Pages: 16 - 22

Authors: Ahmed KHEDR, Martina ADORNI, and Francesco D'AURIA

Abstract

The safety evaluation of nuclear power and research reactors is a very important step before their construction and during their operation. This evaluation based on the best estimate calculations requires qualified codes, qualified users, and qualified nodalizations. The effect of code users on the RELAP5 results during the analysis of loss of flow transient in MTR research reactors is presented in this paper. To clarify this effect, two nodalizations for research reactor different in the simulation of the open water surface boundary conditions of the reactor pool have been used. Very different results are obtained with few choices for code users. The core natural circulation flow with the beginning of core boiling doesn't stop but increases. The increasing in the natural circulation flow shifts out the boiling from the core and the clad temperature decreases below the local saturation temperature.

Key words: research reactor, loss of flow, natural circlulation, user effect, thermal hydraulic, RELAP 5

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