Predicting the Distribution of Fuel Temperatures for a Single Channel Flow Blockage Scenario Using the Newly Developed Code CANSIM-PLE

Abstract

The code, CANSIM-PLE (CANDU Simulation Project Licensing Experience), is under development at Ontario Hydro to examine feedback effects between fuel behaviour and channel thermalhydraulics under high power/low flow, single channel accident conditions. In CANSIM-PLE, the mechanistic fuel behaviour codes, ELESIM (for normal operating conditions) and ELOCA (for accident transients) are combined with a CHAN-like flow ring thermahydraulics calculation to provide an integrated channel model. The resulting code accounts for sheath staining and lift-off from the fuel, transient fission gas release to the gap between the fuel pellets and sheath, the radial temperature distribution in a fuel element, and changes to the flow split ratio between subchannels as a result of the sheath strain, CANSIM-PLE predicts transient channel temperatures and the distribution of fuel temperatures up to the point of channel failure.A detailed description of CANSIM-PLE is presented along with sample results for a single channel flow blockage scenario. Predicting the the condition of channel contents at time of rupture for this high power/low flow event is a rigorous test of the code, Predictions are obtained for a high power channel for two different fuel burnup histories which affect the fuel element fission gas inventories. Based on preliminary results, consequences would appear to be less challenging than bounding analysis (as might be expected). However, additional work is necessary before the code is adequately verified and queued for application to accident analysis.