phenomena identification in severe accident sequence …takamasa/j-us2012/image/prof abe.pdf ·...

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Japan-U.S. Seminar on Two-Phase Flow Dynamics June 7-12, 2012 @ Tokyo, Japan Phenomena Identification in Severe Accident Sequence and Safety Issues for Severe Accident Management of Light Water Reactors University of Tsukuba Department of Engineering Mechanics and Energy Chair & Professor Yutaka Abe Accident progression of light water reactor accident Road map committee on severe accident research in AESJ (2011.03.08, Organizer: Y. Abe) LOCA RIA Transient phenomena Closure of accident Severe accident Accident management AMCooling failure Containment failure FP release to environment Phase I Phase II Accident progression Prevention of nuclear disasters Decay heat removal by Engineering facilitiesECCS)

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Page 1: Phenomena Identification in Severe Accident Sequence …takamasa/J-US2012/image/Prof Abe.pdf · Phenomena Identification in Severe Accident Sequence and Safety Issues ... Three Mile

Japan-U.S. Seminar on Two-Phase Flow DynamicsJune 7-12, 2012 @ Tokyo, Japan

Phenomena Identification in Severe Accident Sequence and Safety Issues for Severe Accident Management of

Light Water Reactors

University of TsukubaDepartment of Engineering Mechanics and Energy

Chair & Professor

Yutaka Abe

Accident progression of light water reactor accidentRoad map committee on severe accident research in AESJ (2011.03.08, Organizer: Y. Abe)

LOCARIA

Transient phenomena

Closure of accident

Severe accident

Accident management (AM)

Cooling failure

Containment failureFP release to environment

Phase I

Phase II

Accident progression

Prevention of nuclear disasters

Decay heat removal by Engineering facilities(ECCS)

Page 2: Phenomena Identification in Severe Accident Sequence …takamasa/J-US2012/image/Prof Abe.pdf · Phenomena Identification in Severe Accident Sequence and Safety Issues ... Three Mile

History of Severe accident research

• (1975) USNRC: WASH-1400。• (1979) TMI-2 Accident (USA)• (1983) Severe accident research starts in Japan by

Nuclear Safety Committee of Japan.• (1982-1990) SFD international cooperation (USNRC)• (1986) Chernobyl Accident (USSR)• (1986-1990)(1991-1995) Nuclear Safety Committee of

Japan: reinforced severe accident research in Japan.– JAERI– NUPEC

• (1991-2000) CSARP international cooperation (USNRC)

Three Mile Island unit-2 pressure vessel final situation (US-NRC, 1981)

Upper plenumCoolant inlet (2B) Coolant inlet (1A)

Upper core support plate Cavity

Upper debris bedCrust

Solidified molten material

Lower plenum debrisInstrument tube

Hole on baffle plate

Solidified molten material on core former

Page 3: Phenomena Identification in Severe Accident Sequence …takamasa/J-US2012/image/Prof Abe.pdf · Phenomena Identification in Severe Accident Sequence and Safety Issues ... Three Mile

Stop nuclear reaction by scram

Cool down core material

Isolate FP within containment vessel

Prepared for a committee meeting for severe accident research in AESJ on March 8, 2011

Hypsometrical Phenomenon at severe accidentbefore Fukushima accident on March 11, 2011

FP release from fuelTransport in primary loop

Transport in containment vessel

Molten core and concrete interaction(MCCI)

Molten material and coolant interaction(FCI)(Vapor explosion)

Core melt progression within pressure vessel

High temperature failure of primary coolant loop

Containment frailer

Pressure vessel

Containment vessel

High pressure melt jet ejection(DCH)

Hydrogen burn/ detonation/explosion

FP release to environment

Molten material cooling out of pressure vessel

Pressure vessel failure

Molten material cooling within pressure vessel

Phenomena Identification and Ranking Table(Magallon, et.al., EURSAFE, NED, 235, 2005, 309-346)• In-vessel

