in the OECD FIRE Database will be examined for conspicuous deviations from normal
fluctuations. Results of such activities can potentially be used for feedback to the operating
experience, and, in particular, for improvements of fire prevention, fire fighting and reporting.
Furthermore, astonishing findings may lead to further improvements of the Coding Guidelines and thecoding itself as well as to more careful event interpretation.
In the following, some conspicuous findings in the actual version of the Database are highlighted
to give rough indications what should be done in the future in this context.
For example, the OECD FIRE Database shows that there are few events in the Database with intotal 344 events that lead to more severe fire effects such as “Structural influence or collapse”,“Adjacent rooms affected”, “Total loss of one room”, or “More than one fire compartment affected”.
Up to now, there are one event each from Canada and Czech Republic, two each from Finland,
Germany and Spain, three events from France, and eight events from Sweden. Up to fate, there are no
events with more severe fire effects in Japan, Korea, The Netherlands, Switzerland and the U.S.A.

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NEA/CSNI/R(2009)6

There is no easy explanation why there are no such events reported from the U.S.A., which has a large
number of reactors, while Sweden, which has a relatively small number of reactors, has reported a
relatively high number of such events. Here, clarifications and/or explanations/interpretations areneeded.
Another example for conspicuous data is a voltage transformer fire due to human error during
maintenance outage reported from Finland (see also Appendix C-1). When performing statisticalanalysis of events with fires and explosions, this event came out with two codings for “Whoextinguished the fire successfully?”. The codings were “self-extinguished” and “on-site plant firebrigade”, which could represent an inconsistency in the coding. The clarification is as follows:“The event description is short and not very good to make others understand all details of theevent, but saying "flames died out quickly" refers to a fire on the ground level which was selfextinguished (small amount of oil leaked down from the voltage transformer, which locates about 4
meters above the ground level). The description also says "The extinguished fire was located on one of
the three protective casings containing the voltage transformers below the generator busbars, thus thefire occurred about 4 m above the ground level." Thus, the plant fire brigade extinguished a fire about
4 m above the ground and the burning oil on the ground level was self-extinguished - the voltage
transformer failure caused spreading of fires: the fire inside the transformer casing and spreading to
the ground level below the transformer casing due to oil leakage.”On the other hand, further fire and explosion events with the titles “An electric arc and fire in the
20 kV switchgear cabinet because of erroneous procedure" and “Fire at 6,6 kV switchgear" could not
be found by the Database search on fires and explosions. For the latter, (which involved an electricarc, fire and severe damages the event description seems to lack the key words “electric arc” and“explosion”, thus also the event description needs to be improved in the future.
The above mentioned examples of conspicuous data in the Database show that additional work
has to be spent on this issue in the future.
6.7 Analysis of homogenous groups
In Sweden a project for the analysis of so-called homogenous groups of fire events (seebelow) is intended to be started. The purpose of this project is to gain knowledge on importantfactors that can affect small fires to become large fires. The project will be performed by the
Department of Fire Safety Engineering and Systems Safety of Lund University, Sweden. The
project will be financed by the Swedish Fire Research Board, BRANDFORSK, the joint
agency of the Swedish government, local authorities, insurance companies and industry, andthe national fire safety group, NBSG. NBSG represents research co-operation between the
Swedish nuclear power plants and the nuclear authorities. The project will perform a numberof case studies. The OECD FIRE Database will be used to support one of the case studies.
The project will consist of the following three sub projects:•

In-depth study of a number of major fires of selected types (so-called homogenous
groups), such as fires in department stores, in terrace houses, or at NPPs, etc., turbinehalls fires;•

Identification if the fire scenarios being analysed differ from statistics collected fromother types of fires;•

Verification if a scenario analysed can be identified in other major fires.

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6.8 Support to analytical approaches from the database (fire development, HRR)
A number of events stored in the OECD FIRE Database contain information on the time-line of
the event as well as a full text description of the fire loads involved and potential fire losses. Currently
a master thesis is being performed under supervision of the GRS aiming to analyse the given data
concerning the thermo-physical characteristics of the fire scenarios. The fire scenarios are evaluated interms of:- the fire stages;- the fire growth coefficients;- the maximum heat release rate;- the total heat released, etc.
The description of the fire scenarios by a few common physical parameters will later on allow fora statistical evaluation. Finally, these parameters can be used for defining design fires with respect to agiven occurrence probability.
The master thesis is written under the boundary conditions given by the OECD FIRE Project(confidentiality agreement, etc.). Results are expected in early summer 2009.
6.9 Application of the database for fire brigade response time estimation
Special training cases for the plant fire brigade are arranged at a NPP. During the training, timingof different steps of the fire brigade’s operation during the attack is recorded to identify the timeneeded for the access to the fire compartment, starting from a fire alarm. Training is performed several
times using different shifts of the fire brigade. An event tree is developed to describe the progress ofthe fire attack and identified dependencies. Later on, conditional probabilities are estimated for
different actions included in the event tree.
Plant fire brigade attack route depends on the fire location. Training cases are performed to attack
a fire in a cable tunnel. First, the time needed for the attack to the cable tunnel is compared to thesequences given in the fire database of the same NPP. Due to the low number of events in the national
database, comparison will be performed with the sequences of foreign NPPs, especially considering
Database events where fire occurred in a cable room or a cable tunnel. The sequences of foreign NPPs
can be partially used for comparison purposes in a general level to understand possible differences inplant fire brigade operation and in communication between operators and fire brigade. Anyway,comparison is possible on a general level, e.g. to identify the time from departure from the fire station
to the start of the fire fighting action.
The application does not include estimation of fire extinguishing, thus the aim is to define time toaccess the fire compartment. Extinguishing of fire depends strongly on the exact location of the firecompartment, local conditions inside the compartment and possible need to switch off high voltage of
certain cables before the extinguishing can be started due to personnel safety. Real events in theOECD FIRE Database may point out different operation of fire brigades in different countries.
6.10 How do fires spread to other compartments
The aim of this application is to identify fire barriers (walls, fire doors, fire dampers, etc.), thatwere destroyed or at least impaired by fires (such that flames occurred on both sides of the fire30

NEA/CSNI/R(2009)6

barrier). Smoke spreading across fire barriers is not considered. Details are provided in Section 4 ofAppendix D.
6.11 Analysis of high energy electric (arcing) faults (HEAF)
International operating experience of nuclear installations reveals a non-negligible number ofreportable events with explosions and fast fires resulting from high energy electric faults e.g. induced
by electric arcs in circuit breakers, switchgears, etc. leading to partly significant consequences.
Investigations of these events have indicated failures of fire protection features due to pressure buildup in the electric cabinets and/or pressure waves. The OECD FIRE Database also reflects theseobservations.
This was the reasons that international experts started to work in common to perform in-depth
investigations on events with HEAF including investigations on their causes and failure mechanisms.
These investigations mainly aim on finding out if these events may represent significant contributors
to impairing nuclear safety. At the actual stage of the investigations focusing on evaluating theoperating experience from nuclear power plants first indications on the typical event sequences andtheir potential contribution to core damage have become available.
The OECD FIRE Database can be used to answer questions the experts want to be answered by
the NPP licensees. As soon as the answers are available and have been statistically examined andinterpreted, first coarse estimates on the contribution of HEAF events to the core damage frequency
should be possible. Furthermore, the investigations may reveal additional findings on the event causes,
possible measures either for event prevention or for limiting the consequences such that nuclear safety
is not impaired.
The OECD FIRE members have meanwhile indicated the need for defining a common OECDtask with the goal to develop deterministic correlations for predicting damage and establish a set of
input data and boundary conditions for more detailed CFD modeling which can be agreed upon by theinternational community. The output of such an OECD project may directly support the developmentof improved treatment methods in fire Probabilistic Risk Assessment (PRA) for nuclear power plant
applications.
This task is to start in 2009.

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7. PERSPECTIVESThe OECD FIRE Database has become a quality assured tool for evaluating the operating
experience from member countries with fire events in nuclear power plants during different plant
operational states. It provides qualitative insights into the root causes of incipient as well as fully
developed fires and the time dependent fire sequences and development.
Although the data are inhomogeneous due to the differing reporting thresholds and criteria in the
Project member states, the existing data from the event sequences, particularly focusing on safetysignificant events, can be used e.g. as input information for fire modeling to support the model
improvement. However, it may become necessary to extend the existing fire event trees to cover all
the scenarios which can be derived from the Database.
It is well known by PSA experts that the quality of a Fire PSA strongly depends on the one handon a careful modeling and, on the other hand, on reliable data; the latter one can be achieved in the
future by further expanding the OECD FIRE Database supported by a continuous and consistentreporting of events by the Project members. Improvements in this direction are expected from thecollection of more event data with additional information appropriate for the analysts.
First national applications of the Database have shown the high importance of a clear andmeaningful fire event description which provides broader insights beyond the information in the coded
fields when needed. Although first applications with respect to Fire PSA are possible on a moregeneral level, it will be important to collect as many events as possible in the future to enlarge the database and to encourage additional OECD Member States to support the OECD FIRE Database Project.
The positive and negative role of human factor in the fire ignition on the one hand, and in
detecting and extinguishing on the other hand, has to be investigated in more detail to generate Fire
PSA results with a higher confidence. Positive effects of human behavior for fire extinguishing canalready be identified in the existing Database, however, with still low statistical significance.
However, quantification with regard to PSA would be helpful in the future.
Improvements in the Database structure and a more consistent and exhaustive reporting to the
Database will give the possibility to provide a high level of information. For meaningful analyticalresults it is essential that a quality assured international database will be available for use in theframework of Fire PSA as well as for application to deterministic fire hazard analyses.
One of the main questions which could be answered by the OECD FIRE Database is how fires
can propagate from the initial fire compartment to other compartments even if there are protectivemeans available for prevention of fire spreading. For generating meaningful event and fault trees forvarious safety significant fire scenarios a clear and as far as possible detailed (with respect to timedependencies and safety significance) description of the initial fire event sequence and its
consequences are essential. The coding of events has to reflect as far as feasible the needs of theanalysts. Therefore the Coding Guidelines are continuously being further improved and enhanced tomeet these requirements.

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8. CONCLUSIONS / RECOMMENDATIONS

8.1 Feedback to CSNI (WGRISK)
The recent activities with respect to fire risk analysis and, in particular, PSA performed in OECDmember countries in the frame of safety reviews, have verified the non-negligible contribution of fires
to the core damage frequencies as indicated in the WGRISK SOAR (state-of-the-art report) on “FireRisk Analysis, Fire Simulation, Fire Spreading and Impact of Smoke and Heat on Instrumentation
Electronics”[1]. To meet the expectations of the WGRISK, the OECD FIRE Database is intended toserve as a basic instrument for enhancing the existing Fire PSA results and for making them morerobust.
In its succession plan WGRISK therefore requests as far as practicable meaningful output fromthe Database project to support risk analysis. Although the existing Database covers fire events from
nuclear power plants in 12 member states generally within a period of 15 years, it is currently not
exhaustive and not sufficiently consistent for statistical use. The main reason for this is the different
accessibility of reportable and non-reportable (to authorities) fire events in the Project member states.
In addition, another inconsistency in reporting events to the Database results from differences in thereporting criteria and thresholds between the member countries and their changes over time. Yet, areliable and statistically meaningful database for PSA applications is expected in the future fulfillingthe needs of analysts in OECD member states.
8.2 Feedback to CNRA (WGIP, WGOE)
One of the main conclusions from the OECD/NEA/CSNI/WGRISK 2005 workshop is that fire,depending on the design and operational characteristics can be a significant or even dominant risk
contributor. In addition, the WGRISK SOAR on “Fire Risk Analysis, Fire Simulation, Fire Spreading
and Impact of Smoke and Heat on Instrumentation Electronics” [1] noted the significance of fire.
Moreover, some countries are in the process of introducing significant changes to the inspection
process of fire protection programs specifically related to the use of risk informed inspections in order
to assess the impact of fire on safety significant safety systems and components (SSC).
Based on these considerations and considering that fire operating experience feedback is very
useful to identify potential weaknesses in the fire protection program and areas for improvements
derived from actual fires, OECD/NEA/CNRA decided to create a specific Fire Working Group. The
objective of this Working Group is to examine international and national databases with events
observed from the NPP operating experience and determine, through analysis and trending, potential
safety issues related to fires and to systems and facilities designed to cope with fires (e.g., prevention,
mitigation, suppression, etc.). In addition, insights can be deduced from fire operating experience
feedback to focus the inspection activities on those areas where the fire is considered to be safetysignificant.

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In comparison to the IRS database that is not well adapted to the analysis of fire events (very low
number of fire events and no specific coding for these), the contents of the OECD FIRE Database canprovide more adequate information to the Fire Working Group.
8.3 Need for improving the database structure in the next term
Experience with the OECD FIRE Database in its current form suggests improvements that would
enable more detailed analyses of fire events. This would entail revisions of the Coding Guidelines andcorresponding changes of the Database coding and structure, as well as substantial re-coding work.
Such improvements are envisaged to be implemented in the next phase of the Project.
Plans of revising the Coding Guidelines for the next phase following a logic of “if … then” havebeen discussed. This new logic would lead to an assessment of the effectiveness of systems, andidentification of the reasons why a system was not effective. It was recommended to apply the logic tothe entire set of codes, where appropriate.
8.4 Interest in extending the database to other OECD member countries for the next term
Although first applications with respect to Fire PSA are possible on a more general level, it will
be important to collect as many events as possible in the future to enlarge the data base and toencourage additional participation of organisations from other OECD Member States to support theOECD FIRE Database Project.

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REFERENCES[1]

Organisation for Economic Co-operation and Development (OECD) OECD/NEA/CSNI:Fire risk analysis, fire simulation, fire spreading and impact of smoke and heat on
instrumentation electronics, OECD/NEA/CSNI/R (99)27, March 2000

[2]

Organisation for Economic Co-operation and Development (OECD) OECD/NEA:
OECD-FIRE Operating Procedures (OECD-FIRE OP 2008:1), January 2008

[3]

Organisation for Economic Co-operation and Development (OECD) OECD/NEA:
OECD-FIRE Coding Guideline (OECD-FIRE CG 2008:2), December 2008

[4]

Organisation for Economic Co-operation and Development (OECD) OECD/NEA:
OECD-FIRE Quality Assurance Program (OECD-FIRE QA 2008:1), January 2008

[5]

Electric Power Research Institute / U.S. Nuclear Regulatory Commission Office of Nuclear
Regulatory Research (EPRI/NRC-RES):
Fire PRA Methodology for Nuclear Power Facilities, Volume 1: Summary & Overview,
Volume 2: Detailed Methodology, Final Report, EPRI 1011989, NUREG/CR-6850, September
2005

[6]

Swedish Nuclear Power Inspectorate (SKI):
Bränder I driftum – Insatssplaner, släckteknik, risker (Fires in operational room – Pre-incident
planning), SKI Report 2006:29, 2006

[7]

Vattenfall, Ringhals:”Vägledning för insatsplanering i kärntekniska anläggningar”, Guidance for pre-incident
planning, rapport 2008-12-11, Darwin 1946399, 2008[8]

Technical Research Institute of Sweden (SP):Utveckling av brand händelseträd (Fire event tree construction), SP Report P802360, “Further
studies in OECD FIRE Database”, 2008[9]

Japan Nuclear Energy Safety Organisation (JNES):
Development of Fire PSA Methodology, JNES/SAE06-090, August 2006[10] Japan Nuclear Technology Institute (JANTI):
Nuclear Information Archives (NUCIA), http://www.nucia.jp/[11] International Atomic Energy Agency (IAEA):
Defence in Depth in Nuclear Safety, A report by the International Nuclear Safety Advisory
Group, INSAG-10, 1996[12] International Atomic Energy Agency (IAEA):
Basic Safety Principles for Nuclear Power Plants, 75-INSAG-3 Rev. 1, A report by theInternational Nuclear Safety Advisory Group, INSAG-12, 1999

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NEA/CSNI/R(2009)6

APPENDIX A - OECD FIRE CODING GUIDELINES

Document No.:

Revision:

OECD

FIRE

OECD

FIRE

Prepared for:Date:

2008:2 VERSION 1
Classification:

DecemberLevel 1
Prepared by:
2008
A. Angner (ES Konsult, Operating Agent)

Total number of pages:

Number of Attachments/Appendices:46

3

Reviewed by:Approved by:

M. Roewekamp (PRG Chair)

PRG

Distribution:

OECD-NEA, OECD-FIRE National Coordinators, Project Website (OECD-FIRE Work Area), OECD
FIRE Archive

OECD-FIRE CODING GUIDELINE(OECD-FIRE-CG-2008:2)
December 200837

NEA/CSNI/R(2009)6

OECD-FIRE Coding Guideline Revision Summary
Rev.
01

Date
2002-07-08

Status
Draft

Author
A. Angner

Version1

8 Nov 2005

Approved

E. Mathet

2005:1VERSION 1

Version2

28 Feb 2007

Approved

J. Gauvain

2007:1VERSION 1

Version3

18 Dec 2007

Approved

M. Roewekamp

2008:1VERSION 1

Version4

18 Jan 2008

Approved

M. Roewekamp

2008:1VERSION 2§ 3.3.1.b – 3.3.2.aVersion5

24 Dec 2008

Approved

A Angner

2008:2
VERSION 1§ 3.3.2a and § 3.4.5
Appendix A-2

38

Saved As

ChangesNEA/CSNI/R(2009)6

CODING GUIDELINES TABLE OF CONTENTS

1.INTRODUCTION ............................................................................................................................ 40
2 FIRE EVENT ANALYSIS SUPPORT DATA ................................................................................ 40
2.1 REPORTING THRESHOLDS .............................................................................................. 40
2.2 FIRE BRIGADE ORGANISATION ..................................................................................... 40
3 DESCRIPTION OF AN OECD FIRE EVENT .............................................................................. 41
3.1 GENERAL DATA ...................................................................................................................... 43
3.2 IGNITION PHASE .................................................................................................................... 47
3.3 EXTINGUISHING PHASE ....................................................................................................... 55
3.4 FUNCTIONAL CONSEQUENCE AND CORRECTIVE ACTIONS ....................................... 59
3.5 REFERENCES ........................................................................................................................... 61
3.6 RELEVANCE INDEX ............................................................................................................... 62
APPENDIX A-1: GLOSSARY OF TECHNICAL TERMS ............................................................. 63
APPENDIX A-2: NATIONAL REPORTING LEVELS ................................................................... 67
APPENDIX A-3: RELEVANCE INDEX DEFINITION.................................................................. 7739

NEA/CSNI/R(2009)6

1.

Introduction

Fire Hazard Analysis (FHA) and Probabilistic Fire Safety Analysis (PSA) have shown that fire
may be an important risk contributor, especially for older nuclear power plants. Uncertainties in firedata have resulted in numerous research projects. However, the lack of reliable data, especially forlarger fires, makes it difficult to realistically model fire scenarios.
CSNI/PWG5 established a Task Group to review the present status and maturity of methods usedin fire PSA for operating nuclear power plants. The Task group issued a questionnaire in May 1997 to
all nuclear power generating OECD countries. One of the concluding remarks presented in thesummary report [NEA/CSNI/R (99)27] was as following:“The shortage of fire analysis data is one of the major deficiencies in the present fire PSA. In
order to facilitate the situation, it would be highly important to establish an international fire analysis
data bank, similar to that set up by OECD for the CCF data collection and processing system(ICDE/CCF data base at OECD). Such a data base would provide fire event data on real fire cases,
incipient fires (smoldering etc.) detected/extinguished before development, dangerous or threatening
situations, reliability data on fire protection measures, and the unavailability’s of fire fighting systems,
for example, due to component failures or operational errors.”
Based on the above concluding remarks several OECD member countries have agreed toestablish the International Fire Data Exchange Project (OECD FIRE) to encourage multilateral cooperation in the collection and analysis of data relating to fire events in nuclear power plants. The
objectives of the Project are to:•record fire event attributes to facilitate quantification of fire frequencies and fire
scenarios frequencies;•

collect and analyse fire events in the long term in order to better understand such events,
their causes, and their prevention;•

generate qualitative insights into the causes of fire events, which can then be used toderive approaches or mechanisms for their prevention or for mitigating theirconsequences; and•establish a mechanism for the efficient feedback of experience gained in connection withfires, including the development of defenses against their occurrence, such as indicatorsfor risk-based inspections.

