PNNL

Abstract

Molten chloride salt reactors may require the use of chlorine that is enriched in the isotope 37Cl so irradiation of 35Cl does not interfere with neutronics, compromise reactor longevity, or promote environmentally undesirable emissions at planned or unplanned reactor shutdown, or from end-of-life storage. To this end, a thermal diffusion isotope separations (TDIS) apparatus was constructed in 2023. Successful shakedown testing was achieved and enrichments of isotopic concentrations relative to natural abundance 35/37Cl were collected. The data validated a TDIS model that drove accurate estimates for column lengths needed to achieve desired enrichments below 450?C and allowed for predictive modeling of power requirements and costs for scaled operations, e.g., serial enrichment arrangements versus cascaded ones. The testing was completed in FY24 prior to the end of the allotted time and under budget. Consequently, the work in FY25 continued, using carryover funding to initiate and finalize the fabrication of an 18-m serial separations system. After required shakedown testing, this system would produce highly enriched Cl-37 gas on its first-pass. Progress for this ongoing work is presented.