– Core degradation – Reflooding– Corium behavior in bottom head – Integrity of primary and secondary circuits

• Ex-vessel / Dynamic loading – Vessel failure and corium release– Molten corium concret interaction – Core catcher: spreading phenomena– Core catcher: corium ceramic interaction – Corium ceramic interaction– Corium coolability– Bottom injection of water into melt – Melt pool in partial enclosure with external water – Core catcher: other specific phenomena

• Long-term loading– Containment thermal-hydraulics– Melt ejection and direct containment heating– Mechanical static behavior of containment and basemat

• Fission products – In-vessel release– Core reflooding– Transport in primary and secondary system – Aerosol behavior in containment – Iodine chemistry

Page 4: Phenomena Identification in Severe Accident Sequence …takamasa/J-US2012/image/Prof Abe.pdf · Phenomena Identification in Severe Accident Sequence and Safety Issues ... Three Mile

History of Severe accident research

• (1975) USNRC: WASH-1400。• (1979) TMI-2 Accident (USA)• (1983) Severe accident research starts in Japan by

Nuclear Safety Committee of Japan.• (1982-1990) SFD international cooperation (USNRC)• (1986) Chernobyl Accident (USSR)• (1986-1990)(1991-1995) Nuclear Safety Committee of

Japan: reinforced severe accident research in Japan.– JAERI– NUPEC

• (1991-2000) CSARP international cooperation (USNRC)• (1992) Nuclear Safety Committee of Japan:

“Recommendation of Accident management for severe accident of light water nuclear power plant”

• (1994) (2002) TEPCO: “Report on accident management”– Closure of severe accident research in Japan.

Severe accident research in Japanjust before Fukushima Daiichi accident on March 11, 2012

• Status summary by “Road map committee on severe accident research in AESJ” (2011.03.08, Organizer: Y. Abe)

– Weak fundamentals of thermal-hydraulic research on light water nuclear reactor safety in Japan:

• Aging of researchers on thermal-hydraulic research, over 50-60 especially in severe accident research field.

• Less younger age Successor on thermal-hydraulic research for severe accident.

• Aging of experimental facilities on thermal-hydraulic research.

– Development of next generation reactor:• Focused Advanced Accident Management, ex. core catcher etc. .• Design based on “realistic” FP source term estimation.

– Regulatory commission on Severe Accident• Nuclear Safety Committee of Japan started to discuss about accident

management for severe accident (2010.12): • International research activity on design considering Severe Accident

(IAEA NS-R-1, WENRA, US-NRC RG1.206 etc.)

Page 5: Phenomena Identification in Severe Accident Sequence …takamasa/J-US2012/image/Prof Abe.pdf · Phenomena Identification in Severe Accident Sequence and Safety Issues ... Three Mile

The Great East Japan Earthquake and Tsunami 2011

http://www.boston.com/bigpicture/2011/03/massive_earthquake_hits_japan.html

Japan Meteorological Agency,release, (17:00, May 29, 2011)

Height of Tsunami reported by collaboration research on earthquake wave, July 16, 2011

Fukushima Daiichi Nuclear Power Station’s Accident, 2011

Fukushima Daiichi site after accident(http://www.tepco.co.jp)

Loss of core cooling

Core melt down

Hydrogen explosion Fukushima Daiichi site at Tsunami arrival (http://www.asahi.com)

Station Black Out

Reactor building

Pressure vessel

Containment vessel

Fukushima Daiichi Power plant site (Jiji press)

BWR Mark-I

Tsunami after Earthquake

Page 6: Phenomena Identification in Severe Accident Sequence …takamasa/J-US2012/image/Prof Abe.pdf · Phenomena Identification in Severe Accident Sequence and Safety Issues ... Three Mile

• May 1114:46 Earthquake

Scram / Loss of external power source.14:52 IC is automatically started.15:35 Tsunami → IC valve is closed due to fail as is.15:37 SBO

• May 120:49 D/W pressure exceeds design value.5:46 Water injection through fire extinguisher line.14:30 W/W vent → PCV pressure decrease.15:36 Hydrogen explosion in reactor building.

