nuclear energy - four months after fukushima · ~100 ebq - activity of power reactor (e - exa -...
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Institut »Jožef Stefan«Odsek za reaktorsko tehniko
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Nuclear energy - four monthsafter Fukushima
Iztok Tiselj
"Jožef Stefan Institute", Reactor Engineering Division &
Chair of Nuclear Engineering, Faculty of Mathematics and Physics
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Contents
•"Great East JapanEarthquake"• Nuclear power plants in the earthquake zone• Accident in NPP Fukushima Daiichi
• Basics of reactor engineering
• Key events,core melt
• Cooling• Restoration plans• Releases of
radioactivity•Local and
global consequences
UPI/Air Photo Service
5,6
2
3
4
1
500 m
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"Great East Japan Earthquake" max acc.: Miyagi prefecture
http://earthquake.usgs.gov/U.S. Geological Service
acceleration
(g)measured(basement)
project
N-S 0.35 0.45
E-W 0.56 0.45
Up-Down 0.31 0.43
Max. accelerations in NPP Fukushima - Daiichi -reactor #2
time (s)
NS
reactor shutdown at 0.135g
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source: JAIF
Japan nuclear power plants - earthquake
Earthquake: - automatic shut down of 11 operating reactors (control rods inserted).- cooling systems remove the residual heat from the cores.
Japan: 54 (+ 2 - 4 - X) nuc. power plants
48 GW electric (~27 %)(before quake: plans for
increase to 50% by 2030)
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Boiling water reactor - BWR
pump
river/sea
generator
condenser
turbine
turbine building
containment suppression chamber
containment drywell
steam dryer & moisture separator
jet pumpreactor core
recirculation pump
steam linereactor vessel
~20% of world power reactors.
Cooling system: p~70 bar, T~285 oC
source: NRCNuclear Regulatory Commission
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BWR reactor vessel
h=20m
diam.=5-6 m
fuel assembly
h=4m
source: General Electric
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Containment:
volume ~10000 m3
filled with N2
pressure: - design 5 bar - rupture ~8-9 bar
3000 tons of water in suppression chamber (Daiichi 2,3)
Spent fuel pool
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Nuclear physics and engineering - fundamentals ...
Fission ~200 MeV energy
Out of that ~15 MeV due to the radioactive decay of fission products!
235Un
fission products:I, Cs, Sr, Xe...
Decay heat in MW
0
10
20
30
40
50
0 5 10time after shutdown (hours)
Fukushima-Daiichi-1
Fukushima-Daiichi-2,3
0
4
8
0 7 14 21 28 35 42 49 56
time after shutdown (days)
Thermal power:
Daiichi 1 - 1380 MW
Daiichi 2,3 - 2380 MW
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RHR:
Residual Heat Removal System
Residual Heat Removal systems cool the reactors. Fukushima Daiichi - RHRs powered by diesel generators cool the cores.Fukushima Daini, Onagawa - RHRs powered by external electricity.
1st hour after earthquake:
Accident -Earthquake
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Loss of all power in Fukushima Daiichi 1-4 (blocks 5,6 slightly higher elevation)
Accident - Tsunami
D/G
source: TEPCO - Tokyo Electric Power COrporation
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Accident -Fukushima Daiichi
Cooling after Tsunami - with systems working with (almost) no electricity
Daiichi 1 ~ 8h (ICC)
Daiichi 2 ~70 h (RCIC)
Daiichi 3 ~40 h (ECCS/RCIC)
RCIC - Reactor Core Isolation Cooling System, ICC - Isolation Condenser Cooling System
Scheme of High pressure Emergency Core Cooling System (ECCS)
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Sever accident - core melting
Energy balance (boiling water reactor ~700 MW electric power):
1) Decay heat 10-20 MWh/h2) Above 1500 K - rapid Zirconium-water reaction (50 ton):
Zr + 2H2O -> ZrO2 + 2H2 + ~20 MWh/10 ton Zr
3) H2 combustion ~20 MWh/10 ton Zr
-1) Vaporization of H2O ~5 MWh/10 ton (3 h ~ 100 ton)unknown mass ~100-200 ton, unknown leak rate
-2) Heating and melting of fuel and internal structures of the reactor ~20 MWh/100 ton UO2
Three Mile Island core (PWR) 1979, core status known after few years.
source: NRC
Reactor #1 :
~ 1 day without cooling
- largest core damaged
(estimates by TEPCO, NRC)
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Source: NISA - Nuclear and Industrial Safety Agency
Containment vessel of Reactor #1 not damaged.
Accident - Fukushima Daiichi - Reactor #124 h after quake
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Source: NISASea water replaced with fresh water after 2 weeks (electricity in plant after 1 week)
Cooling restoredAccident - Fukushima Daiichi - Reactor #1 - cooling restored
30 h after quake
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Fukushima Daiichi Reactor 3similar events - strong explosion
Fukushima Daiichi Reactor 2
hydrogen(?) explosion near the suppression chamber ruptured the containment.
#2 Probably responsible for the majority of the radioactive releases!
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Problems with Spent Fuel Pools
Major problem - Reactor #4
Reactor #4 stopped in Nov. 29, 2010 -all fuel moved to Spent fuel pool.
Reactors #5 and #6 -stopped at time of earthquake - fuel in reactors and SFPools. No problems with cooling.
No problems with cooling of commonSFPool
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Spent fuel pool
Explosion
Containment vessel
Reactor vessel
1500 m3 water
~ 4 MW heat
Boiling acceptable in emergency conditions
Water level "low" 4 days after the earthquake.
