1. From the “Le Blayais NPP” flooding in 1999 to the review of French regulation for the protection of nuclear installations against external flooding BgNS International Conference “NUCLEAR POWER FOR THE PEOPLE” 26 – 29 September 2010, Nesebar, Bulgaria By Patricia DUPUY, IRSN

2. 2 INTRODUCTION Flooding event at “Le Blayais” NPP in 1999 Description, lessons learned “Le Blayais” flooding follows-up Review of the protection of all operating NPPs against external flooding Review of French regulation: preparation of a “Guide” on external flooding Conclusion INTRODUCTION BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria

3. 3 FRENCH CONTEXT – NPPs LOCATION NPPs location: 14 river NPPs 4 coastal NPPs 1 estuarine NPP A single utility: EDF (Electricité de France) NPPs BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria

4. 4 1999 Storm « « Le Blayais » NPP partial flooding Safety Eqpts Nuclear island High water level (high tide + storm surge) + waves (generated by the wind) in the estuary  Important water volumes over the dykes  Site and buildings flooding “LE BLAYAIS” NPP FLOODING in 1999 BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria

5. 5 Water ingress from surrounding flooded swamp through an access road DESCRIPTION OF THE FLOODING EVENT (1/3) Water ingress in trenches through unleaktigh metalic plates Water ingress in trenches through concrete panels Dykes “LE BLAYAIS” NPP FLOODING in 1999 BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria Waves

6. 6 DESCRIPTION OF THE FLOODING EVENT (2/3) Water progression in Unit 1 Fire door burst open Galleries flooded Damaged electrical penetration in the unit 1 Fuel Building basement Water ingress through pipes penetrations into the Fuel building basements Some rooms flooded into the « pumping station » building To unit 2 “LE BLAYAIS” NPP FLOODING in 1999

7. 7 12 Some components of safety systems flooded in units 1&2 2 essential service water pumps of train A (unit 1) 2 low head safety inject. pumps and 2 containment spray pumps (units 1&2) Not much water in units 3&4 Pumping station “LE BLAYAIS” NPP FLOODING in 1999 DESCRIPTION OF THE FLOODING EVENT (3/3) STATE OF UNITS 1-2 AFTER FLOODING

8. 8 PROBLEMS IDENTIFIED DURING « LE BLAYAIS » FLOODING Severe storm-driven waves coincident with high estuary level exceeded the worst-case “design scenario” Flooding hazards considered in the design Insufficient level and shape of the dykes Insufficient protection of the rooms containing safety equipment Difficulties to detect water in affected rooms Inadequate warning system All units affected, on-site organization difficulties Protection means defined at the design and operation stages Temporary site inaccessibility (blocked roadways) Partial temporary loss of offsite power supplies Clogging-up of filters of the water intake Effects of the storm on the NPP’s support functions and surroundings “LE BLAYAIS” NPP FLOODING in 1999 BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria

9. 9 OVERVIEW OF « LE BLAYAIS » FLOODING FOLLOWS-UP « Le Blayais » flooding Short-term actions: - at Le Blayais - at other NPPs Review of the protection of all NPPs against ext. flooding « REX Blayais methodology » (2001) Application of the methodology to NPPs: Many modifications and improvements at all NPPs Need for a new Guide on protection of nuclear installations against ext. Flooding Working Group (2006-2009) “LE BLAYAIS” NPP FLOODING FOLLOWS-UP BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria

10. 10 REVIEW OF THE PROTECTION OF NPPs AGAINST EXTERNAL FLOODING REVIEW OF THE PROTECTION OF EXISTING NPPs AGAINST EXTERNAL FLOODING: METHODOLOGY Identification of all phenomena which can generate a flood of any of the 19 French NPP sites Characterization of flooding hazards Flooding hazards Identification of the equipments to be protected Review of the existing protection means (structures, devices, procedures, organization) Modifications and improvements if needed Protection means Analysis of the risks of site inaccessibility, loss of offsite power supplies / heat sink / communications Provisions defined to avoid them or to cope with them Flooding effects on NPP’s support functions and surroundings BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria

11. 11 Water retaining structures Canal Atmosphere Circuits Equipments River Estuary Sea Water retaining structures Groundwater (1) (2) (3) (4) (5) Prior to “Le Blayais” event : Basic Safety Rule (BSR) that defines requirements for river/estuary/marine water levels to consider in the design of French NPP (DBF) (1) River flood, (2) Dam failure, (3) Tide, (4) Storm surge and (5) Tsunami Flooding hazards BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria

12. 12 New methodology: 8 “complementary” phenomena (13) (11)(12) (10) (9) Water retaining structures Canal Atmosphere Circuits Equipments River Estuary Sea Water retaining structures Groundwater (1) (2) (3) (4) (5) (6) (7) (7) (6) Wind-waves on sea (7) Wind-waves on river or channel (13) Groundwater rising (11) Rainfalls on site, brief and intense (12) Rainfalls on site, regular and continuous (10) Circuits or equipments failure (9) Water retaining structures (other than dams) deterioration (8) Swelling due to operation on valves or pumps (8) Flooding hazards BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria + some combinations of phenomena considered

13. 13 Protection means Site protection REVIEW OF THE PROTECTION OF NPPs AGAINST EXTERNAL FLOODING Protection structures/devices reviewed: type, height, margins, settling, stability, safety classification, seismic resistance, power- supply, maintenance … Le Blayais dykes Protection against swelling (canal) raised extendedreinforced…)  Modifications/Improvements at many sites (dykes/walls raised or extended or reinforced…) BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria

