1. FRENCH PWR’S ULTIMATE HEAT SINKS THREATENED BY THEIR ENVIRONMENT
“Nuclear power for the people”
Nesebar, September, 2010
Véronique BERTRAND
IRSN, France
Système de management
de la qualité IRSN certifié

2. SUMMARY Heat sink: generalities
Total loss of heat sink at Cruas unit 4 in December 2009
Total loss of heat sink management from the initial design
EPR Flamanville 3 pumping station’s design
Conclusion
Nuclear power for the people – September, 2010 – Nesebar, Bulgaria – Page 2

3. FRENCH NPPs IMPLANTATION
Heat sink - generalities
FRENCH NPPs IMPLANTATION
58 reactors in operation
(+1 under construction–EPR at Flamanville)
19 sites :
 4 coastal
Flamanville (2×1300 MWe)
Paluel (4×1300 MWe)
Penly (2×1300 MWe)
Gravelines (6×900 MWe)
 1 estuarine
Blayais (4×900 MWe)
 14 riverside
(including 11 with cooling towers)
Nuclear power for the people – September, 2010 – Nesebar, Bulgaria – Page 3

4. Heat sink - generalities
Pre-filtration and filtration in the pumping station
2 circuits supplied ensuring the reactor’s cooling
Cooling circuit of the nuclear island including safety systems called Essential Service Water System (ESWS)
Cooling circuit of the conventional island
Conventional island
Role of the cooling circuit
The cooling circuit of the conventional island isn’t a system important to safety
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5. Conventional heat sink
Heat sink - generalities
REACTORS COOLING: CASE WITH COOLING TOWER
CONVENTIONAL ISLAND
ALTERNATOR
TURBINE
HEATER
CONDENSER
MSS
AFS
FFCS
CSS
RHRS
Conventional heat sink
NUCLEAR ISLAND
SIS
COOLING TOWER
Reactor coolant system
CCWS
Safety heat sink
ESWS
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6. REACTORS COOLING: A SAFETY FUNCTION
Heat sink - generalities
REACTORS COOLING: A SAFETY FUNCTION
ESWS: cooling of an intermediate cooling system, the Component Cooling Water System (CCWS)
ESWS and CCWS are systems important to safety
ESWS: two redundant trains
CCWS responsible for cooling of safety equipment
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7. PROTECTION AGAINST EXTERNAL HAZARDS
Heat sink - generalities
PROTECTION AGAINST EXTERNAL HAZARDS
External hazards considered from the initial design
earthquakes
external flooding
cold weather
snow
extreme wind
other phenomena
External hazards underestimated
freezing
frazil ice
high air temperatures
seaweed
vegetable matter
external flooding with or without extreme wind
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8. TOTAL LOSS OF HEAT SINK AT CRUAS 4 IN DECEMBER 2009
Expérience feedback in 2009
TOTAL LOSS OF HEAT SINK AT CRUAS 4 IN DECEMBER 2009
CRUAS NPP (900 MWe): 4 units
Date of the incident: 1st December, 2009
Rated level 2 on the INES scale
Nuclear power for the people – September, 2010 – Nesebar, Bulgaria – Page 8

9. Total loss of heat sink at Cruas 4 in December 2009
Nuclear power for the people – September, 2010 – Nesebar, Bulgaria – Page 9

10. Total loss of heat sink at Cruas 4 in December 2009
Train B
Unit 1
Unit 2
Train A B
Unit 4
Unit 3
Navigation Channel
River Rhône
Discharge basin
Discharge ducts B1 A1 A2 B2 B3 B4 A3 A4
Intake channel
Rhône river bed
Floating
dyke
ESWS Galleries
trains A & B of unit 1
trains A & B of unit 4
Intake coarse filtration
& trash removal system
(1 grid/train) –
units 1&2
CCWS Building
units 3&4
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11. Total loss of heat sink at Cruas 4 in December 2009
Nuclear power for the people – September, 2010 – Nesebar, Bulgaria – Page 11

12. WHAT HAPPENED ? Total loss of heat sink at Cruas 4 in December 2009
01/12/2009 : massive unprecedented blockage
ESWS train A unavailable
Reactor 4 shutdown
ESWS train B unavailable
Unit 4: total loss of heat sink  the first time in France concerning a PWR
National Crisis Organization activated
French public authorities (ASN)
Technical support (IRSN)
French utility (EDF)
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13. Total loss of heat sink at Cruas 4 in December 2009
Application of the Emergency Operating Procedures (EOPs)
Difficulties in the procedure
Unit 4 in a safe state 3 hours later
Use of the thermal inertia of the refuelling water storage tank (RWST) reserve
Efficient cleaning of filtration device and ESWS/CCWS exchangers
Total loss of heat sink lasted 10 hours
Units 2&3 partially lost heat sink
Nuclear power for the people – September, 2010 – Nesebar, Bulgaria – Page 13

