Microstructured Semiconductor Neutron Detectors for Spent Nuclear Fuel in Dry Storage Canister Inspection and Monitoring

A need persists for innovative sensor solutions to monitor the integrity and internal conditions of dry storage cask systems for spent nuclear fuel. Spent fuel is loaded in these dry storage cannisters (DSC) which are typically welded, 5/8-inch-thick stainless steel that are then inserted for long term storage in metal or concrete overpacks. The objective of this project is to design, fabricate, and demonstrate a radiation detector capable of measuring the radiation profile of Spent Nuclear Fuel (SNF)-loaded DSCs. Abnormal changes, i.e., changes other than those expected by radioactive decay and burnup, between measurements could give early indication of changes within the DSC. Neutrons are born within the SNF and a fraction of the neutrons are able to penetrate and escape the neutron shielding on the DSC. The factors that dictate the energy dependent neutron flux that emanates from the cannister include the geometry of the SNF, the activity of the SNF, amount of neutron moderator in the DSC (e.g. hydrogen/water, shielding), and neutron absorbers in the DSC (e.g. Xenon, neutron shielding). Therefore, by continually monitoring or periodically measuring the neutron flux profile radiating from the DSC and correcting for radioactive decay of the SNF, internal changes to the SNF physical geometry, intrusion of water or hydrogen, and the leakage of Xe can be detected by detecting changes in neutron flux over time. The scientific and commercial impact of the proposed research is expected to be significant. The results from this project will directly impact the quality of data accessible for studying, developing, and implementing radiological inspection protocols for long term spent nuclear fuel storage and transportation. The DSC-Domino inspection system will enhance the toolkits of those in charge of ensuring safe operation nuclear fuel storage facilities. The novel technology proposed in this work will have farther reaching impact than just fuel storage. RDT has long had customers requesting fast-neutron sensitive, small form factor, low power radiation detectors. The hydrogenous-material-backfilled MSNDs provide a solution to this ongoing market need. The final product developed by this effort, a DSC-Domino (fast, thermal, gamma) satiates DSC inspection, source search and localization, active dosimetry applications, and a newly expanding market in space radiation research (see Letters of Support appended to the commercialization plan).