Mixed thorium-uranium dioxide fuel for high burnup in light water reactors

Conference · Wed Sep 15 00:00:00 EDT 1999

OSTI ID:23142183

Herring, J. Stephen; MacDonald, Philip E. ^[1]

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1. Advanced Nuclear Energy Products, Idaho National Engineering and Environmental Laboratory (United States)

Our objective is to develop a fuel for the existing light water reactors (LWRs) that (a) is less expensive to fabricate than the current uranium-dioxide (UO{sub 2}) fuel, (b) allows longer refueling cycles and higher sustainable plant availability factors, (c) is very resistant to nuclear weapons material proliferation, (d) results in a more stable and insoluble waste form, and, (e) generates less high level waste. Our calculations indicate that the mixed ThO{sub 2}-UO{sub 2} fuel could be burned to 72 MWd/kg (megawatt days (thermal) per kilogram) using 25 wt% UO{sub 2} and the balance ThO{sub 2}. The uranium is enriched to 19.5 wt%. Economic analyses indicate that the ThO{sub 2} UO{sub 2} fuel will require less separative work and less total heavy metal (thorium and uranium) feedstock. Because ThO{sub 2}-UO{sub 2} fuel will operate cooler, and retain within the fuel more of the fission products, especially the gasses, ThO{sub 2}-UO{sub 2} fuel can probably be safely and successfully operated to higher burnups than UO{sub 2} fuel. This will allow for longer refueling cycles and better plant capacity factors. The uranium in our calculations remained below 20 wt % total fissile fraction throughout the cycle, making it unusable for weapons. Total plutonium production per MWd was a factor of 4.5 less in the ThO{sub 2}-UO{sub 2} fuel than in the conventional fuel. Pu- 239 production per MW d was a factor of 6.5 less in the ThO{sub 2}-UO{sub 2} fuel than in the conventional fuel. The plutonium produced was high in Pu-238, leading to a decay heat 5 times greater than that from plutonium derived from conventional fuel and 40 times greater than weapons grade plutonium. This level of decay heat will require active cooling of any crude weapon, lest the components surrounding the plutonium be melted. Spontaneous neutron production for plutonium from ThO{sub 2}-UO{sub 2} fuel was 2.3 times greater than that from conventional fuel and 15 times greater than that from weapons grade plutonium. High spontaneous neutron production drastically limits the probable yield and usability of a crude weapon. Because ThO{sub 2} is the highest oxide of thorium, while UO{sub 2} can be oxidized further to U{sub 3}O{sub 8} or UO{sub 3}, ThO{sub 2}- UO{sub 2} fuel appears to be a superior waste form if the spent fuel is ever to be exposed to air or oxygenated water. And, finally, use of higher burnup fuel will result in proportionally fewer spent fuel bundles to handle, store, ship, and dispose of permanently.

• Research Organization: American Nuclear Society - ANS, 555 North Kensington Avenue, La Grange Park, IL 60526 (United States)
• OSTI ID: 23142183
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
FISSION PRODUCTS
FUEL ELEMENT CLUSTERS
GAS FUELS
HEAVY METALS
HIGH-LEVEL RADIOACTIVE WASTES
NEUTRONS
NUCLEAR WEAPONS
PLUTONIUM
PLUTONIUM 238
PLUTONIUM 239
SPENT FUELS
THORIUM
THORIUM OXIDES
URANIUM
URANIUM DIOXIDE
URANIUM OXIDES U3O8
URANIUM TRIOXIDE
WASTE FORMS
WATER COOLED REACTORS
WATER MODERATED REACTORS