• May 231:40 Recover external power source.

Major events in Fukushima Daiichi unit-1

No cooling

A day after No cooling

Trend data of Fukushima Daiichi unit-1 until March 15(from TEPCO/NISA HP)

Page 7: Phenomena Identification in Severe Accident Sequence …takamasa/J-US2012/image/Prof Abe.pdf · Phenomena Identification in Severe Accident Sequence and Safety Issues ... Three Mile

SBO

Pressure vessel: Loss of cooling capability

Containment vessel: Pressure and temperature increase

Depressurization by- SR valve- ADS

1-2 hours- Core damage start- Hydrogen generation start

A few hours- Pressure increase- Temperature increase

A day- Containment failure

A few hours- Core melt start -> Pressure vessel failure- Large Hydrogen generation

Degraded /Melted core behavior- Debris bed cooling- Molten material behavior- IVR

PossibleManagement

Severe Accident Transients and possible accident management according to the transients

Phenomena Transient under No management

Phenomena Transient under Nomanagement

• May 1114:46 Earthquake

Scram / Loss of external power source.14:52 RCIC is manually started.15:35 Tsunami15:37 SBO

• May 1413:25 RCIC stopped.-18:00 PCV Depressurization by SRV.19:54 Sea Water injection through fire extinguisher line.

• May 150:02 D/W vent-6:00 Large sound around suppression chamber.

• May 2015:46 Recover external power source.

Major events in Fukushima Daiichi unit-2

No core cooling for 6.5 hours

Succeed core cooling for 3 days without electricityHydrogen explosion

in unit-1

Page 8: Phenomena Identification in Severe Accident Sequence …takamasa/J-US2012/image/Prof Abe.pdf · Phenomena Identification in Severe Accident Sequence and Safety Issues ... Three Mile

• May 1114:46 Earthquake

Scram / Loss of external power source.15:06 RCIC is manually started.15:35 Tsunami15:42 SBO

RCIC restarted• May 12

11:36 RCIC stopped.12:35 HPCI automatically started.

• May 132:42 HPCI stopped.9:08 PCV Depressurization by SRV.]9:25 Water injection through fire extinguisher line.13:12 Sea water injection through fire extinguisher line.

• May 1411:01 Hydrogen explosion in reactor building.

• May 2210:36 Recover external power source.

Major events in Fukushima Daiichi unit-3

No core cooling for 6.5 hours

20 hours core cooling without electricity

14 hours core cooling without electricity

Hydrogen explosion in unit-1

SBO

Steam condensation by- suppression pool scrabbling- PCCSHydrogen dealing

Pressure vessel: Loss of cooling capability

Core cooling at High pressureWithout no electricity(Passive cooling system)- IC (gravity driven) / SG- HPCI (steam turbine driven)- RCIC (steam turbine driven)

Containment vessel: Pressure and temperature increase

Depressurization by- SR valve- ADS

Filtered vent to PreventCV failure- Depressurization- Heat release

1-2 hours- Core damage start- Hydrogen generation start

A few hours- Pressure increase- Temperature increase

A day- Containment failure

A few hours- Core melt start -> Pressure vessel failure- Large Hydrogen generation

Degraded /Melted core behavior- Debris bed cooling- Molten material behavior- IVR

PossibleManagement

Severe Accident Transients and possible accident management according to the transients

Alternative core cooling byPassive cooling system under Low pressure

+

Phenomena Transient under No management

PossibleManagement

Phenomena Transient under Nomanagement

Extend containment failure and can wait electricity recover

Page 9: Phenomena Identification in Severe Accident Sequence …takamasa/J-US2012/image/Prof Abe.pdf · Phenomena Identification in Severe Accident Sequence and Safety Issues ... Three Mile

