The Impact of 234U α-emission Induced Radiolysis on UF6 Storage Composition for Non-destructive Verification via Passive Neutron Counting

Volume: 66, December 2024, pages 28-34

Authors: Stephen Byrne^a, Andrea Favalli^b and Stephen Croft^a

_{^a Lancaster University, School of Engineering, Bailrigg, Lancaster, UK, LA1 4YR
^b European Commission, Joint Research Centre (JRC), Ispra, Italy}
 

Abstract: The mass of ²³⁵U present in storage cylinders containing low enriched uranium (LEU) in the form of uranium hexafluoride (UF₆) may be verified nondestructively using a combination of gamma-ray based enrichment meter and passive neutron counting techniques. A hypothetical concern is that the (α,n) production rate in aged bulk UF₆ might differ from that of fresh material if the chemical composition changes over time, the thought being that this could be initiated by the self-induced radiation field, the process known as radiolysis. To support the physics-based interpretation of the observations Croft et al. measured, in 2020, for the specific ²³⁴U-driven (α,n)-yield in UF6, this work reviews available literature to quantify the possible impact of radiolysis on (α,n) production rate. Building on the review, a radiochemical yield value, G = 0.5 molecules of F₂ per 100 eV is selected, to calculate the impact of UF₅ production – via radiolysis – on the (α,n)-yield. Calculations demonstrate a negligible impact on bulk UF₆ concentration and respective neutron yield.

Keywords: UF₆ radiolysis, UF₆ verification, non-destructive assay, nuclear safeguards.

Reference guideline:

Byrne, S., Favalli, A., and Croft, S. ( 2024, December). The Impact of 234U α-emission Induced Radiolysis on UF6 Storage Composition for Nondestructive
Verification via Passive Neutron Counting, ESARDA Bulletin - The International Journal of Nuclear Safeguards and Non-proliferation, 66, 28-34. https://doi.org/10.3011/ESARDA.IJNSNP.2024.3