Effect of highly enriched/highly burnt UO₂ fuels on fuel cycle costs, radiotoxicity, and nuclear design parameters

A study of high-burnup pressurized water reactor (PWR) fuel management schemes extending to 100 GWd/tonne is presented. The Studsvik Scandpower code suite was used to model a Westinghouse three-loop PWR core, and realistic loading patterns were derived. The loading patterns were optimized for minimum power peaking and maximum cycle length using engineering judgment and automated binary shuffles. Gadolinia was found to control power peaking to within current F_ΔH design limits up to 70 GWd/tonne, with only a slight deterioration thereafter. The moderator temperature coefficient, boron coefficient, and control rod worth were calculated and shown to fall within existing design limits. An economic analysis was carried out to determine the most economic discharge burnup based on fuel cycle costs only. It was found that the lowest fuel cycle costs were obtained with average discharge burnups between 70 to 75 GWd/tonne (initial enrichments between 6 to 7 wt%). Th e energy generated per tonne of uranium ore used was calculated and shown to peak between 40 to 60 GWd/tonne. Also, the radiotoxicity generated per GW.yr(electric) was calculated for each fuel management scheme and found to reduce considerably with burnup between 100 and 100 000 yr.