BgNS International Conference “ NUCLEAR POWER FOR THE PEOPLE”

From the “Le Blayais NPP” flooding in 1999to the review of French regulationfor 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

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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

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FRENCH CONTEXT – NPPs LOCATION

NPPs location:

14 river NPPs

4 coastal NPPs

1 estuarine NPP

A single utility: EDF (Electricité de France)

NPPs


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1999 Storm 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 dykesSite and buildings flooding

“LE BLAYAIS” NPP FLOODING in 1999


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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



Waves

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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


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1 2

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


DESCRIPTION OF THE FLOODING EVENT (3/3)

STATE OF UNITS

1-2 AFTER

FLOODING

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PROBLEMS IDENTIFIED DURING « LE BLAYAIS » FLOODING



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OVERVIEW OF « LE BLAYAIS » FLOODING FOLLOWS-UP

“LE BLAYAIS” NPP FLOODING FOLLOWS-UP


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REVIEW OF THE PROTECTION OF NPPs AGAINST EXTERNAL FLOODING

REVIEW OF THE PROTECTION OF EXISTING NPPs AGAINST EXTERNAL FLOODING: METHODOLOGY


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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


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New methodology: 8 “complementary” phenomena

(13)

(11) (12)

(10)(9)

(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)

(8)

Flooding hazards


+ some combinations of phenomena considered

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Protection means

Site protection


Protection structures/devices reviewed: type, height, margins, settling, stability, safety classification, seismic resistance, power-supply, maintenance …

Le Blayais dykes

Protection against swelling (canal)

Modifications/Improvements at many sites (dykes/walls raisedraised or extendedextended or reinforced…)reinforced…)


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Protection means

Protection of sensitive rooms/equipments (1/2)


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”


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EX: Qualified material to plug the waterpaths and penetrations


+ 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)


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Protection means

Warning system, « flooding » procedure


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


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- 17


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


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1999Le

Blayais flooding

New methodology « REX Blayais » defined by the utility, analyzed by IRSN

End 2001Advisory Committe

e

New methodology globally approved

by the safety authority

Some methodological

points to be enhanced

Complementary methodologicalaspects

+ Application to the 19 NPPs Sites

2007Advisory Committe

e

Level of protection of the 19 NPP sites against external flooding globally

satisfactory

Some modifications and issues to be finalized



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FUTURE FRENCH GUIDEFUTURE 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 GuideDirected by the Nuclear Safety Authority and IRSNWith representatives of:

Nuclear utilities Qualified experts (hydrology, hydraulics and meteorology)

FUTURE FRENCH GUIDE


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FUTURE GUIDE APPLICABLE TO:FUTURE GUIDE APPLICABLE TO:

Nuclear power plants (NPPs)

All other surface nuclear installationsNo safety rule related to their protection against external floodingNeed for more consistency with the approach for NPPsImpact of “Le Rhône” River flood on nuclear facilities in 2003

Guide applicable first to future installations

FUTURE FRENCH GUIDE


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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 RFSMostly based on REX Blayais methodology but some

differences

Principles for protection of the installationsGood practices, relying on Le Blayais flooding to a large

extent

THE FUTURE GUIDE DEALS WITH:THE FUTURE GUIDE DEALS WITH:

FUTURE FRENCH GUIDE


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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 safetyThe general safety goals assigned to the installationThe 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 functionsRooms inside the buildingsSafety systems and components themselves

FUTURE FRENCH GUIDE

FUTURE GUIDE: SOME PRINCIPLESFUTURE GUIDE: SOME PRINCIPLES


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From Le Blayais NPP flooding event… …to the revision of the Basic Safety Rule

1999Le

Blayais flooding

New methodology« REX Blayais »defined by the utility, analyzed by IRSN

End 2001Advisory Committe

e

New methodology globally approved by the safety authority

Some methodological

points to be enhanced

Complementary methodologicalaspects

+ Application to the 19 NPPs Sites

2007Advisory Committe

e

Level of protection of the 19 NPP sites against

external flooding globally satisfactory

Some aspects to be enhanced or finalized


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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

2011Advisory

Committee

Advisory commitee comments

Working Group on

Guide (2006)


2011/2012

Guide

Adaptation

of the Guide

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CONCLUSIONCONCLUSION

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 “ NUCLEAR POWER FOR THE PEOPLE”

Documents

dykesle blayais npp

blayais dykesprotection

protection of npps

protection of existing

water progression

operating npps

external floodingreview

structures groundwater1