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8/7/2019 Le document d'Areva sur Fukushima
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.1
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.2
The
Fukushima DaiichiIncident
1. Plant Design2. Accident Progression3. Radiological releases4. Spent fuel pools5. Sources of Information
Matthias BraunPEPA4-G, AREVA NP GmbHMatthias.Braun@AREVA.com
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.3
The Fukushima Daiichi Incident1. Plant Design
Fukushima Daiichi (Plant I)
Unit I - GE Mark I BWR (439 MW), Operating since 1971Unit II-IV - GE Mark I BWR (760 MW), Operating since 1974
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.4
The Fukushima Daiichi Incident1. Plant Design
nucleartourist.com
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. w i k i p e
d i a
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/ w i k i / B r o w n s
_ F e r r y
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P l a n t
Building structureConcrete Building
Steel-framed Service Floor
Containment
Pear-shaped Dry-WellTorus-shaped Wet-Well
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.5
The Fukushima Daiichi Incident1. Plant Design
Service Floor
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.6
The Fukushima Daiichi Incident1. Plant Design
Lifting the Containment
closure head
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7/33The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.7
The Fukushima Daiichi Incident1. Plant Design
Reactor Service Floor
(Steel Construction)
Concrete Reactor Building(secondary Containment)
Reactor Core
Reactor Pressure Vessel
Containment (Dry well)
Containment (Wet Well) / Condensation Chamber
Spend Fuel Pool
Fresh Steam line
Main Feedwater
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8/33The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.8
The Fukushima Daiichi Incident2. Accident progression
11.3.2011 14:46 - EarthquakeMagnitude 9
Power grid in northern Japan fails
Reactors itself are mainlyundamaged
SCRAMPower generation due to Fissionof Uranium stops
Heat generation due to radioactive
Decay of Fission ProductsAfter Scram ~6%After 1 Day ~1%After 5 Days ~0.5%
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.9
The Fukushima Daiichi Incident2. Accident progression
Containment Isolation
Closing of all non-safety relatedPenetrations of the containment
Cuts off Machine hall
If containment isolation succeeds,a large early release of fissionproducts is highly unlikely
Diesel generators startEmergency Core cooling systemsare supplied
Plant is in a stable save state
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.10
The Fukushima Daiichi Incident2. Accident progression
11.3. 15:41 Tsunami hits the plantPlant Design for Tsunami height ofup to 6.5m
Actual Tsunami height >7m
Flooding ofDiesel Generators and/or
Essential service water buildingcooling the generators
Station BlackoutCommon cause failure of thepower supply
Only Batteries are still available
Failure of all but one Emergencycore cooling systems
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.11
The Fukushima Daiichi Incident2. Accident progression
Reactor Core Isolation Pump still
availableSteam from the Reactor drives aTurbine
Steam gets condensed in theWet-Well
Turbine drives a Pump
Water from the Wet-Well getspumped in Reactor
Necessary:Battery powerTemperature in the wet-wellmust be below 100C
As there is no heat removal fromthe building, the Core isolationpump cant work infinitely
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.12
The Fukushima Daiichi Incident2. Accident progression
Reactor Isolation pump stops
11.3. 16:36 in Unit 1(Batteries empty)
14.3. 13:25 in Unit 2(Pump failure)
13.3. 2:44 in Unit 3(Batteries empty)
Decay Heat produces still steam inReactor pressure Vessel
Pressure rising
Opening the steam relieve valvesDischarge Steam into the Wet-Well
Descending of the Liquid Level inthe Reactor pressure vessel
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.13
The Fukushima Daiichi Incident2. Accident progression
Reactor Isolation pump stops
11.3. 16:36 in Unit 1(Batteries empty)
14.3. 13:25 in Unit 2(Pump failure)
13.3. 2:44 in Unit 3(Batteries empty)
Decay Heat produces still steam inReactor pressure Vessel
Pressure rising
Opening the steam relieve valvesDischarge Steam into the Wet-Well
Descending of the Liquid Level inthe Reactor pressure vessel
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.14
