Assessment of the power deposition on the MEGAPIE spallation target using the GEANT4 toolkit

This work aims at evaluating the reliability of the GEANT4(GEometry ANd Tracking 4) Monte Carlo(MC) toolkit in calculating the power deposition on the Megawatt Pilot Experiment(MEGAPIE), the first liquid–metal spallation target worldwide. A new choice of codes to study and optimize this target is provided. The evaluation of the GEANT4 toolkit is carried out in comparison with the MCNPX and FLUKA MC codes. The MEGAPIE is an international project led by the Paul Scherrer Institute in Switzerland. It aims to demonstrate the safe operation of an intense neutron source to power the next generation of nuclear reactors, accelerator-driven systems(ADSs). In this study, we used the GEANT4 MC toolkit to calculate the power deposited by fast protons on the MEGAPIE target.The calculation focuses on several structures and regions.The predictions of our calculations were compared and discussed with that of the MCNPX and FLUKA codes,adopted by the MEGAPIE project. The comparison shows that there is a very good agreement between our results and those of the reference codes.

Production threshold impact on a GEANT4 calculation of the power deposition in a fast domain: MEGAPIE spallation target

The calculation time in the Monte Carlo simulations consistently represents an essential issue. It is often very long, and its decrease constitutes a challenge for the simulator. Generally, an MC simulation is qualified as quality or not according to two main criteria: the calculation time and the accuracy of the results. However, in most cases, the optimization of one criterion affects negatively the other. Therefore, a compromise between both of them is always required in this kind of simulation. The present work aims at studying the impact of the production threshold(or cut) of the GEANT4 toolkit on the calculation of the power deposition in the MEGAPIE spallation target.The production threshold of secondaries is a GEANT4 intrinsic parameter. It indicates the limit of energy we can reach in the production of secondary particles. This study has allowed us to make the following conclusions. First,the influence of the cut on the calculation of the deposited power depends on the volume size, its arrangement and the importance of the electromagnetic processes occurring within. Second, the accuracy of the calculations can be acceptable only below a given value of the cut energy.Third, this accuracy remains almost unchangeable from a certain value of the cut. The study has also made it possible to explore the prevalence of certain interactions in the zone of spallation in the MEGAPIE target.