The guide provides instruction how to describe a fire event by use of a narrative description. The
guide also defines codes to be used for classifying the event. The narratives and the coding are basedon documented references.
The classifications of the fire event by use of codes provide the possibility to search for andidentify specific fire events of interest in the OECD FIRE Database. The coding will also form a basis
for statistical calculations.
2.

Fire event analysis support data

The support data is supposed to be used in the fire data analysis phase. Support data is stored in
two database support modules and one separate table “Plant data and table of correspondence”. The

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support modules “Reporting thresholds” and “Fire brigade organisation” are accessible from thegeneral data page in the OECD FIRE DB. The separate table includes following information:•

General data such as, plant code, operator, type of reactor, commercial operation start,
etc. The general data is mainly based on the IRS Database.

•Dates for plant specific start of OECD FIRE data collection.

•

A table of correspondence for the anonymous OECD Plant code ID

2.1 Reporting thresholds
The reporting threshold module defines reporting thresholds for reporting fire events from theutilities to authorities. The reporting threshold module is a part of the OECD FIRE DB.
The reporting thresholds for fire events vary amongst member countries. If collected fire data are to be
used for statistical purposes it is essential to know the reporting routines applied in the various
countries. There are two different reporting threshold levels:•

LER level Fires - If the reporting to OA only consists of Licensee event reports (LERs),
LER definition history has to be known. The LER is normally defined in the technicalspecifications. Today there exist several different definitions depending on member
country and date of the fire event. In some member countries a fire event will be reported
as a LER if it had affected a safety component. Other LER definitions are based on the
duration of the fire.

•

All Fires - Some OECD FIRE member countries have access to all fire reports. This fact
also has to be documented in the OECD FIRE database threshold history module.

To enter and edit reporting thresholds in the database you have to click the button “Reporting
thresholds EDIT” under the “fire event general data” page. The criteria for reporting fires in OECDFIRE participating countries are listed in Appendix A-1.
2.2 Fire brigade organisation
The fire brigade organisation module contains the general description of on-site and off-site firebrigade organisation. Distance in kilometers between plant and off-site fire brigade as well as off-site
fire brigade response time are also given. Changes over time in the organisation can be addressed in
the database.
3.

Description of an OECD FIRE event

The scope for reporting fires to the OA is limited to nuclear power plants. Fires at research
reactors, nuclear waste storage facilities, etc. are excluded. The reporting includes all plant internalfires on site (inside and outside buildings) as well as plant external fires if these have the potential toimpact nuclear safety.
The reporting shall include fires in all operation modes. Also fires during construction anddecommissioning shall be reported. The OECD FIRE PRG determines the observation period forwhich fires are to be reported.
A fire is defined as follows:

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NEA/CSNI/R(2009)6•

A process of combustion characterised by the emission of heat accompanied by (open)
flame or smoke or both;•

Rapid combustion spreading in an uncontrolled manner in time and space.

Note:
This includes incipient fires as well as fully developed fires. Fires shall be included in the
database if they are relevant to safety and also if the same type of fire has the potential to be
relevant/significant for safety under different boundary conditions (such as different ventilation
conditions, other plant operating states (POS), same components affected in other locations, etc.).
Explosions not resulting in an open flame shall be excluded.
The OECD FIRE event is described in documented references. The database into which it isincluded is divided into the following major parts:• Fire event general data
• Description of the fire’s initiating course of events• Description of the fire’s continuing course of events such as extinguishing measures etc.
• Description of the fire’s consequences on the plant• References• Relevance index
Narrative event descriptions as well as coded fields are used for the description of the event. The
narrative event description consists of:
1. Event description: it begins with a short description or title of the event, followed by adetailed factual description of the fire event, including all relevant circumstances.
2. Sequence of events: it is a structured record of the evolution of the event in form of a bullet
list with time and description of the event. The reader should be able to understand how theevent developed in time.
3. Event interpretation: it provides further explanations and interpretation, if required.
4. Ignition phase comments: may provide further details and comments on the fire ignition
phase.
5. Extinguishing phase comments: may provide further details and comments on the fire
extinguishing phase.
6. Comments on consequences and corrective actions
The entries of the coded fields are normally derived from the narrative event description. Coding
can also be based on documented references. They are grouped into:
7. Ignition phase: Describes (by use of codes) the initial course of the fire including items
such as location of the fire, type of detection, fire loads, ignition mechanism and root
cause.
8. Extinguishing phase: This section describes (by use of codes) the course of the event after
the fire alarm trigged, type of extinguishing equipment used, who extinguished the fire.

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9. Consequences: Heat and smoke influence on plant operation and systems are described (byuse of codes). Secondary effects and corrective actions are included.
10. References: References used, and where to find more information on the specific fire event.
The major part of the information asked for in the narratives and coded fields is compulsory
information. However, there is information, such as amount of fire load that is time consuming tocollect. This type of information is marked as “if available”. This information can be collected in alater stage, if necessary, for a limited number of events.
Terms used are listed in the glossary in Appendix A-2. They are consistent with terms used
elsewhere in the literature. If any abbreviations will be used to describe the event, their contents or
unabbreviated expressions should be described for avoiding misunderstandings.
3.1

General data

3.1.1 Event title
Text

The title should indicate the nuclear safety impact of the event (if any) as
well as the apparent lack, failure or deficiency.

3.1.2 Plant
Code

The nuclear power plant where the fire event occurred. The table ofcorrespondence is needed to identify the plant.

3.1.3 Registrar
Text

Name of the initial creator of the OECD FIRE event record. Note: This
description field is to be found on page “References”.

3.1.4 Date and time of detection (YYYY-MM-DD HH:MM)
Alpha-numericTime of detection of the fire, manually, automatic, etc. Year/ month/ day/hour/minute

3.1.5 Date of OECD FIRE event description (YYYY-MM-DD)
Alpha-numeric

Date when the OECD FIRE event record was first created.
Year/month/day.
Note: This description field is to be found on page “References”.

3.1.6 Date of OECD FIRE event revision (YYYY-MM-DD)
Alpha-numeric/
Text

Date and cause (text) of OECD FIRE event revision.
Note: This description field is to be found on page “References”.

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3.1.7 OECD FIRE Event description
Text:
The text begins with a short description or title of the event, followed by a detailed factual
description of the fire event, including relevant circumstances. As the factual event
description forms the basis for the event interpretation and the coding it has to be as clear
and complete as possible. Below are important items to be described:• Operational mode (physical parameters; power level (% of full power) RCR coolant
pressure and temperature prior to the fire
• Operation mode prior to the fire and after the fire
• Building and type of room where the fire started• Type of component where the fire started and, if possible, age of component• Ignition mechanism (Mechanical, electrical, etc.)• Root cause (the most basic reason for the fire ignition)• How was the fire detected? What type of detector?
• Fuel properties (quantities and materials)• Permanently and temporarily available fire loads (information if available)• Type of fire extinguishing• Causes for fire protection equipment not activating/failing/not working as intended• Multiple fires and dependencies• If the fire spreads to adjacent rooms, specifying the pathway of hot gas propagation• Influence (impact and/or functionality as well as damage) on equipment due to heat,
hot gases and/or smoke; actuated safety functions and occurred radioactive releases;
description of spurious actuation, control circuit response to cable damage from fire,
instrumentation response and readout on the control panels. Influence on fire barriers(dampers, floor, ceiling, doors)• Smoke influence on people’s movement; smoke influence on main control room
habitability• At what elevation above the base of the fire was heat damage observed? At what
radius around the centre-line of the fire was damage observed at the base? At what
radius around the centre-line of the fire was damage observed at the ceiling(information if available)? Distance between fire source and damaged component(information if available)• Damage due to secondary effects and cause of secondary effects• Actions taken by the licensee to prevent the fire event from re-occurring

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3.1.8 Sequence of events
Text
This narrative is a structured record of the event in form of a bullet list with time anddescription of the event. The reader should be able to understand how the event unfolded intime and logic. Short sentences or statements increase clarity. It should be easy to identify theindividual occurrences. Below are examples of important occurrences:
•
•
•
•
•
•

Time of the event
Time of the alarmTime of the physical localisation of the fire
Time when extinguishing started
Time when fire was under control
Time when fire was extinguished3.1.9 Event interpretation
Text
Event interpretation or added text by the analyst(s) or (registrar) to clarify parts of the event
which are neither clearly described elsewhere in the text fields nor in potentially availablereferences. It is also possible to add reflections made such as:• Applicability to other operational modes (information if available);• Safety implications to other plants (information if available).
The interpretation of the event from the safety viewpoint should at least include informationsuch as:•Initiating event due to the fire events, e.g., SCRAM automatically, Manual Reactor
Shutdown, or Transient Initiation etc.;•

Safety significant structures, systems and components (SSCs ) affected by the fire
event;•

Degradation of safety functions (e.g. degradation of (fire) resistance due to fire but
safety function was not impaired. Such degradation can be identified by tests after thefire events.);•

SSCs utilised to bring the plant to a safe operational mode;•

Applicability to other operational modes, if available;•

Safety implication to other plants, if available.

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3.1.10 Operation mode prior to the event
Code/Text

Plant operational mode prior to the fire.

Codes

Definitions

Construction phase
Power operation

Power level > than 5 % of full power level

Hot stand byPower level 0 (Residual heat system not connected)

Shutdown mode

The shutdown modes normally include several sub-modes such as
hot shutdown (RHR connected), cold shutdown, refuelling
shutdown and service/ maintenance shutdown (outage) (refuelling
included), if possible add sub-mode in the narrative text field. The
water level in the primary circuit is also important for events during
shutdown operation of PWR (e.g. Mid-Loop Operation).

Start-up mode
Decommissioning
Unknown
3.1.11 Confirmation time (HH:MM)
Alpha-numeric/text

Confirmation time in hours and minutes; time interval between time ofdetection (field 3.1.4) and time of confirmation of the fire. The event
specific definition of “Confirmation time” can be explained in thecorresponding text field “Confirmation time clarification”.

3.1.12 Suppression time (HH:MM)
Alpha-numeric/text

Suppression time in hours and minutes; time interval between time ofdetection (field 3.1.4) and time of suppression of the fire. The event
specific definition of “Suppression time” can be explained in thecorresponding text field “Suppression time clarification”.

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3.2

Ignition phase

3.2.1 Building where the fire started
Code/Text

The exact location of the fire can be documented under item 3.2.2
and/or by use of 3.2.3.
If a code is not available, select one of the following alternatives:• “Other building” and describe type of building by use ofnarratives• Unknown

Codes

Definitions

Reactor building

The fire has started inside the reactor building. The reactor building
includes rooms inside the containment (including usually the reactor
vessel, primary circuit and the areas of the primary circulation pumps),
the space between containment and secondary containment and otherrooms included in the reactor building according to the room coding.

Electrical building

The electrical building normally includes switchgear rooms, battery
rooms, relay rooms and the unit control room.

Auxiliary building

The auxiliary building includes safety systems (pumps, valves, etc). The
building may also include local switchgear rooms and the unit controlroom.

Turbine building

The turbine building includes turbines, feed water systems, condenser,
etc.

Diesel generator
building

Diesel generator building including rooms for diesel generator anddiesel generator support systems

Intake building

Cooling water intake building including mechanical filters (sometimes
also service water pumps)

Switchyard

Including external transformers such as start-up transformers (for thetransformers which are really located at the switchyard), even if
surrounded by protective walls. Compare to “Outside the plant”

Spent fuel building

Building where spent fuel and further nuclear waste is stored

Workshop(controlled area)

Plant area inside the controlled area of the NPP, where maintenanceactivities can be performed and materials/and equipment for these
activities can be temporarily stored

Independent
emergency building

Building including diverse auxiliary safety systems and normally also aback-up CR

Outside the plant(not switchyard)

Fire started on site area outside NPP buildings, e.g. main transformers
and other outside areas. Fire in switchyard is specified by code
Switchyard.

Other buildingThis code shall be used if the predefined codes are not applicable. The
code shall be combined with a descriptive text that describes the type ofbuilding.

Unknown

There is no information on the type of building or area where the firestarted.

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3.2.2 Room/Plant area where the fire started
Numeric/
If available

Identify the room/plant area where the fire started. Use normal(local) plant coding system (room ID numbers).
If the room code is known the following information can beobtained from general plant documentation (database or othertypes of register):• Fire loads and their distribution in the room (limited to a
specific location, spread homogeneously over the room,
distributed inhomogeneously over the room)• Room volumes (floor area, room height, if available)• Type of ventilation• Type, no. and location of fire detection equipment• Type, no. and location of fire extinguishing equipment
This information is mainly intended for verification of the
distribution factors. Distribution factors are used to generate room
specific fire frequencies from the overall fire frequency of thebuilding

3.2.3 Type of room where the fire started
Code/Text

If a code is not available, select one of the following alternatives:• “Other type of room” and describe type of room by use ofnarratives• Unknown

Codes

Definitions

Cable spreading room

Rooms typically including cables and electrical cabinets

Other cable room

Rooms including mainly cables, such as cable corridors, cablecellars, cable shafts, cable vaults

Room for electricalcontrol equipment

Local electrical rooms in auxiliary buildings, relay room inelectrical building, rooms for system control, etc.

Switchgear room

Room containing 6 kV buses, 6kV breaker, or power supply tovalves and smaller pumps and fans (mainly 400 V and 220 V
supplies etc). The type of breaker is described in the narrativedescription fields and by use of the field “component were the firestarted”.

Battery room

Rooms containing a large number of batteries

MCR

Main unit control room or reserve/emergency control room

Room for ventilation

Rooms containing fans and filters

Room for off-gas
equipment
Process room

Pumps, valves, mostly mechanical equipment; whether or not thisequipment is part of a safety system does not affect theclassification as “process room”.

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Staircase and/or
corridors
OfficeWorkshop

Plant area where maintenance activities can be performed andmaterials/and equipment for these activities can be temporarily
storedStorage for nuclear
waste
Storage for otherwaste
Storage for
combustibles (liquids,
gas, etc.)
Elevator shaft
Diesel generator room
Transformer
room/bunker

E.g. main transformers, auxiliarytransformers located at switchyardtransformers,

start-up

Hydrogen cylinder
bunkerE.g. containing process supply systems.

Switchyard

Switchyard includes outside area containing circuit breakers,
disconnectors, measuring devices, busbars etc. Transformers
located at the switchyard are coded with the type of room
“Transformer room/bunker”.

Other type of room

This code shall be used if the predefined codes are not applicable.
The coding shall be complemented by a descriptive text that
describes the type of room.

Unknown

There is no information on the type of room where the fire started.

3.2.4 Component where the fire started
The types of components listed below are representative of components used in risk analysis models.
The components can be looked upon as “main components” or a “function”. The number of types istherefore limited. Within the component boundaries several sub-components normally can be
identified. The coding procedure should follow the examples given below:
1. A short circuit in a coil (relay or electronic circuits) inside an electrical cabinet has caused afire; select code “electrical cabinet” and describe in the narrative description field all specificcircumstances.
2. A lubrication oil pipe connected to the turbine generator broke and resulted in a turbine hallfire; Select code “turbine generator”

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Code/Text

Codes

If a code is not available, select one of the following alternatives:
1. “Other component” and describe type of component by useof narratives
2. Unknown
3. Not applicable. No component can be linked to the fire (ascause of the fire, as fire load or damaged by the fire).
Definitions

High voltage breaker

Generator breakers 15-20 kV, Whether or not the breakers use oilshould be described in the narrative description field.

High or medium
voltage electricalcabinetElectrical cabinets such as cabinets used for 6 kV breakers or 400 V
motor breakers. Normally this type of cabinet is located in theswitchgear room.

Low voltage electricalcabinetElectrical cabinets such as cabinets used for instrumentation andcontrol, logic build-up, regulation, etc. The type of cabinet can be
described in narrative description fields. Normally this type ofcabinet is located in relay rooms.

High voltage
transformer

Start-up transformers etc.

Medium and low
voltage transformer –oil filled

Cabinet external transformers using oils as coolant

Medium and low
voltage transformer dry

Cabinet external transformers, typically dry transformers withlower fire load

Rectifier or inverter

Including rotating and solid-state systems

Turbine generator

Including turbine and turbine generator

Diesel generator

Including diesel engine and generator

Electrically driven
pumpIncluding motor, pump and support equipment for cooling,
lubrication, etc.

Turbine driven pump

Turbine driven pump, such as auxiliary feed water pump (BWR,
some PWR)

Motor operated valve

Including motor and valves

Pneumatic valve

Including solenoids and valve

Power Cable

6 kV, 500 V or 200 V power cable on a cable tray. Types of cables
should be described in the narrative description field (IEEE/nonqualified, fire retardant, fire retardant cable coating).

Control Cable

Instrumentation or control cable on a cable tray. Add current level(control cable) in milli Amps and voltage level in the narrativedescription field.

HeaterDryer
Battery
Battery charger

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BusbarBusbar normally located in switchgear room. Level of voltage shallbe specified in the narrative description field.

Mobile electric
equipment
Fan
Compressor
Separator

E.g. oil separator

Equipment for
illumination
Other component

This code shall be used if the predefined codes are not applicable.
The coding shall be complemented by a descriptive text that
describes the type of component.

Unknown

A component can be linked to the fire, but type is unknown.

Not applicable, nocomponent involved

No permanently available component can be linked to the fire(cause to the fire, as fire load or damaged by the fire); e.g. fire due
to hot work, human activity, ignition of transient fire loads.

3.2.5 Ignition mechanism
Code/Text

Codes

Use available codes to identify the ignition mechanism. Multiple
alternatives can be selected. If a code is not available, select one of
the following alternatives:• “Other ” and describe type of ignition mechanism by use ofnarratives• Unknown. There is no information on ignition mechanism.
Definitions

Mechanical

Mechanical failure, machinery breakdown.

Electrical

Short circuit, short to ground, arcing, etc.

Self-ignition

E.g. oil in insulation (auto-oxidation), cable ignition

Hot component

Example: oil on hot pipes (no mechanical failure); “Hotcomponent” can be a hot steam pipe or a hot component due to lossof cooling.

Hot work

Welding, cutting, etc.

Other

Other types of ignition mechanism such as lightning, explosions,external sources

Unknown

There is no information on the ignition mechanism.

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3.2.6 Root Cause
Use available codes to identify the root cause (the most basic reason
for the fire ignition). Multiple alternatives can be selected. If a code
is not available, select one of the following alternatives:• “Other” and describe type of root cause by use of narratives• Unknown. There is no information on root cause.
Root cause codes (categories) are used in IAEA-TECDOC-1112
Root cause analysis for fire events at nuclear power plants.

Code

Codes

Definitions

Equipment

Design, operational failure, maintenance

Human

Fire caused by non-observance of procedures, e.g. due to welding,cutting, not-appropriate treatment of flammable / combustible
materials, etc.

ProceduresFire caused by deficient procedures

Other

Other type of root cause than equipment, human error orprocedures. This could also include external events, such as
earthquake, high winds, vehicle collision, etc.

Unknown

There is no information on the root cause.

3.2.7 Type of fire detection
By which means was the fire detected? Use available codes anddescribe by use of the narrative description field. Multiple
alternatives can be selected. Indicate only the detection means being
involved.

Code(s)

Codes

Definitions

Fire alarm system

Automatic fire detection by fire alarm systems

Fire guard/watch

Manual fire detection

Plant walk down

Manual fire detection

Other personnel

Manual fire detection

Indirect signals

E.g. fire induced influence on process instrumentation

Signals from the fixed
extinguishing systems

Signals from the fixed extinguishing systems

Undetected

An identified self-extinguished fireUnknown

There is no information on fire detection.

3.2.8 Detector TypeIf the fire alarm system was actuated, what type of detector indicatedthe fire? Multiple alternatives can be selected. Indicate only theactuated detector types.

Code(s)

Codes

Definitions

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Optical detector

Optical including optical smoke detecting devices (ionisation detector
coded separately below). A device that senses visible or invisible
particles of combustion.

Heat detector

Temperature gradient, (fix temp.). A device that detects abnormallyhigh temperature or rate-of-temperature rise.

Flame detector

A device that senses the presence of a flame

Ionisation detector

The principle of using a small amount of radioactive material toionise the air between two different charged electrodes to sense thepresence of smoke particles. Smoke particles entering the ionisation
volume decrease the conductance of the air by reducing ion mobility.
The reduced conductance signal is processed and used to convey analarm condition when it meets preset criteria.

Infrared detector
Other type of detector
No detector actuation

The fire was detected by other means. Example, heat detectors did notalarm immediately, plant personnel detected the small fire.

