The Fukushima Daiichi Incident

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The Fukushima Daiichi Incident

• Matthias Braun
• PEPA4-G
• AREVA NP GmbH

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The Fukushima Daiichi Incident

• Unit I - GE Mark I BWR (439 MW), Operating
  since 1970
• Unit II III - GE Mark I BWR (760 MW), Operating
  since 1974

Spiegel.de
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The Fukushima Daiichi Incident
Service Floor (Steel)
Building (Concrete)
RPV
Containment
Pressure suppression pool
nucleartourist.com
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The Fukushima Daiichi Incident
nucleartourist.com
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The Fukushima Daiichi Incident
nucleartourist.com
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The Fukushima Daiichi Incident
nucleartourist.com
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The Fukushima Daiichi Incident
www.zwentendorf.com
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The Fukushima Daiichi Incident
nucleartourist.com
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The Fukushima Daiichi Incident
Fresh Steam
Main Feedwater
Core
RPV
Containment
Pressure suppression pool
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The Fukushima Daiichi Incident
Containment
Pressure suppression pool
Containment closure Head
en.wikipedia.org/wiki/Browns_Ferry_Nuclear_Power_P
lant
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The Fukushima Daiichi Incident

• Progression of the accident
• 11.3.2011 1446Earthquake
• SCRAM
• Containment-Isolation
• Close of fresh steam and main feed water valves
• Only a failure of these Valves could lead to an
  early large release

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The Fukushima Daiichi Incident

• 11.3.2011 341pm Station-Blackout
• Loss of off-site power due to Earthquake
• Diesel startet as planed
• Tsunami damaged either Diesel generators or
  Service water supply(Tsunami height gt7m, plant
  designed for 6.5m)
• Failure of all active cooling systems
• Core Isolation Pump / Einspeisesystem TJ
• Steam from Reactor drives Turbine
• Turbine pumps water form pressure suppression
  pool
• Needs Battery power

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The Fukushima Daiichi Incident

• Reactor Isolation pump stopped
• Either Run-out of Batteries
• Or pressure suppression pool boils
• Pressure buildup in reactor
• Decay heat produces steam
• Opening of pressure relief valves
• Steam gets blown in pressure suppression pool

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The Fukushima Daiichi Incident

• Dry-out of the RPV

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The Fukushima Daiichi Incident

• Dry-out of the RPV

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The Fukushima Daiichi Incident

• Dry-out of the RPV

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The Fukushima Daiichi Incident

• Dry-out of the RPV

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The Fukushima Daiichi Incident

• Dry-out of the RPV
• Heat-up of the exposed fuel

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The Fukushima Daiichi Incident

• At 900C
• 1/3 of Core uncovered
• Fracture of the Cladding
• Release of first fission products
• At 1200C
• 1/2 of Core uncovered
• Zirconium burns Steam
• Zr H20 -gtZrO H2
• Strong core heat-up
• 300-600kg Hydrogen
• Strong Pressure buildup in containment

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The Fukushima Daiichi Incident

• Strong release of fission products
• Xenon
• Cesium
• Iodine
• .
• Aerosols (Smoke)
• Large fraction of fission products get scrubbed
  in pressure suppression pool, not Xenon
• Uranium/Plutonium remain in core
• At 1800C
• Melting of the cladding
• Unknown if this stadium was reached

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The Fukushima Daiichi Incident

• Due to hydrogen, pressure build-up up to 8bar in
  containment
• Venting of containment down to 4 bar
• Venting via pressure suppression pool removes
  significant amount of aerosols
• Release of small amounts of Aerosols (Iodine,
  Cesium) and
• most of radioactive noble gases (Xenon) and
• Hydrogen

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The Fukushima Daiichi Incident

• Vented gas was released inside Reactor service
  floor
• Hydrogen combustion blows of Service Floor
• Explosion Unit 1 14.3.2011 1101AM
• Explosion Unit 3 14.3.2011 1101AM
• Concrete Reactor building unaffected
• Explosion of the building spectacular, but minor
  importance
• Deduced Informations
• Service Floor 8000m3
• ? 100 to 200kg H2
• ? 20 to 40 Core oxidation

dailycaller.com
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The Fukushima Daiichi Incident

