A New Fuel Material for Once-Through Weapons Plutonium Burning

TLDR

Once-through oxide fuels for burning plutonium from nuclear warheads have been studied for proliferation resistance, environmental safety, and fabrication, with two‑phase fluorite–alumina mixtures and fluorite‑type hosts such as thoria and fully stabilized zirconia identified as promising due to high solubility, irradiation stability, and chemical stability. The authors evaluated phase relations of ceramic materials and performed reactor burnup calculations, showing that these two‑phase fluorite–alumina fuels and fluorite‑type hosts can be fabricated and that light‑water reactors with a moderator‑to‑fuel ratio above 1.4 can burn plutonium once through. The study shows that the resulting spent fuels are mineral‑like waste forms suitable for deep geological disposal, that light‑water reactors can transmute about 99 % of 239Pu and 85 % of weapons‑grade plutonium, and that the plutonium in the spent fuel is rendered essentially unusable.

Abstract

For the burning of plutonium derived from nuclear warheads, once-through type oxide fuels have been studied by considering their proliferation resistance and environmental safety as well as their technological backgrounds of fuel fabrication and reactors.From phase relations of ceramic materials and their chemical properties, it seems that a two-phase mixture of a fluorite-type phase and alumina has favorable characteristics as a once-through-type fuel of plutonium burning. It also seems that the fluorite-type phases such as thoria and fully stabilized zirconia are acceptable as host phases of plutonium because of high solid solubility of the actinide elements and fission products, irradiation stability, and chemical stability. The spent fuels finally obtained will become mineral-like waste forms, which could be buried under deep geological formations without further processing.From reactor burnup calculations with the use of the fuels, light water reactors (LWRs) with the larger volume ratio of moderator to fuel than 1.4, such as conventional LWRs, are considered to be suitable for the once-through plutonium burning. Furthermore, such LWRs can transmute nearly 99% of 239Pu and 85% of initial loaded weapons-grade plutonium. The quality of plutonium becomes completely poor in the spent fuels.