SBO

Steam condensation by- suppression pool scrabbling- PCCSHydrogen dealing

Pressure vessel: Loss of cooling capability

Core cooling at High pressureWithout no electricity(Passive cooling system)- IC (gravity driven) / SG- HPCI (steam turbine driven)- RCIC (steam turbine driven)

Containment vessel: Pressure and temperature increase

Depressurization by- SR valve- ADS

Filtered vent to PreventCV failure- Depressurization- Heat release

1-2 hours- Core damage start- Hydrogen generation start

A few hours- Pressure increase- Temperature increase

A day- Containment failure

A few hours- Core melt start -> Pressure vessel failure- Large Hydrogen generation

Degraded /Melted core behavior- Debris bed cooling- Molten material behavior- IVR

PossibleManagement

Severe Accident Transients and possible accident management according to the transients

Alternative core cooling byPassive cooling system under Low pressure

+

Phenomena Transient under No management

PossibleManagement

Phenomena Transient under Nomanagement

Passive core cooling system without electricity

High performance steam condenser

High performance filtered venting

Filtered containment venting through an inerted multi venturiscrubber system in Swedish National Report (Dec. 29, 2011)

FILTRA/MVSS connection to containment

General view of venting function

Page 10: Phenomena Identification in Severe Accident Sequence …takamasa/J-US2012/image/Prof Abe.pdf · Phenomena Identification in Severe Accident Sequence and Safety Issues ... Three Mile

Available cooling system at Severe Accident transient equipped to BWR Mark-I

Gravity driven

Steam turbine drivenPassive system is available at SBO,

But

Electricity driven pump is not available

Supersonic steam injector (SI)

Water

Steam

Discharged water

Mixing nozzle Throat Diffuser

Water jet is driven by steam condensationon water jet surface, simultaneously steam is accelerated by condensation above sonic speed.

Supersonic steam injector is• Passive water pump without electric power supply.• High performance heat exchanger to condense steam.• Simple, compact and low cost.

SI can be a Passive Safety System to prevent core meltdown at severe accident of nuclear power plant.

Page 11: Phenomena Identification in Severe Accident Sequence …takamasa/J-US2012/image/Prof Abe.pdf · Phenomena Identification in Severe Accident Sequence and Safety Issues ... Three Mile

Proposed safety systems for NPP using SI

Passive Containment Cooling System(PCCS)

SI-PCCSSI-PCIS

Passive Core Injection System(PCIS)

• Realize passive coolant injection system without electricity.• Realize high performance steam condenser.• Realize simple and compact safety system.

SI is in operation by steam generated at the accident, can supply water into core and can condense steam into water.

S. Ohmori et al., (2007)

Proposed safety systems for NPP using SI

Passive Containment Cooling System(PCCS)

SI-PCCSSI-PCIS

Passive Core Injection System(PCIS)

• Multiple passive cooling systems should be prepared from “defense in depth” point of view.

SI is in operation by steam generated at the accident, can supply water into core and can condense steam into water.

S. Ohmori et al., (2007)

Page 12: Phenomena Identification in Severe Accident Sequence …takamasa/J-US2012/image/Prof Abe.pdf · Phenomena Identification in Severe Accident Sequence and Safety Issues ... Three Mile

SBO

Steam condensation by- suppression pool scrabbling- PCCSHydrogen dealing

Pressure vessel: Loss of cooling capability

Core cooling at High pressureWithout no electricity(Passive cooling system)- IC (gravity driven) / SG- HPCI (steam turbine driven)- RCIC (steam turbine driven)

Containment vessel: Pressure and temperature increase

Depressurization by- SR valve- ADS

Filtered vent to PreventCV failure- Depressurization- Heat release

1-2 hours- Core damage start- Hydrogen generation start

A few hours- Pressure increase- Temperature increase

A day- Containment failure

A few hours- Core melt start -> Pressure vessel failure- Large Hydrogen generation

