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The Methodology of IRSN Fire PSA

June 16 th 2014 By Fabienne NICOLEAU Nuclear Safety Division (PSN) Systems and Risk Assessment Department. The Methodology of IRSN Fire PSA. Contents. Introduction Method Input data Selection of Critical Rooms Modeling and quantification of fire scenarios Modeling with RiskSpectrum

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The Methodology of IRSN Fire PSA

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  1. June 16th 2014 By Fabienne NICOLEAU Nuclear Safety Division (PSN) Systems and Risk Assessment Department The Methodology of IRSN Fire PSA

  2. Contents Introduction Method Input data Selection of Critical Rooms Modeling and quantification of fire scenarios Modeling with RiskSpectrum Fire simulation with SYLVIA Use of research and development

  3. Introduction Context of the IRSN Fire PSA for 1300 MWe NPP The Third Periodic Safety Review of these plants in 2010 Analysis by IRSN (TSO) of the licensee Fire PSA for 1300 MWe NPP In French Regulation : The reference PSA study : licensee The objective of the IRSN PSA is to support the analysis of the reference PSA study Experience feedback from the IRSN Fire PSA for 900 MWe NPP Improved method to select the important rooms Less conservative critical temperature criteria The effects of soot or pressure which were not considered for 900 MWe will be assessed for 1300 MWe

  4. First step Critical room’s selection - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Second step Init frequency Operating experience feedback Fire simulation Fire scenario Compare duration Quantification of frequency of fire scenario - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Third step Modeling and quantification of core damage Results Method of the Fire PSA R&D

  5. Input Data for the Fire PSA for 1300MWe (1/2) Needs of a lot of data for fire scenario modeling, fire simulation and functional analysis For critical rooms and their adjacent rooms to take fire spreading into account: Compartment geometry Ventilation conditions Fire protection devices: fire dampers, fire extinguishing system, automatic detection Components and cables Structure of component (type, dimension, position of penetrations) Electrical trains A or B and location in a room; cables position Characteristics, number of connectors, components the cable is connected to, Specific data about panels and control desks of Control Room

  6. Input Data for the Fire PSA for 1300MWe (2/2) • IRSN fire database : FeuxREP (Fire PWR) • From 1975 to 2005 EDF operating experience (1180 reactor x years ) • More than 600 fire events, all plant operating states • 489 init fire studied in the Fire PSA for 1300 MWe NPP • Available data • Origin of the fire, type of detection • Chronology of event, intervention time • Impact on equipments, consequences on safety • Used to develop statistical parameters : • Fire frequency of equipments • Failure rate of fire protection systems (e.g fire dampers) • Delay of the intervention team to extinguish a fire • Human factors (e.g. operating, intervention, etc … ) • Design and operation data collected by :  • Official request by the Nuclear Safety Authority at the studied NPP for specific and technical data • Walkdown on plant

  7. Selection of Critical Rooms • Identification of the safety targets • A target is a component or a mitigation component whose failure contributes to the core damage • Choice by sensitivity studies : Importance calculations on the level 1 PSA model (Risk Spectrum) to determine components whose failure leads to an initiator event of level 1 PSA : • Risk Achievement Worth (RAW) or Risk Increase Factor (RIF) • Fussel-Vesely (F&V) • Pre-selection of Critical Rooms • A Critical Room is a compartment : • Which contains targets • Which is adjacent to a compartment which contains target • With components whose failure leads to the loss of targets • Visit of NPP • To verify the risk of fire in the selected Critical Rooms • Selection of 27 rooms as critical rooms • Electrical Building (Cable rooms, 6.6kV Electrical switchboard room, Electrical switchboard rooms lower than 6.6kV, Controbloc of electrical trains A and B, Relay room of Controbloc, electrical trains A and B, Batteries rooms of electrical cabinet, Control Room)

  8. Modeling and quantification of fire scenarios • Example of an event tree of fire scenario • Event tree adapted to • Fire fighting features and operating organization • Procedures implemented in each room of French NPP • Quantification • Frequency of fire scenario with same consequence • Duration of fire scenario

