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Nuclear Power Plants

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Fission

QuickTime an d a

TIFF (Uncompressed) decompressorare needed to see this picture.

http://www.chm.bris.ac.uk/motm/uf6/fission.gif

Moderator

Slow

neutron

Uranium-235

fission

Moderator

U-235

Control

rods

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Concepts

Review

Prompt neutrons vs Delayed neutron

Capture to Fission ratio a

New

Multiplication factor - k the number ofneutrons in this generation/number of

neutrons in the previous generationk

or keff

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Neutron cycle in a reactor

100 fission

259 neutrons produced

59 lost

Activation

products

100

absorbed

in

Fuel

no fission

100

absorbed

in

Fuelfission

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Multiplication factor

Four factor formula - Reactor of infinite size

Reproduction factor, number of nts releasedin fission per nts absorbed

f Thermal utilization, thermal nts absorbed infuel per thermal nts absorbed in fuel +thermal nts absorbed in everything else

e Fast fission factor, fast nts produced per fastneutron from thermal fission

p resonance escape probability, fraction of ntsnot captured while slowing down.

kfep

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Neutron Cycle - infinite reactor

Fast Fission

e

ep

Resonance

absorption

Thermal

absorption

epf Neutronproduction

epf = k

Captured

Absorbed

non fuel

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Real reactors

Four factors become 6

Fast non-leakage Lf

Thermal non-leakage Lt L=LfLt

keff fepLfLt

keff fepL

keff kL

QuickTime and a

TIFF (Uncompressed) decompressorare needed to see this picture.

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Neutron Cycle - finite reactor

Fast Fission e

eLfp

Slowing

Thermal

absorptionepfL

Neutron

productionepfL

Fast leak

e(1-Lf)

Absorbed

non fuel

Resonance

absorption

eLf

Captured

eLf(1-p)

Diffusion

Thermal

leak

eLfpLt

eLfp(1-Lt)

eLp(1-f)

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Basic Components

Fuel

Controlrod

Steam

generato

r

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Control Rods

Used to control the chain reaction

Materials that have larger cross-

sections than fuel

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Typical cross sections

Thermal neutron sf=572 b

U-235 B-10

sc=3000 b

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Coolant Flow q=w(hout-hin)

Steam

Tout

Water

Tin

Tin

Tout

q

q

Recirculating

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Pressurized Water Reactor

PWR

150 bar 2200 psia

Light water coolant/moderator

~ 3-4 % enriched

Steam

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Boiling Water Reactor

BWR

No separate steamgenerator

70 bar 1000 psia

10% of converted tosteam

steam

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Comparison PWR-BWR

BWR core power density 1/2 of the PWR butstill greater than Gas cooled

Steam generators for PWR requires moreupkeep

PWR coolant loop is more contained

Corrosion in the turbine can pass directly to

the BWR causing activation and higherexposures to the operating staff

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Comparison Continued

PWR have high decay heat requirecooling even when shut down

SS piping in BWR is more susceptibleto cracks

PWR have a similar issue with the

steam generator

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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

UpsetsEmergencies

Limiting Fault Conditions includes

Design basis accident DBA

Unprotected or beyond DBA

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Engineered Safety Systems

The actions aredone as a result ofinstrument signals

Reliability

Duplication

Diversity

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Most common ESS

Alternate cooling

SCRAM - Tripping - insert control rods

to stop fission

Control

Cool

Contain

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Environmental Release

Acid Rain Contribution

1000 MWe

Nuclear

SO2 - 0

Coal (1.5% S)

SO2 - 90,900 tons

Fuel oil (0.37%S)

SO2 - 22,496 tons

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Gen IV Program (INL.gov)

Gas-Cooled Fast Reactor(GFR) features a fast-neutron-spectrum, helium-cooled reactor andclosed fuel cycle

Very-High-Temperature Reactor(VHTR) agraphite-moderated, helium-cooled reactor with aonce-through uranium fuel cycle

Supercritical-Water-Cooled Reactor(SCWR) a

high-temperature, high-pressure water-cooledreactor that operates above the thermodynamiccritical point of water

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Gen IV Program

Sodium-Cooled Fast Reactor(SFR) features a fast-spectrum, sodium-cooled reactor and closed fuel cycle forefficient management of actinides and conversion of fertile

uranium

Lead-Cooled Fast Reactor(LFR) features a fast-spectrum lead of lead/bismuth eutectic liquid metal-cooledreactor and a closed fuel cycle for efficient conversion offertile uranium and management of actinides

Molten Salt Reactor(MSR) produces fission power in acirculating molten salt fuel mixture with an epithermal-

spectrum reactor and a full actinide recycle fuel cycle

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Gas-cooled fast reactor GFR

He

600 MW th

48% net eff

Coolant

Inlet 490C

Outlet 850C

Pressure 90 bar

Ave power density100 MWth/m3

Burn-up 5%

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Very High Temperature Reactor

H

production

He

Core outlet 1000 C

600 Mw t

Water

O2 H2

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Super Critical Water Cooled

Operates above thethermodynamiccritical point ( 374 C

22.1 MPa

1700 MWe

Pressure 25 MPa

T outlet is 550C

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Sodium cooled fast

T out 550 C

Mixed oxide fuel

Two sizes 150-500 MWe

500 - 1500 Mwe

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Lead Cooled Fast

300 to 1200 MWe

T outlet 550 - 800 C

Fuel is metal ornitride based

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Molten Salt

1000 MWe

T outlet 700-800 C

Molten salt fuel

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Questions