Degraded /Melted core behavior- Debris bed cooling- Molten material behavior- IVR

PossibleManagement

Severe Accident Transients and possible accident management according to the transients

Alternative core cooling byPassive cooling system under Low pressure

+

Phenomena Transient under No management

PossibleManagement

Phenomena Transient under Nomanagement

Extend containment failure and can wait electricity recover

Molten material jet break up behavior

Diameter= 20[mm]U-alloy78 : 270[℃], 400[g]Water temperature=70[℃]

0.00s 0.05s 0.10s 0.15s 0.20s 0.25s 0.30s 0.35s

Page 13: Phenomena Identification in Severe Accident Sequence …takamasa/J-US2012/image/Prof Abe.pdf · Phenomena Identification in Severe Accident Sequence and Safety Issues ... Three Mile

Estimation of solidified fragments

U-alloy78: 300℃Water temperature: 70℃Injection nozzle diameter: 7mm

Vj: Penetration Velocity

0

10

20

30

40

50

60

1 10 100 1000 10000 100000

Fragment diameter [μm]

Par

ticle

siz

e di

stri

buti

on[%

]

Df = 4.54mm

Df: Median Diameter of Fragment

0

10

20

30

40

50

60

1 10 100 1000 10000 100000

Fragment diameter [μm]

Par

ticle

siz

e di

stri

buti

on[%

]

Df = 1.16mm

0

10

20

30

40

50

60

1 10 100 1000 10000 100000

Fragment diameter [μm]

Par

ticle

siz

e di

stri

buti

on[%

]

Df = 0.53mmVj = 3.92m/s Vj = 5.00m/sVj = 2.10m/s

Critical Weber number

18=cWe

( )218

wjj

j

uud

⋅=ρ

σ

wujρ

ju

Rayleigh-Taylorinstability

( )gwj

j

ρρσ

πλ−

=3

2

Heavier density fluid

Lighter density fluidGravity

Heavier density fluid

Lighter density fluidGravity

Kelvin-Helmholtz instability

( )wj

wjj

U ρρρρπσ

λ2

2 −=

wuwρ

jρju

Time growth rate of K-H instability

( ) ( )( ) kgk

khcukhcu

ljj

llljjj

ρρσ

ρρ

−+=

−+− cothcoth 22

rit kc ⋅=γTime growth rate

wu wρ

jρju

h

jh

wh

Estimation of generated fragments

0.1

1

10

100

0 2 4 6Relative velocity [m/s]

Wave lengt

h [

mm

]

Rayleigh-TaylorCritical Weber numberKelvin-HelmholtzMost-unstable wavelength of K-HNeutral-unstable wavelength of K-H

●Φ7mm▲Φ10mm■Φ15mm×Φ20mm

Nozzle diameterExperimental results

0

5

10

15

20

25

30

0 2 4 6 8 10 12

Median diameter = 5.40mmPenetration velocity = 1.85m/s

Fragment diameter [mm]

[ %

/ m

m ]

Page 14: Phenomena Identification in Severe Accident Sequence …takamasa/J-US2012/image/Prof Abe.pdf · Phenomena Identification in Severe Accident Sequence and Safety Issues ... Three Mile

Experimental result of atomization behavior

0ms 10ms 20ms 30ms 40ms

50ms 60ms 70ms 80ms 90msDiameter=φ10mm

PIV result of Jet inside flow distribution

envdtdr

−=ju ρ,

wwu ρ,

21

00 2

1⎟⎟⎠

⎞⎜⎜⎝

⎛=

c

j

j

brk

EDL

ρρ

Epstein’s correlation

(3) PVI result

Page 15: Phenomena Identification in Severe Accident Sequence …takamasa/J-US2012/image/Prof Abe.pdf · Phenomena Identification in Severe Accident Sequence and Safety Issues ... Three Mile

