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Heat Pipe Based Emergency Cooling System For Removing Decay Heat from Nuclear
Reactor and Spent Fuel Pool
Japan Association of Heat Pipe Meeting, Waseda University, 09 July 2011
Randeep Singh, Masataka MochizukiFujikura Ltd. Tokyo
Nuclear Fuel Emergency Cooling System should be fully passive and
functional in adverse conditions without any consequences of failure.
Background
Radiation leak and destruction caused in Fukushima Nuclear Power Plant due to Emergency Cooling System (diesel generator) failure
Types of Reactors: Boiling Water Reactor (BWR)
Reactor Reactor Reactor Reactor
vesselvesselvesselvessel
Fuel core Fuel core Fuel core Fuel core
elementelementelementelement
Control rod Control rod Control rod Control rod
elementelementelementelement
Circulation Circulation Circulation Circulation
pumppumppumppump
Control rod Control rod Control rod Control rod
motorsmotorsmotorsmotors
SteamSteamSteamSteam
Inlet Inlet Inlet Inlet
circulation circulation circulation circulation
waterwaterwaterwaterHP HP HP HP
turbineturbineturbineturbine
LP LP LP LP
turbineturbineturbineturbineElectrical Electrical Electrical Electrical
generatorgeneratorgeneratorgeneratorEG EG EG EG
exciterexciterexciterexciter
Steam Steam Steam Steam
condensercondensercondensercondenser
Water circulation Water circulation Water circulation Water circulation
pumppumppumppump
Cold water for Cold water for Cold water for Cold water for
condensercondensercondensercondenserPrePrePrePre----
warmerwarmerwarmerwarmer
Condenser cold Condenser cold Condenser cold Condenser cold
water pumpwater pumpwater pumpwater pump
Concrete chamberConcrete chamberConcrete chamberConcrete chamber
Connection to Connection to Connection to Connection to
electricity gridelectricity gridelectricity gridelectricity grid
BWR is prone to radiation leak out in case of any mechanical leakage
Types of Reactors: Pressurized Water Reactor (PWR)
Electricity Electricity Electricity Electricity
transmissiontransmissiontransmissiontransmissionElectricity Electricity Electricity Electricity
consumptionconsumptionconsumptionconsumption
Sea Sea Sea Sea
water water water water
PWR is more safe against radiation leakage
1 kg U-235 ~ 3M x 1 kg Coal
Nuclear Fuel: Massive Energy Source
Fuel Pellet
Zirconium rod
(179-264 fuel rods per fuel
bundle)
� Japan has 54 Nuclear power reactors with 49GW electric power production (30% of country demand)
� 19 new reactors with 13 GW electricity output has been proposed to be built until 2017.
� All of Japanese Nuclear Power Plant are constructed along the seashore to use sea water for cooling.
Location of Nuclear Power Plant in Japan
Now, nuclear electric power support approx. 30 % of nations demand and will increase to 41% in 2019.
Share of Nuclear Power is Increasing
x 108 kWh
Nuclear
Oil
Coal
Gas
HydroelectricGeothermal
There are total 432 nuclear reactors in the world which will increase to 572 reactors in near future.
