Actinide waste for the once-through thorium-fueled heavy water reactor

Reduction of long-lived actinide waste generated by nuclear fission reactors has become a major topic of study. The use of thorium as fertile material might offer an easy solution because the production of plutonium and higher actinides is low when {sup 238}U is absent. This paper presents the waste production of once-through thorium-fueled heavy water reactors (THWRs) related to the waste production of a natural-uranium-fueled heavy water reactor (HWR). All once-through THWRs require externally supplied fissile fuel since natural thorium does not contain fissile isotopes. The possible choices are {sup 233}U, {sup 235}U, or plutonium from light water reactor discharges. Uranium-233 is not considered because it is not commercially available. Two enrichments of uranium topping were considered: highly enriched uranium (HEU-235) (enrichment 93 wt%) and medium enriched uranium (MEU-235) (enrichment 20 wt%). The plutonium topping is from pressurized water reactor (PWR) fuel with a discharge burnup of 45 MWd/kg (fissile fraction 66 wt%).