FLASHPOINT - – A Tool to Routinely Calculate the Heat Load in the Irradiated Fuel Bays

Abstract

At the recommendation of the World Association of Nuclear Operators (WANO) following the events at Fukushima, a tool was developed for Ontario Power Generation (OPG) and Bruce Power as an enhancement of the fuel accounting and tracking software NuFLASH (Nuclear Fuel Location and Storage History) in order to routinely calculate the heat load in the Irradiated Fuel Bay (IFB). The tool, FLASHPOINT, uses information stored in NuFLASH regarding the location and details of irradiated fuel bundle properties to calculate the decay heat on a bundle by bundle basis and then sum the decay heats of all bundles in a particular IFB. FLASHPOINT employs a two-step approximation of the bundle irradiation history based on the record of the life cycle for each individual fuel bundle. The primary parameter affecting the decay power of any individual irradiated CANDU® fuel bundle following its discharge from core is the period of time elapsed since the bundle last operated at power within the reactor. The remaining factors influencing the decay power of an individual fuel bundle concern the irradiation history of that bundle while in core. The accuracy of the FLASHPOINT methodology has been assessed primarily through comparison of results obtained using the two step history representation implemented in FLASHPOINT against results from a more explicit ORIGEN-S calculation of the decay heat based on simulating the detailed SORO power history for a randomly selected sample of bundles. The comparisons based on individual bundles and the aggregate group confirmed that the two-step approximation approach provides the desired accuracy.