Japan
German
Canada
China
Brazil
Japan is 3rd
Nuclear Power Plant in the World
USA
France
Russia
Korea
UK
India
NO.1NO.1NO.1NO.1 NO.2NO.2NO.2NO.2 NO.3NO.3NO.3NO.3 NO.4 NO.4 NO.4 NO.4 NO.5NO.5NO.5NO.5 NO.6NO.6NO.6NO.6Electric-Power (MW)Electric-Power (MW)Electric-Power (MW)Electric-Power (MW) 460460460460 1,1001,1001,1001,100Thermal Power (MW)Thermal Power (MW)Thermal Power (MW)Thermal Power (MW) 1,3801,3801,3801,380 3,2933,2933,2933,293ConstructionConstructionConstructionConstruction Sept, 1967Sept, 1967Sept, 1967Sept, 1967 May, 1969May, 1969May, 1969May, 1969 Oct, 1970Oct, 1970Oct, 1970Oct, 1970 Sept, 1972Sept, 1972Sept, 1972Sept, 1972 Dec, 1971Dec, 1971Dec, 1971Dec, 1971 May, 1973May, 1973May, 1973May, 1973Commercial OperationCommercial OperationCommercial OperationCommercial Operation March, 1971March, 1971March, 1971March, 1971 July, 1974July, 1974July, 1974July, 1974 March, 1976March, 1976March, 1976March, 1976 Oct, 1978Oct, 1978Oct, 1978Oct, 1978 April, 1978April, 1978April, 1978April, 1978 Oct, 1979Oct, 1979Oct, 1979Oct, 1979Type of Nuclear ReactorType of Nuclear ReactorType of Nuclear ReactorType of Nuclear ReactorType of ReactorType of ReactorType of ReactorType of Reactor MarkMarkMarkMark----ⅡⅡⅡⅡContractorContractorContractorContractor GEGEGEGE GE+ToshibaGE+ToshibaGE+ToshibaGE+Toshiba ToshibaToshibaToshibaToshiba HitachiHitachiHitachiHitachi ToshibaToshibaToshibaToshiba GE+ToshibaGE+ToshibaGE+ToshibaGE+ToshibaNumber of Fuel BundleNumber of Fuel BundleNumber of Fuel BundleNumber of Fuel Bundle 400400400400 764764764764Length of Fuel Core(m)Length of Fuel Core(m)Length of Fuel Core(m)Length of Fuel Core(m) 4.354.354.354.35Number of Control RodNumber of Control RodNumber of Control RodNumber of Control Rod 97979797 185185185185Reactor VesselReactor VesselReactor VesselReactor Vessel
ID(m)ID(m)ID(m)ID(m) 4.84.84.84.8 6.46.46.46.4Height(m)Height(m)Height(m)Height(m) 20202020 23232323
Weight(Ton)Weight(Ton)Weight(Ton)Weight(Ton) 440440440440 750750750750Concrete ChamberConcrete ChamberConcrete ChamberConcrete Chamber
Height(m)Height(m)Height(m)Height(m) 32323232 48484848OD of Top(m)OD of Top(m)OD of Top(m)OD of Top(m) 10101010 10101010
OD of Bottom(m)OD of Bottom(m)OD of Bottom(m)OD of Bottom(m) 18181818 25252525
TurbineTurbineTurbineTurbineRotation(rpm)Rotation(rpm)Rotation(rpm)Rotation(rpm)
Inlet TempInlet TempInlet TempInlet Temp. . . . of vaporof vaporof vaporof vapor((((℃℃℃℃))))
Vapor Pressure(Kg/cmVapor Pressure(Kg/cmVapor Pressure(Kg/cmVapor Pressure(Kg/cm2222.G).G).G).G)
FuelFuelFuelFuelType of FuelType of FuelType of FuelType of FuelWeight(Ton)Weight(Ton)Weight(Ton)Weight(Ton) 69696969 132132132132
Oxide UraniumOxide UraniumOxide UraniumOxide Uranium94949494
3,2003,2003,2003,200
1,5001,5001,5001,50028228228228266;866;866;866;8
Water Volume ofWater Volume ofWater Volume ofWater Volume ofSuppression Pool(Ton)Suppression Pool(Ton)Suppression Pool(Ton)Suppression Pool(Ton)
2,3812,3812,3812,381784784784784
1,7501,7501,7501,750 2,9802,9802,9802,980
500500500500
33333333 3434343411111111
4.474.474.474.47137137137137
5.65.65.65.622222222
Boiling Water Reactor(BWR)Boiling Water Reactor(BWR)Boiling Water Reactor(BWR)Boiling Water Reactor(BWR)MarkMarkMarkMark----ⅠⅠⅠⅠ
548548548548
20202020
Mark-ⅡⅡⅡⅡ
Mark-ⅠⅠⅠⅠ
Fukushima No.1 Nuclear Power Facility (TEPCO) Details
Construction of Reactor Vessel (Mark-I) in 1968
In 2011 before the disaster
Fukushima Nuclear Power Plant
1 sec 1 hr 1 day
0.5%
1.1%
6.4%
Decay heat is the heat mainly released by beta decay of the fission products sometime after the actual fission has taken place. After reactor shutdown, the decay heat is around 7% of the total
fission energy during steady state operation. About one hour after shutdown, the decay heat reduces to 1.5% and after one day it accounts to heat generation of 0.6% of previous core power.
