Comparison of ion exchange methods for lithium-7 isotopic enrichment for application in PWR reactors

Abstract

7Li in the form of lithium hydroxide monohydrate (LiOH·H₂O), remains liquid over a wide temperature range (180 to 1340ºC), making it an excellent pH controller on reactor coolant in Pressurized Water Reactors (PWRs). In contrast, 6Li is a strong neutron absorber and unsuitable for PWRs, whereas 7Li has a low neutron cross-section, making it ideal for reactor use. Enriching 7Li to over 99.95% is essential but complex. The Colex method, involving mercury, was used for enrichment but was banned in the USA due to environmental concerns. Currently, Russia and China are the primary sources of enriched 7Li. A mercury-free procedure to obtain this isotope is necessary, ion exchange techniques, including frontal analysis, elution, and displacement chromatography, offer alternative enrichment methods. This study evaluates these techniques to achieve the required 7Li enrichment for PWR applications. Preliminary results showed an abundance of 7Li at 95.65% after displacement of 830 cm.