Selection Logic
Neutron Spectrum
Coolant
Fuel PinGeometry Loop
Configuration
Accident Response
Energy Conversion
Specific Mass Specific
Area
Safety
Nuclear Core Issues
Reactor Type Mean Neutron Energy ExamplesFast 0.30 MeV SP-100, Cosmos-1900
Epithermal 1-10 eV Rover (NERVA)Thermal 0.05-0.1 eV SNAP-10A, TOPAZ
Key Differences-Thermal vs Fast Reactors
• Low 235U Critical Mass for Thermal Reactor
- Advantage where unit cost is paramount or many units are required
- Unsuitable for long life time, very high power reactorsOverly large burn-up fractionLoss of control capabilityFuel degradation
• Hydrogen Moderated Reactors Temperature Limited(900 to 950 °K unless moderator is separately cooled)
• Beryllium Moderated reactors Similarly Limited in Temperature(Helium Formation)
• Graphite (Carbon) Moderated Reactors large and Relatively Heavy
• Fast Reactor Restart Not Limited by Fission Product Poisoning
• Compactness Favors High Fuel Density Fast Reactor Designs------------------------------------------------------------------------------------------
Fissile Fuel Depletion
• 1 MWd (thermal) ≈ 1 g 235U burned
• 7 years at 2.0 MWt ≈ 5 kg 235U burned
This is:
50% of 235U loading of 2.0 MWt Thermal Reactor
3% of 235U loading of 2.0 MWt Fast Reactor
300025002000150010005000
Thermoelectric
Rankine-Organic
Rankine-Hg
Rankine-K
Brayton
Stirling
Thermionics -in core
Thermionic-out of core
Amtec
Operating Temperature Range for SP-100 Power Conversion Schemes
Temperature ° K
35302520151050
Thermionic-out of core
Thermoelectric
Rankine-Hg
Thermionics -in core
Brayton
Rankine-Organic
Rankine-K
Stirling
Amtec
5
5.4
7
10
18.6
20
20
25.4
28.5
Conversion Efficiencies for SP-100 Systems
Efficiency-%
Mass Distribution of SP-100 Power Source (1988)
Shield
Heat Rejection
Reactor
Primary Ht.Transport
Structural
Power Conv.
Power Conditioning
I & C
23 %
19 %
15 %
12 %
10 %
8%
7%
7 %
Total Mass = 5422 kg