The evaluation of the subcritical experiments performed in the IPEN/MB-01 research reactor facility for the IRPHE project

This work presents the evaluation of the subcritical experiments performed at the IPEN/MB-01 research reactor facility. The experimental method developed at the IPEN facility showed itself very valuable in the resolution of the several subcritical parameters employed in the subcritical kinetic model of Gandini and Salvatores. The evaluated data which were acceptable for publication in the IRPhE handbook are of very good quality and suitable for a benchmark problem. The theoretical analyses show that the MCNP5 results, together with the ENDF/B-VII.0 library, for for k_eff, ρ_gen, Σρ_gen, and k_sub are in a very good agreement to the benchmark values. In the case of the calculation of ζ MCNP5 does a good job when there is just one additional source, but with the source is distribute like in the case of the intrinsic source, MCNP5 misses part of the physics because the intrinsic source is not weighted by the adjoint flux according to their position. In other words, the intrinsic source that it is in the center of the core is more effective to induce fissions than the one that it is in the periphery. This kind of MCNP5 deficiency imposes restrictions in the determination of ζ and consequently in the determination of ϕ^*. The k_sub MCNP5 results were insensitive to the source treatment and only a few cases were slightly outside of the 3σ range of the benchmark values.