Analysis of thorium-salted fuels to improve uranium utilization in the once-through fuel cycle

Technical Report · Tue Sep 01 00:00:00 EDT 1981

DOI:https://doi.org/10.2172/6049032· OSTI ID:6049032

Eschbach, E A; Merrill, E T; Prichard, A W

Calculations and analyses indicate that no improvement can be achieved in uranium utilization for the once-through LWR fuel cycle over use of slightly enriched uranium by employing thorium distributed with uranium. The study included thorium additions: (1) slight amounts, (2) larger amounts, in either intimately mixed or in duplex pellets, (3) in spectrally shifted or not spectrally shifted reactors, and (4) in three- or five-year reactivity limited exposures. While thorium-uranium combinations improves the initial conversion ratio, the reactivity lifetime was not extended enough to override the additional uranium required. The effective fission cross-section of the bred /sup 233/U relative to /sup 239/Pu's in typical LWR neutron spectra is not large enough for /sup 233/U to make as great a contribution to end-of-life reactivity as /sup 239/Pu in a slightly enriched uranium fuel element. /sup 233/U's reactivity contribution relative to /sup 239/Pu's is lower in fuel configurations such as slightly enriched uranium LWR fuel loads. On the other hand, /sup 233/U's reactivity contribution appears more positive for reactors that involve lower average concentrations of thermal neutron absorbers. If /sup 238/U-thorium fuels reprocessed, the recovered /sup 233/U would increase uranium utilization, but may not reduce fuel cycle costs. The thorium-salted fuels exhibit substantially flatter reactivity characteristics with exposure time. Spectral shift helped the utilization of uranium and thorium.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 6049032
• Report Number(s): PNL-3977; ON: DE82000809
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
THORIUM REACTORS
REACTOR PHYSICS
WATER COOLED REACTORS
FUEL MANAGEMENT
FUEL CYCLE
FUEL PELLETS
PLUTONIUM 239
REACTIVITY
THORIUM
THORIUM OXIDES
URANIUM 233
URANIUM DIOXIDE
ACTINIDE COMPOUNDS
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
ACTINIDES
ALPHA DECAY RADIOISOTOPES
CHALCOGENIDES
ELEMENTS
EVEN-ODD NUCLEI
HEAVY NUCLEI
ISOTOPES
METALS
NUCLEI
OXIDES
OXYGEN COMPOUNDS
PELLETS
PHYSICS
PLUTONIUM ISOTOPES
RADIOISOTOPES
REACTORS
THORIUM COMPOUNDS
URANIUM COMPOUNDS
URANIUM ISOTOPES
URANIUM OXIDES
YEARS LIVING RADIOISOTOPES
220100* - Nuclear Reactor Technology- Theory & Calculation