Analytical Tool for Evaluating Critical Power Ratio of Irradiated Fuel String in NRU Reactor

摘要

A fuel irradiation program has been established to study fuel characteristics under various operating maneuvers at CANDU?1 reactor conditions of interest. This program includes fuel irradiation experiments performed in either the U-1 or U-2 loop of the National Research Universal (NRU) reactor using a string assembly consisting of multi-type bundles of 37-element, 43-element and material test bundles. A thermalhydraulic analytical tool has been developed in support of the fuel irradiation program. It is designed to evaluate the critical heat flux (CHF) and critical power ratio for a proposed irradiated string to ensure the fuel irradiation experiment meets the thermalhydraulic safety margin. The critical power of the fuel string is established using CHF criteria. Correlations applied in the CHF calculations have been validated against experimental results obtained with full-scale simulators of 37-element and 43-element bundles. In addition, the predicted critical powers using the relevant CHF correlation are assessed against the measurements. Overall, good agreements have been observed in the predictions of CHF and critical power for both 37-element and 43-element bundles.