The decay heat decreases exponentially and can be approximated by:
P: Decay Heat (W)Po: Normal Thermal power before shutdown (W)t: Time since reactor shutdown (s)ts: Time of reactor shutdown measured from startup (s)
Decay Heat from Nuclear Power Reactor
Reactor startup
Reactor shutdown
Observed time
tts
Assume:Fukushima reactor No.1Thermal power: 1380 MWElectrical output: 460 MW
Condenser
Reactor Building
Concrete Chamber
Vapor (282℃℃℃℃,66.8 kg/cm2)
Control Rod
Suppression Pool1,750 Ton
Vent
Turbine Generator
WaterPump
CoolingPump
Circulation Pump5,400KW
180℃℃℃℃
280℃℃℃℃
Reactor Vessel
460MW-e BWR (Thermal Power:1,380KW)
Fuel
ECCS/ Water Spray for Chamber
ECCS/ High PressureWater Spray for Core
ECCS/ Low Pressure Water Spray for Core
Turbine Building
Water WaterWasteWater
Sea waterInlet
Current System: Fukushima No.1 Reactor
Condenser
Reactor Building
Concrete Chamber
Vapor (282℃℃℃℃,66.8Kg/cm2)
Control Rod
Suppression Pool1,750 Ton
Vent
Turbine Generator
WaterPump
CoolingPump
Circulation Pump5,400KW
180℃℃℃℃
280℃℃℃℃
Reactor Vessel
460MW-e BWR (Thermal Power:1,380KW)
Fuel
ECCS/ Water Spray for Chamber
ECCS/ High PressureWater Spray for Core
ECCS/ Low Pressure Water Spray for Core
Turbine Building
Water Water
Valve
Water reservoir
Heat Pipe Condenser
Heat Pipe Evaporator
Sea waterInlet
WasteWater
Proposed Heat Pipe ECCS System for BWR Plant
Cross section (A-A’)
Jet Pump
Fuel rod
Core Shroud
Control RodHeat Pipe Evaporator
180℃℃℃℃Water
280℃℃℃℃Vapor
Vapor Dryer
Vapor Separator
Water Spurger
Top Plate
Core Shroud
Vent
ControlRod
Fuel
Jet Pump
Circulation Pump5,400KW
A A’
Vapor
Liquid
HeatPipe
Vapor (282℃℃℃℃,66.8Kg/cm2)
Internal Details of BWR Reactor with Heat Pipe ECCS
Natural Air
Cooled Condenser
Vapor FlowReservoir
Water
Valve
Liquid Flow
Evaporator
Reactor VesselBuilding
Separated Type Loop Heat Pipe Concept
Material of TubeMaterial of TubeMaterial of TubeMaterial of Tube SUS-316L with Ti coatingSUS-316L with Ti coatingSUS-316L with Ti coatingSUS-316L with Ti coating
OD of Evaporator Ring (m)OD of Evaporator Ring (m)OD of Evaporator Ring (m)OD of Evaporator Ring (m) 6666OD of Evaporator Tube (m)OD of Evaporator Tube (m)OD of Evaporator Tube (m)OD of Evaporator Tube (m) 0.150.150.150.15ID of Evaporator Tube (m)ID of Evaporator Tube (m)ID of Evaporator Tube (m)ID of Evaporator Tube (m) 0.140.140.140.14Length of Evaporator (m)Length of Evaporator (m)Length of Evaporator (m)Length of Evaporator (m) 6666No. of EvapaoraorNo. of EvapaoraorNo. of EvapaoraorNo. of Evapaoraor 62626262Heat Transfer EnhansementHeat Transfer EnhansementHeat Transfer EnhansementHeat Transfer Enhansement With NeidleWith NeidleWith NeidleWith Neidle
