The experimental determination and evaluation of the three-dimensional fission density distribution of the IPEN/MB-01 research reactor facility for the IRPhE project

Experiments for the determination of the three-dimensional fission density distribution were successfully carried out at the IPEN/MB-01 research reactor facility. The experiment is of very good quality for utilization in the benchmark of computer codes and related nuclear data library commonly used for the calculation of fission density distribution in reactor cores. The complete experimental data set comprises a very massive set of measured fission density distribution. The experiment was evaluated and included in the IRPhE handbook. Two calculation methodologies were employed for the theoretical analysis of the proposed benchmark; one stochastic (MCNP-5) and the other one deterministic (NJOY/AMPX-II/TORT); both utilizing ENDF/B-VII.0 as the source of nuclear data. The theory/experiment comparison reveals in general a good agreement for both methodologies. However, MCNP-5 results are in a better shape than those of TORT. TORT underestimates the relative power distribution mainly in the axial upper part of the fuel rod. This effect is mostly credited to the over-prediction of the control bank worth.