Not applicable

Use this code for rooms where no detector exists.

Unknown
3.2.9 Detection system performance
Performance of detection systems

Code
Codes

Definitions

NormalNormal performance of the detection system

Fire detectors were not
involved

Criteria for automatic actuation of fire detectors were not met.
Detectors were not actuated (correct performance) but would haveworked as intended (e.g. in case of low amount of smoke, lowtemperatures, etc.), fire was detected by other means (e.g. indirect
signals, humans being present).

Malfunction

The detection system did not work as designed (complete failures orpartial failures). Such as delayed automatic detection, unsuitably
located detector, etc.

Not applicable

The fire was detected by other means (e.g. people available in the firecompartment), because detectors were not installed in the firecompartment.

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3.2.10 Fuel/Combustibles/Fire loads
Identify the type of fuel(s) that was involved in the initial phase of thefire. Fuel properties (quantity and material) relevant to combustion in
the narrative description field. Multiple alternatives can be selected.

Code(s)

Codes
Permanent
combustibles

Definitions
The fuel is permanently available at the fire location. The coding
shall be complemented by a descriptive text.

Gas
Hydrogen
Other gases

The coding shall be complemented by a descriptive text that
describes the type of gas.

LiquidFlammable liquid

Liquid with low ignition temperature, e.g. gasoline or other mineraloils. If possible, add ignition temperature limits in narrativedescription field.

Hardly inflammableliquidFire retardant (hardly inflammable) liquid, normally with highignition temperature, e.g. lubrication oil, grease, hydraulic fluid, fueloil, etc. If possible, add ignition temperature limits in narrativedescription field.

Solid
Cable insulationmaterials
Wood
Paper
Trash/waste
Plastics/Polymericmaterials
Other insulations
Charcoal
Other solid material

The coding shall be complemented by a descriptive text that
describes the type of solid combustibles.

Transient
combustibles

The fuel is only temporarily available at the fire location (transient
fire loads). The coding shall be complemented by a descriptive textthat describes the type(s) and configuration of the transientcombustibles, such as scaffolding, staging area, etc.

Gas
LiquidSolid

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3.2.11 Ignition phase comments
Text
In this text field specific comments concerning the ignition phase can be added such as:• Reflections made;• Clarification of coding.
3.3

Extinguishing phase

This section describes the course of the event after the fire alarm has been signaled. The section
provides instructions how to describe OECD FIRE event scenarios. The fire’s or the smoke’s
influence on the plant are described in section 3.4
3.3.1 Type of Extinguishing
Identify the equipment used for fire fighting. Multiple codes canbe selected.

Code(s)
Codes

Definitions

3.3.1.a - Type of extinguishing
Manual fire fighting

The fire was extinguished by use of e.g. portable fire fighting
equipment or by use of water from fire hydrant and/or hose.

Fixed systems
automatic actuation

The fixed extinguishing system was actuated automatically by thefire detection system.

Fixed systems manual
actuation

The fixed extinguishing system was actuated manually.

Controlled burn out

An active decision has been made to not directly extinguish the fire.

Fire source isolation

If the fire source is an electrical arc, the fire (arc) can be
extinguished by disconnection of electrical power source. Anotherexample for the fire source isolation is the isolation of the oil orhydrogen source.

Self-extinguishedNot applicable
Other means
Unknown
3.3.1.b - Type of system/equipment used
Fixed systems
Wet pipe sprinkler

Wet pipe sprinklers are fixed systems consisting of a network ofoverhead pipes releasing water through nozzles onto the fire, whena predetermined temperature has been reached, The only operating
components are the automatic sprinklers and (commonly, but notalways) the automatic alarm check valve . An automatic watersupply provides water under pressure to the system piping. All of
the piping is filled with water. Until sufficient heat is applied,causing one or more sprinklers to fuse (open), the automatic
sprinklers prevent the water from being discharged.

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NEA/CSNI/R(2009)6

Dry pipe sprinkler

Pre-action sprinkler

Spray water deluge

Dry pipe sprinklers are fixed fire extinguishing systems consistingof a network of overhead pipes releasing water through nozzles
onto the fire. Water is not present in the piping until the system
operates. The piping is pressurised with air, at a relatively low"maintenance" pressure compared with the water supply pressure.
When one or more of the automatic sprinklers is exposed to
sufficient heat, it operates, allowing the maintenance air to ventfrom that sprinkler. As the air pressure in the piping drops, thepressure differential across the dry pipe valve changes, allowing
water to enter the piping system.
Pre-action systems are hybrids of wet, dry, and deluge systems,
depending on the exact system goal. There are two sub-types of preaction systems: single interlock, and double interlock. The single
interlock systems operation is similar to dry systems except thatthese systems require that a “preceding” and supervised event prior
to the “action” of water introduction into the system’s piping due toopening of the pre-action valve. The operation of double interlock
systems is similar to deluge systems except that automatic
sprinklers are used. These systems require that both a “preceding”
and supervised event and an automatic sprinkler actuaation takeplace prior to the “action” of water introduction into the system’s
piping.
Deluge systems are fixed water based fire extinguishing systems
that have open sprinklers, i.e. the heat sensing operating element isremoved during installation, so that all sprinklers connected to thewater piping system are open. Water is not present in the piping
until the system operates. Because the sprinkler orifices are open,
the piping is at ambient air pressure. To prevent the water supply
pressure from forcing water into the piping, a deluge valve(mechanically latched) is used in the water supply connection.
Water flows from all sprinklers simultaneously.

Water mist

Fixed water based systems using water sprays with very small
droplet sise

Foam system

A foam fire extinguishing system is a fixed water based system,
discharging a mixture of water and low expansion foam
concentrate, resulting in a foam spray from the sprinkler.

Carbon dioxide

Fixed gas extinguishing systems using CO2 as extinguishing agent

Halon

Fixed gas extinguishing systems using halon gas as extinguishing
agent

Other inert gas

Fixed gas extinguishing systems using special inert gases, such as
Inergen (a composition of N2, Ar, and CO2) as extinguishing agent

Other gases

Other type of fixed gas extinguishing systems. The coding shall becomplemented by a text describing the type of the fixed gas system.

Water hose

Water from fire hydrant and/or hose with fixed water supply

Portable means
Dry chemical

Portable fire fighting equipment, dry chemical (powder)

Gas

Portable fire fighting equipment, gas (e.g. carbon dioxide, etc.)56

NEA/CSNI/R(2009)6

Foam (water based)

Portable fire fighting equipment:, foam (water based)

Other equipment

Other portable fire fighting equipment. This also includes watersupply from fire trucks, etc. The coding shall be complemented by atext describing the type of equipment.

Not applicable
Unknown
3.3.2a Fixed fire extinguishing system performance
Performances of fixed extinguishing systems. Manual fire fighting
Codeperformance by use of e.g. portable fire fighting equipment or byuse of water from fire hydrant and/or hose is coded under 3.3.4.
Codes
Definitions
Activation
The fixed extinguishing system was activated as per design
requirements and was effective in suppressing the fire. This includes
manual and automatically actuated systems, including automatic
systems which are activated manually prior to automatic activation
conditions being reached. For automatic systems activated manually
because of failures in the automatic initiating system the code
“malfunction” should be used.
Malfunction
The fixed extinguishing system did not work as designed. This
includes situations involving malfunctions in:• system activation;• failure to discharge when activated manually, and;• general failure to perform or suppress the fire when
operating.
Did not Activate
Criteria for automatic actuation of the fixed extinguishing systems
were not met. The fixed extinguishing systems were not actuatedmanually. Details associated with the event should describe any
information on why the automatic actuation criteria were not met
and why manual activation was not initiated.
No system present
No fixed extinguishing systems were installed in the room where
the fire occurred.
Unknown
3.3.2b Portable fire fighting equipment performance
Performances of portable fire fighting equipment and otherequipment used by the fire brigade such as water hoses, etc..
Manual fire fighting performance is coded under item 3.3.4.

Code

Codes

Definitions

NormalThe portable fire fighting equipment worked as designed.

Malfunction

The portable fire fighting equipment did not work as designed.

Not applicable

The of portable fire fighting equipment was not used because ofother types of fire extinguishing (fire source isolation, fixed fire
extinguishing systems performance successful, fire selfextinguished, controlled burn out, etc.).

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No portable firefighting equipment
available

Portable fire fighting equipment was neither available in the room
where the fire occurred nor in the vicinity of the fire compartment.

Unknown
3.3.3 Who successfully extinguished the fire
Identify who extinguished the fire. Multiple alternatives can beselected. Identify the number of fire brigade members or number offire engines brought to fight the fire, give the number in narrativedescription field.

Code

Codes

Definitions

Self-extinguished
Fixed extinguishingsystemFire extinguished automaticallyextinguishing system

by

fixed

(stationary)

fireFire guard/watch
People available in thefire area
Shift personnel
On-site plant firebrigadeExternal (off-site) firebrigade participatedExternal (off-site) firebrigade was notified
for backup
Unknown
3.3.4 Manual fire fighting performance
Manual fire fighting performance.

Code
Codes

Definitions

Initial attack
successful
Several attacks needed
Not applicableNo manual extinguishing actions were needed because the fire wasextinguished by other means (fire source isolation, selfextinguished, controlled burn out, etc.).

3.3.5 Extinguishing phase comments
Text
In this text field specific comments concerning the extinguish phase can be added such as:• Reflections made• Clarification of coding

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3.4

Functional consequence and corrective actions

3.4.1 Change in operational mode due to the fire
Code/Text

Plant operational mode just after the fire.

Codes

Definitions

No change inoperational mode

The fire did not result in any influence on operation mode.

Change to hot standby

Change to power level 0 (Residual heat system notconnected)

Change to shutdownmode

The shutdown modes normally include several sub-modes such as
hot shutdown (RHR connected), cold shutdown, refueling shutdown
and service/ maintenance shutdown (outage) (refueling included), if
possible add sub-mode in the narrative text field.

Unknown
3.4.2 Heat or hot gases influence
Identify the influence due to heat or hot gases on systems andcomponents. Use specified codes. If feasible, identify the names of
SSC s affected by the fire,

Code
Codes

Definitions

None

No components took damage from the heat developed by the fire.

Limited to a single
component

One component (main) has been damaged by the fire (a breaker, apump).

Multiple component
fire in one room

Part of a room is destroyed (e.g. a complete electrical cabinet) or
several components in a room.

Total loss of one room

Significant damaged in a room up to total damage of one room

Adjacent rooms wereaffected

In addition, it may be also useful to include in the field the pathwayof hot gas propagation. Components have been destroyed in tworooms due to the fire. The fire did not spread beyond the firecompartment.

More than one firecompartment affected.

The fire has spread between fire compartments. (Loss of a firebarrier or degradation of fire barriers, not only complete failures)

Structural influence orcollapse

Structural influence or collapse of building structure

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3.4.3 Smoke influence
Identify the damage caused by the smoke spreading to the plant.
Smoke on electrical cards, relays or breakers, shortcuts due to lackof insulation

Code

Codes

Definitions

None

The smoke has not damaged components.

Smoke influence

Damage to components by smoke, or influence of smoke on plant
personnel and actions of accident mitigating actions. Describe in
the narrative description field smoke influence on people’s
movement, smoke influence on main control room habitability.

3.4.4 Secondary effects
Identify the collateral secondary effects, e.g. from extinguishing.
Use available codes

Code
Codes

Definitions

None

No secondary effects

Flooding

Flooding from sprinklers etc.

OthersE.g. electric components failed due to extreme low temperaturefrom fire extinguishing by carbon dioxide.

Unknown
3.4.5 Impact to Safety Trains
Code
Codes
No safety trains lost
One safety train lost
Loss of more than one
train
Loss of all safety
trains.
Unknown

Identify the number of safety trains affected by the event including
the information on the total number n of safety trains
Definitions
No loss of safety train functionality
Functionality lost for one safety train. No impact to remaining
trains. Text input should identify total number of trains and theirfunction.
More than one, but not all safety trains affected. Text input should
identify total number of trains affected, function of trains, and total
number of safety trains.
Functionality of all safety trains lost. Text should identify total
number of safety trains and their function.

3.4.6 Corrective actions
Code(s)

CodeThis field describes the actions taken by the licensee to prevent thefire event from re-occurring. Multiple alternatives can be selected.
The following coding is used:
Definition

No corrective actions

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Procedures
modification

Modifications to general administrative /procedure controls.
Modifications to specific maintenance /operation practices

Designmodifications

Design modifications such as addition of diversity. This includes
diversity in fire detection and fire fighting equipment, types ofequipment, procedures, equipment functions, manufacturers,
suppliers, personnel, etc. or modification of the equipment barrier(functional and/or physical interconnections). Physical restriction,
barrier, or separation.

3.4.7 Comments on consequence and corrective actions
Text
In this text field specific comments concerning consequence and corrective actions as wellas lessons learned can be added such as:• Reflections made;• Feedback for database coding.
3.5

References

Identify references, which have been used to describe the OECD FIRE event.
NOTE: References are documented in the “table of correspondence – references list”
separately from the OECD FIRE DB.
3.5.1 References
Examples of relevant references

Describe reference ID and how to find the reports.

Local fire brigade report
Operation log
Fire root cause analysis
Investigation report
LER report
3.5.2. Registrar
Text

Name of the initial creator of the OECD FIRE event record

3.5.3 Date of OECD FIRE event description (YYYY-MM-DD)
Alpha-numeric

Date when the OECD FIRE event record was first created.
Year/month/day

3.5.4 Date of OECD FIRE event revision (YYYY-MM-DD)
Alpha-numeric/
Text

Date and cause (text) of OECD FIRE event revision61

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3.6

Relevance index

The index is used to simplify the identification of reports especially suitable for different purposes(applications). Predefined search profiles can be used to perform the relevance search. Click the
button “Search relevance index” on the main menu.
The relevance index is assigned by the OA. The definition of the relevance index is documented inAppendix A-3.

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APPENDIX A-1: GLOSSARY OF TECHNICAL TERMS
Glossary
This report defines the terminology and abbreviations used in OECD FIRE Project documents.
Codes used to classify OECD FIRE events should be defined in the OECD FIRE Coding Guidelines
and are therefore omitted in this document. Reference to the source of the definition is given in manycases.
Abbreviations used
Below abbreviations used in OECD FIRE documents can be found. Codes for classifying theOECD FIRE events are defined in the OECD FIRE Coding guidelines.
OA: Operating Agent
NC: National Co-ordinator
CG: OECD FIRE Coding Guideline
PRG: OECD FIRE Project Review Group
LER: Licensee Event Report
Terminology and technical terms used for the project
Below the terminology specially used for the OECD FIRE Project is provided.
Other technical terms used in the OECD FIRE Project shall use and apply definitions according
to NFPA Glossary of Terms (Fire term definitions) [1] and IAEA Safety glossary for terminology used
in NPPs [2]. Both documents are available on OECD FIRE home page. Some terms from [1] and [2]often used in the OECD FIRE project are also listed below.
Classify: Assignment of key words to a fire event based on OECD narrative descriptions or
related references
Codes: In order to make the data searchable and to make it easier to develop statisticalconclusions, the data are classified with codes according to the OECD FIRE Coding Guidelines.
Coding Guidelines: The guide provides instruction how to describe a fire event by use of anarrative description. The guide also defines codes to be used for classifying the event.
Compulsory information: Most fields in the database are compulsory, which means that the
information should be provided unless either it takes an unreasonable time to retrieve this information
or it is unknown.
Description fields: Except for the narrative description fields the database contains a number ofdescription fields, often with predefined codes. Examples of description fields are; “Title of event”,“Root cause” and “Detector type”
Detect: (1) Sensing the existence of a fire, especially by a detector from one or more products ofthe fire, such as smoke, heat, ionised particles, infrared radiation, and the like. (2) The act or processof discovering and locating a fire [1].

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Explosion: The sudden conversion of potential chemical energy (l) into kinetic energy with the
production and release of gases under pressure, or the release of gas under pressure. These highpressure gases then do mechanical work such as moving, changing, or shattering nearby materials [1]Fire alarm system: A system or portion of a combination system consisting of components andcircuits arranged to monitor and indicate the status of fire alarm or supervisory signal initiating
devices and to initiate appropriate response to these signals [1]Fire compartment: A building or part of a building comprising one or more rooms or spaces,
constructed to prevent the spreading of fire to or from the remainder of the building for a given periodof time. A fire compartment is completely surrounded by a Fire Barrier [2].
Fire department: An organisation providing rescue, fire suppression, and related activities,
including emergency medical operations; this includes any public, private, or military organisation
engaging in this type of activity [1]Fire extinguished: The point in time when there is no longer any abnormal heat or smoke being
generated in material that was previously burning [1]Fire Hazard Analysis (FHA): An analysis to evaluate potential fire hazards and appropriate fire
protection systems and features to mitigate the effects of fire in any plant location
Fire load: The weight of combustibles in a fire area [ft2] or [m2] or on a floor in buildings andstructures, including either contents or building parts, or both [1]Fire load density: Fire load [MJ] per floor area [m2] of the fire compartment
Fire frequencies: The number of occurrences per time unit, at which observed fire events occur
Fire scenarios: A description of a fire and any factors affecting or affected by it from ignition to
extinguishment, including, as appropriate, ignition sources, nature and configuration of the fuel,ventilation characteristics and locations of occupants, condition of the supporting structure, andconditions and status of operating equipment [1]Ignition: The initiation of combustion evidenced by glow, flame, detonation, or explosion, either
sustained or transient. The moment when a fire first occurs [1]Ignition source: Any item or substance capable of an energy release of type and magnitude
sufficient to ignite any flammable mixture of gases or vapors that could occur at the site [1]Incipient fire: Small or initial phase of fire, can evolve to a fire if nothing is done
Licensee Event Report: Report that the nuclear power plant has to send to the authority to reportincidents
Member country: A country member of the OECD
Narrative description: A textual description of the fire event
National co-ordinator: Each Participant shall nominate one or more national coordinators who
shall be responsible for the administration of the OECD-FIRE Project within his/her respective
country
Observation period: The period of time for which fire events should be collected64

NEA/CSNI/R(2009)6
OECD FIRE Database: MS ACCESS database where all events downloaded from the webinterface are stored. This database is distributed on a CD to project members
OECD fire event: Defined in the CG as:•

A process of combustion characterised by the emission of heat accompanied by (open)
flame or smoke or both
• Rapid combustion spreading in an uncontrolled manner in time and space
Off-site fire department: A fire brigade located in a nearby city or village. The fire brigadeorganisation is independent from the NPP organisation.
On-site fire brigade: A fire brigade located at the NPP site or in the vicinity of the NPP. The firebrigade organisation is often subordinate to the NPP organisation.
Operating Agent: The Operating Agent operates the databank and verifies that the data from the
National coordinators complies with the OECD FIRE Coding Guidelines.
Participant: An organisation that has signed and complies with OECD FIRE Project Terms andConditions
Probabilistic Fire Safety Analysis: A comprehensive, structured approach to identifying failure
scenarios, constituting a conceptual and mathematical tool for deriving numerical estimates of risk [2]Project archive: All documents and databases generated within the project are stored in the
Operating Agent server. All participants of the project can download the documents.
Project Review Group: All national coordinators together constitute the OECD FIRE Project
Review Group.
Project Website: The OECD FIRE Project has a web site, where all referenced documents
generated by the project are available for all participants. Access is restricted. The website is password
protected. OECD-NEA provides participants with username and password.
Reporting routines: Reporting routines are either routines for reporting between a nuclear power
plant and the authority or internal routines for describing and distributing the fire event at the nuclear
power plant.
Reporting thresholds: This refers to the incident reporting level between utilities andauthorities. What is to be reported is normally defined in the technical specifications (utilities
document) as well as when or for which incidents information should be sent to the authorities.
Safety component: Component included in Final Safety Analysis Report (FSAR)
Safety system: A system important to safety, provided to ensure the safe shutdown of the reactor
or the residual heat removal from the core, or to limit the consequences of anticipated operational
occurrences and design basis accidents [2]Self-extinguished fires: The fire extinguishes without fire extinguishing efforts.
Sequence of events: A narrative description in form of a bullet list sorted by the date and time ofactionSignificant damage: to be defined
Suppression - The sum of all the work done to extinguish a fire from the time of its discovery [1]65NEA/CSNI/R(2009)6
Technical specification: Rules that state how the nuclear power plant should be operated
Web interface: A web-based interface where data should be entered when submitting fire data to
the project. Access is restricted. Username and password can be requested by sending an email to the
NEA secretariat.