OD of Tube (m)OD of Tube (m)OD of Tube (m)OD of Tube (m) 1111ID of Tube (m)ID of Tube (m)ID of Tube (m)ID of Tube (m) 0.960.960.960.96
OD of Tube (m)OD of Tube (m)OD of Tube (m)OD of Tube (m) 0.30.30.30.3ID of Tube (m)ID of Tube (m)ID of Tube (m)ID of Tube (m) 0.260.260.260.26
Top HeaderTop HeaderTop HeaderTop Header
BotomBotomBotomBotomHeaderHeaderHeaderHeader
EvaporatorEvaporatorEvaporatorEvaporator
6m
6m
0.15m
Evaporator
Bottom Header
Top Header
Specification of Heat Pipe Evaporator
Reservoir
Water
Air Cooled Condenser
0.4m x 42 = 16.8m
0.346m x 20= 6.92 m
5m
0.15m
Material of TubeMaterial of TubeMaterial of TubeMaterial of Tube SUS-316L with Ti coatingSUS-316L with Ti coatingSUS-316L with Ti coatingSUS-316L with Ti coating
Tube Pitch(m)Tube Pitch(m)Tube Pitch(m)Tube Pitch(m) 0.40.40.40.4OD of Condenser Tube (m)OD of Condenser Tube (m)OD of Condenser Tube (m)OD of Condenser Tube (m) 0.150.150.150.15ID of Condenser Tube (m)ID of Condenser Tube (m)ID of Condenser Tube (m)ID of Condenser Tube (m) 0.140.140.140.14Length of Condenser (m)Length of Condenser (m)Length of Condenser (m)Length of Condenser (m) 5555No. of CondenserNo. of CondenserNo. of CondenserNo. of Condenser 42 x 20 =84042 x 20 =84042 x 20 =84042 x 20 =840Fin MaterialFin MaterialFin MaterialFin Material Aluminum Aluminum Aluminum Aluminum Fin Size (m)Fin Size (m)Fin Size (m)Fin Size (m) OD:0.3, T=0.003OD:0.3, T=0.003OD:0.3, T=0.003OD:0.3, T=0.003Fin Pitch (m)Fin Pitch (m)Fin Pitch (m)Fin Pitch (m) 0.020.020.020.02
OD of Tube (m)OD of Tube (m)OD of Tube (m)OD of Tube (m) 1111ID of Tube (m)ID of Tube (m)ID of Tube (m)ID of Tube (m) 0.960.960.960.96
OD of Tube (m)OD of Tube (m)OD of Tube (m)OD of Tube (m) 0.30.30.30.3ID of Tube (m)ID of Tube (m)ID of Tube (m)ID of Tube (m) 0.260.260.260.26
Volume (mVolume (mVolume (mVolume (m3333 )))) 1.51.51.51.5
SizeSizeSizeSize ID: 1m, H: 1.5mID: 1m, H: 1.5mID: 1m, H: 1.5mID: 1m, H: 1.5m
Volume (mVolume (mVolume (mVolume (m3333 )))) 32.232.232.232.2
SizeSizeSizeSize ID: 4.6m, H: 4.6mID: 4.6m, H: 4.6mID: 4.6m, H: 4.6mID: 4.6m, H: 4.6mWater TankWater TankWater TankWater Tank
Top HeaderTop HeaderTop HeaderTop Header
BotomBotomBotomBotomHeaderHeaderHeaderHeader
CondenserCondenserCondenserCondenser
ReserverReserverReserverReserver
Top Header
Bottom Header
Specification of Heat Pipe Condenser
Evaporator Tubes
SUS316 (Ti-coating) OD/ID:150/140 mm Pitch=0.3m, N=62, L = 6 m, L/D = 40
6m
6m
Reactor Vessel
Valve
Air Cooled Condenser
Reservoir
Top Header
Bottom Header
Fuel
Thermal Circuit Diagram
Heat Pipe Design & Thermal Resistance
