FRENCH PWR’S ULTIMATE HEAT SINKS THREATENED BY THEIR ENVIRONMENT “Nuclear power for the...
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Transcript of FRENCH PWR’S ULTIMATE HEAT SINKS THREATENED BY THEIR ENVIRONMENT “Nuclear power for the...
FRENCH PWR’S ULTIMATE HEAT SINKS THREATENED BY THEIR ENVIRONMENT “Nuclear power for the people”
Nesebar, 26-29 September, 2010
Véronique BERTRAND
IRSN, France
Système de managementde la qualité IRSN certifié
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 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 – 26-29 September, 2010 – Nesebar, Bulgaria – Page 3
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)
Heat sink - generalities
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 4
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
Heat sink - generalities
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 5
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
Reactorcoolantsystem
CCWS
Safetyheat sink
ESWS
Heat sink - generalities
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 6
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
Heat sink - generalities
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 7
PROTECTION AGAINST EXTERNAL HAZARDS
External hazards considered from the initial design
earthquakesexternal floodingcold weathersnowextreme windother phenomena
External hazards underestimatedfreezingfrazil icehigh air temperaturesseaweedvegetable matterexternal flooding with or without extreme wind
Heat sink - generalities
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 8
CRUAS NPP (900 MWe): 4 units
Date of the incident: 1st December, 2009
Rated level 2 on the INES scale
TOTAL LOSS OF
HEAT SINK AT
CRUAS 4 IN
DECEMBER
2009
Expérience feedback in 2009
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 9
Total loss of heat sink at Cruas 4 in December 2009
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 10
Total loss of heat sink at Cruas 4 in December 2009
Train B
Unit 1 Unit 2
Train A Train B
Unit 4Unit 3
Train A
Navigation Channel
River Rhône
Discharge basinDischarge ducts
B1 A1 A2 B2 B3 B4A3 A4
B1 B2 A1 A2 A3 B4A4 B3
Intake channel
Rhône river bed
Discharge basinDischarge ducts
Floating dyke
ESWS Galleries trains A & B of unit 1 ESWS Galleries
trains A & B of unit4
Intake coarse filtration& trash removal system (1 grid/train) –units 1&2
Train B
Unit 1 Unit 2
Train A Train B
Unit 4Unit 3
Train A
Navigation Channel
River Rhône
Discharge basinDischarge ducts
B1 A1 A2 B2 B3 B4A3 A4
B1 B2 A1 A2 A3 B4A4 B3
Intake channel
Rhône river bed
Discharge basinDischarge ducts
Floating dyke
ESWS Galleries trains A & B of unit 1
CCWS Building CCWS Building
ESWS Galleries trains A & B of unit4
Intake coarse filtration& trash removal system (1 grid/train) –units 1&2
Intake coarse filtration& trash removal system (1 grid/train) –
Intake coarse filtration& trash removal system (1 grid/train) units
3&4
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 11
Total loss of heat sink at Cruas 4 in December 2009
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 12
WHAT HAPPENED ?
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)
Total loss of heat sink at Cruas 4 in December 2009
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 13
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
Total loss of heat sink at Cruas 4 in December 2009
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 14
Canadian pondweed plants
Total loss of heat sink at Cruas 4 in December 2009
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 15
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
Total loss of heat sink at Cruas 4 in December 2009
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 16
OTHER EVENTS
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
Experience feedback in 2009
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 17
CONSEQUENCES
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
Experience feedback in 2009
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 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
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 19
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
Total loss of heat sink management from the initial design of French NPPs
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 20
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
Total loss of heat sink management from the initial design of French NPPs
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 21
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
Total loss of heat sink management from the initial design of French NPPs
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 22
EPR Flamanville 3 pumping station’s design
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 23
Improvement of the pumping station’s initial designFour independent water trainsTwo diversified types of filtration devices with screens and chain filtersStrengthening of the cleaning means of pre-filtration and filtration devicesEnhanced 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 coolsThe 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
EPR Flamanville 3 pumping station’s design
Nuclear power for the people – 26-29 September, 2010 – Nesebar, Bulgaria – Page 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 – 26-29 September, 2010 – Nesebar, Bulgaria – Page 25
THANK YOUFOR YOUR ATTENTION