References[1] Nuclear Fire Protection Association (NFPA)NFPA 97 Standard Glossary of Terms Relating to Chimneys, Vents, and Heat-Producing
Appliances, 2003 Edition (US$ 27.00)[2] International Atomic Energy Agency (IAEA)
Safety glossary: Terminology used in nuclear, radiation, radioactive waste and transport safety,
Version 1.2, September 2005

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APPENDIX A-2: NATIONAL REPORTING LEVELS
Criteria for Reporting Fires in NPP in the OECD FIRE Member Countries
Country /Organisation
Canada/ AECB

CNSC

Czech Republic/ REZ

Source Document
Draft Reg. Guide R-99
Reporting Requirements
for Operating Nuclear
Power Plants.

Reg. Standard S-99
Reporting Requirements
for Operating Nuclear
Power Plants(March 2003)

Reportable Fire Event•

Declaration of an alert or emergency, within the nuclear power plant,
where personnel or resources are mobilized by the licensee in response toan unexpected occurrence of a radiological condition, chemical spill, fire,or potentially explosive mixture of gases that creates an actual hazard to
the safe operation of the plant or the safety of persons.

•

The occurrence of any unusual external conditions at the site, including
fire, flood, plane crash, gas explosion, gas release, high winds, missile orice conditions, which results in operational transients.

•

Quarterly Operation report (6.4.1): (t) a description of any fires that
occurred at the nuclear power plant and an assessment of their safetysignificanceGlossary: "Fire: any uncontrolled combustion, not restricted to open
flame, that causes personal injury, death, property damage or results in themobilization of the response emergency team."•

Unscheduled reporting (6.3.1) External event (38): The occurrence of any
unusual external conditions at the site, including fire, flood, plane crash,gas explosion, gas release, high winds, missile or ice conditions that
resulted in or had significant potential to result in operational transients atthe nuclear power plantThree levels of records about fire events exist:A) Regulatory body for fire safety (DFRCCR)
Unique to the Czech Republic is that exists another regulatory body (fireregulatory body), the “Directorate of Fire Rescue Corps Czech Republic”(separate from SONS) reports to the “ministry of the interior” with primary
responsibility for fire protection.
67

Start Date

End Date
2003

2003

NEA/CSNI/R(2009)6

Country /Organisation
Czech Republic(Cont’d)Source Document

Reportable Fire Event

Start Date

Legislative act about fireFire events are reported under the same system as other incidents andprotection No.133/1985, events. Specifically, fire reports are required to the regulator within 8 hours.
§5Fire events are reported according to legislative rules. Reports include:
Fire definition according
1. Place of the fireto § 51 Directive of
2. Character of place
3. Year of putting in operation
Ministry of Interior CR
4. Time of ignition fire
No.21/1996.
5. Fire loss
6. Number of intervening fire force
7.Cause of fire
8. Cause of propagation fire
9. Corrective actions and prevention
Etc.

B) Regulatory body for nuclear safety energy (SONS):SONS (State Office for Nuclear Safety) fire protection inspections are
based on equipment performance data, and operational history. Fire is not
explicitly mentioned but if a fire should affect a safety component or unit
operations, the event should be reported.
C) OEF on NPP:OEF (Operation Experience Feedback) system is based on IAEA and
WANO guidelines. Reporting criteria are translated from IAEA NS-G-2.11.
Basic reporting criteria include: Fires, failures and spurious initiations of fire
protection and fire detection systems.
Reporting duty due to every fire (report for Regulatory body for fire
safety).

1985

Reporting duty due to fire which is I accord with fire definition (reportfor Regulatory body for fire safety).

1996

68

End Date

NEA/CSNI/R(2009)6

Country /Organisation

Source Document

Reportable Fire Event
A fire or an explosion has occurred at the plant site and at the same timesatisfy following:“The fire is each undesirable burning leading to the injury or kill of
persons or animals. The fire is also each undesirable burning leading to thefire material damage.”
According to methodical directive of the Head Fire Director of 1997 as
fire are not considered:
Explosives explosions, if there it is not accompanied with fire of materials
and constructions.
2. Burning of coils of electric rotating machines as a result of short circuit, if
burning has not propagated outside coil volume.
3. Glowing of electric installation, if it has not propagated outside of
installation.
Ignitions, which occur during manufacturing, if the technologicalprocedure could not exclude such cases and their liquidation is technicallyensured, under assumption that burning will not spread outside the anticipatedpart of the technology, or the cases are not exclusively specified as operational
accidents.
1.

69

Start Date

End Date

NEA/CSNI/R(2009)6

Country /Organisation
Finland/ STUK

Source Document
Reg. Guide YVL 1.5
rev: 8 Sept; 2003

Reportable Fire Event

Start Date

The regulatory guide 1.5, "Reporting nuclear facility operation to theRadiation and Nuclear Safety Authority" is published 8 September 2003.

1977

This Guide is in force as of 1 March 2004 until further notice.
It replaces the earlier version of the Guide YVL 1.5, issued on 11 January
1995. (The formulation has been very similar also in all the older versions ofreporting guide, thus similar criteria is assumed since the first NPP started its
commercial operation in Finland, 9th May 1977. Anyway, the Finnish fire data
is provided to this project by the utilities and they will submit “all fires”
according to the criteria given in this guideline: Chapter 2.1 and the beginningof Chapter 3).
Accordingly to chapter 3.2 (item q.) Special report is provided if“A fire, an explosion or a chemical damage has occurred at the plantsite.”
Nowadays STUK In Annual report covers Events with safety significanceincluding also as summary of fire brigade alarms.

70

End Date

NEA/CSNI/R(2009)6

Country /Organisation

Source Document

France/ EDF

EDF DI 060(8 June 1994)
The Autorité de sûreté
nucléaire (ASN) and theInstitut deradioprotection et desûreté nucléaire (IRSN),
its technical support
organization, agree withthese criteria.

Reportable Fire Event

Start Date

End Date

Before 1994, fire events reported along NEA-IAEA/IRS Guidelines

1978

1994

Any fire event or situation caused by a fire event:• solicitation of external help (fire brigade call);• bodily injury;• material damage in excess of EUR 1500;• use of more than one hand-held fire extinguisher;• use of fire hose or mobile (non portable) fire extinguisher;• true actuation of fire suppression device;• fire event within the nuclear island or in an auxiliary building;• fire event affecting or potentially affecting a safety-relevant component;

1994

•

fire event generating information of generic interest to safety.

•

It has to be underlined that one the criteria "solicitation of external help
(fire brigade call)" that is a demanding criteria, has been specified later(beginning of years 2000).
As all the fires events that can be provided to the data base occurred after
1994, it is not necessary to add older criteria.

71

NEA/CSNI/R(2009)6

Country /Organisation

Source Document

Reportable Fire Event

Start Date

End Date

Germany/ BMU

AtSMV Anlage 1
Meldekriterien fürmeldepflichtige
Ereignisse in Anlagenzur Spaltung vonKernbrennstoffen.
(Reporting Criteria for
Reportable Events in
Installations for Fissionof Nuclear Fuels)

In addition to the fire events reported to the authorities due to the following
criteria, all fire events in German NPP GRS knows about will be reported(these events are incomplete up to now but might become complete in the
future)“Any fire.”
There are three classes of reportable events. They differ in their importance tosafety and in the way they have to be reported. Fires belong to the class A
events (immediately significant), but actually they were reported as class B(potentially significant) sometimes also as class C (other events).

1975

1985

“Any damage to systems and components by plant internal fire, explosion or
flood that affects normal operation (of the affected system or component).”
There are three classes of events reflecting the significance in terms of safety.
In contrast to the 1975 version most events show up in all three classes,
depending on the systems affected and/or the severity of the event.
The cited definition for fire events corresponds to the lowest level (N). A fire
has to be reported as type E event, if systems or components important tosafety are affected. There are no S class fires.

1985

1991

“Internal fire, explosion or flood causing the unavailability of a safety subsystem or a redundancy of a system or component important to safety.”
The system is similar to the 1985 version using event classes S, E, and N.
However, the new structure is such that the safety significance defines subclasses of the event type. E.g., there is the event type 3.2 “fire, explosion, or
flood” which is subdivided into the classes S, E, N.

72

1991

NEA/CSNI/R(2009)6

Country /OrganisationJapan/ JNES

Source Document

Reportable Fire Event

Start Date

End Date

Law for Regulations of
Nuclear Source Material
Nuclear Fuel Material
and Reactors (LRNR)

LRNR, Corresponding Ordinance: When there is a failure of equipment etc.
important to safety by the fire. Excluding the concerned failure is due to themeasure of fire extinguishing or prevention of the spread of fire;

1965

September

The Electric Utility
Industry Law (EUIL)

2003

EUIL, Corresponding Ordinance: Electrical fire accidents.
Both Laws have not changed but the Corresponding Ordinance article
numbers were changed in 2003.
LRNR Article 62-3, Corresponding Ordinance Article 19-17, Item 4: When
there is a failure of equipment etc. important to safety by the fire. Excluding
the concerned failure is due to the measure of fire extinguishing or preventionof the spread of fire;

September
2003

EUIL Article 106, Corresponding Ordinance Article 3, Item 2: Electrical fire
accidents.
Korea
/KINS

Netherlands/KFD

Reg. Guide 2008-29•

Reporting criteria forevent or failure within
the nuclear facility

The occurrence of any unusual external conditions at the site, including
fire, leakage of the radioactive material, which results in operationaltransients.

•

The occurrence of fire, leakage, robbery, loss etc of the radioactive
material while it is wrapped or transported.

NPPs technicalspecifications

Fire is not explicitly mentioned but if a fire should affect a safety component,
the event should be reported as LER report to KFD (if the component function
is degraded)

73

2008

NEA/CSNI/R(2009)6

Country /Organisation
Spain
/ CSN

Source Document
Guia de Seguridad no.
1.6 - Sucesos notificables
en Centrales Nucleares
en explotación.
(Safety Guide n. 1.6
Reporting events for
operating NPPs).
Instrucción IS-10
Criterios de notificaciónde sucesos al Consejo
por parte de las centrales
nucleares.
(Instruction IS-10
Reporting criteria of
events to the CSN from
NPPs).

Sweden

NPPs technicalspecification

Reportable Fire Event

Start Date

End Date•

fire in the plant lasting more than 10 minutes from the time ofdetection [Section 3.1.5]

January
1990

November
2006•

fire in the plant with the potential to impact plant safety or with thepotential to impair the plant personnel's ability to safely operate theplant [Appendix: reporting form for abnormal events]•

Fires that are confirmed with duration below 10 minutes and incipient
fires that activate the corresponding detection systems, provided that theyoccur in cubicles, areas or fire zones in which structures, systems orsafety-related components are located [Section 5.E.4].

•

Uncontrolled fire situated to less than 5 Km away from plant’s fence andit moves toward the plant [Section 5.H.1].

•

A fire in the plant lasting more than 10 minutes activates the Internal
Emergency Plan (PEI). Any activation of the PEI involves the report to
the CSN.

Fire is not explicitly mentioned but if a fire should affect a safety component
the event should be reported as a LER report to Swedish Radiation Safety
Authority (SSM) (if the components function is degraded).
In addition to these events all fire are reported which have activated the fire
alarm.
Swedish observation time starts in 1977.

74

November
2006

August1977.

NEA/CSNI/R(2009)6

Country /Organisation
Switzerland/ HSK

Source Document

Reg. Guide HSK-R-15
Berichterstattung überden Betrieb von
Kernkraftwerken(1980, 1981)
Reg. Guide HSK-R-15(1984, 1987)
Reg. Guide HSK-R-15(1994, 1999, 2004)

Reportable Fire Event

Start Date

End Date

No formal reporting requirements

1969

1980

Any fire or explosion if it either (1) causes a scram or (2) if it does notcause a scram but if there is an oil leakage with a risk of ignition or (3) if
there is a major oil leakage

1981

1984

1985

1994

Any fire or explosion in a building containing safety relevant (classified)equipment
Any fire or explosion within the perimeter of the plant

75

1995

NEA/CSNI/R(2009)6

Country /Organisation
USA
NEIL

USNRC

Source Document
NEIL
Loss
ControlStandards (Sept. 2002)

10 CFR 50.73
Licensee event
system.

report10 CFR 72.75
Reporting requirements
for specific events andconditions.

Reportable Fire Event•

Any fire involving activation or malfunction of a fixed fire
extinguishing or detection system OR any physical damage loss inexcess of $100,000.00•

Impairments to fire suppression systems, which exceed, or are
expected to exceed 48 hours•

Any event that posed an actual threat to the safety of the nuclear
power plant or significantly hampered site personnel in theperformance of duties necessary for the safe operation of the nuclear
power plant including fires, toxic gas releases, or radioactive releases.

-

Non-emergency notifications: Four-hour reports. Each licensee shallnotify the NRC as soon as possible but not later than 4 hours after the
discovery of any of the following events or conditions involving spent
fuel, HLW, or reactor-related GTCC waste:•

An event that prevents immediate actions necessary to avoid
exposures to radiation or radioactive materials that could
exceed regulatory limits, or releases of radioactive materials
that could exceed regulatory limits (e.g., events such as fires,
explosions, and toxic gas releases).

•

An unplanned fire or explosion damaging any spent fuel,
HLW, and/or reactor-related GTCC waste, or any device,container, or equipment containing spent fuel, HLW, and/or
reactor-related GTCC waste when the damage affects theintegrity of the material or its container.

76

Start Date
2002

End Date

NEA/CSNI/R(2009)6

APPENDIX A-3: RELEVANCE INDEX DEFINITION
Relevance Indices are implemented to characterise the quality of fire event reports collected in theOECD FIRE Project.
The rationale to introduce relevance indices is twofold:•

The Operating Agent wants to have a mechanism that allows filtering out issues in the reports
for which more information must be sought.

•

The user desires to have knowledge of the completeness of the information in the database andof the degree of confidence he can put in the information in the database if he wants to analyse
data for various purposes.

The relevance indices essentially are “completeness indices”, i.e. they measure how complete anddetailed the reported information is and by what kind of references it is supported.
The relevance index grades are to be derived from information in the “event description” , “sequenceof events”, from the fire phase comment fields, and from the respective coded fields, if the latter
contain information beyond that in “event description”, “sequence of events” and fire phase comment
fields. This qualification process requires to examine event descriptions and event sequencedescriptions with respect to the six listed items and to assign the appropriate quality index to each of
the listed items as part of the database.
The assignment of grades in the database will be made after quality control is completed.
Predefined relevance indices are assigned only to a limited number of important items, for example:
•
•
•
•
•
•
•

Total
Causes of fire (Concerned fields: 3.2.1, 3.2.4, 3.2.5, 3.2.6)
Fire scenario (Concerned fields: 3.1.7, 3.1.8, 3.1.10, 3.2.7, 3.2.9, 3.2.10, 3.2.11, 3.3.2a, 3.3.2b,
3.3.4, 3.3.5)
On-site fire brigade response (Concerned fields: 3.1.7, 3.1.8, 3.1.10, 3.1.11, 3.1.12, 3.3.1,
3.3.2b, 3.3.4, 3.3.5)
Off-site fire brigade response (Concerned fields: 3.1.7, 3.1.8, 3.1.10, 3.1.11, 3.1.12, 3.3.1,
3.3.2b, 3.3.4, 3.3.5)
Consequences of fire (Concerned fields: 3.1.10, 3.4.1, 3.4.2, 3.4.3, 3.4.4, 3.4.5, 3.4.7)
Customise the grouping of fields: a software tool is implemented to groups any fields together.

Assignment of grades:
The calculation of the total index is based on the set of all narrative fields and most of the coded fields.
The calculation of the indices 2. through 6. is based on subsets of the indices used for the calculationof 1.
Each index is calculated as the sum of the numerical attributes of its relevant indices.
Three different grades "H" (High), "M" (Medium) and "L"(Low) can be assigned to each narrative andcoded field. The corresponding numerical attributes (values) differ for the various fields are defined
below.
Note: The narrative fields 3.1.9, 3.2.11, 3.3.5, 3.4.7 have been added after the first events were
inputted in the database. Previously only 3.1.7 was available for event description. This explains thedifferent rating system in place. From now on, the system covers all narrative fields.

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NEA/CSNI/R(2009)6

For events inputted before Sept 2004, the rating system is:•••

Narrative field 3.1.7 : H~30, M~14, L~5Sequence of events field 3.1.8 H~10, M~5, L~0
Coded fields: H~2, M~1. L~0

For events inputted after Sept 2004, the rating system is:••••

Narrative field 3.1.7 : H~30, M~14, L~5Sequence of events field 3.1.8 H~10, M~5, L~0
Narrative fields 3.1.9, 3.2.11, 3.3.5, 3.4.7: H~4, M~2. L~0
Coded fields: H~2, M~1. L~0"H" is assigned to 3.1.7, if this field contains a detailed and complete description that does notnecessitate further explanations in other fields.
"M" is assigned to 3.1.7, if the description is complete and detailed, but is distributed over all fivenarrative fields. Thus, the maximum that can be attained by the narrative fields plus the sequence of
events field is 40, regardless of how the information is spread out over the five narrative fields.

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NEA/CSNI/R(2009)6

APPENDIX B - STRUCTURE OF THE NARRATIVE PART AND THE CODED FIELDS IN
THE OECD FIRE DATABASE
Narrative part in the OECD FIRE Database
Event description:
It begins with a short description or title of the event, followed by a detailed
factual description of the fire event, including all relevant circumstances
Sequence of events:
It is a structured record of the sequence of the event in form of a bullet list
with time and description of the event. The reader should be able to understandhow the event developed in time;
Event interpretation:
It provides further explanations and interpretation, if required
Ignition phase comments:
They may provide further details and comments on the fire ignition phase
Extinguishing phase comments:
They may provide further details and comments on the fire extinguishingphase
Comments on consequences and corrective actions
Coded fields in the OECD FIRE Database
Ignition phase:This section describes (by use of codes) the initial course of the fire including
items such as location of the fire, type of detection, fire loads, ignition
mechanism and root cause
Extinguishing phase:This section describes (by use of codes) the course of the event after the fire
alarm trigged (type of extinguishing equipment used, who extinguished thefire)Consequences:
Heat and smoke influence on plant operation and systems are described (byuse of codes). Secondary effects and corrective actions are included
References:
References used, and where to find more information on the specific fire event
The classification of the fire event through coded attributes provides the possibility to search for andidentify specific fire events of interest and for specific features in the OECD FIRE Database for a wide
range of applications.

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NEA/CSNI/R(2009)6

APPENDIX C - NATIONAL APPLICATIONS OF THE DATABASE
C-1 FIRE AND EXPLOSION
One application of the OECD FIRE Database was a closer look at those events that were associatedwith explosions. As there is no specific field in the Coding Guideline to indicate explosions, the filter
and the main source of information is by the event description field (Field 3.1.7).
The following filters were used for field 3.1.7:-

search for *explo* (explosion, exploded, etc.):
search for *defla* (deflagration, deflagrated, etc.):
search for *deto* (detonation, detonated, etc.):

26 events
no events
no events

Of these 26 hits, in three cases no explosion occurred according to the event description but the term
“explo” was used in another meaning. In one event the explosive release of INERGEN gas out off agas cylinder happened. Within the 344 events 22 reported explosions represent an amount of 6.4 %.
Some interesting details of the explosions are listed in Table 1.
Concerning the process distinction should be made between an explosion as a process of rapid
combustion (chemical explosion) and an explosion as a physical process that is resulting from asudden air pressure rise by a high energy electric (arcing) fault (HEAF). A chemical explosion was
clearly found in only three cases (solvent vapor, diesel fuel, hydrogen). In the other 18 cases, HEAF
events obviously took place at the same time, which indicates a physical explosion. In some of thesecases the electric fault might have caused a fuel pyrolysis/spread and acted as an ignition source for achemical explosion, thus a HEAF event and a chemical explosion may have taken place
simultaneously.
In one case, a fire led to the explosion of diesel fuel vapor (event no. 16 in Table 1 of this Annex),
while in another case a fire and an explosion occurred independently from each other in parallel (event
no. 15 in Table 1). In all other cases explosions induced the fire.
The buildings/locations where the events took place are also listed in Table 1. Thirteen events took
place outside buildings. Clearly, most (13 events, 59 %) components where the event started weretransformers. The other nine events took place at electrical cabinets, other electrical equipment, or
process equipment (each 3, 14 %).
External fire brigades were needed in 4 of 22 cases (18 %).
The 22 events were also evaluated concerning the fire duration:-

fire duration between 0 and less than 15 minutes:
11 events
fire duration between 15 and less than 30 minutes: 3 events
fire duration between 30 and 60 minutes: 3 events
fire duration longer than 60 minutes: 3 events

For the remaining two events no information is provided on the fire duration.