14. 14 Protection means Protection of sensitive rooms/equipments (1/2) REVIEW OF THE PROTECTION OF NPPs AGAINST EXTERNAL FLOODING Additional flood hazards (rainfalls, groundwater rising…) Water level At all NPPs, including the substructures of the buildings sheltering equipments to be protected Depending on the sites vulnerabilities, including superstructures up to the required protection level  Definition of a compact “watertight area” BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria

15. 15 EX: Qualified material to plug the waterpaths and penetrations REVIEW OF THE PROTECTION OF NPPs AGAINST EXTERNAL FLOODING + Provisions to prevent water ingress into the watertight area:  Water paths plugged with qualified material  Provisions to close potential ways of bypassing quickly if opened  Mobile pumps and detection means in case of residual leakage ... Protection means Protection of sensitive rooms/equipments (2/2) BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria

16. 16 Protection means Warning system, « flooding » procedure REVIEW OF THE PROTECTION OF NPPs AGAINST EXTERNAL FLOODING T0 Stand-by phase Vigilance phase (early actions) Early warning phase (site protection preparedness) Alert phase (  safe state) T0–12h T0–24h Warning system associated to a “flooding” procedure, to prepare the site protection during the warning phases Warning systems for predictable hazards: graduated phases depending on site vulnerabilities BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria

17. 17 - 17 REVIEW OF THE PROTECTION OF NPPs AGAINST EXTERNAL FLOODING Flooding effects on NPP’s support functions and surroundings Adaptation of the on-site emergency organization:  All units might be affected and require staff/material resources  The site might be “isolated” Analysis of the flooding effects  provisions to cope with them End 2003 « La Loire » flood Early warning phase  on-site emergency team Alert phase  national emergency organization activated Examples: Modifications to avoid flooding of sensitive switchyards components BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria

18. 18 REVIEW OF THE PROTECTION OF NPPs AGAINST EXTERNAL FLOODING 1999 Le Blayais flooding New methodology « REX Blayais » defined by the utility, analyzed by IRSN End 2001 Advisory Committee New methodology globally approved by the safety authority Some methodological points to be enhanced Complementary methodological aspects + Application to the 19 NPPs Sites 2007 Advisory Committee Level of protection of the 19 NPP sites against external flooding globally satisfactory Some modifications and issues to be finalized REVIEW OF THE PROTECTION OF NPPs AGAINST EXTERNAL FLOODING BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria

19. 19 FUTURE FRENCH GUIDE « Le Blayais » flooding has called into question the design bases for the protection against external flooding (Basic Safety Rule I.2.e) 2006-2009: Working Group for preparation of a draft Guide Directed by the Nuclear Safety Authority and IRSN With representatives of: Nuclear utilities Qualified experts (hydrology, hydraulics and meteorology) FUTURE FRENCH GUIDE BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria

20. 20 FUTURE GUIDE APPLICABLE TO: Nuclear power plants (NPPs) All other surface nuclear installations No safety rule related to their protection against external flooding Need for more consistency with the approach for NPPs Impact of “Le Rhône” River flood on nuclear facilities in 2003 Guide applicable first to future installations FUTURE FRENCH GUIDE BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria

21. 21 Identification of phenomena that can lead to site flooding Definition of “Reference Flooding Situations (RFS)”  For each phenomena, RFS = the minimum hazard level to be considered in the design of future installations Methods for the characterization of the RFS  Mostly based on REX Blayais methodology but some differences Principles for protection of the installations  Good practices, relying on Le Blayais flooding to a large extent THE FUTURE GUIDE DEALS WITH: FUTURE FRENCH GUIDE BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria

22. 22 Intended “target” for the definition of RFS (not explicitly mentioned in the Guide): return period of 10 000 years In several cases, difficulties to reach the target All nuclear surface installations must cope with the same RFS The level of protection and the margins depend on: The type of installation and the flooding consequences on safety The general safety goals assigned to the installation The potential “cliff-edge” effect of a situation of higher intensity  Margins might be required for new reactors Successive lines of defense recommended (as possible) to protect: Buildings housing systems/components involved in safety functions Rooms inside the buildings Safety systems and components themselves FUTURE FRENCH GUIDE FUTURE GUIDE: SOME PRINCIPLES BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria

23. 23 From Le Blayais NPP flooding event… …to the revision of the Basic Safety Rule 1999 Le Blayais flooding New methodology « REX Blayais » defined by the utility, analyzed by IRSN End 2001 Advisory Committee New methodology globally approved by the safety authority Some methodological points to be enhanced Complementary methodological aspects + Application to the 19 NPPs Sites 2007 Advisory Committee Level of protection of the 19 NPP sites against external flooding globally satisfactory Some aspects to be enhanced or finalized BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria

24. 24 From Le Blayais NPP flooding event… …to the revision of the Basic Safety Rule Working Group Hazards & Protections End 2009 Draft Guide Consultation of Operators & General Public 2011 Advisory Committee Advisory commitee comments Working Group on Guide (2006) BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria 2011/2012 Guide Adaptation of the Guide

25. 25 CONCLUSION Following the partial flooding of « Le Blayais » NPP in 1999: Design bases used for the protection of NPPs and existing measures called into question Comprehensive reassessment of the protection of all French NPPs against external flooding and to a large number of modifications and improvements Update of the French requirements and submission of a draft Guide on the protection of all nuclear surface installations against external flooding  Guide expected 2011/2012 BgNS International Conference - 26–29 September 2010, Nesebar, Bulgaria