24-month PWR Fuel Cycles - Two Decades of AREVA Design and Operating Experience

摘要

AREVA has over two decades of design and successful operational experience with 24-month nuclear fuel cycles for PWRs (and BWRs) in the USA. No safety, licensing or equipment problems have occurred. Twenty-four month cycles increase cycle capacity factors, but fuel cycle economics should not be neglected. The most economical 24-month cycles with efficient use of uranium that minimize the metric kg U235 feed / GWd thermal energy production require assembly designs with heavy U-metal loadings, which is equivalent to low core power density in watts thermal per gram U-metal (w/g U-metal). For 24-month cycles, PWRs with high core power density (above 40 w/g U-metal) require very large inefficient feed batch sizes (i.e. large values of the metric kg U235 feed / GWd th) with degraded fuel cycle economics. The core power density can be lowered by switching to an assembly design with heavy U-metal loading. The AREVA (B&W) plants operating in the USA and the AREVA EPR plants being built around the world are all low power density cores and are thus very suited to economical 24-month cycles. For 24-month cycles, the UO_2-Gd_2O_3 integral burnable neutron absorber is needed to control reactivity and peaking to avoid supplementary removable burnable poison components and to minimize gas pressure buildup in fuel rods.