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

Problem: 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 DOE needs sensor solutions to periodically monitor the condition of the dry storage canisters to ensure that pre-identified safety regulations are being met. Addressing the Problem: RDT proposes to study the feasibility of deploying a modified-Domino® to perform concurrent measurements of gamma-ray, fast neutron, and thermal neutron populations within the overpack vent chases. The modified-Domino would be affixed to a flexible wand and cart that travels the length of the vent and measures radiation dose as a function of axial position on the exterior of the cannister. A thermocouple could be attached to the cart as a supplementary sensor to log the DSC temperature profile. RDT proposes to use our commercially available standard MSND for thermal neutron detection and to modify the backfill material and microcavity geometry to make fast neutron sensitive and gamma-ray/x-ray sensitive detectors for this application. The MSNDs would be arrayed on the modified-Domino wherein the count rate for each MSND can be readout individually and logged. The Domino/MSND technology is well suited for this application due to its small size, low weight, and low power features. The Phase I period of performance will focus on proving the feasibility of a modified-Domino system to operate in the vent spaces of a DSC/overpack system and buildout of a low-fidelity detector prototype. In Phase II, the Team will focus on calibration, ruggedization, refinement, and deployment of a commercialized DSC inspection and monitoring system. RDT will work closely with manufactures, customers, and stakeholders of DSC systems to ensure our inspection systems satisfies the needs of all those involved in this complicated and important challenge of long term spent nuclear fuel storage. Commercial Applications and Other Benefits: The scientific and commercial impact from the modified MSNDs and Dominos is expected to be significant. Primarily, the detector is designed to perform radiological surveys in the harsh radiation environment between the spent nuclear fuel loaded dry storage cannister wall and the wall of the concrete or metal overpack to ensure the integrity of the storage system per DOE guidelines. Secondarily, the thermal neutron, fast neutron, and gamma-ray sensitive MSND/modified Dominos can easily be adapted to the wearable active dosimetry market due to its compact size, low weight, and low power requirements. Tertiarily, the modified MSND platform developed in the proposed work would allow for RDT to offer a 2x2 array of fast-neutron sensitive MSNDs on the Domino footprint, which has been a common product availability query to RDT over the past 5 years from potential and current customers. If successful, RDT could see immediate commercial sales spun out from the work performed in this proposal to satisfy fast-neutron detection needs.