A Qualitative Reactivity and Isotopic Assessment of Fuels for Lead-Alloy-Cooled Fast Reactors

Various methods have been proposed to transmute and thus consume the current inventory of transuranic waste from spent light water reactor (LWR) fuel and plutonium from weapons. We discuss the neutronics performance of nonfertile, fertile metallic, and fertile nitride fuels loaded with 20 to 30 wt% LWR-grade plutonium plus minor actinides and burned in an open-lattice lead-alloy-cooled fast reactor, with an emphasis on the fuel cycle life and spent fuel isotopic content. As a comparison, similar fuel was also studied in a sodium-cooled fast reactor. Our calculations show that the average actinide burn rate for fertile-free fuel is similar for both the sodium- and lead-bismuth-cooled cases, ranging from 1.02 to 1.16 g/MWd, compared to a typical LWR actinide generation rate of 0.303 g/MWd. In addition, our calculations show that the effective full-power days (EFPDs) of operation (or equivalent reactivity-limited burnup) using fertile fuel can extend beyond 20 yr, and the average actinide burn rate is similar for both the sodium- and lead-bismuth-cooled cases, ranging from 0.5 to 0.9 g/MWd. Using the same parameters (i.e., a large pitch-to-diameter ratio, same linear power, and fissile/fertile loading, etc.), the lead-alloy-cooled cases had an EFPD that was 18% to several times greater than their sodium-cooled counterparts. However, tight sodium-cooled lattices are equivalent to the looser lead-alloy lattices in terms of beginning-of-life excess reactivity.