• Radiation released
• Maximum 1mSv/h on site after venting of unit 1
• Probably similar dose at Venting of Site 2
• Expected order of magnitude by German crisis
  documents
• Rapid falling values to 0.07mSv
• Indicating main release was noble gases
• INES4 classified
• Most probably no land permanently contaminated

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The Fukushima Daiichi Incident

• Current Information
• RPV Flooded by See water in all 3 Units
• Containment flooded at least in Unit 1
• Liquid level stable
• Further cooling of the containment by venting
• Clogging of fuel by sea water?
• Rough estimate after 100h by flooding by pure sea
  water
• Core status
• Unit1 Core damaged
• Unit2 unknown
• Unit3 Core oxidized, possibly damaged

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• Informations supplyed by
• Google.com
• GRS.de
• Yoshiaki Oka, Waseda university
• .
• .
• .
• .

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TEPCOs Nuclear Power Plants suffered from big
earth quake of March 11,2011

• Yoshiaki Oka
• Waseda university

Prepared for the presentation at ISSCWR5 on
March 14, 2011 from the request of the organizer
based on the information until March 13 in
Canada. Available Information is very limited.
Recovery action is in progress. The presentation
may contain misunderstandings.
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The big earth quake

• Attached northern part of Japan at 246pm of
  March 11, 2011.
• Magnitude is 9 in Richter scale. The biggest in
  history.
• Some earth quakes occurred along the boundary of
  plates. Hundreds of km of the boundary moved,
  similar to the big earth quake in Indonesia.
• Big Tsunami (10m) attacked northern Japan and
  NPP. It was bigger than expected.
• There is no damage in the central Tokyo.
• Power plants including gas and coal fired ones
  were automatically shut down. NPPs were also
  automatically shut down.

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Fukushima site 1 (1F)

• 6 units , Unit 1, 2 , and 3 in trouble.
• Unit 1 460MWe BWR ,Unit 3,2 768MWe BWR
• 246pm March 11 The earth quake happened. Plants
  automatically shut down. Offsite power lost.
  Emergency DG started up.
• 341pm Emergency DG stopped due to loss of
  equipment cooling water. (Tsunami was bigger than
  expected.) All AC power was lost and
  consequential isolation from UHS, except for IC
  (isolation cooling system) in 1F1. RCIC in 1F 2
  Blackout (mostly) loss of UHS
• RCIC was available to makeup water in the initial
  stage.
• SAM (Severe Accident Management) prepared in the
  90s in place such as containment scrubbing
  venting, supply of water from portable water tank
  using Fire Protection pump or Fire Engine and
  inter-connection of power supply with other
  units.
• Site emergency announced. (After JCO accident,
  emergency law was settled. It requires report to
  the central government.) Evacuation up to 20km
  around 1F, 10km around 2F.

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Summary of Site 1, Unit 1 and 3

• Loss of All AC power.
• Partial core uncover (1-2m) occurred.
• Hydrogen generated by Zr-water reaction
• CV pressure increased and CVs were vented to
  maintain the integrity.
• Hydrogen detonation occurred in the upper part of
  the reactor buildings (unit 1 on March 12 and
  unit 2 on March 14). 14 workers injured.
• Area evacuated in 20km.
• Radiation levels are low, 1mSv/h highest at the
  site. (Dose limit of public ImSv/y)
• Sea water with boric acid injected into RPV and
  CV.
• CV integrity is maintained. Large release will be
  not likely.
• Cores are covered by water now.
• Level 4 accident of IAEA.

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Fukushima site 1 Unit 2 (1F2)

• Loss of all AC power.
• RCIC was in operation but is now lost.
• Low water level in RPV and High CV pressure
  continue. Mobile power supply is tried but not
  working well. CV vent my be considered.
• Fuel is covered by water (3am of March 14), but
  there is a threat to core uncovery.
• Depressurization of RPV, CV venting and Seawater
  injection are in preparation.

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Fukushima site 2 (2F)10-20km from site 1

• 4 units 110MWe BWR
• Sea water pumps of unit 1,2 and 4 did not work
  due to Tsunami. The motors were being replaced
  unit by unit. Recovery of the cooling were
  successful for unit 1 at 3am and for unit 2 at
  7am of March 14.