SUS316 (Ti-coating) OD/ID:150/140 mm, L = 5mFin: 0.3 m OD x 3 mm thk, Pitch: 20 mm, N = 42 x 20 = 840 pcs
Rreq=(282-50) / 27 x 106 = 8.6 x10-6 K/WRact = 8.35 x10-6 K/W < Rreq
Tair ~50 °°°°C
Tcondenser inner
Tvapour
eoeo
eo
AhR
1=
Tevaporator outer
Treactor water ~ 282 ºC
heo = 2000 W/m2.K Aeo = 175 m2
eiei
ei
AhR
1=
hei = 10,000 W/m2.K Aei = 163 m2
cici
ci
AhR
1=
coa
co
AhR
η
1=
hci = 10,000 W/m2.K Aci = 1850 m2
ha = 20 W/m2.K η = 0.9Aco = 24200 m2
Q = 27 MWWall resistance neglected
P=0.4m
Condenser tubes with radial fins
Loop Heat Pipe Design
Reactor Vessel
WL
Pressure balance Tube
Water Tank: 32.2 m3
Vapour: 66.8Kg/cm2
VelocityV =10 m/s
Valve
Emergency Cooling Water
Fuel
d
ID:3 m
Gravity Assisted Emergency Water Charge System
Initial short time (600 sec) water charge by gravity (without pump) will reduce HPHE system size and thus cost:
∫Q (t) =20,100 MJt=0,600
Volume of water required: Assume, water inlet ~ 50 °°°°C and outlet ~ 282 °°°°C
= 32.2 m3
After 600 sec, decay heat will reduce from 1380 MW to just 27 MW which can be cooled by HPHE
Assume, water velocity, v, ~ 10 m/s at tube exit, Height of reservoir:
For tank ID: 3 m & water volume, V = 32.2 m3, tank height ~ 4.6 m
Tube diameter : = 0.0827 m
= 5.1 m4.
6 m
5.
1 m
Total Passive ECCS System
Operation
After reactor shutdown, charge 32.2 tons of
water in 600 sec
After 600 sec, stop water charging & passive removal of decay heat by HP ECCS
Vapor FlowReservoir
Water
Valve
Liquid FlowEvaporator
Reactor Vessel
Emergency Cooling
Water Tank
Air Cooled Condenser
Fuel Rod
Valve
Summary Design of Heat Pipe ECCS
Stopped Water ChargedContinue to cool by Heat Pipe ECCS
Inserted Control Rod, Stopped Nuclear Fission
Decay Heat: (Q(t)=Qto x t 0.2
ECCS operation, Charge Cooling Water(0.0383Ton/s, Tw=50℃℃℃℃)
Heat Pipe ECCS Operation
Normal Operation282℃℃℃℃
Water Volume inside Vessel:200Ton
Flow Chart
t=0
t >600 s
Y
N
Heat Pipe ECCS: Thermal Simulation
0000
50505050
100100100100
150150150150
200200200200
250250250250
300300300300
350350350350
0000 100,000100,000100,000100,000 200,000200,000200,000200,000 300,000300,000300,000300,000 400,000400,000400,000400,000 500,000500,000500,000500,000 600,000600,000600,000600,000 700,000700,000700,000700,000
Boundary Condition
1. Water Volume of Reactor Vessel: 200Ton
2. Initial Temperature of water: 282℃℃℃℃3. Ambient Temperature: 50℃℃℃℃4. Thermal Resistance of HP ECCS:
5.77 X 10-5 K/W
Change of Water Temperature Inside of Reactor
Vessel Cooled By Heat Pipe ECCSW
ater
Tem
pera
ture
(℃℃ ℃℃
)
14hr.
1day
Elapsed Time (Seconds)
2day 3day 4day 5day 6day 7day 8day
Approximately 14 hours cooling can reduce the temp. less than 100℃℃℃℃.
