Control rods reactivity worth calculation using deterministic and Monte Carlo approaches for an MTR type research reactor

Reactivity worth of control rods as a main parameter in different nuclear reactor fields such as safety, design, and operation that could be calculated or measured with different experimental and theoretical methods. Reliable answers in calculations necessitate taking into account different characteristics such as geometries, materials, temperatures, spatial nodes, libraries, and energy groups. Reactivity worth of different core states of a Material Testing Reactor (MTR) is calculated using MCNPX 2.6.0 code and MTR_PC package as Monte Carlo and deterministic approaches respectively. It is seen that the MTR_PC and MCNPX results has considerable differences up to 51%. Therefore, an exhaustive study is done concentrating on different involved parameters. Precise modification of inputs, applying one common library in the two approaches, correcting spatial nodes, and employing more energy groups in the deterministic approach are performed. It is determined that the effect of the spatial nodes is much more important than the other parameters in the deterministic method. Finally, results of two approaches are found to be satisfactory as discrepancy is less than 11%.