Bruce A Restart initial core loading

Bruce A Nuclear Generating Station (NGS) Units 3 and 4 are to be restarted with cores containing completely fresh fuel. The reactor power will be 92.5% of the originally designed power, or 2492 MW of thermal power to coolant. Depleted uranium fuel bundles, with an enrichment of 0.4% 235U by weight, will be used to reduce fresh-core excess reactivity and to provide the required flattening for flux and power distributions in the operating period before refuelling. The computer codes RFSP-IST, WIMS-IST and DRAGON have been used to define a new initial core loading (ICL) scheme for the 'Bruce A Restart'. The study assessed 14 different ICLs, based on simulations of initial operating periods of about 60 days at 92.5% full power (FP) (the plutonium peak is near day 50). The chosen ICL was examined in more detail, with a simulation of 350 days of operation at 92.5% FP (including channel refuellings, which started at day 100). The ICL scheme for the Bruce A Restart will use 714 depleted uranium fuel bundles per reactor. There will be from one to three depleted uranium bundles per channel in the 332 central fuel channels of the core. The bundles will be placed in bundle positions 8 (58 channels), 8 and 9 (114 channels), 9 and 10 (52 channels), and 8, 9 and 10 (108 channels). The ICL scheme recommended above will allow Bruce A NGS Units 3 and 4 to safely operate at 92.5% FP with practically no loss in power output, and with comfortable operating margins and conservative allowances for calculation uncertainties. (author)