IFMIF-DONES concrete neutron shielding benchmarks

Experiments have been performed to qualify the radiation shielding performance of concrete for the test cell of the IFMIF-DONES (International Fusion Materials Irradiation Facility - Demo Oriented NEutron Source) facility. A mock-up of ordinary concrete (OC) with local lime-dolomite aggregate was prepared, representing the structural concrete. Also, a mock-up of heavy concrete (HC) with magnetite aggregate was prepared, representing the radiation shielding concrete, particularly for removable biological shielding blocks inside the test cell. These mock-ups were irradiated by neutrons with a continuous energy spectrum up to 33 MeV using a fast neutron generator at the U-120M cyclotron facility at the Nuclear Physics Institute of the Czech Academy of Sciences, Řež. Activation foils were used for neutron diagnostics and were positioned throughout the mock-ups. There were five foil materials used: Au, In, Fe, Ti and Al. Gamma spectrometry of the foils was performed at the experimental site to measure the activities of the post-irradiation radionuclides. The experimental results are compared to calculated results obtained via radiation transport code modelling of the experiments and subsequent inventory code simulations of transmutation and activation. The comparison of calculated/experimental (C/E) results determines the confidence in the calculation methods to accurately represent the shielding performance of the concrete materials. Within the uncertainties, 100% of the OC results and 73% of the HC showed C/E agreement. Future calculations using these concretes should include safety factors of 2 and 3 for OC and HC respectively. The discrepancies for HC in particular should be considered in future calculations.