  9. Modeling with RiskSpectrum • Three event trees • Fire scenario • Intermediate event tree for success or not of FAI-Op • Adapted event tree of 1300 MWe level 1 PSA • With RiskSpectrum • Quantification of dependencies between events is automatic (Boolean fusion) • Input or output of each event tree: by consequence • Sum of the frequencies of fire scenarios with same consequences in terms of loss of components and cables

  10. Fire simulation with “SYLVIA” (IRSN two-zone modeling code) • To identify damaged components located • in the adjacent room by simulating fire • of electrical cabinet or battery or cables • Estimates in critical room and adjacent • room • Pressure • Temperature • Concentration in carbon • Failure time of various safety related • component • Damage Criteria • Temperature • Soot • Comparison between failure time and the duration of fire scenario • If the failure time is lower than the fire scenario duration and if damage criteria are reached : the component is lost • Definition of the consequence by fire scenario

  11. Exposure room Hot source Transfert dispositif Electric plateform Use of R&D (1/3) • First experiment called “Cathode” (analytic test) • Contents : estimate critical temperature and define curve with duration of exposition by different critical temperature • Tests performed to assess the heat effects on electrical components of a 1300 MWe NPP switchboard • Components most affected by temperature: • 2 electronic relays • 1 circuit breaker • The components are lost at a • temperature higher than the • value of the damage • temperature chosen in fire • PSA for 900 MWe NPP

  12. Use of R&D (2/3) • Second experiment called “Cathode soot” (real scale test) • Four tests performed to assess the soot effects on relay components of a 1300 MWe NPP switchboard • Diva Experimental Device at Cadarache • The relay is located in the fire room at 2 heights : 0.55 and 1.8 meters • Fire of electrical cabinet

  13. Use of R&D (3/3) • Results from the second experiment “Cathode Soot” • Components are lost at a temperature lower than the temperature estimated in the first experiment “Cathode” • For safety analysis : take value of damage temperature less than the temperature found in the analytic test • Preliminary results • The malfunction of component seems generated by combination of two or more parameters (temperature, soot concentration) • The malfunction of the relay is found for the same temperature and same soot concentration • Comparison between the four tests: value of different parameters at each failure time (curve: temperature by soot concentration) • Perspective: New experiments • Objective: Verify our assumptions • Test the impact of combined soot and temperature effects on the 1300 MWe NPP switchboard relays • The relay will be exposed at different value of soot and temperature to verify the real scale test and to complete the failure curve (temperature by soot)

  14. LC 0702 LGB, LGE LD 0701 LGA, LGD LD 0702 LHA, LGC, LLA, LLI Application of FIRE PSA (1/3) • Ajout d’une porte coupe-feu entre deux locaux critiques • Local critique : LD 0701 • Contenant les tableaux électriques de puissance file A • Local adjacent LC 0702 contenant les tableaux électriques alimentant la voie B • Local adjacent LD 0702 contenant les tableaux électriques alimentant la voie A • But : Impact sur la fréquence de fusion du cœur

  15. Application of FIRE PSA(2/3) • Ajout d’une porte coupe-feu entre deux locaux critiques • Conséquences sur l’ADE des scénarios d’incendie • Mission supplémentaire pour prendre en compte la sectorisation • Nouvelles conséquences à considérer • Résultats • LD 0701 : fréquence de fusion du cœur a diminué de 69 % • Les tableaux électriques dans le local LC 0702 ne sont pas perdus quand la mission « sectorisation » de l’ADE est en succès • LC 0702 : fréquence de fusion du cœur a diminué de 74 % • Les tableaux électriques dans le local LD 0701 ne sont pas perdus quand la mission « sectorisation » de l’ADE est en succès • La fréquence totale de fusion du cœur diminue de 50 %

