Sensitivity analysis of hot channel calculation methods

In safety analysis, the fulfillment of acceptance criteria is usually evaluated by separate hot channel or/and hot assembly thermal hydraulic/fuel behavior calculations. The whole range of the relevant input parameters (e.g. power distributions, burnup, heat conduction data, inlet temperature, etc.) must be taken into account. Concerning these parameters, the most frequent conservative approach is to select the limiting values, partly leading to the most adverse consequences, partly covering the uncertainties of methodological origin. Focusing on two specific problems, the paper analyzes the influence of the above parameters and the consequences of the most frequently used simplifications applied in the usual thermal hydraulic hot channel model of Reactivity Initiated Accidents. The first investigated problem is the influence of the burnup via power distribution and heat conduction in the fuel gap and pellet, while the second one is the single closed sub-channel approach.