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NEA/CSNI/R(2009)6
Table 1: List of fires and explosions
No.

Event Title

Location

Component

1

Trip of main transformer,
followed by fire in phase "S" dueto manufacturing defect.
Subsequently, turbine trip and,with permissive P-7, reactor trip
(event #1)

outside the plantbuildings(not switchyard)

high voltage
transformer

hardlyinflammableliquidHEAF

fixed extinguishing system;
on-site plant fire brigade;shift personnel

00:58

2

Trip of main transformer,
followed by fire in phase "S" dueto manufacturing defect.
Subsequently, turbine trip and,with permissive P-7, reactor trip
(event #2)

outside the plantbuildings(not switchyard)

high voltage
transformer

hardlyinflammableliquidHEAF

fixed extinguishing system;
on-site plant fire brigade;shift personnel

00:15

3

When energising with sub-critical
reactor, main transformer tripped,
followed by fire in phase "R"outside the plantbuildings(not switchyard)

high voltage
transformer

hardlyinflammableliquidHEAF

fixed extinguishing system;
on-site plant fire brigade;shift personnel

00:08

4

Loss of a 6.6 kV emergency
switchboard

electrical building,room for electricalcontrol equipment

high or medium
voltage electricalcabinetcable insulation HEAF
materials

shift personnel

00:07

5

Fire of the station service loadtransformer caused by a defect on
the power part of the branch lines
switch followed by an explosion

switchyard

high voltage
transformer

flammableliquidHEAF

on-site plant fire brigade

00:16

6

Reactor trip due to a failure in afast switch-over connection
function. Failure in a commuterfuse in an electrical cabinet

electrical building,switchgear room

medium and low
voltagetransformer - dryother solidmaterial

HEAF

shift personnel< 00:05

7

Unit Main Transformer fault andfiretransformer yard

high voltage
transformer

flammableliquidHEAF

on-site plant fire brigade

00:14

81

Fuel

Process

Extinguished byDuration[h:min]NEA/CSNI/R(2009)6

No.

Event Title

Location

Component

Fuel

Process

Extinguished by

explosion of shift personnel
capacitor

8

Incipient fire in a Site
Communication System roomsite communication
system room

rectifier orinverterplastics /polymericmaterials

9

Incipient fire on ultimate
emergency diesel generator

diesel generator
building,
electrical/process roomhigh or medium
voltage electricalcabinetother
HEAF
insulations;plastics/polyme
ric materials

10 Loss of 400 kV power supply
following a fire in the 6.6 kV AC
Normal Distribution System
cubicleelectrical building,switchgear roomhigh or medium
voltage electricalcabinethardlyinflammableliquid;plastics/polyme
ric materials

11 Switchyard fire in 34.5 kV circuit
breakerswitchyard

high voltage
breaker

12 Failure of Startup Transformer
ST-20

transformer yard

13 Explosion and injured persons
following maintenance work

turbine building,
process room

Duration[h:min]00:15

self-extinguished

00:05

HEAF andvaporisedoil
explosion

shift personnel;
external fire brigade
participated

01:11

flammableliquidHEAF

on-site plant fire brigade

unknownhigh voltage
transformer

flammableliquidHEAF

fixed extinguishing system< 00:10

filter of theturbine control
fluid system

vapors of acleansingsolvent

solvent
vapor
explosion

self-extinguished

00:01

14 Explosion of an oil-filled current switchyardtransformer leading to a fire in the
400 kV platform

high voltage
transformer

hardlyinflammableliquidHEAF

shift personnel;
external fire brigade
participated

00:48

15 Unit 6 forced outage due to M. O.
T. failure

switchyard,
switchgear roomhigh voltage
transformer

flammableliquidHEAF

fixed extinguishing system< 00:08

16 Liquid fuel discharge during a
Diesel generator fire

auxiliary building,pumping station

diesel generator

flammableliquiddiesel fuelexplosion

shift personnel;
external fire brigade
participated

02:35

82

NEA/CSNI/R(2009)6

No.

Event Title

Location

Component

Fuel

Process

Extinguished byDuration[h:min]17 Reactor trip due to Main
Transformer Fault and Fireoutside the plantbuildings(not switchyard),
main transformer

high voltage
transformer

flammableliquidHEAF

fixed extinguishing system;
on-site plant fire brigade

18 Voltage transformer fire due tohuman error during maintenanceoutageoutside the plant (notswitch yard), voltage
transformers near to themain transformer

medium and low
voltagetransformer - oilfilledhardlyinflammableliquid; otherinsulations

HEAF

on-site plant fire brigade (onefire); self extinguished (another
fire)

00:05

19 Fire (explosion like) in local
transformer. The reactor tripped
due to the fire.

outside the plantbuildings (notswitchyard),
on-site electrical
distribution systemhigh voltage
transformer

cable insulation HEAF
materials;
flammableliquid;other solidmaterial

on-site plant fire brigade;external fire brigade
participated~ 01:40

20 Automatic Reactor Trip due toCirculating Water Pump Surge
Capacitor Failure

intake building,
process roomelectrically driven capacitor,
pump
insulationmaterial

HEAF

self-extinguished

00:34

21 Hydrogen fire at high pressurehydrogen cylindershydrogen station,hydrogen cylinder
bunkerpressure gauge at
the hydrogen
supply line

Hydrogenhydrogen
explosion

on-site plant fire brigade

00:13

high voltage
transformer

hardlyinflammableliquid;transformer oil

HEAF

on-site plant fire brigade

00:12

22 Automatic Reactor Trip Due to a transformer yard
Turbine-Generator Trip Caused bya Fault on the 31 Main
Transformer Phase B High
Voltage Bushing83

unknown

NEA/CSNI/R(2009)6

C-2 FILTER FIRES
A further application of the database was a closer look at fires at filters used for cleaning of gaseous
media. These filters are mainly used in HVAC systems or as local filter systems at welding/cutting
workplaces. As there is no extra field in the CG to indicate filter fires, the interesting events were
singled out by different description fields. Hints were the words:-“filter” or “precipitator” in the description field (Field 3.1.7),“room for ventilation” as the type of room where the fires started (Field 3.2.3),“other component” in connection with “filter” or “heater” as the component where the firestarted (Field 3.2.4) or“Charcoal” as fuel/combustibles/fire loads (Field 3.2.10).

By these criteria 35 events were found and had to be examined. From these 35 hits, in only nine events
an air purification filter was actually involved in a fire. Within the 343 events, 9 filter fires represent
2.6%. Some interesting details of these events are listed in Table 2: Three fires (no. 2, no. 6, and no. 9
in Table 2:) occurred at filters which belonged to HVAC systems. The typical source of ignition is aheater which is not turned off after the fan of the system was turned off. Five events (no. 1, nos. 3-5,
and no. 7 in Table 2:) occurred at local filter systems for purifying air from welding or cutting
processes. These were ignited by hot work. One event (no. 8) occurred at a charcoal filter vessel of theradiolysis gas recombiner train, which was ignited either by self-ignition or an explosion. This case no.
8 is somewhat unique compared to the other cases. The time of 125 h until the temperatures werenormal again is extremely long. Also it is the only event out of the 35 selected events where the plant
operation mode changed to shutdown mode. All filter fires were fought by manual fire fighting.
External fire brigades were not needed. The fire duration is also listed in Table 2:84

NEA/CSNI/R(2009)6
Table 2: List of filter fires

No.

Event Title

Location

Component

Fuel

Process1

Welding Equipment Fire

unknown

welding smoke eater filter

other solid material

2Fire in fan room in the waste
disposal building. Fire has mostprobably started in the electricalequipment dedicated to anelectrical heating battery.

waste disposal
building, room forventilations

HVAC / fancable insulation materials; other overheating ofelectricalgases; other insulations; otherequipment
solid material;
plastics/polymeric materials

3

Fire at welding smoke extractor - auxiliary building
filterwelding smoke extractor filter

other solid material

hot work

unknown

4

Small Fire in Unit 4 - 254'
elevation, RAB

auxiliary building

welding smoke extractor filter

other solid material

hot work

unknown

5

Incipient fire on a cutting-off
auxiliary building,machine's filter in the mechanical workshop
workshop of an auxiliarybuilding

cutting-off machine's filter

other solid material; trash/waste hot work, cutting

00:20

6

Incipient fire on a heater in the
Spent Fuel Building

HVAC / Heatercharcoal; plastics/polymericmaterials

hot component

00:43

7

Smoldering Fire in Air Filtration controlled area,
workshop
Unit Attached to Welding andCutting Table

air filtration unit of welding other solid materialand cutting table

hot work: sparkor a hot molten
particle

00:19

8Fire in a vessel of the delay line
in one recombiner train

reactor building,
process room

BWR, filter vessel withactivated charcoal
belonging to the radiolysis
gas recombiner train

charcoal

self-ignition or
resulting from an
explosion> 08:00

9

Smoldering fire in a preliminary
air filter caused by an electricheater failed to switch off

reactor building, room HVAC / bag filter and finefor off-gas equipment filter located close to theheaterfilter material (organic
bounding of glass fibre andpolypropylene) and organic
materials collected by the filter

electric heater

00:51

spent fuel building,Room for ventilations

85

hot work

Duration[h:min]unknown
01:33

NEA/CSNI/R(2009)6

C-3 FIRE EVENT TREEThe Technical Research Institute of Sweden (SP) has, on behalf of Ringhals AB and NBSG (Nationalfire safety group), studied the OECD FIRE Database in order to assess what further studies can be
conducted in order to improve fire safety efforts in nuclear power plants and gain as much insight as
possible from the Database (cf. [8]). One idea is to develop fire event trees. By studying the Database
and the developed event trees it would be possible to identify some common denominators that exist
for those fire scenarios that have the most severe consequences. One can divide this into two different
studies, one where the denominators are identified based on how severe the fire is, i.e. how large, andone where the impact on the reactor safety is also included (this would then probably be based onwhether the operational mode was changed). The denominators would be expressed e.g. as failure of
the detection system due to:- wrongly designed detection system,- failure to interpret the alarm as an alarm,- other reasons.
These sub-denominators could then also be grouped into other denominators, e.g. a failure to interpretthe alarm as an alarm, identifies something lacking in the organisation and training.
A fire event tree takes a certain starting point, in this case it is that a fire has started and then there is aquestion in each node with an answer “yes” or “no” and a probabilistic value for yes and norespectively. At the far right hand side there is a consequence. From a fire safety engineering
approach, SP suggests fire stop or mitigation mechanism nodes such as:• Fire is self extinguished due to lack of fuel or oxygen;• The fire is detected by an automatic or human system.
• The fire is extinguished by an automatic or manual system.
• The fire is limited to one room due to the construction.
• The fire is limited to one fire cell or fire compartment due to construction.
Similarly, development of the consequences could be conducted as:• Fire and damage contained to starting object,• Fire spread or damage to at least one more object in room,• Loss of one room,• Impact on adjacent rooms within one fire compartment,• Impact on more than one fire compartment,• Structural damage.
A generic event tree with these nodes and consequences will be rather large as the stop and mitigation
mechanism can be active after each of the consequence steps, i.e. a fire can be extinguished either
early on when only one component is damaged or later when several components have been damaged
or even the entire room. It is possible to draw up a specific event tree for each event in the Database.
This is probably of limited value for some of the events in the database as the information is very
limited and some trees would be very similar. Setting up the event trees requires a thorough readthrough of the database and especially the event description. The event trees must take their starting
points from the assumption that a fire has started since the information in the Database is too limited
on how the fire started. A first estimate of probability values to be used at the different nodes in thegeneric fire event tree can be made from the event trees developed from the database. The uncertainty86

NEA/CSNI/R(2009)6
in the probability values needs to be estimated by statistics and the values can be refined as the
database grows.
C-4 SWEDISH TEST APPLICATION FOR DETERMINISTIC DATABASE USE
ES Konsult AB has, on behalf of NBSG (National fire safety group), studied the OECD FIRE
Database in order to get insights in fire scenarios [1]. The study was limited to 42 fires that occurred
between 1990 and 2005 in Swedish NPP. The work was limited to qualitative insights, no statistical
calculations were performed. A review group was made up by representatives from different
categories of profession. The fire protection is built up by a defense in depth strategy including a
number of barriers. The aim was to identify failure of barriers and their root causes. The review was
based on the defense in depth strategy presented in INSAG-10 “Defence in Depth in Nuclear Safety”[11] and also in INSAG-12 “Basic Safety Principles for Nuclear Power Plants” [12]. The method isgraphically presented in the Figure 1 below.

Incident

No fire1st Barrier: “Ignition”
Incipient fire
2nd Barrier: ”Detection”
Small fire
3rd Barrier: ”Suppression”
Fire spreading
4th Barrier: ”Fire cell”
Fire spreading

Figure 1:

Fire defense in depth

The purpose of the analysis was to get answers on following questions:- Are there any recurrent types of fires?
- Are there any problems with detecting fires?
- How did the extinguishing phase work?
- What are the safety consequences?

Results and observations of the study for Swedish NPPs:--

Due to the fire events occurred in Swedish NPPs, the first barrier has been affected. In twocases the initial fire extinguishing failed affecting the third barrier. Fire spreading affecting thefourth barrier has not occurred. However, smoke has spread between fire compartments due todesign weakness of the ventilation systems. None of the fire events reported posed any risk ofradioactive release to the public.
Oil on hot pipes resulted in several fires and was the most frequent fire initiator. The
phenomena are well known and material for insulation is changed to a less flammablematerial.
Electrical failures were the most frequent fire causes. Fires in electrical cabinets are relatively
frequent and often caused by overheated electrical coils.

87

NEA/CSNI/R(2009)6---

Fire detection by automatic means has been working as designed in almost all cases. Some
smaller problems may be identified in fast detection in large rooms such as the turbine hall.
No problems were identified in the fire extinguishing phase, except in two cases including
electrical fires caused by arcing, where the first attempt of fire extinguishing failed. The
selection of extinguishing equipment and the routines of how to deactivate electricalequipment such as bus bars have to be improved.
Some cases of smoke spreading have been identified in the OECD Fire Database. In his
respect, fires with the potential of propagation are of high interest. However, overall
conclusions from these observations cannot be drawn, as fire effects on safety functions andpossibilities for safe shutdown have not yet been analysed in detail.
From the Swedish fire data it can be seen that the co-operation between shift personnel(control room staff) and the local fire department worked well, except for one case related toan electrical fire from arcing.
However, fire does rarely affect reactor safety functions, and the safe shutdown function has
not been jeopardised in any case, as documented in the Swedish fire data. Nevertheless, there
is an example on long decision time before the shutdown order could be executed. As
mentioned before, this study was performed only on Swedish data from the Database;
therefore not all events have been analysed in this respect.

Experience feedback reporting has improved in Sweden, however well documented fire events are still
rare. It was recommended that the OECD FIRE Coding Guidelines could be used as a tool to improvethe event description and the experience feedback.
C-5 COMPARISON OF THE OECD FIRE DATABASE WITH NATIONAL DATABASES(VALIDITY CHECK)

C-5.1 FranceThis section provides the method implemented by IRSN for the evaluation of the fire frequency. The
fires occurred in French NPP have been inventoried and analysed. This inventory has been used todefine the reference numbers permitting to estimate the frequency of fires in a given area of a NPP.
The same methodology, as far as possible, has been applied to the OECD FIRE Database. Then acomparison of the results obtained using the French data and the OECD FIRE Database has been
carried out.
C-5.1.1 Methodology implemented by IRSN for fire frequency estimation
C-5.1.1.1 Inventory of fires
The information collected to establish the Database on those fires which occurred in France in
Pressurised Water Reactors (PWR) covers the period from April 21, 1975 to December 31, 2005. An
analysis of the incidents caused by fires in the French NPP shows that in most cases it is possible toisolate the type of equipment or human intervention representing the origin of the fire. In order tofacilitate the utilisation of operational experience as well as the approach which may be taken toevaluate the frequency of fires, it is better to group the materials of the same type into referencegroups. This will make it possible to have, for each source of ignition, the broadest possible
operational experience, while making the results more reliable. Fires reported in the French NPP
operation were classified into groups. After analysing the operational experience and without entering
into too many details, these groups were separated into sub-groups in order to better represent the risks
of ignition. The equipment or interventions which were the cause of fires are indicated below for the
French nuclear facilities.

88NEA/CSNI/R(2009)6
Electrical equipment
Equipment for conversion of electrical energy:• E1: high tension equipment > 6.6 kV: In this group are the fires which occurred on the equipmentof high power electrical supply such as the Auxiliary Transformer, the Main Transformer, theExtraction Transformer.
• E2: Turbo generator group: All the fires which originate in the turbine generator or in a system
whose operation depends on it are grouped together. This group also includes hydrogen fires
associated with the cooling system of the generator.
• E3: Diesel generator set• E4: Batteries• E5: Low and medium voltage equipment (lower or equal to 6.6 kV): This group is made of fires
which occurred on low and medium voltage equipment: inverters, rectifiers, transformers andelectrical panels (30 V, 48 V, 125 V, 220 V, 230 V, 380 V and 6.6 kV).
E5-1: Inverters
E5-2: RectifiersE5-3: Transformers
E5-4: Electrical switchboards < 6.6 kV
E5-5: 6.6 kV electrical switchboards: All the 6.6 kV electrical panels as well as theircomponents (contactor, circuit breaker, disconnect switch, etc.) are part of this sub-group.
Control-command equipment:• E6: Decentralised control consoles and boxes: In this group are the fires which occurred in thedecentralised control stations in which the terminal block is the main cause of fire.
• E7: Control cabinets (fire detection system cabinet, relaying circuitry cabinet, control cabinet(regulator): The electrical switchboards are not to be considered as cabinets (see group E5). The
cabinets classified in this group are the control, relaying and command cabinets which containmostly electronic components.
Actuators:• E8: Motors (rotating machines other than motor driven pumps and fans) and motorised
valves: The initiating events in this group are broken down into the following sub-groups:
E8-2: Compressors, refrigerating units, and motorised reducers
E8-3: Overhead cranes, elevators and loading machinery
E8-4: Motorised valves
E8-5: Other motors: This sub-group includes all other motors (coils, electromagnets, etc.) not
described above, electric valves, clusters control box, fire dampers, etc.
• E9: Motorised pumps assemblies: In this group are found all the fires which occurred in pumps
powered by an electric motor, except for pumps integrated within refrigerating units, compressors,loading machinery, etc. Except for the specific case of ISBP and EAS (Low Head Safety Injection
and Containment Spray System), motorised pumps whose motor is in a location different from theone of the pump, we shall consider both the pump and its motor as being the cause of the fire. The
origin of the fires is linked to electrical short circuits, to oil leaks on heat insulators or to lack oflubrication.

89

NEA/CSNI/R(2009)6
E9-1: Primary motorised pumps
E9-2: Oil lubricated motorised pumps: From this sub-group the primary motorised pumps are
excluded, because they are classified in the prior group. In this sub-group, we note that the
majority of the fires are due to oil leaking on the hot pump.
E9-3: Motorised pumps not lubricated by oil: This sub-group includes all the pumps lubricatedby grease as well as the non lubricated pumps.
Other cases• E11: Electric heaters, electric resistors: This group includes all the fires which occurred atelectric heaters and electric resistors. Many fires are caused by defective operation of electric
resistors. If the electrical resistor is indeed the origin of the fire, it is still important to note that amalfunction of the control thermostat induced an overheating.
Hydrogen (H2 explosion in a tank, hydrogen leak following a valve repair)• H: Hydrogen (outside of turbo generator group): This group includes the fires caused by a leak ofhydrogen, not including the fires linked to the cooling system of the generator (see group E2).
Hydrogen leaks have the distinction of catching fire spontaneously in air as soon as a sufficientconcentration is reached within an area; this means that each leak is a potential source of fire.
Maintenance work (soldering, grinding, solvent catching fire during a cleaning process)• M: Maintenance: This group includes all the fires which occurred during maintenance, undervarious states of unit operation. Note that the most frequent fires are those where cutting or
soldering work was in progress, generating sparks which ignited flammable materials.
Turbine driven pump
• TP: Turbine driven pump (pumps powered by steam turbines): This group includes fires
which occurred in turbine pump assemblies. The only turbine driven pumps installed in the units
are the turbine pumps supplying steam generators: turbine driven feedwater pumps are turbinedriven auxiliary feedwater pumps.
Fans/blowers (motor or belt of the fan)
• V: Fans (electric motors included): In this group are listed the fires which occurred on air heaters
and fans in ventilation systems. They are all caused by a motor-fan assembly. Very often the motor
overheats and starts the fire.
Table 3 below sums up the constitution of the reference groups.