  16. Application of FIRE PSA (3/3) • Autres applications • Incident de CHINON (1998) • Analyses fonctionnelles sur les conséquences potentielles d’une explosion hydrogène sur le RCV • Participation à la demande de mise en place des CCF (PAI) • Etude de sensibilité sur la fiabilité des CCF • Groupes Permanents • GP incendie (novembre 2002) – Examen de l’étude sur la salle de commande • GP thématique VD3 900 MWe (2005) – Examen des séquences dominantes de l’EPS_Incendie • GP EPS de niveau 1 (2012) - Réexamen de sûreté dans le cadre des VD3 1300 MWe • EDF s’est engagé à réaliser des études de sensibilité (température de dysfonctionnement, modélisation du foyer, application de la FAIOp,…) • GP EPS de niveau 1 pour l’EPR (DMES), N4 (VD2) et 900 (VD4)

  17. Example for the development of FPSA (1/7) • Presentation of the Compartment ROOM1 • Regroupement de 3 locaux étudiés sous la forme d’un seul local car séparation physique partielle entre les locaux (propagation) • Equipements électriques (transformateurs, tableaux électriques, chargeurs-redresseurs,…) et câbles électriques de la voie A • Caracteristic of the compartment • Situé au niveau 7 m du bâtiment électrique (BL+BW) • Surface totale : 200 m² • Ventilation assurée par le DVL voie A avec un taux de renouvellement horaire de 11 r/h • Clapets coupe-feu 2 heures installés dans les gaines de ventilation de soufflage et d’extraction • Portes coupe-feu • Système de détection automatique • Pas de système d’extinction fixe de type sprinklage

  18. Tableau LDA Tableau LCC Tableau LNE Gaines de ventilation Tableau LCA Tableau LLC Portes coupe-feu Tableau LAA Tableau LBJ Tableau LKB Tableau LBA Tablettes de câbles Example for the development of FPSA (1/7) • Presentation of compartment ROOM1

  19. Portes pare-flamme 1h Example for the development of FPSA (1/7) • Presentation of adjacent compartment Portes coupe-feu 1h30 ROOM1

  20. Example for the development of FPSA (1/7) Fire scenarios without spreading (AdE) Fire Simulation with SYLVIA Scenarios with failure of componant

  21. Example for the development of FPSA (1/7) Naissance incendie Détection automatique Détection locale Extinction rapide Arrêt ventilation Extinction E2I Extinction pompiers Sectorisation Fréquence Conséq 6 min Sc 1 3,2.10-5 13 min Sc 2 6,3.10-6 2,0.10-6 Sc 3 47 min 1,1.10-7 >90 min Sc 4 Success . . . . . . . . . SPREADING Failure

  22. Example for the development of FPSA (1/7) • Adapted of Event tree of level 1 « internal event » PSA in case of fire Perte de source électrique Mission 1 Mission 2 Mission 3 Mission 4 Conséquences Cœur sauf Prise en compte des équipements perdus par l’incendie et quantification du FH Cœur dégradé 3,5.10-7 Cœur sauf Cœur dégradé 2,7.10-7 Cœur dégradé 4,2.10-7 Cœur dégradé 5,5.10-7

  23. Example for the development of FPSA (1/7) • Results for the compartment ROOM1 2,1

  24. Conclusion • EPS = pas seulement une quantification du risque • Démarche structurante des scénarios incendies, prise en compte des missions FH, systèmes… • plus exhaustif • Capitalisation de connaissances • Besoin de R&D • Coopération entre plusieurs unités et domaines de compétences • R&D incendie • Modélisation incendie • Conduite • Systèmes (électriques, mécaniques,…)

  25. Conclusion • Exemples de retombées concrètes sur la conception et l’exploitation • Modifications sur REP • Détection ponctuelle interne dans certaines armoires électriques pour les REP de 900 MWe • Bouton TPL « Tourner-Pousser-Lumineux » en salle de commande pour la baie Controbloc évitant l’ouverture intempestive de la soupape SEBIM du pressuriseur en cas d’agression de la baie par un incendie • EDF va faire évoluer sa documentation de conduite, dans le cadre du dossier d’amendement VD3 1300, pour que la « bonne pratique », qui consiste à consulter au plus tôt la fiche « Mesures » de la FAIOp et en tout état de cause avant que le feu soit confirmé par le chef des secours, soit prescrite

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