phenomena identification in severe accident sequence …takamasa/j-us2012/image/prof abe.pdf ·...
Post on 04-Jun-2018
217 Views
Preview:
TRANSCRIPT
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)
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
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
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.)
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
• 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)
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
• 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
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
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.
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)
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
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
wρ
wujρ
dσ
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 ]
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
Velocity distribution and fragmentation behavior
Shear stress distribution in x direction
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
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
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.
END
top related