14. Canadian pondweed plants
Total loss of heat sink at Cruas 4 in December 2009
Canadian pondweed plants
Nuclear power for the people – September, 2010 – Nesebar, Bulgaria – Page 14

15.  IRSN started an in-depth analysis of this incident
Total loss of heat sink at Cruas 4 in December 2009
LESSONS LEARNT
First ever occurrence on a PWR in France
Partial loss of heat sink on units 2 and 3 together with the total loss on unit 4
Efficient management needs quick and reliable diagnosis of the situation and mitigation means
Need to improve the emergency procedure
Use of thermal inertia of RWST water proved to be effective
On-site trash rack pre-filtration cleaning devices proved to be insufficient
 IRSN started an in-depth analysis of this incident
Nuclear power for the people – September, 2010 – Nesebar, Bulgaria – Page 15

16. OTHER EVENTS Experience feedback in 2009
Frazil ice event at Chooz B NPP in January
Vegetable matter ingress in Le Blayais NPP, February and March
Drum screens clogging at Fessenheim NPP in December
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17. CONSEQUENCES Experience feedback in 2009
Action plan from the utility EDF
Heat sink operating conditions and design
Operating procedures
Criteria for emergency organization activation
IRSN analysis
Characterisation of hazards
Monitoring and protection of the pumping station
Existing means, procedures, organization
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18. TOTAL LOSS OF HEAT SINK MANAGEMENT FROM THE INITIAL DESIGN
Incident procedure evolution
Probabilistic safety assessment (PSA) contribution
Loss of heat sink on all units of a NPP
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19. INCIDENT PROCEDURE EVOLUTION
Total loss of heat sink management from the initial design of French NPPs
INCIDENT PROCEDURE EVOLUTION
Use of the thermal inertia of the refuelling water storage tank (RWST) reserve
Emergency heat sink for cooling temporarily the component cooling water system (CCWS)
Throughout a containment spray system (CSS) heat exchanger
Foreseen enhancement: operation of one reactor cooling pump and one charging pump
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20. PROBABILISTIC SAFETY ASSESSMENT (PSA) CONTRIBUTION
Total loss of heat sink management from the initial design of French NPPs
PROBABILISTIC SAFETY ASSESSMENT (PSA) CONTRIBUTION
PSA for PWR 900 MWe developed at IRSN
Potential scenarios resulting from a total loss of ultimate heat sink with a high frequency
Beyond the initial design
Implementation of modifications
Automatic disconnection of the reactor coolant letdown line
Nuclear power for the people – September, 2010 – Nesebar, Bulgaria – Page 20

21. LOSS OF HEAT SINK ON ALL UNITS OF A NPP
Total loss of heat sink management from the initial design of French NPPs
LOSS OF HEAT SINK ON ALL UNITS OF A NPP
Recently subject to particular attention in France
Wide study following the partial flooding of Le Blayais NPP
Analysis of the guaranteed available on-site resources
Modifications: sufficient required capacities of steam generator water supply
Equivalent program for next safety reviews of other series
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22. EPR Flamanville 3 pumping station’s design
Nuclear power for the people – September, 2010 – Nesebar, Bulgaria – Page 22

23. EPR Flamanville 3 pumping station’s design
Improvement of the pumping station’s initial design
Four independent water trains
Two diversified types of filtration devices with screens and chain filters
Strengthening of the cleaning means of pre-filtration and filtration devices
Enhanced reliability of head loss measurements to pre- filtration trash racks and filters
New system: the ultimate cooling water system (UCWS)
Foreseen for cooling an intermediate cooling system, which in turn cools
The containment heat removal system (CHRS)
The fuel pool cooling system (FPCS) third train
Normal supply for ESWS and UCWS: pumping station
Diversified cooling source: connexion to the outfall structure
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24. CONCLUSION
Environmental conditions can impact the safety of nuclear reactors
 Come back to the initial design
3 lines of defence
Prevention: identification and knowledge of hazards  Appropriate design equipment
Pumping station: monitoring, detection and protection means
 To ensure a permanent ESWS flow rate
Management of a total loss of heat sink
 To cool the reactor until the heat sink recovery
Expectation for EPR Flamanville 3 pumping station: to cope with external hazards
Nuclear power for the people – September, 2010 – Nesebar, Bulgaria – Page 24

25. THANK YOU FOR YOUR ATTENTION
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