The Fukushima Daiichi Incident2. Accident progression
Reactor Isolation pump stops
11.3. 16:36 in Unit 1(Batteries empty)
14.3. 13:25 in Unit 2(Pump failure)
13.3. 2:44 in Unit 3(Batteries empty)
Decay Heat produces still steam inReactor pressure Vessel
Pressure rising
Opening the steam relieve valvesDischarge Steam into the Wet-Well
Descending of the Liquid Level inthe Reactor pressure vessel
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.15
The Fukushima Daiichi Incident2. Accident progression
Reactor Isolation pump stops
11.3. 16:36 in Unit 1(Batteries empty)
14.3. 13:25 in Unit 2(Pump failure)
13.3. 2:44 in Unit 3(Batteries empty)
Decay Heat produces still steam inReactor pressure Vessel
Pressure rising
Opening the steam relieve valvesDischarge Steam into the Wet-Well
Descending of the Liquid Level inthe Reactor pressure vessel
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.16
The Fukushima Daiichi Incident2. Accident progression
Reactor Isolation pump stops
11.3. 16:36 in Unit 1(Batteries empty)
14.3. 13:25 in Unit 2(Pump failure)
13.3. 2:44 in Unit 3(Batteries empty)
Decay Heat produces still steam inReactor pressure Vessel
Pressure rising
Opening the steam relieve valvesDischarge Steam into the Wet-Well
Descending of the Liquid Level inthe Reactor pressure vessel
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.17
The Fukushima Daiichi Incident2. Accident progression
Measured, and here referenced
Liquid level is the collapsed level.The actual liquid level lies higherdue to the steam bubbles in theliquid
~50% of the core exposedCladding temperatures rise, but stillno significant core damage
~2/3 of the core exposed
Cladding temperatureexceeds ~900C
Balooning / Breaking of thecladding
Release of fission products formthe fuel rod gaps
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.18
The Fukushima Daiichi Incident2. Accident progression
~3/4 of the core exposedCladding exceeds ~1200C
Zirconium in the cladding starts toburn under Steam atmosphere
Zr + 2H 20 ->ZrO 2 + 2H 2
Exothermal reaction furtherheats the core
Generation of hydrogenUnit 1: 300-600kgUnit 2/3: 300-1000kg
Hydrogen gets pushed via thewet-well, the wet-well vacuumbreakers into the dry-well
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.19
The Fukushima Daiichi Incident2. Accident progression
at ~1800C [Unit 1,2,3]Melting of the Cladding
Melting of the steel structures
at ~2500C [Block 1,2]Breaking of the fuel rods
debris bed inside the core
at ~2700C [Block 1]Melting of Uranium-Zirconiumeutectics
Restoration of the water supplystops accident in all 3 Units
Unit 1: 12.3. 20:20 (27h w.o. water)
Unit 2: 14.3. 20:33 (7h w.o. water)
Unit 3: 13.3. 9:38 (7h w.o. water)
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.20
The Fukushima Daiichi Incident2. Accident progression
Release of fission products duringmelt downXenon, Cesium, Iodine,
Uranium/Plutonium remain in core
Fission products condensate toairborne Aerosols
Discharge through valves into waterof the condensation chamber
Pool scrubbing binds a fraction ofAerosols in the water
Xenon and remaining aerosolsenter the Dry-Well
Deposition of aerosols on surfacesfurther decontaminates air
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.21
The Fukushima Daiichi Incident2. Accident progression
ContainmentLast barrier between Fission
Products and EnvironmentWall thickness ~3cm
Design Pressure 4-5bar
Actual pressure up to 8 bars
Normal inert gas filling (Nitrogen)Hydrogen from core oxidation
Boiling condensation chamber(like a pressure cooker)
Depressurization of thecontainment
Unit 1: 12.3. 4:00
Unit 2: 13.3 00:00
Unit 3: 13.3. 8.41
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.22
The Fukushima Daiichi Incident2. Accident progression
Positive und negative Aspects ofdepressurizing the containmentRemoves Energy from the Reactorbuilding (only way left)
Reducing the pressure to ~4 bar
Release of small amounts ofAerosols (Iodine, Cesium ~0.1%)Release of all noble gases
Release of Hydrogen
Gas is released into the reactor
service floorHydrogen is flammable
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.23
The Fukushima Daiichi Incident2. Accident progression
Unit 1 und 3
Hydrogen burn inside the reactorservice floor
Destruction of the steel-frame roof
Reinforced concrete reactorbuilding seems undamaged
Spectacular but minor safetyrelevant
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.24
The Fukushima Daiichi Incident2. Accident progression
Unit 2