Velocity distribution and fragmentation behavior

Shear stress distribution in x direction

Page 16: Phenomena Identification in Severe Accident Sequence …takamasa/J-US2012/image/Prof Abe.pdf · Phenomena Identification in Severe Accident Sequence and Safety Issues ... Three Mile

Experimental result of jet break up length

( )cjjD ρρ0 ( )cjjD ρρ0 FrFr

Epstein’ equation

Saito’ equation21

0

221

0

1.2 ⎟⎟⎠

⎞⎜⎜⎝

⎛⎟⎟⎠

⎞⎜⎜⎝

⎛=

J

J

w

j

J

brk

gDV

DL

ρρ

( ) 21

2 wjo

jobrk E

DL ρρ=

PREMIXPresent experimentsFARO

CCM

MELT2Saito

Moriyama

Epstein type Saito type

Diameter=7-20mm

U-alloy78:100~200g

270~300℃

Water temp.=60-70℃

Experimental conditions

E0=0.065

Schematic diagram of test apparatus Bird-eye view of test rig

Counter-current flow limitation in debris bed

Page 17: Phenomena Identification in Severe Accident Sequence …takamasa/J-US2012/image/Prof Abe.pdf · Phenomena Identification in Severe Accident Sequence and Safety Issues ... Three Mile

Wallis correlation for gas-liquid flow Void fraction in debris bed

Counter-current flow limitation in debris bed

SBO

Steam condensation by- suppression pool scrabbling- PCCSHydrogen dealing

Pressure vessel: Loss of cooling capability

Core cooling at High pressureWithout no electricity(Passive cooling system)- IC (gravity driven) / SG- HPCI (steam turbine driven)- RCIC (steam turbine driven)

Containment vessel: Pressure and temperature increase

Depressurization by- SR valve- ADS

Filtered vent to PreventCV failure- Depressurization- Heat release

1-2 hours- Core damage start- Hydrogen generation start

A few hours- Pressure increase- Temperature increase

A day- Containment failure

A few hours- Core melt start -> Pressure vessel failure- Large Hydrogen generation

Degraded /Melted core behavior- Debris bed cooling- Molten material behavior- IVR

PossibleManagement

Severe Accident Transients and possible accident management according to the transients

Alternative core cooling byPassive cooling system under Low pressure

+

Phenomena Transient under No management

PossibleManagement

Phenomena Transient under Nomanagement

Extend containment failure and can wait electricity recover

Page 18: Phenomena Identification in Severe Accident Sequence …takamasa/J-US2012/image/Prof Abe.pdf · Phenomena Identification in Severe Accident Sequence and Safety Issues ... Three Mile

Accident progression of light water reactor accidentRoad map committee on severe accident research in AESJ (2011.03.08, Organizer: Y. Abe)

LOCARIA

Transient phenomena

Closure of accident

Severe accident

Accident management (AM)

Cooling failure

Containment failureFP release to environment

Phase I

Phase II

Accident progression

Prevention of nuclear disasters

Decay heat removal by Engineering facilities(ECCS)

Schematics of Accident management• DBA: Succeed decay heat removal by ECCS

– PCV: High pressure, CV: Low pressure.– Fuel is intact.

• Phase I -AM: Succeed to operate engineering cooling system by alternative emergency power sources to avoid severe accident.– Fuel is intact.

• Phase II-AM: Succeed alternative coolant injection without any electric power source under low PCV pressure. – PCV: Low pressure by ADS and/or SRV. – CV: Medium pressure below design value.– Fuel is intact or slight damaged.– No or little FP release to environment.

• Prevention of nuclear disasters:– PCV: High pressure, CV: High pressure– Fuel is damaged and is melted.– CV is damaged and FP is released to environment.– Closure of molten material in damaged PCV and CV.

Page 19: Phenomena Identification in Severe Accident Sequence …takamasa/J-US2012/image/Prof Abe.pdf · Phenomena Identification in Severe Accident Sequence and Safety Issues ... Three Mile

END