H2 explosion & fire in unit 4 (after ~90 hours).
Spent fuel pool - Reactor #4 source: NRC, General Electric
TEPCO 16.5: H2 came from Reactor #3 !
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Current cooling of Spent fuel poolsExternal water spray in pools #1 & #4 - sea water in the first 2 weeks, fresh water later.
Concrete pump trucks used today. Structural integrity of pool #4 questionable. Reinforcement of the pool #4 (steel & concrete) by the end of July.
"Standard" path of water injection in spent fuel pool #2 and #3 since May.
Pools of reactors #5 and #6 and common spent fuel pool: operating cooling systems.
pool#3 10.5.
pool#4 8.5.
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Current status of Fukushima Daiichi reactors- Reactors 1,2,3 - water injected into reactor vessels ~3-9 m3/h - Evaporative cooling, cores solid, partially uncovered,
Tvessel~100-160 0C, p~1 bar (reactor #1 p ~2-3 bar)- Closed cooling circuits established in June - leaking water
decontaminated/desalinated and injected back into reactors
source: TEPCO 19.7.2011
Nitrogen injected into containment vessels of #1, #2, #3 reactors
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Radiological consequences (quantities, units, orders of magnitude)
Activity - basic unit: Bq - decay/s
~100 EBq - activity of power reactor (E - Exa - 1018)
~0.1 mBq - activity I-131 per m3 in Slovenia in March 2011 (m - mili - 10-3)Fukushima reports - units used (no prefixes): Bq/m2, Bq/m3, Bq/cm3, Bq/l , Bq/kg
Activity in US: [Ci] (1 Curie - 1 g radium-226 = 3.7*1010 Bq)
Biological radiation effects - activities and doses:
1 Bq element A ≠ 1 Bq element B
1 Bq elem. A on the ground ≠ 1 Bq A inhaled ≠ 1 Bq A ingested
Dose:
Absorbed Gy (Gray, J/kg) - for acute consequences of radiation (USA: rad=0.01 Gy)
Equivalent Sv (Sievert) - for stochastic consequences (USA: rem =0.01 Sv)
Effective (Sv) - for non-uniform irradiation (weighted sum of equivalent doses per tissue)
1 Sv ~ 1 Gy for gamma in beta radiation
Fukushima - orders of mag.: ~ 0.1 μSv/h (natural background without Radon)
~ 0.01 - 1 mSv/h (Fukushima site)
~ 10-100 mSv/h (Reactors 1,2,3,4 rooms)
~ 10 Sv/h (inside containment buildings)
Limitations: public 1 mSv/yearprofessionals 20 mSv/yearemergency 500 mSv
Radiation sickness ~ 0.5-1 Gy (Sv) in short time,
lethal ~2-5 Gy
This slide intentionally made complex!
human body ~100 Bq/kg
Radon
~0.2 μSv/h
natural background dose ~2-3 mSv/year
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Dose rate (microSv/h) at the NPP site - Main entrance
Releases:
cumulative ~5*1017 Bq
(~10% Chernobyl)
End of April ~1012 Bq/h
Limitations: public 1 mSv/yearprofessionals 20 mSv/yearemergency 500 mSv
Gesellschaft für Anlagen- und Reaktorsicherheit
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source: TEPCO
~500 m
Background: 0.1 micro Sv/h
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TEPCO
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U.S. Department of Energy, 6.5.2011
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DOE (Dept. of Energy) - measurements and predictions
First year dose (19.April)
mSv>2010-205-101-5<1
natural background dose ~2-3 mSv/year
Average Slovenian -~1 mSv from Chernobyl
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Rough estimate: 3000 Fukushima workers, average 20 mSv:Collective dose = 60 man-Sv ... 5% -> 3 additional cancer fatalities in the next
decades ... (1003 instead of 1000)...
ICRP recommendations 2007
Radiological consequences
(LNT - Linear-No-Treshold model)
Dose => Deaths:
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Fatalities, DamageEarthquake & tsunami fatalities ~23,000 (111.000 people lost homes, 37.000 new house built 11.7.2011)Fukushima accident ~100 (ICRP methodology)
Damage:Total earthquake and tsunami damage ~200-300 G$ (sources: World Bank. 21.March, 122-235 G$,
newspapers)
Sum ~ nuclear damage - without compensations for land and evacuated residents ~50-100 G$
Nuclear power - global impact:- Extensive re-assessment of nuclear safety and risks.- Setback to "Nuclear renaissance".
- Germany - nuclear phase-out in ~10 years, Italy - remains non nuclear, Japan - unclear?- UK - no change of energy plans - Nuclear energy - important part, Finland - call for new reactor, USA - nu
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Institut »Jožef Stefan«Odsek za reaktorsko tehniko
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Thanks: colleagues of R4, F8, RPU
Sources:- NISA - Nuclear and Industrial Safety Agency
http://www.nisa.meti.go.jp/english/- TEPCO - Tokyo Electric Power COrporation
http://www.tepco.co.jp/en/index-e.html- JAIF - Japan Atomic Industrial Forum
http://www.jaif.or.jp/english/index.php- DoE - Dept. of Energy (USA)
http://www.energy.gov/news/10194.htm
- World Nuclear Associationhttp://www.world-nuclear.org/info/fukushima_accident_inf129.html
- IAEA - International Atomic Energy Agencyhttp://www.iaea.org/
- NRC - Nuclear Regulatory Commission (USA)http://www.nrc.gov