SNOK005 October 2024 LMP7704-SP
VPT Rad performed neutron displacement damage irradiations in a low-enriched, open-pool, water moderated, thermal neutron reactor at the University of Massachusetts Lowell. The reactor uses flat-plate type fuel and has a maximum thermal energy output of up to 1MW. The Fast Neutron Irradiator (FNI) faces one side of the reactor core. The experimental facility replaces three beam ports that originally existed on the left side of the research reactor. The FNI is designed to give a fast flux level ≥ 1011 n/cm2–s, with relatively low thermal fluence and gamma dose rates. Samples with a cross-sectional area as large as 30cm (12in) × 30cm (12in) and up to 15cm (6in) thick can be irradiated. The fast neutron flux is designed to be nearly uniform over the 30cm (12in) × 30cm (12in) area facing the core, and the fast fluence variation through the sample thickness is minimized through a single 180° rotation of the sample canister at the midpoint of the irradiation period. The fluences are calculated based on 1MeV equivalences.
The neutron fluence rate is determined using the previously-measured neutron radiation field for the FNI, performed in accordance with ASTM standards (ASTM F1190), and correlated to the measured reactor power level. The neutron dose is timed to meet the fluence specified for the irradiation. Neutron dosimetry meeting ASTM standards (ASTM E265) is used to track and make sure that irradiations meet the required minimum. The facility retains source design with the Defense Logistics Agency (DLA) Laboratory Suitability Program for ASTM Test Method 1017.