Volatilization of technetium-99 (⁹⁹Tc) is of concern during vitrification of Hanford low-activity waste (LAW) to produce a borosilicate glass waste form at the Waste Treatment and Immobilization Plant. Addition of reducing agents to LAW glass feed has been known to increase the retention of ⁹⁹Tc in the final glass product. We investigated rhenium incorporation into glass by performing crucible melting tests on simulated LAW glass feeds, prepared without and with iron oxalate as a reducing agent, to understand the mechanism how the reducing agent influences Re retention in glass. Deionized water leaches were conducted on the dried feed and heat-treated samples to analyze the compositions of soluble and insoluble phases separately and to profile the partitioning of components into different phases during melting. The results in this study do not support the previous hypothesis that the low volatility of reduced Re⁴⁺ and Tc⁴⁺ is responsible for higher Re and Tc retention in glass when a reducing agent is added. We propose that early reaction of nitrate/nitrite and faster incorporation of sulfate into glass caused by iron oxalate are the two contributing factors that can explain the experimental findings in this study regarding the positive effect of iron oxalate on Re incorporation and retention.

在废物处理和固定化工厂将Hanford低活度废料（LAW）玻璃化以生产硼硅酸盐玻璃废料的过程中，-99（⁹⁹ Tc）的挥发是令人关注的。已知在LAW玻璃饲料中添加还原剂可提高⁹⁹的保留率最终玻璃产品中的Tc。我们通过对模拟草酸盐玻璃进料（在不使用草酸铁和使用草酸铁作为还原剂的情况下进行制备）进行坩埚熔化测试，研究了in掺入玻璃的过程，以了解还原剂如何影响玻璃中Re保留的机理。在干燥的饲料和热处理过的样品上进行去离子水浸提，以分别分析可溶相和不溶相的组成，并分析熔融过程中组分在不同相中的分配情况。本研究的结果不支持先前的假设，即还原的Re ⁴⁺和Tc ^4+的挥发性较低。当添加还原剂时，可以使玻璃中的Re和Tc保留更高。我们认为草酸铁引起的硝酸盐/亚硝酸盐的早期反应和硫酸盐更快地掺入玻璃是两个可解释本研究中草酸铁对Re掺入和保留的积极作用的实验结果的两个因素。