Water Temperature Variation Inside Reactor Vessel Under
Charged Water and Heat Pipe ECCS
Boundary Condition
1. Water Volume of Reactor Vessel: 200Ton
2. Initial Temperature of water: 282℃℃℃℃3. Ambient Temperature: 50℃℃℃℃4. Thermal Resistance of HP ECCS:
5.77 X 10-5 K/W
6. Water Charge for initial 600 Seconds,
0.0383 Ton/s
600 SecondsWater Charge
6hr.
Wat
er T
empe
ratu
re (℃℃ ℃℃
)
Elapsed Time (Seconds)
9hr. 12hr. 15hr. 18hr.3hr.
Approximately 6 hours cooling can reduce the temp. less than 100℃℃℃℃.
Heat Pipe Based ECCS: Design Details
Air cooled
condenser
Initial water
charge systemReactor
vessel
Evaporator
sectionVapour
line
Liquid
line
Fuel rods
Control
rods
Heat Pipe Based ECCS: Design Details
Initial water
charge systemEvaporatorCondenser
Reactor
vessel
Evaporator
header
Fuel rods
HPHE-ECCS: Lab Scale Test Prototype Details
Vapour
line
Condenser
Liquid
line
Immersion
heater
Evaporator
section
Liquid
level
HPHE-ECCS: Lab Scale Test Prototype Details
Heater
tankEvaporator
assembly
Heater
Condenser
assemblyVapour line
Liquid line
Condenser
support
Flange
joint
Fittings
Tank
bottom
Refueling bay
Steel containment
vessel
Concrete shell
(drywell)
Secondary containment
Wetwell (torus)
Reactor vessel
Spent fuel pool
Spent Fuel Pool
� Used nuclear fuel� Pools are typical 12 m deep
with bottom 4.3 m equipped with steel racks used to hold spent fuel from reactor
� Water used as coolant and to shield radiation
� Maximum temperature of the spend fuel drops significantly between 2 to 4 years time
� Fuel assemblies, after being in reactor for 3 – 6 years, are stored in spent pool for 10 – 20 years before sending for reprocessing or dry cask storage
Nuclear Fuel Bundle
Specification of Fuel Bundle
No of Fuel Rods
Rod Dia Rod Length Thermal power/tonThermal power/rod
Nuclear Fuel Bundle: Structure
Handle
Upper tie plate
Fuel rod
Spacer
Containment
Lower tie plate
Pellet
Zircaloy ferrule spacer
Fuel Pellet
Pushing spring
Fuel rod
Control rod
Channel box
Water rod
Cooling water
12m
4m
SUS lining + 1.5m thick concrete.
Fuel bundle
12m
10m
0.14m0.2m
Assumptions:• Number of spent fuel rods in the
pool: 29 x 35 = 1,015
• After cooling fuel inside of reactor for approx. 30 days, it was transported to the water storage pool. The decay heat is estimated approx. 100 x 40,000 = 4MW.
