Year
2025
Abstract
Dounreay was the UK’s hub for fast reactor research, including the Prototype Fast Reactor (PFR). With Dounreay now in the decommissioning stage, Nuclear Restoration Services (Dounreay) plans to transfer some of its fuel material inventory to Sellafield. For some of this inventory material knowledge is limited; given the inability to identify some of the material IDs and trace back their origins, and limited ways to interrogate the material given their present storage location. A basic assumption must be made, that all materials in this part of the inventory are fissile. At present, the uncertainties and pessimisms associated with fissile mass content for fuels being repackaged is making a justifiable transport safety case difficult and limiting this material being transferred from the Dounreay site.
Independently verifying the fissile material content through assaying and comparison to the operator’s records will enable more accurate declarations to be made and may significantly reduce current transport safety case pessimisms. Gamma-ray spectroscopy offers a potential route to independently validate the fissile masses contained in each repackaged can, which can be determined by measuring SNF Burn-up (BU), Cooling Time (CT), and Initial Enrichment (IE) from fission product activity.
Given the cost and safety concerns associated with physical measurement of Spent Nuclear Fuel (SNF), it is beneficial to first take a computational approach to the problem.
The project aims to use Monte Carlo N-Particle (MCNP) software to model fuel and simulate gamma-ray emission, transportation, and detection to generate gamma-ray spectra for analysis of fission product activity. The results will demonstrate the feasibility of independent validation of Dounreay’s SNF material inventory using gamma-ray spectroscopy and will indicate the feasibility of the technique for the remainder of the UK’s SNF inventory and beyond.