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

Topics

�Emergency Core Cooling System

�Spent Fuel Cooling System

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

Heat Pipe Based Emergency Core Cooling System for Removing Decay Heat from Nuclear Reactor

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

Heat Pipe Based Passive Cooling System For Removing Decay Heat From Spent Fuel

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

Heat Pipe Spent Fuel Cooling System: Design Details

Condenser

Evaporator

Front View

Top View

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

Thanks