90

NEA/CSNI/R(2009)6
Table 3: Definition of reference groups
Reference Group

Origin of the Fire (equipment or human activity)
1.Electrical equipment (E)1.1 Equipment for conversion of electrical energy

E1

High voltage equipment > 6.6 kV

E2Turbo generator assembly

E3

Diesel generator set

E4

Batteries

E5

Medium and low voltage equipment lower or equal to 6.6 kV
E5-1

Inverters

E5-2

Rectifiers

E5-3

Transformers

E5-4

electrical switchboard < 6.6 kV

E5-5electrical switchboard 6.6 kV
1.2 Control-command equipment

E6

Cabinets and consoles for decentralised command

E7

Control-command, command-relay and regulation cabinets
1.3 Operators

E8

Motors (rotating machines other than E9-V) and motorised valves
E8-2

compressors, refrigeration units, RAM assemblies and motorised
reducers

E8-3

overhead cranes, elevators and loading machinery

E8-4

motorised valves

E8-5

other motors
Motorised pumps assemblies

E9-2

oil lubricated pumps

E9-3

pumps not oil lubricated

E11Electric heaters, electric resistors

H

2. Hydrogen
3. Human activity

M

Maintenance work (soldering, cutting, ...)

TP

4. Turbine driven pumpsV

5. Fans/Blowers (including electric motors)

From the fire inventory, it is possible to associate with a reference group the number of fires whose
origin is equipment in this group.

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NEA/CSNI/R(2009)6
In addition, the T cumulative time of operation of French pressurised water reactors, from the start ofcommercial operation, can be estimated.
Knowing the number of fires associated with a reference group and the cumulative time definedearlier, we can estimate the FRi frequency of fires associated with this reference group:
FRi = number of fires / T
For equipment in the reference group for which the operational experience does not list any fires, theCHI Square law with a 50 % margin of error was used. This situation is encountered for equipmentthat is not at the origin of fire in the French NPP, but has experienced fire in foreign NPP. The
frequency of the corresponding reference groups is considered and estimated using the relation below:
FRi = 0.7 / T
The following Table 4 shows the FRi reference frequencies associated with each reference group.
Table 4: Frequency of reference groups (FRi)Frequency of Fires for
Reference Groups [/ry]Reference Group
E1: High voltage equipment

1.8 10-2

E2: Turbo generator group (including H2 leak)

4.7 10-2

E3: Diesel generators

1.2 10-2

E4: Batteries

1.4 10-3

E5: Medium and low voltage equipment- E5-1: inverters

7.9

10-3

E5-2: rectifiers

.9

10-3

- E5-3: transformers

5.9

10-3

- E5-4: low voltage electric switchboard (< 6.6 kV)

1.6

10-2

- E5-5:medium voltage electric switchboard (6.6 kV)

1.2 10-2

E6: Decentralised command consoles and cabinets

5.9 10-3

E7: Control/command, relay and regulat. cabinets

1.6 10-2

E8: Motors- E8-2: compressors, refrigeration units, …

5.9

10-3

- E8-3: overhead cranes, elevators, …

•

10-3
.6

- E8-4: motorised valves

1.4 10-3. E8-5: other motors
E9: Motorised pumps groups- E9-1: primary motorised pumps

.8

10-3

- E9-2: oil lubricated motor pumps

.8

10-3

- E9-3: non oil lubricated motor pumps

5.,9 10-3
92

10-3

NEA/CSNI/R(2009)6
E11: Electric heaters, electric resistors

2.6 10-2

H: Hydrogen (not included in turbo generator group)

1.2 10-2

M: Maintenance work
- MP: under power

2.6

10-2

- MA: shut down

6.1 10-2

TP: Turbine driven pumps

9.8 10-3

V: Fans/blowers (including electric motors)

3.3 10-2

C-5.1.1.2 Evaluation of the fire frequency in a given rooma) Plant under poweri. Equipment: To estimate the frequency of fires at a given room we use the frequency of referencegroups and the distribution of the equipment within the facility. We consider the frequency of fires tobe proportional to the number of possible sources of ignition (equipment from the reference group).
Contribution of a reference group to the frequency of fires within a given room: Within areference group i (i = E1, E2...), the reference frequency FRi has been evaluated. If Ni is the number ofpieces of equipment in a room and NTi the number of pieces of equipment from the reference group iin the NPP, the contribution from this reference group to the fire frequency in a room is:

Fi = FRi xNi
NTi

Frequency of fire at a given room: Knowing the contribution from each i reference group, the F1
frequency of fire at a room, due to the equipment, is obtained by adding the contributions of Fi
frequencies from the various groups:

F1 = ΣFi
ii. Human interventions: The number of human interventions in a room being unknown, we have toconsider that their contribution is uniform over the entire NPP. If MP is the reference frequency for aplant under power associated with the human interventions, their contribution to the frequency of fireon a given room is:MP
NL
where NL is the total number of rooms in the plant where the human activities are taking place.
Frequency of fire when unit is under power: When the reactor is under power, the frequency of fire
at a given room is:
FP = F1 +

93

MP
NL

NEA/CSNI/R(2009)6b) Shutdown state
For shutdown states of the reactor, the frequency of fires due to equipment in a given room will beconsidered as proportional to the duration of the considered shutdown. The contribution from theidentifiable equipment is thus:
In this formula, D is the duration of the shutdown state. For estimation of the fire frequency in a room,
the following table can be used.
Table 5: Frequency of fires per reactor year

Plant Under Power in The Given Location: (X)
Number of
Number ofReferen Frequency of
Ignition Sources
Reference FRi Sources ofce
Ignition in the in a 900 MWe
Group
Plant (NTi)Room (Ni)Proportion
Factor
Pi = Ni/NTi

Contribution Due To Identifiable Equipment
-2

8

E2

-2

4.7 101E3

1.2 10-2

3E4

1.4 10-330

E5-1

7.9 10-3

9

E5-2

-3

40

E5-3

-3

5.9 1043

E5-4

2.6 10-284

E5-5

1.2 10-2

7E1

1.8 103.9 10

-3

1475

-2

1706

E8-4

-3

1.4 10130E8-5

1.4 10-3

587

E9-1

9.8 10-3

3

E9-2

-3

41

-3

5.9 10153E11

2.6 10-2473

H

1.2 10-2

210

TP

9.8 10-3

1

V

-2

E6
E7

E9-3

5.9 101.6 109.8 103.3 10208
TOTAL (F1=ΣFi)

94

Frequencyof FireFi = FRi*Pi

NEA/CSNI/R(2009)6

Contribution Due To Maintenance Work, Plant under Power
2.6 10-2

MP:
Maintena
nce under
power

NL: Number of locations
where human interventions

664

Frequency of fire in the given room

Contribution due tomaintenance underpower = MP/NL

3.92 10-5

TOTAL FP =F1+ MP/NL

C-5.1.2 Information deduced from the OECD FIRE Database
For each fire event of the OECD-FIRE Database, the equipment that is at the origin of the fire has
been identified. Then the events compiled in this Database have been distributed on the referencegroups defined in the IRSN fire frequency methodology. This application has been performed for thefire data delivered to the OECD FIRE Project for the observation period from January 1, 2001 to
December 31, 2004. The data of the OECD FIRE Database is sufficient to carry out this application.
Moreover, no additional reference group has been revealed by the data collection of OECD FIRE
Project.
The operation time of the reactors corresponding to this period is actually not provided by the Project,
so it is not possible to estimate the fire frequency of the reference groups. For this reason, only the rateof fire events contained by each referenced group has been estimated. The table below provides theresults obtained.
Table 6 :Fire frequencies of reference groups

Reference Group

Fire Event Rate [%]E1: High voltage equipment

11

E2: Turbo generator group (including H2 leak)

9.6

E3: Diesel generators

2.9

E4: Batteries

0.7

E5: Medium and low voltage equipment- E5-2: rectifiers

1.5- E5-3: transformers

3.7-

E5-4: low voltage electric switchboard (< 6.6 kV)

14- E5-5: medium voltage electric switchboard (= 6.6 kV)

10.3

E7: Control/command, relay and regulat. cabinets
E8: Motors- E8-2: compressors, refrigeration units, …

0.7- E8-4: motorised valves

2.2- E8-5: other motors

2.9

E11: Electric heaters, electric resistors

8.1

H: Hydrogen (not included in turbo generator group)

4.4

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NEA/CSNI/R(2009)6

M: Maintenance work
- MP: under power

8.8- MA: shut down

8.1

TP: Turbine driven pumps
V: Fans/blowers (including electric motors)

2.2This Table 6 shows that the reference groups that have the most important contribution to the fire
frequency are, by decreasing importance:•

Low voltage electrical switchboards,•

High voltage equipment,•

Electrical switchboard of medium voltage (approx. 6.6 kV),•

Turbo-alternator assembly,•

Maintenance works during power operation,•

Maintenance works during shutdown state,•

Electric heaters and the electric resistors.

C-5.1.3 Comparison of the results obtained from the OECD FIRE Database and from the French
operating experience
In order to compare the results based on the French operating experience and the results deduced from
OECD FIRE, the French fire event rate of each reference groups has been estimated. The table below
presents the results obtained.

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NEA/CSNI/R(2009)6
Table 7: French fire event rate of reference groupsOECD FIRE
Fire Event Rate

FrenchFire Event Rate

E1: High voltage equipment

11

4.4

E2: Turbo generator group (including H2 leak)

9.6

11.4

E3: Diesel generators

2.9

3

E4: Batteries

0.7

0- E5-2: rectifiers

1.51…..- E5-3: transformers

3.7

1.5

…..- E5-4: electric switchboard < 6.6 kV

14

6.4

10.3

3

- E8-2: compressors, refrigeration units, etc.

0.7

1.5

- E8-4: motorised valves

2.2

0- E8-5: other motors

2.90E11: Electric heaters, electric resistors

8.1

6.4

H: Hydrogen (not included in turbo generatorgroup)

4.4

3- MP: under power

8.8

6.4

- MA: shutdown

8.1

15.3

2.2

8.4

Reference Group

E5: Medium and low voltage equipment- E5-5: electric switchboard of medium voltage
E8: Motors

M: Maintenance work

V: Fans/blowers (including electric motors)

The table above shows that the list of reference groups having the most significant contribution to
the fire frequency are almost the same in the 2 databases but with a different ranking and somedifferences in the level of the event rate. Generally speaking, the fire event rate of the OECD FIRE
Database is higher for the switchboards and transformers. The most important differences are for thehigh voltage equipment (11% for OECD FIRE and only 4.4% for French operating experience), forthe medium voltage electric switchboard (10.3% for OECD FIRE and 3% for French data). The
contribution of fans is higher in the French operating experience (rate of 8.4 instead of 2.2).
Concerning the motorised valves and the other electric motors, the OECD FIRE Project showsthat an electric motor can be at the origin of a fire. Even if this kind of fire did not occur in a French
NPPs, this initiator cannot be excluded from the Fire PSA. This example shows that, when at national
level there is no operating experience, the international data could be used for the estimation of fire
frequency of the corresponding reference group instead of the CHI square law.

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NEA/CSNI/R(2009)6C-5.1.4 Conclusions
This application shows that the statistical use of the OECD FIRE Database is easy and well
adapted for defining the reference numbers needed for the fire frequency estimation. This data basepermits to know the kind of equipment that can be at the origin of a fire. Each kind of equipment
according to their general design can be put together in families called reference groups. For eachreference group from the Database it is possible to deduce the number of fire events occurred at the
NPP. Knowing the plant operational time of the NPP corresponding to the observation period, the fire
frequency of a reference group can be estimated.
At the time being, this operational time is under estimation by the Project. So, in the future, theestimation of the reference group fire frequencies will be possible. These frequencies, combined withthe data of a NPP (more particularly the number of each piece of equipment), will permit to estimate
the fire frequency in each room of the NPP. The fire frequencies of reference groups will be very
useful for countries whose operating experience feedback is insufficient for a statistical use of fire
events. Even if this operating experience is sufficient, for equipment for which no fire event occurred,
the fire frequency of the corresponding reference group can be very helpful.
C-5.2 USAThis section provides details on the methods used by the United States Nuclear Regulatory
Commission (NRC) in the development and evaluation of fire frequency data. Currently, the NRC isusing two fire events databases supported by U.S. nuclear power plant (NPP) experience. The first
database is essentially the EPRI fire events database, which has had a few additional features added
due to the NUREG/CR-68501 [5] project, and the second is a separate NRC database containing LER
and some smaller fire event data. In the near future, the NRC will be integrating the best features ofeach database to develop a single NRC fire events database. Once NRC has established the new
database, it will compare those frequencies with the OECD FIRE Database frequencies, to the extent
the frequency bins are comparable.
The database used for NUREG/CR-6850 [5] contains data from 1968 to 2000, and that data wasanalysed to determine the fire ignition frequencies. Data was from power operations, and low power,
as long as the lower power operating mode did not affect the likelihood of ignition of a particularcomponent. U.S. data between the years 2000 and 2008 will be collected and analysed. The NRC alsoplans to examine the international OECD FIRE Database for insights which will improve the overall
NRC database. The NRC currently views the OECD FIRE Database program as a very effective
program to better understand international NPP fire events. NUREG/CR-6850 [5] contains the data
used by the NRC and the methods used to collect and analyse this data. This is the primary source of
information and should be referenced for a more detailed understanding of the process developed andimplemented by the U.S. NRC.
With respect to the database, NUREG/CR-6850 [5] developed a classification on which to retain
data for its frequency calculation. Fires which were classified as potentially challenging or
undetermined were retained and counted as one full event and one-half of an event, respectively.
Potentially challenging fires were those which have the potential to become self-sustaining fires thatchallenge plant safety. Practically, these fires had the potential to produce damage beyond theinitiating source, and include fires where personnel intervened to prevent such a consequence fromoccurring. For example, fires which required multiple extinguishers to extinguish the fire wereretained for frequency; fires which were judged severe by heavy smoke were also retained. Of course,
fires which actuated automatic suppression systems or had hose streams applied were kept as well. In
1

EPRI/NRC-RES Fire PRA Methodology for Nuclear Power Facilities, Vols. 1 and 2, Electric Power
Research Institute (EPRI), Palo Alto, CA, and U.S. Nuclear Regulatory Commission Office of Nuclear
Regulatory Research (RES), Rockville, MD. September 2005. (Found at the following web address:
www.nrc.gov/reading-rm/doc-collections/nuregs/contract)98

NEA/CSNI/R(2009)6
some cases, judgment of the event is needed to establish if a fire is potentially challenging, a necessary
limitation due to lack of information for certain events in the database. In cases where a fire may havethe potential to be challenging, but it is difficult to ascertain, a weighting of ½ is given to the fire
event. The full set of criteria for retaining an event for a frequency determination is documented in
NUREG/CR-6850 [5].
Since fire PRAs typically develop fire scenarios from either an ignition source or a set of sources,
the NRC predominantly uses component-based fire ignition frequencies developed in NUREG/CR6850[5]. In this document, a generic set of fire ignition frequencies in units of per reactor year weredeveloped for specific components. A two-stage Bayesian approach has been applied to develop thesefire frequencies to account for plant to plant variability. Such variability occurs from differences inrecord keeping and reporting which affect the content and completeness of reporting. Prior
distributions for this two-stage Bayesian approach were developed by a panel of experts and assumed
a lognormal distribution. The smallest fires possible were assumed to be the lowest distribution’s 5th
percentile; the largest fire frequencies were assigned the 95th percentile; and an error factor of 10 was
assigned. Uncertainty distributions are determined using the R-DAT program, a computer-based
Bayesian reliability, data collection and analysis tool. This prior distribution was updated by the 19682000 data available to produce a posterior distribution. The full characterisation of component
frequency is available in NUREG/CR-6850 [5] and can readily be integrated into an uncertainty
analysis.
Fire frequency for a component is generally assumed the same on a reactor basis. Furthermore,different types of fires can be assumed for certain ignition sources. For example, both electrical and oil
fires can arise from emergency diesel generators and pumps. Formulae for weighting factors have beendeveloped to account for the distribution of frequency within a plant to account for differences in
configuration. For example, factors for maintenance, occupancy, and storage have been developed in
NUREG/CR-6850 [5] to distribute transient fire frequency across the plant.
The approach to counting plant components is also a key factor in distributing the frequency
within the plant. Refinements in applying NUREG/CR-6850 [5] in the counting method have beendeveloped and documented as a part of the U.S. NRC NFPA 805 Frequently-Asked-Questions
program. Although NUREG/CR-6850 [5] provided counting guidance for plant electrical cabinets,
clarifications were needed to ensure that the community as a whole consistently identifies a single
electrical cabinet, and guidance was provided on the means to count outlier configurations as well.
Counting guidance also extends to plant components beyond cabinets, such as transformers andpumps. Finally, a refinement in high energy arcing fault fire frequency has also been documented inthis program, to apportion the majority of fires to medium voltage cabinets to be more consistent withthe damage model for such fires.
NUREG/CR-6850 [5] has identified 37 different classifications of components, or bins. Each bin
has an associated fire frequency. Such a classification is developed to enable the user to distinguish thefire scenario based on the type of fire expected to arise from such a component. For this analysis, thebins used in NUREG/CR-6850 [5] are compared to those used by OECD. Differences in theorganisation and structure of each group’s bins exist. For example, the OECD database has separatebins for High/Medium Voltage Electrical Cabinet and Low Voltage, whereas the NUREG/CR-6850[5] has one general bin, plus a separate bin for high energy arcing fault events. (Note that the U.S.
NRC NFPA 805 FAQ process has established two separate bins for high energy arcing faults fire
frequency in order to align the majority of fires with medium voltage cabinets, consistent with thedamage model in NUREG/CR-6850 [5]) With respect to fires due to transients, or fires from cutting
and welding, NUREG/CR-6850 [5] breaks down these fires into fires from the turbine building andfires from other locations in the plant. Such a distinction is made due to the more numerous activities
related to those sources in the turbine building. The OECD FIRE Database would allow such

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discrimination, but this distinction has not been drawn in the OECD frequency bins2. Main feedwater
pumps are also called out separately in the NUREG/CR-6850 database due to the presence ofsignificant amounts of oil and the potential damage of the fire, whereas the OECD database doesn’t
make such a distinction. Some other bins are similar between the OECD and NUREG/CR-6850 fire
events databases.
Estimates of the fire frequency per year for those events in the OECD FIRE Database is on theorder of 0.1.2 Although higher, the same overall order of magnitude holds for the frequency ofpotentially challenging fires from the NUREG/CR-6850 database. The fire frequency per reactor year
for a BWR or PWR is approximately 0.25 and 0.28, respectively. A comparison of frequencies at agreater resolution is difficult as the frequencies from the NUREG/CR-6850 database are on acomponent level, as opposed to the OECD FIRE Database frequency calculations for a room level.
Extracted tables of fire ignition frequency from NUREG/CR-6850 [5] follow:

2“Proposals for the Future Use of the OECD Fire Database,” Wolfgang Werner (SAC) and Anders Anger(ESKonsult), Presented at the 11th OECD FIRE Meeting, October 2008.

