ch 8 heat transfer

8/2/2019 Ch 8 Heat Transfer

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Heat Transfer for a NuclearReactor


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Review Heat Transfer Terms

Conduction-occurs across the medium1

Convection-occurs between a surfaceand a moving fluid

2

Radiation Heat Transfer-occursbetween two surfaces

3

q kdt

dx

q h(Tc Tb )

q Ts4 T

sur

4


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Heat Generation

200 MeV/ fission (ER)

Ed = Energy deposited in locally ~180MeV

Number of fissions in a core are afunction of the FLUX(f

FLUX is a function of position in thecore fr,z


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Heat Generation

H

R

r

z

qr(r) 2.32PE

d

nERJ0

2.405r

R

qmax 1

2Ha2qr(0)


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Decay heat

Heat is released asthe accumulated

fission productsdecay

The amount of heatis fission products to the power level

P t0,ts P

P ts P

P t0 ts

P


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Coolant Flow q=w(hout-hin)

Steam

Tout

Water

Tin

Tin

Tout

q

q

Recirculating


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Plate fuel

X

a a+ba

a+b

Tfuel Tmax q a2

2kf

Tclad Ts x a

bTs Tc

q TmaxTc

a2kfA

bkcA


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Cylinder

z

Tmax

Ts

Tc

TF

Tfuel Tmax q r2

4kf;

Tclad Ts ln(a b) Tc ln a (Ts Tc )ln r

ln 1b

a

a

a+b

q 2Hkc (Ts Tc )

ln 1b

a


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Coolant Channels

Now you need toremember more

heat transfer andfluid mechanics

The heat transfer fora channel is

h Ck

De

Re

mPr

n

C 0.042P

D

0.024

Re D

;Pr

;Nu

hL

kf


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Other coolants

Gas cooled Helium

Pebble bed in development

Liquid sodium and potassium

Need corrosive resistant structure


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The Boiling Crisis

ln q

T

Annular flow

Partial film

Full film


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LOCA

Address component breakdown or acombination of component breakdowns

that lead to interruption of normalcooling

When an interruption occurs, the fission

process is terminated, however heatgeneration continues


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Classifications of operation

Normal

Operational transients

Upsets

Emergencies

Limiting Fault Conditions includesDesign basis accident DBA

Unprotected or beyond DBA


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Engineered Safety Systems

The actions aredone as a result of

instrument signalsReliability

Duplication

Diversity


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Most common ESS

Alternate cooling

SCRAM - Tripping - insert control rodsto stop fission

Control

Cool

Contain


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Some examples

Millstone 1(660 MWe BWR) - corrosion ofcondensers leads to sea water to enter

primary cooling circuitBrowns ferry fire -(2 1065 MWe BWR 1 inconstruction) fire affected 2000 cables causeabout $10 M

Three mile island- relief valve stuck openGinna 490 MWe PWR- rupture in a steamgenerator tube

Mihama-2 - 500 MWe PWR rupture in a

steam generator tube


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More examples

Chornobyl-Chernobyl

Chalk River - NRX- control rod/ operator error

forerunner to the CANDUWindscale fire- UK large air cooled piledesigned for Pu burst fuel cartridge

St. Laurent - French

Hunterston scotland - Seawater in the reactorvessel

Hinckley point

EBR-1 and Fermi -1 fast breeder.

ch 8 heat transfer

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