Analysis of the Sensitivity and Uncertainty of Calculation Using the KORSAR/GP Code for Accidents with a Failure of Storage Pools’ Cooling System

An analysis into the sensitivity and uncertainty of the results obtained on the basis of the computational model of the experimental stand ALADIN, performed on the basis of the computational software tool KORSAR/GP, was carried out. The ALADIN facility is designed for experimental monitoring of the processes occurring in the near-reactor pools of spent nuclear fuel at NPPs in case of violation of its cooling (boiling of water and drying of stored spent fuel assemblies), which is of great importance for justifying the safety of NPPs, especially in the conditions of the existing limited data bank for similar processes in the spent fuel pool. The results obtained using the calculation model and the experimental data were published earlier and showed good agreement. Sensitivity and uncertainty analysis was carried out on the basis of the PANDA software tool, which implements special statistical methods. Based on the results of the analysis, the parameters whose uncertainty has the greatest impact on the temperature of the fuel assembly simulator and the water level in the test bench were determined. It is shown that it is permissible for the considered model to use a simplified approach to the analysis of uncertainty based on the consideration of only the limiting options for the deviation of the uncertain parameters of the model. In this case, one can certainly cover the entire tube of uncertainty of the results. In this case, the number of calculation options is significantly reduced, and the uncertainty tube expands to the maximum possible limits determined by the superposition of the most unfavorable deviations. The ALADIN stand simulates one fuel assembly under accident conditions in the spent fuel pool. If the obtained result is correct for the considered model then, with the similarity of the processes occurring in the pool and thermophysical characteristics, there is a potential possibility that a simplified approach to sensitivity and uncertainty analysis can also be applied in the analysis of the safety of spent fuel pools.