Hydrogen burn inside the reactorbuilding
Probably damage to thecondensation chamber(highly contaminated water)
Uncontrolled release of gas from
the containmentRelease of fission products
Temporal evacuation of the plant
High local dose rates on the plantsite due to wreckage hinder furtherrecovery work
No clear information's why Unit 2behaved differently
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.25
The Fukushima Daiichi Incident2. Accident progression
Current status of the Reactors
Core Damage in Unit 1,2, 3Building damage due to variousburns Unit 1-4
Reactor pressure vessels floodedin all Units with mobile pumps
At least containment in Unit 1flooded
Further cooling of the Reactors byreleasing steam to the atmosphere
Only small further releases offission products can be expected
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.26
The Fukushima Daiichi Incident3. Radiological releases
Directly on the plant siteBefore Explosion in Unit Block 2
Below 2mSv / hMainly due to released radioactive noble gasesMeasuring posts on west side. Maybe too small values measured due to wind
After Explosion in Unit 2 (Damage of the Containment)Temporal peak values 12mSv / h(Origin not entirely clear)Local peak values on site up to 400mSv /h (wreckage / fragments?)Currently stable dose on site at 5mSv /hInside the buildings a lot more
Limiting time of exposure of the workers necessary
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.27
The Fukushima Daiichi Incident3. Radiological releases
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.28
The Fukushima Daiichi Incident3. Radiological releases
Outside the Plant siteAs reactor building mostly intact=> reduced release of Aerosols (not Chernobyl-like)
Fission product release in steam=> fast Aerosol grows, large fraction falls down in the proximity of the plant
Main contribution to the radioactive dose outside plant are the radioactive
noble gasesCarried / distributed by the wind, decreasing dose with time
No Fall -out of the noble gases, so no local high contamination of soil
~20km around the plant
Evacuations were adequateMeasured dose up to 0.3mSv/h for short times
Maybe destruction of crops / dairy products this year
Probably no permanent evacuation of land necessary
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.29
The Fukushima Daiichi Incident3. Radiological releases
GRS.de
~50km around the plantControl of Crop / Dairy products
Usage of Iodine pills(Caution, pills can interferewith heart medicine)
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.30
The Fukushima Daiichi Incident4. Spend fuel pools
Spend fuel stored in Pool on
Reactor service floorDue to maintenance in Unit 4 entirecore stored in Fuel pool
Dry-out of the poolsUnit 4: in 10 daysUnit 1-3,5,6 in few weeks
Leakage of the pools due toEarthquake?
ConsequencesCore melt on fresh air
Nearly no retention of fissionproducts
Large release
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.31
The Fukushima Daiichi Incident4. Spend fuel pools
Spend fuel stored in Pool on
Reactor service floorDue to maintenance in Unit 4 entirecore stored in Fuel pool
Dry-out of the poolsUnit 4: in 10 daysUnit 1-3,5,6 in few weeks
Leakage of the pools due toEarthquake?
ConsequencesCore melt on fresh air
Nearly no retention of fissionproducts
Large release
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The Fukushima Daiichi Incident Dr. Matthias Braun - 27 March 2011 - p.32
The Fukushima Daiichi Incident4. Spend fuel pools
Spend fuel stored in Pool on
Reactor service floorDue to maintenance in Unit 4 entirecore stored in Fuel pool
Dry-out of the poolsUnit 4: in 10 daysUnit 1-3,5,6 in few weeks
Leakage of the pools due toEarthquake?
ConsequencesCore melt on fresh air
Nearly no retention of fissionproducts
Large release
It is currently unclear if releasefrom fuel pool already happened
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h k h h d h h
The Fukushima Daiichi Incident5. Sources of Information
Good sources of InformationGesellschaft fr Reaktorsicherheit [GRS.de]
Up to dateRadiological measurements publishedGerman translation of japanese/englisch web pages
Japan Atomic Industrial Forum [jaif.or.jp/english/]Current Status of the plantsMeasurement values of the reactors (pressure liquid level)
Tokyo Electric Power Company [Tepco.co.jp]Status of the recovery workCasualties
May too few information are released by TEPCO, the operator of the plant
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