Cofrentes Reload Licensing Methodology with Retran-03

Abstract

The development of a reload transient analysis methodology for Cofrentes nuclear power plant is presented based on the RETRAN-03 code. The starting point of this methodology was the Cofrentes best-estimate RETRAN model, which had been benchmarked against a number of startup and operational transients. In addition, the best-estimate model had been used to support plant operation and to analyze actual operational and abnormal transients.A number of sensitivity studies have been carried out with the best-estimate model to analyze the effect of the uncertainty associated with the key parameters on the critical power ratio in the most limiting Cofrentes reload transients. The individual uncertainties of key parameters have been combined to obtain the change in critical power ratio (ΔCPR) with a 95% probability level (ΔCPR95).Finally, the Cofrentes licensing model has been defined using conservative values for some significant parameters with the criterion that the calculated ΔCPR cover ΔCPR95. The results obtained with the licensing model have been checked against vendor calculations for the licensing reload transients.This methodology has been submitted to the Spanish Regulatory Commission, and it is expected to be used for the next Cofrentes reload licensing analysis.