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Table 8: Fire Frequency Bins and Generic Frequencies

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NEA/CSNI/R(2009)6C-6 SWEDISH USE OF "TYPE FIRE"
In Sweden a study “Guidance for pre-incident planning in NPP facilities” [2] has been
performed. Ringhals AB has been a model for this study, but the purpose has been to make the reportapplicable for all NPP in Sweden. The work has been performed in close co-operation with theSwedish NPP and Rescue Services in the nuclear power municipalities Östhammar, Oskarshamn, andVarberg. The plant internal fire brigades at the nuclear power plants have also been involved.
The idea with the emergency planning is to plan the efforts and working steps in order to give theoperational and emergency staff effective support for making decisions and for starting the mission
without delay.
The guidance expressed in the SKI Report 2008:54 [2] gives the readers suggestions on how tocreate a modern pre-incident planning documentation with instructions on how buildings, building
areas, corridors, rooms, equipment can be reached in case of a fire extinguishing situation. It also
includes guidance on what kind of fire extinguishing equipment is recommended to be used indifferent locations and rooms affected in a fire situation.
The pre-incident planning documentation for a NPP is to a large extent created on basis of theidentified and most common type fires and relevancy checked against the information stored in theOECD FIRE Database.
A Report “Pre-incident planning” has been prepared by the Department of Fire Safety
Engineering and Systems Safety of Lund University in Sweden [3]. The aim of this report is toillustrate that a well done pre-planning effectively helps fire fighting in nuclear power plants.
Experiences from this study of fire in nuclear power plants can be used in forthcoming pre-planning.
In a nuclear power plant there are several hazards, which can contribute to complex fire scenarios anddifficult rescue actions for the fire fighters. To cope with these rescue actions, good pre-planning isneeded. Such pre-planning is also demanded by Swedish law.

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Experiences from this study of fires in nuclear power plants can be used in forthcoming preplanning. The background material for this study was the international OECD FIRE Database. The
following issues of the study are:• What is pre-planning?
• Which parts is included in the pre-planning?
• How do you pre-plan in a nuclear power plant?
• Is the OECD FIRE Database a good reference for use in pre-incident planning for NPPs?
A method was created to study the database and the result is presented in diagrams. During thestudy of the database, the content, the functionality and the fields of application were analysed.
Simultaneously with the database study, a literature study of extinguishing equipment was performed.
This study is a theoretical study of extinguishing equipment and it is a complement to use in the preplanning of fires. The result of the study shows that a fire in electrical components is the most frequent
type of fire incident in a nuclear power plant. The study also illustrates that all type of extinguishingequipment in needed depending on what type of fire is to be extinguished. The choice of
extinguishing equipment depends on the type of fire, availability and personnel safety. The analysis of
the Database can also be used to examine the training of the personnel involved.
C-7 EXAMPLES OF IMPORTANT FIRES AND THEIR CONSEQUENCES INCLUDINGEVENTS WITH POTENTIALLY SEVERE CONSEQUENCES
C-7.1 Swedish Examples
In the following, a short summary of a report by SKI (reference [6 9 of the main CSNI report) ona safety significant fire event in a Swedish NPP is given. On July 1, 2005 a fire occurred in anelectrical switchgear room at Forsmark NPP. The cause of the fire is yet to be determined; however
the starting point of the fire was an arc, due to failure in a rectifier inside an electrical cabinet. By theevaluation of the incident it was identified that the pre-fire plans did not provide sufficient information
for making the appropriate decisions. Lessons learned from the fire at Forsmark were that pre-incident
planning was at hand but the information was not sufficient to make the correct initial decisions thatmight be critical for life and property.
The overall aim of the project has been to give general pre-incident planning recommendations
with respect to electrical switchgear room fires, to determine and establish an appropriate delegation
order and clarify the overall responsibility of the fire fighting operation as well as the operation of theplant before, during and after an incident. The project has been funded by NBSG (National fire safetygroup). The report is presented as an SKI Rapport due to the interesting topic and that it is important to
spread the information and lessons learnt to a larger public.
The aim of the SKI report is as follows:•

to clarify the appropriate fire fighting tactics•

and to give recommendations on the type of extinguishing media to be used, based on therisk and consequence of a fire with respect to smoke, radiation, chlorides etc. resulting fromthe extinguishing media.

C-7.2 Czech Examples
First Event “Fire of the station service load transformer …”
The service load transformer 3BT02 exploded, while the unit was operating in mode 1 at 100 %power. The defect occurred due to the failure of the power part of the left branch lines switch. As a103

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result, in a very short time a large volume of gases was generated which caused the explosion of theswitch power part and subsequent rupture of the transformer vessel, ejection of oil in the adjacent area,
and oil fire. The accident led to the discharge of approximately 32 t of oil from the collecting tankunderneath the transformer, and subsequently into the aeration channel and to cable ducts. The event
led to the loss of 400 kV with the subsequent unit transient. This was the most serious event in thehistory of that Czech NPP.
The fire did not spread to the turbine building, because the fire was extinguished on-site by theplant fire brigade. As a result of transformer oil leak and foam fire extinguishing a part of the waste
water purification system was lost and subsequently oil products escaped into the environment (theroot cause was in unsuitable design). The transformer damaged by the explosion was replaced with a
new one.
Event “Self-ignition of hydrogen in a battery car …”
The plant fire brigade received a report about a fire at the outside hydrogen storage Fire wasreported by the shift engineer of the secondary circuit, who heard an emergency call of the worker
who performed manipulations for operational hydrogen make-up in the distribution lines to unit
generators. The fire occurred on the reduction valves box by self-ignition. Pressure bottles were cooled
and the flame was extinguished by water.
Analysis of the event has shown that the fire was caused by incautious manipulation by theworker. Opening o fan incorrect valve led to the burst of a dust blind and subsequently to uncontrolledhydrogen leakage. It was confirmed that if the rate of hydrogen escape is higher than 4 m/s, it selfignites. The hydrogen system is housed in the self-contained, well vented building, sufficiently distantfrom the reactor units. For the reasons mentioned before hydrogen could eventually have exploded.
Safety significance is "Unknown", because of difficult judgment of extent and consequences in theevent of explosion hydrogen.
C-7.3 Spanish Examples
Event “Fire in the Main Turbine Generator Group N.2”
In October 1989, a fire occurred when the NPP was at power operation. The fire affected themain turbine generator group no. 2, due to a failure in the corresponding turbine.
The facts of the fire were that pipes of the turbine lubrication oil system were broken and coolinghydrogen for the alternator was released. The ignition mechanism was, consequently, a hydrogendeflagration. The root cause was a mechanical failure in the rotor of the high pressure turbineAs a consequence of the fire, several components were damaged (burned and marred):
1. Some electric power cables of main auxiliary equipments, necessary for the operation of
turbine driven fans no. 3 and 4;
2. Some electric power cables of the pumps related with RAiE function;
3. Pump motors related with EDOR function;
4. Part of the control and regulation circuits (48 V);
5. Several auxiliary components of the main turbine generator groups no. 1 and 2.
Water and foam were used massively in the fire extinguishing by the fire fighters (both on-siteand external brigades). The elevation “3.5 meters” was flooded by the fire fighting action.
Additionally, demineralised water from EDOR tanks and sea water, due to loss of isolation in theexternal cooling circuit of the condenser, contributed to the flood. Estimated volume of water ranged
from 4,000 to 5,000 cubic meters.

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After the event, several investigations were carried out and subsequent actions took place,
though, in the end, the NPP was shutdown.
Event “Fire in the Alternator Area (Turbine Building), due to the Actuation of a Differential
Protection in the Main Transformer”
In August 2008, a 3-loop Westinghouse PWR plant was operating at 100 % power operation(1055 MWe) when an unplanned reactor shutdown occurred due to a turbine trip.
This turbine trip happened because of the actuation of the differential protection in the maintransformer. The direct cause was an electrical fault (short circuit) in the 21 kV phase “S” of the main
circuit breaker (from the main generator towards the main transformer).
Detection of the fire in the alternator area occurred 8 seconds after the reactor scram, as thedetection alarms from the fire detectors triggered in the area close tohe main generator. The
corresponding fire pump started immediately.
The fire is likely to have started inside the box of bushes of the neutral from the main alternator.
When the differential protection of the main transformer triggered, the phases “R” and “T” cut the
short circuit current but the over-current kept on running through the phase “S”.
The actuation of the on-site fire brigade occurred 2 minutes after the shutdown, by means of the
public address system. The fire extinguishing tasks started 5 minutes later. First, the fire brigade wassent to the transformer area, because it was assumed that the fire was in this area. However, it wasverified that there was no fire in that area, but smoke was coming out from the Turbine Building.
Inside that building, smoke was discovered in the 2 bearings of the alternator, and the extinguishing
was started using all the carbon dioxide extinguishers available in the area and the smoke stopped
coming out. Later, smoke started coming out again from the bearings area of the alternator. It wasnecessary to use water and foam. Then, fire was found in the bushing box of the neutral of the main
generator. After checking that there was no voltage, the fire brigade used water hoses and the fire wasextinguished. In total, 16 people took part in the fire extinguishing (all of them from the plant), and 10of them were professional fire fighters.
The pre-alert emergency was declared at the plant due to the fact that the fire lasted more than 10
minutes, without having affected any safety systems.
The fire was completely extinguished after one hour and a quarter of extinguishing tasks, though
the emergency was maintained. The total duration of the emergency was 1h. 25’.
The fire supposedly damaged the seals of the bush box and, subsequently, caused a hydrogenleakage in the alternator that could be the direct source of the fire.
C-8

JNES APPLICATION TO IGNITION MECHANISM ANALYSISJNES has developed the internal fire PSA methodology and is developing the seismic-induced
fire PSA methodology. Preliminary results from internal fire PSA revealed that the total core damage
frequency of internal fire events might be larger than that of internal events. Then JNES would intend
to enhance the internal fire PSA methodology, in order to evaluate the precise fire risk, to identify
vulnerabilities of structures, systems and components, and to assess the validity of fire prevention andmitigation measures quantitatively.
JNES began to analyse the ignition mechanism of internal fire events that were registered in thedomestic NUCIA Database and in the OECD FIRE Database as a part of methodology enhancement.
The NUCIA Database that is disclosed on the website has been voluntarily developed by the Japan

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Nuclear Technology Institute (JANTI) in co-operation with the Electric Power Companies, andincludes the information of any accidents and incidents with plant data.
Fire events where a component itself was ignited or a component affected by the fire lost its
function were analysed. Fire events due to human error during test and maintenance and events forwhich the ignited component or the fire cause could not be identified were screened out.
The number of fire events analysed was 11 events in NUCIA Database and 41 events in theOECD FIRE Database, where FIRE data was applied if event was overlapped in both Databases. The
analysed events were categorised into seven classes of fire causes in the following Table 9. Thirty-one
events out of 52 (62 %) were related to electric components. Devices that were responsible for fire
were identified in Table 10 and the key fire ignition mechanisms were are explained in Figure 2
through Figure 6.
JNES had analysed the selected fire events for the study of fire initiation mechanism as a firststep of a qualitative analysis on the OECD FIRE Database. Preliminary results were as follows;-

Due to the failure of the device, or to ignition of leaking gas (such as hydrogen) or volatilegas, the fire occurred directly. So, for such kind of fire event, its frequency itself might beconsidered to be a fire frequency.

-

A fire caused by a lubricant required leakage, contact, and heat up as ignition mechanism.

-

All the phenomena analysed here are related to a defective insulation or a poor contact of theconnecting section of the electric device or wiring such as power cable or panel.

Analysis results will be applied to the deterministic fire development analysis, Fire PSA and soon, in phased approach. Collection and analysis of fire events will be performed subsequently toevaluate fire frequencies in the future. For discussing fire severity and fire scenario, a fire intensity
distribution will be assigned to each fire ignition source.
Table 9: Fire Event Classification by Fire Causes

Class

Fire Cause

Number of
EventsA-1

Leakage of current (ground fault) caused by defective insulation orothers of the electric device or wiring

6

A-2

Short circuit caused by defective insulation or others of the electric
device or wiring

16

A-3

Intrusion or adhesion of foreign materials such as dust particles orwater droplets to the connection section of the electric device orwiring5

A-4

Poor contact of the connection section of the electric device or wiring

4

B

Problem of the device

4C

High-temperature section’s contact with oil such as a lubricant oradhesion of such an oil to that section

12

D

Ignition of a leaked gas (such as hydrogen) or volatile gas

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Table 10:Device responsible forfire

Device Contribution to Fire Occurrence
Fire Event Classification

A-1

Inverter

A-2

A-3

A-4

B

X

Air Pre-heater

X

Pump

X

Circuit Breaker

X

Charger

X

Control Valve

X

Rectifier, Storage Battery

X
X

Turbine Generator

X

Diesel Generator

X

Electric Board
Power Cable

X
X

X

X
X

PipingX

Bus DuctX

Heater

X

Fan

X

Valve

X

Motor Control Center

X

X

Motor-Driven Pump

TransformerDX

Gas Circulator (Filter)

Power-Transmission Line

C

X

X

X
X

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X

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Damage of insulators by external forces ordeterioration of insulators by aging

Leakage of current (ground fault) to peripheraldevices caused by defective insulation

Heating caused by increased resistanceArc discharging

Ignition in the heated part when it reaches theignition temperature

Ignition of flammable materialcaused by arc discharging

Figure 2:

Ignition Mechanism of Class A-1

Damage of insulators by external forces ordeterioration of insulators by aging

Short circuit caused by defective insulation

Passing of currents in excess of amounts
allowed for the circuit or wiring (overcurrents)

Arc discharging

Heating of the circuit or wiring

Ignition of flammable materialcaused by arc discharging

Ignition in the heated part when it reaches theignition temperature
Figure 3:

Ignition Mechanism of Class A-2

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Intrusion or adhesion of foreign matters to theconnection section of the electric device orwiringOccurrence and removal of partial discharging
on the insulator surface repeated by adheredmaterial

Spark discharging

Insulation destroyed by occurrence of trucking
phenomenon

Ignition of flammable materialcaused by spark discharging

Short circuit caused by destruction of
insulation

Arc discharging

Passing of currents in excess of amounts
allowed for the circuit or wiring (overcurrents)

Ignition of flammable materialcaused by arc discharging

Heating of the circuit or wiring

Ignition in the heated part when it reaches theignition temperature

Figure 4:

Ignition Mechanism of Class A-3

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Looseness of connection (poor contact) causedby external forces, defective installation, orothers in the electric device or wiring

Intermittent passing of currents in the section
with poor contact

Heating of the section with poor contact

Arc discharging

Ignition in the heated part when it reaches theignition temperature

Ignition of flammable materialcaused by arc discharging

Figure 5:

Ignition Mechanism of Class A-4

Oil leakage from an auxiliary device such as apump or fan

Adhesion of the leaked oil to moistureretentive material, filter, or others

High-temperature section’s contact
with the leaked oil in piping orothersIgnition in the part with oil adhered when it
reaches the ignition temperature

Ignition in the high-temperaturesectionFigure 6:

Ignition Mechanism of Class C

References[1]ES Rapport 2002042:001 “NBSG 09#05 Qualitative analysis of fires in Swedish NPPs”
Year of publication 2006[2]Swedish Nuclear Lnspectoarate (SKI):“Guidance for pre-incident planning in NPP facilities” Summary of SKI Report 2008:54,
2008[3] Lund University, Department of Fire Safety Engineering and Systems Safety:“Pre-incident planning” Report 5272008, Lund, 2008110

NEA/CSNI/R(2009)6
APPENDIX D - DETAILS OF FUTURE APPLICATIONS OF THE OECD FIRE DATABASEThis Appendix contains detailed explanations of some of the issues listed in the report.
D-1 INITIATOR FREQUENCIES
Initiator frequencies are an important input to Fire PSA. Currently they are frequently obtained byanalytical estimates that are rather poorly supported by statistical data, or they are directly obtained
from national databases. Initiator frequencies are either assigned to individual rooms of a certain type,or to certain components. If these initiator frequencies were to be obtained from national databases thesmall amount of observations and the limited observation periods would lead to very large
uncertainties. In practice a screening process is applied to the rooms (or components), at the end ofwhich only rooms or components are retained which are considered significant for PSA purposes.
Initiator frequencies are an important element in this screening process.
The information collected in the OECD FIRE Database represents the reality of fire events observed ina large international population. This provides the basis for estimating “real” initiator frequencies thatcan be used to corroborate or eventually update the frequencies currently used in Fire PSAs.
The OECD FIRE Database provides generic counts of fire occurrences for buildings and various typesof rooms, for example, process rooms or cable rooms/tunnels, and also for components. If the total
operating years of the included plants and the average number of rooms of a given type is known
generic “real” fire initiator frequencies for individual rooms of the specific type can be estimated andused in the PSA analyses.
The “real” frequencies also provide a basis for putting the screening process on a more realistic basis
and simplifying it. In this context it is important to be aware of the existence of different reportinglevels in the countries contributing to the OECD FIRE Database. Coarsely speaking, there is adichotomy into countries reporting all or almost all events, and others that report only events above acertain severity level, for example, only LER events, which means that they report only events with“severe consequences”, for details see Figure 1
Severity ofeventsOECD FIRE Project fire data reporting levels

LER Level

A fire defined by technical specifications or
regulatory rules. A fire will normally be reported
as a LER if it has affected a safety component, or
if the fire have resulted in reactor shutdown, or
if the fire, in some way is defined as a sever fire

Reporting level for US,
SPN, KOR, JPN and GER

Incipient fire level.
Reporting level for CAN,CZE, FIN and SWD

False Alarms

Minor fire level.
Reporting level for FRA

Any fire

Number of
eventsFigure 1: Overview of reporting levels in OECD FIRE member countries111

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Table 1Table 1 shows the number of events collected in the participating countries for the various
reporting levels.
Table 1: Overview of the statistics of events collected in the OECD FIRE Database
Country

No ofreported
eventsObservation
periodEstimated
reactor years[ry]

Reporting level

Canada64

2000-2008132

all events

Czach Republic

12

1991-200846

all events

Finland19

1991-200768

all events

France53

1999-2008548

all events

Sweden102

1981-2007292

all events

Germany

26

1987-2008

449

LER

Japan

10

1976-2008

1293

LER

Korea

2

2003-2008

120

LER

The Netherlands

12006-2008

3

LER

Switzerland

7

1984-2008

125

LER

Spain

24

1987-2008190

all events, but
incomplete

USA

24

1997-2008

1249

LER

Grand Total

344

4515

Total, all events
reported

248

1086

Total, only LER
events reported

96

3429

Propagation and consequences of fire
The OECD FIRE Database also contains information on the propagation of fires after initiation and on
the consequences of fires, including the associated conditional probabilities. These conditional
probabilities obtained from the OECD FIRE Database can be used for comparison with thecorresponding conditional probabilities generated by the computational models in fire PSAs, as
manifested by the fire event trees, thus providing the possibility to check the models' validity.
Definition of “severe consequences”
In the discussion in this proposal of using information from the database for screening purposes
reference is made to the notion “severe consequences”. This is defined as follows:
The plant state is changed from “power operation” to “shutdown” and one or more of the following
options apply:• Structural influence or collapse,• More than one fire compartment affected,• Total loss of one or more rooms,• Two or more trains of one or more safety systems affected,• All trains of a safety system affected.
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D-2

Example for initiator frequencies, based on data in the OECD FIRE Databaseand on preliminary assumptions

The potential results of the proposed activity can be depicted by an example, which is based on the fire
event data currently collected in the OECD FIRE Database for power operation states and on theavailable information on the assumed average operation time factor of 0.85 of the plants included in
the data collection. The activity to collect numbers of individual rooms of certain types is stillongoing. Therefore, estimates of average numbers based on the currently available information areused in the example. These assumed numbers are shown in the bottom rows of Table 2 and Table 3 (inparentheses).
The conclusions presented in the example heavily depend on the estimated numbers of individualrooms used for calculating fire initiator frequencies for rooms. A final decision on the numbers to be
adopted has to be made by the OECD FIRE national co-coordinators, once information from all
countries is available. Currently, information on the room numbers is available from Czech Republic,
Finland, and Sweden, shown in the Tables in Appendix D. As can be seen, the numbers differ widely,making it difficult to define “averages”.
Table 2 is based on information from countries that report all or almost all events, Table 3 on
information from all countries, because it can be assumed with high confidence that all countries with
an elevated reporting level have reported the events with severe consequences.
Table 2 shows an overall fire frequency of approx. 1.0 E-01/ry, and, with the assumed number ofrooms, fire initiator frequencies per room and reactor year in the E-04 range. (The numbers of rooms
still have to be estimated and agreed upon) This is significantly lower than the E-03 range used insome Fire PSA as initiator frequencies for process rooms, switchgear rooms and cable rooms/ducts.
Fires in process rooms, switchgear rooms and cable rooms/ducts typically dominate the fire induced
core damage contribution in Fire PSA. As the calculated core damage frequencies are directly
proportional to the fire initiator frequencies the presented example suggests (with all mentioned
reservations) that the results of some Fire PSA are too conservative.
The comparison of the frequencies per room and reactor year in Table 2 and Table 3 permits toestimate the conditional probability that a fire occurring in a room of a certain type leads to severe
consequences of that fire. These probabilities are, for example:•

Process rooms:

0.02

•

Switchgear rooms:

0.07

•

Rooms for electrical control equipment:

0.025

•

Cable rooms:

0.11

These numbers suggest that fires originating in cable rooms/ducts and switchgear rooms are
significantly more likely to lead to severe consequences than fires originating in other rooms.
Since the populations supporting Table 2 and Table 3 respectively, are relatively small and differ
significantly; the “conclusion” is still not well founded.
In all fire PSAs screening processes are used to eliminate probabilistically insignificant event
sequences, often on basis of cut-off criteria based on fire frequencies for individual rooms andassociated average unavailability’s of safety functions. Other issues like availability of fire detection
and suppression means and fire loads are also considered. Such screening processes are used to avoid
the costly analysis of areas (or components) that are insignificant contributors to core damage.