1,400 Ton
Design Condition (Basis: Fukushima No.4 Reactor)
Air Cooled condenser7.6mx 4m x 0.6 m(42 x3=126 tubes)
Liquid
Evaporator9.5mx 8m (95 tubes)
Used Fuel
Vapor
Water Pool
Number of Cooling Loop : 35
Summary Design of Heat Pipe Cooler
Condenser
0.18 x 42= 7.56m
0.18 m OD: 50.8m x t: 2m
4m
Evaporator
0.1 x 95= 9.5m
0.1m
8m
x 3333 rows
OD:50.8m x t: 2m
x 1 row
Thermal Circuit Diagram
Heat Pipe Design & Thermal Resistance
Rreq=(40-30) / (35 loops)x 4 x 106
= 8.75 x 10-5 K/WRact = 7.675 x10-5 K/W < Rreq
Tair ~30 °°°°C
Tcondenser inner
Tvapour
eoeo
eo
AhR
1=
Tevaporator outer
Tpool water ~ 40 ºC
heo = 1000 W/m2.K Aeo = 121 m2
eiei
ei
AhR
1=
hei = 5,000 W/m2.K Aei = 112 m2
cici
ci
AhR
1=
coa
co
AhR
η
1=
hci = 5,000 W/m2.K Aci = 74.1 m2
ha = 20 W/m2.K η = 0.9Aco = 868 m2
Q = 4 MW
Wall resistance neglected
P=0.18m
Condenser tubes with radial fins (OD: 0.15 m)
Loop Heat Pipe Design
Condenser
0.18 x 42= 7.56m
0.18 mOD: 50.8m x t: 2m
4m
Evaporator
0.1 x 95= 9.5m
0.1m
8m
x 3333 rows
OD:50.8m x t: 2m
x 1 row
x 35 Loops
Fins:0.15 m OD x 2mm thk, Pitch:0.02m
0000
50505050
100100100100
150150150150
200200200200
250250250250
300300300300
350350350350
0000 20202020 40404040 60606060 80808080 100100100100 120120120120 140140140140
Conditions
1. Amount of water pool: 1,400 Ton
(Initial temp.: 30℃℃℃℃)
2. Decay heat of start of cool: 4MW
3. Neglecting heat dissipation from
water surface
Decay Heat
After just 1 day, it is estimated that temp. of cooling water is reached to 100℃℃℃℃ over.
Wat
er T
empe
ratu
re (℃℃ ℃℃
)
Elapsed Time (Hours)
No Cooling Case
P: Decay Heat (W)Po: Normal Thermal power before shutdown (W)t: Time since reactor shutdown (s)ts: Time of reactor shutdown measured from startup (s)
0000
200200200200
400400400400
600600600600
800800800800
1 ,0001 ,0001 ,0001 ,000
1 ,2001 ,2001 ,2001 ,200
1 ,4001 ,4001 ,4001 ,400
1 ,6001 ,6001 ,6001 ,600
0000 1 ,0001 ,0001 ,0001 ,000 2 ,0002 ,0002 ,0002 ,000 3 ,0003 ,0003 ,0003 ,000 4 ,0004 ,0004 ,0004 ,000 5 ,0005 ,0005 ,0005 ,000
Without Cooling
With Heat Pipe coolingWat
er T
empe
ratu
re (℃℃ ℃℃
)
Elapsed Time (Hours)
Condition
1. Amount of water pool: 1,400 Ton (Initial
temp.:30℃℃℃℃)
2. Decay heat of start of cool: 4MW
3. Neglect of heat dissipation of water surface
4. Ambient temp.: 30℃℃℃℃5. Cooling capacity of HP/Hex.: 2.19 x 10-6 K/W
Heat Pipe Cooling Case
Decay Heat
P: Decay Heat (W)Po: Normal Thermal power before shutdown (W)t: Time since reactor shutdown (s)ts: Time of reactor shutdown measured from startup (s)
Heat Pipe Spent Fuel Cooling System: Design Details
Condenser Evaporator
section
Water level
Concrete
tank with
steel lining
Fuel rods
Vapour line
Liquid line
Conclusions
1. Heat pipe based ECCS and Spent fuel cooling systems can be used to dissipate decay heat generated by nuclear fuel without needs of any electricity and in fully passive mode.
2. Heat Pipe ECCS system with cooling capacity of 27 MW decay heat (2% of reactor heat at shutdown) has been designed with initial 600 sec of gravity assisted water cooling.
3. The proposed system will be able to reduce the core temperature below 100 ºC within 6 hours of reactor shutdown.
4. Heat pipe based spent fuel cooling system with 4 MW capacity has been proposed which will be able to maintain pool temperature close to ambient.
5. The proposed systems will provide safer operational environment to the nuclear power plants and avoid any crisis situations.
� Mochizuki, et al, “Application of Heat Pipe to JSPR safety”,
Proceedings of Design Feasibility for JSPR, PP 31-39, UTNL-R0229,
Dec, 1988
References