The low enriched uranium miniature neutron source reactor (LEU-MNSR) neutron spectrum characterization for k0-INAA

Ghana's highly enriched uranium (90.2%) research reactor has been converted to a low enriched uranium (13.0%) type. Its neutron parameters have been characterized for the application of k(0)-instrumental neutron activation analysis. The magnitude of the LEU epithermal neutron shaping factor (alpha) at the irradiation site increased by about 25% as compared to the HEU, while the thermal neutrons decreased by about 5%. This indicates that the epithermal neutron spectrum is much dependent on the 1/E1+alpha. Similarly, the measured fast neutron flux increased by about 22%. Generally, the results show that the LEU core's neutron spectrum is relatively harder, i.e., there is a marginal increase in high-energy neutrons. The reactor spectrum parameters have been used to validate the k(0)-IAEA software. Two certified reference materials (Carbonate rock GBW 07108 (GBW2) and NIST Standard Reference Material 1646a, Estuarine Sediment (EST)) and the synthetic multi-element standard (SMELS I, II & III) were analyzed based on a routine irradiation scheme. The process quality assurance was evaluated based on a u-score test. Most (80 %) of the elements determined were within vertical bar u-score vertical bar < 1.64, while a few were observed within 1.964 > vertical bar u-score vertical bar > 1.64. The results show a suitable characterization process and the general applicability of the k(0)-IAEA software.

Automated summary

The research reactor in Ghana has been converted from highly enriched uranium to low enriched uranium, resulting in a neutron spectrum that is relatively harder with a marginal increase in high-energy neutrons. The reactor's spectrum parameters were used to validate the k(0)-IAEA software, which showed suitable characterization process and general applicability. Analysis of certified reference materials using routine irradiation scheme demonstrated good quality assurance, with most elements within acceptable u-score limits.