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The numbers of rooms of certain types are currently collected. The result of this activity will be
estimates of the average number of rooms. This will enable estimates of generic average fire
frequencies for the individual rooms of the types listed in Table 2 and Table 3.
The use of these average frequencies can be two-fold:• Guidance for screening processes to eliminate insignificant event sequences,• Guidance and support to production and review of Fire PSA.
Example of the kind of results that could eventually be obtained:
Based on the provisionally assumed numbers of rooms (shown in parentheses in the bottom rows ofTable 2 and Table 3), the two tables together suggest that process rooms, switchgear rooms and cablerooms/ducts, perhaps with the exception of such rooms in the containment and intake building, should
always be included in a fire PSA, eventually also rooms for electrical control equipment, but rooms inworkshops and offices, battery rooms, storage rooms and rooms for ventilation are candidates forgetting screened out on basis of fire initiator frequencies and the associated average unavailability ofsafety functions. In an existing fire PSA the average unavailability of safety functions is ~ 6.5 E-05.
Assuming 40 rooms each for workshops, offices, battery rooms, storage rooms (empty columns inTable 2) the initiator frequency per room and year is < 2.5 E-05. With the average unavailability 6.5 E05, the core damage contribution from each room is 1.6 E-09.
If fire frequencies for components are the starting point of a fire PSA, analogous methods can be used
to corroborate or improve initiator frequencies for components.

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Table 2: Reported occurrences of fire events in the OECD FIRE Database. Only events from countries reporting all events(no restriction on reporting level) during power operation until 2007
Room Type Process
rooms

Switchgear
rooms

Rooms forelectricalcontrolequipment

Workshop

OfficeBattery
rooms

Cable rooms,
cable ducts

Storagerooms

Rooms forventilation

Other
types of
rooms

Total
EventsFrequency
per ry

5

29

2

3

4

18

Building Type
Turbine building

22

1

Diesel generator
building

01

Auxiliary building

7

Reactor building

3

Containment

1

Electrical building

1

Intake building2

Switchyard

12

Independent
emergency building

1

1

Others

1

Total

39

8

13

1

1

3

Total frequency/ry(989 x 0.85 ry)

4.4 E-02

8.8 E-03

1.05 E-02

1.0 E-03

1.0 E-03

Frequency/(room xry)(number of rooms
assumed)2.3 E-04

1.3 E-04

1.9 E-04

2.5 E-05

(186)

(63)

(54)

(40)

1

2

1

1

1

1

2

1

5
1

4

8

1

1

15
2

3

6
2

1

115

3

4

9

1

5

19

90

3.5E-03

1.0E-03

6E-03

2.3E-02

1.0E-01

2.5 E-05

3.0 E-05

2.5 E-05

6.0 E-05< 7.0 E-05

(40)

(116)

(40)

(~ 100)(> 300)NEA/CSNI/R(2009)6
Table 3: Reported occurrences of fires with severe consequences in the OECD FIRE Database until end of 2007. Severe consequences:(Plant state changes from power operation to shutdown) and (structural influence or collapse, more than one fire compartment affected,
total loss of one or more rooms, two or more trains of one safety system affected, all trains of a safety system affected)
Room Type

Processrooms

Building Type
Turbine building3

Switchgear Rooms forrooms
electricalcontroli1Workshop

OfficeBattery
rooms

Cable rooms,
cable ducts

Storagerooms

Rooms forventilation

Other
types of
rooms

Total

5

1

Diesel generator
buiklding
Auxiliary building
Reactor building
Containment
Electrical building

1

1

2

Intake building
1

1

1

1

2

9

2 E-04chi sq.50%

6.0 E-04

2.6 E-03

Switchyard
Independent
emergency building
Others
Total

3

2

1

1

Total frequency/ry(3891 x 0.85 ry)

9 E-04

6.2 E-04

2.6 E-04

Frequency/(# ofrooms x ry)(number of rooms
assumed)4.8 E-06

1 E-05

4.8 E-06

2.7 E-06

2 E-06<2 E-06

(186)

(63)

(54)

(116)

(~100)(>300)

2 E-04chi sq.50%

2 E-04chi sq.50%

116

2 E-04chisq.50%

3.2 E-04

2 E-04chi sq.50%

NEA/CSNI/R(2009)6

D-3 BRANCH POINT PROBABILITIES FOR FIRE EVENT TREES
A frequently used tool in fire PSAs is the fire event tree. It permits to conveniently track and describe
the sequences resulting from fires. To be successful, corroborated branch point probabilities areneeded at the branch points of the tree. In most existing PSAs the branch point probabilities are only
poorly supported by statistical evidence For the purpose of the proposed activity it is attempted todesign a generic fire event tree and to derive the branch point probabilities from the statisticalevidence in the OECD FIRE Database. Important fire propagation issues for which such probabilities
have to be estimated are listed below.
Branch points:• The fire is detected by an automatic system;• The fire is detected by plant personnel;• Fire is self extinguished due to lack of fuel or oxygen;• The fire is extinguished by an automatic system;• The fire is extinguished by a manual system.
End states of event trees
The ensuing consequences of fires have to be characterised by end states of the event tree(consequence categories), for example:0.

No heat or smoke influence (denoted as “none” in the following)

1.

Fire and damage contained to fire initiating object

2.

Fire spread or damage to at least one more object in room

3.

Loss of one room

4.

Impact on adjacent rooms within one fire compartment

5.

Impact on more than one fire compartment

6.

Structural damage

7.

Impact limited to one safety train

8.

Safety significant impact on safety trains

The various end states of the event tree result from different combinations of successes/failures of fire
detection/fighting activities. Note that the consequence categories are not mutually exclusive, forexample, categories 7 or 8 can occur concurrently with one of the categories 3 to 6).
The estimates of the branch point probabilities (including uncertainties) for the different nodes in thegeneric fire event tree are derived from the Database. The database is now large enough to givereasonable assurance of the credibility of the derived figures. The values can be refined as the
Database grows. In this way the results of fire PSAs can be corroborated or improved.
The structure of the generic event tree derived from the data collected in the OECD FIRE Project andthe estimated branch point probabilities are shown in Figure 2 and Figure 3. The tree structure is a
simplified example, as it does not yet account for fire fighting details like fire source isolation andcontrolled burn-out, and others. Table 4 through Table 7 show the numbers of occurrences of thevarious consequence categories and their conditional probabilities of occurrence, given a fire event for
power generation states and non-power generation states, respectively.

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Note:
Table 4 and Table 5 cannot be compared with Table 3, because in the latter, the additional assumption
is made that the plant went from power generation to shutdown.
As the current update of the Database is not yet complete, these numbers are preliminary.
Nevertheless, they show that the conditional probabilities of fires leading to severe consequences arevery low.
The next step will be the comparison of the OECD FIRE generic event tree and fire event trees used inexisting PSAs.

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NEA/CSNI/R(2009)6
Figure 2:Fire detection
successful

Illustration of potential applications of branch point probabilities for power generation states only
Conditional probability of minor effects (categories 0, 1, 2, 7 in Table 4): 0.932
Conditional probability of severe effects (categories 3 - 6, 8 in Table 5):
0.068

Fire
self-extinguished

Fixed automatic
system available

Fire suppressedby fixed
automatic system

Fire suppressedby manual firefighting (fixed or
portable) Initialattack successful

0.110

Contributions ofminor
consequences(categories
0, 1, 2, 7)

Contributions ofmore severe
consequences (seecategories intables 4 and 5)

1.000

0.110

0.000

0.000

1.000

0.016

0.000

0.000

0.840

0.053

0.160

0.011

0.800

0.020

0.200

0.005

0.960

0.630

0.040

0.022

0.830

0.107

0.170

0.030

Continued innext table

A

0.890

1.000
0.150

↑

0.000

0.850

yes

0.120
0.880
0.710

B

0.290

0.983
0.840

177 events
0.017

↓

no

C

0.160
to tables 4 and 5

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NEA/CSNI/R(2009)6
Figure 3:Fire detection
successful

Illustration of potential applications of branch point probabilities for non-power generation states
Conditional probability of minor effects (categories 0, 1, 2, 7 in Table 6):
0.959
Conditional probability of severe effects (categories 3 - 6, 8 in Table 7):
0.041

Fire selfextinguished

Fixed automatic
system available

Fire suppressedby fixed
automatic system

Fire suppressedby manual firefighting (fixed or
portable) Initialattack successful

0.100

Contributions ofminor
consequences(categories
0, 1, 2, 7)

Contributions ofmore severe
consequences (seecategories intables 6 and 7)

0.820

0.082

0.180

0.018

1.000

0.023

0.000

0.000

Continued in next
table

A

0.900

1.000
0.570

↑

0.000

0.000

0.430

yes

0.046
0.954
1.000

0.850

0.016

0.150

0.003

0.000

0.000

0.000

0.000

0.950

0.750

0.050

0.050

1.000

0.050

0.000

0.000

B

0.000

0.983
0.930

166 events
0.017

↓

no

C

0.070
to tables 6 and 7

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NEA/CSNI/R(2009)6
Table 4: Numbers of occurrences of fire events in specific consequence categories for power generation only
Consequences

A

B

C

D

Sum
(contains double
counts)0 None

9

7

29

1

46

1 Fire and damage contained to fire initiating object

11

10

73

2

96

1

20

21

1

1

2

3

3

3

1

2

3

3

26

1

2

24

158

2 Fire spread to at least one more object in room
3 Loss of one room
4 Impact on adjacent rooms in one fire compartment

1

5 Impact on more than one fire compartment
6 Structural damage
7 Impact is limited to only one safety train(partly double count, coincidence with 0, 1, 2)

6

8 Safety significant impact on safety trains(partly double count, coincidence with 3, 4, 5 or 6)
Total (contains double counts)

26

121

1

36
3

4

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NEA/CSNI/R(2009)6
Table 5: Conditional probabilities of occurrences of specific consequence categories, given a fire event for power generation only
Note: events are not mutually exclusive
Consequence

A

B

C

D

Sum

0 None

0.05

0.039

0.164

0.005

0.226

1 Fire and damage contained to fire initiating object

0.06

0.056

0.412

0.011

0.54

0.005

0.11

0.118

0.005

0.005

0.011

0.016

0.015

0.016

0.005

0.011

0.015

0.033 0.017

0.147

0.005

0.011

2 Fire spread to at least one more object in room
3 Loss of one room
4 Impact on adjacent rooms in one fire compartment

0.005

5 Impact on more than one fire compartment
6 Structural damage
7 Impact is limited to only one safety train(partly double count, coincidence with 0,1,2)
8 Safety significant impact on safety trains(partly double count, coincidence with 3, 4, 5 or 6)

122

0.005

0.20
0.016

NEA/CSNI/R(2009)6
Table 6: Numbers of occurrences of fire events in specific consequence categories for non-power generation
Consequences

A

B

C

0 None11

156

1 Fire and damage contained to fire initiating object

5

5

71

2 Fire spread to at least one more object in room2

3 Loss of one room

D

68
2

9

1
2

5 Impact on more than one fire compartment

2

1

1

6 Structural damage
7 Impact is limited to only one safety train(partly double count, coincidence with 0,1,2)

1

1

8 Safety significant impact on safety trains(partly double count, coincidence with 3, 4, 5 or 6)
Total (contains double counts)

20

123

83
11

1

4 Impact on adjacent rooms in one fire compartment

Sum(contains
double counts)

8

1

1

5

7

2

2

146

2

176

NEA/CSNI/R(2009)6

Table 7: Conditional probabilities of occurrences of specific consequence categories, given a fire event for non-power generation
Consequences

A

B

0 None0.065 0.03

1 Fire and damage contained to fire initiating object

0.03

2 Fire spread to at least one more object in room

0.012

3 Loss of one room

C

0.012
0.054

0.006

0.006

6 Structural damage

0.006 0.006

8 Safety significant impact on safety trains(partly double count, coincidence with 3, 4, 5 or 6)

0.066

0.012
0.006

0.006

7 Impact is limited to only one safety train(partly double count, coincidence with 0,1,2)

0.497

0.006
0.012

5 Impact on more than one fire compartment

Sum

0.406

0.012

4 Impact on adjacent rooms in one fire compartment

D

0.006
0.042
0.012

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NEA/CSNI/R(2009)6

D-4

IDENTIFICATION OF SCENARIOS TYPICAL OF FIRES LEADING TO SEVERECONSEQUENCES

By studying the OECD FIRE Database and the developed event trees, commonalties potentiallyexisting for the fire scenarios with the most severe consequences can be examined. The commonalties
could consist of failures of detection systems due to:- wrongly designed detection system,- failure to interpret the alarm as an alarm,- other reasons;or deficiencies of fire fighting activities due to:- equipment failures,- misinterpretation of the situation,- faulty fire fighting strategy,- inadequate training of the fire fighting crew.
D-5 HOW DO FIRE EFFECTS SPREAD TO OTHER COMPARTMENTS
The aim of this application is to identify fire barrier elements (walls, fire doors, fire dampers, etc.)
whose integrity was degraded by fires (such that flames occurred on both sides of the fire barrier).
Smoke spreading across fire barriers is not considered. If a failure of a fire barrier is identified itshould be examined what kind of barrier did fail and how this happened (e.g. by a door left open, or bya cable penetration seal not being functional after installation works).
According to the Coding Guideline, the events of interest for the analysts can be filtered by field 3.4.2(Heat or hot gas influence), where the field must be coded “More than one fire compartment affected”
or “Structural influence or collapse” (see the Coding Guidelines as provided in Appendix A).
Table 8: Coding of fire spreading
Identify the influence due to heat or hot gases on systems andcomponents. Use specified codes. If feasible, identify the names of
SSC s affected by the fire,

Code
Codes

Definitions

None

No components took damage from the heat developed by the fire.

Limited to a single
component

One component (main) has been damaged by the fire (a breaker, apump).

Multiple component
fire in one room

Part of a room is destroyed (e.g. a complete electrical cabinet) or
several components in a room.

Total loss of one room

Significant damaged in a room up to total damage of one room

Adjacent rooms wereaffected

In addition, it may be also useful to include in the field the pathwayof hot gas propagation. Components have been destroyed in tworooms due to the fire. The fire did not spread beyond the firecompartment.

More than one firecompartment affected.

The fire has spread between fire compartments. (Loss of a firebarrier or degradation of fire barriers, not only complete failures)

Structural influence or Structural influence or collapse of building structure
collapse
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The field must be coded with “More than one fire compartment affected” or possibly “Structural
influence or collapse”. From the 315 events of the 2008 version of the Database CD there are four
events for each of the two codes mentioned above.
Results for coding “More than one fire compartment affected”:“Maintenance oversight in transformer 6.9/0.4 kV T5AB3 (star point in low voltage side was left
disconnected) that caused damage to some components”
No loss of a fire barrier or degradation of fire barriers. Instead the fire was ignited at three different
locations by an electrical failure.
“A and B protection on 230 kV ring breaker damaged from fire”
The fire occurred in the station A switchyard relay building cable trench. Any fire spread in othercompartments or degradation of fire barriers is not recorded in the event description.
“Safety relevant cable fire”
This event occurred in the Greifswald NPP in 1975, being located in the former German Democratic
Republic. The fire was ignited by a short circuit on a 6 kV cable that lasted for about 7.5 minutes andoverheated the cable over a distance of about 120 m. After ignition of the power cable the fire spreadover the whole cable tray also destroying other power and control cables.
The 6 kV cable was located in an intermediate building which was situated between the reactor
building and the turbine building. The fire occurred in the intermediate building, the turbine building
and the outside the turbine building at the offsite transformer RT1. It is mentioned that fire barriers in
the turbine building were degraded during the event – the fire-rating of them is not reported. It is notrecorded whether the fire spread through barriers or did ignite separately at different locations due thepowerful long lasting ignition source.
“Fire in an electrical cabinet …”
The event description shows that the fire did not degrade any fire barriers. Instead components ofredundant trains in the same room have been affected by smoke and chloride. The coding should bechecked. and might be improved to “Multiple component fire in one room”.
Results for coding “Structural influence or collapse”:“Fire (explosion like) in local transformer …”
The fire ignited at a local transformer and spread by leaking oil via the sand bed to the cabinet of themain transformer. Both transformers were located outside the plant in the same concrete structure
which has no roof and which has a concrete separation between both transformers. Damage ofconcrete structures is not reported. The local transformer was completely destroyed by an explosion at
the beginning of the event. The explosion is assumed to have also destroyed a cable penetration to theturbine building. The fire rating of the cable penetration is not reported. Smoke leaked into the turbine
building via the cable penetration.
“Structural influence or collapse” is not reported in the event description. The Coding Guideline might
be extended to distinguish between “Structural damage” and “Damage of fire barriers”.
“Fire in main turbine-generator group no. 2 and flooding of the cellar”
Turbine lubrication oil and cooling hydrogen were released and first ignited and then ignited or
destroyed electrical cables and other components. “Structural influence or collapse or building
structure” is not reported in the event description. The coding might be a lapse or might refer to areported “loss of insulation in the external cooling circuit of the condenser” which resulted into waterleaking out of some tanks causing a flood.

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NEA/CSNI/R(2009)6“Fire in turbine hall, room D1.80. Lubrication oil for turbine bearings caught fire. There were someindications of turbine bearing damage”
Lubrication oil for turbine bearings was released through a 12 mm oil pipe which was broken. The oilcaught fire. In the event description it is reported that “there were some indications of turbine bearing
damage”, however it is not reported whether this was confirmed and whether the assumed damage
came from the fire or from missing lubrication due to the broken pipe. A “Structural influence orcollapse of building structure” is not reported in the event description.
“Isolation material in roof caught fire”
The event occurred 1977 during the construction phase of the NPP. The roof of the diesel generator
building was set on fire by the diesel generator exhaust piping. After structural modifications havebeen undertaken this type of events can be ruled out.
D-6 OUTLOOK ON FURTHER STATISTICAL AND OPERATION EXPERIENCE USE
The OECD FIRE Database can be used statistically not only for assessing fire detection andsuppression means. It also should be able to provide more information on incipient /pilot) fires, theircauses, effects and frequency.
One further goal of the Database is to gain more and more reliable insights in the fire propagation
pathways, the propagation of flames, heat, smoke and soot inside the fire compartment as well as toother compartments and/or fire cells including their corresponding probabilities.
In the future, it should be possible to estimate how small fires grow to large ones. From viewpoint of
the nuclear safety it will be essential to find out from the Database the contributions of changes in theplant operational mode, of reactor trips due to fire and all the further impact on the plant safety.
Further deterministic as well as probabilistic applications of the OECD FIRE Database may become
obvious with the continuously increasing amount of events in the Database.

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APPENDIX E – OECD FIRE DATABASE MEMBERS
Member Country

Institution

National Co-coordinator
Name

Canada

CNSC

Grant Czerkas

Czech Republic

NRI Rez

Ladislav Kolar & Milan Patrick

Finland

STUK

Jouko Marttila & Matti Lehto

FranceIRSN

Remy Bertrand & Karine Delalande-Pelissier

Germany

GRS

Marina Roewekamp

Japan

JNES

Yusuke Kasagawa & Katsunori Ogura

Korea

KINS

Jong Seuk Park

The Netherlands

MVROM

Arend Rooseboom

Spain

CSN

Francisco Olivar

SwedenSSM

Ralph Nyman

Switzerland

ENSI

Annette Ramezanian

United States

NRC

J.S. Hyslop
Operating Agent

Institution

Name

ESKonsult AB

Anders Angner

SAC

Wolfgang Werner
OECD/NEA Secretary

Institution
NEA / NSD

NameJean Gauvain

128