Vitrified magnesia dissolution and its impact on plutonium residue processing

Aqueous chloride operations at the Los Alamos Plutonium Facility cannot directly dispose of acidic waste solutions because of compatibility problems with existing disposal lines. Consequently, all hydrochloric acid must be neutralized and filtered prior to exiting the facility. From a waste minimization standpoint, the use of spent magnesia pyrochemical crucibles as the acid neutralization agent is attractive since this would take a stream destined for transuranic waste and use it as a reagent in routine plutonium residue processing. Since Los Alamos National Laboratory has several years of experience using magnesium hydroxide as a neutralizing agent for waste acid from plutonium processing activities, the use of spent magnesia pyrochemical crucibles appeared to be an attractive extension of this activity. In order to be competitive with magnesium hydroxide, however, size reduction of crucible shards had to be performed effectively within the constraints of glovebox operations and acid neutralization time using crucible shards had to be comparable to neutralization times observed when using reagent-grade magnesium hydroxide. The study utilized non-plutonium contaminated crucibles for equipment evaluation and selection and used non-radioactive acid solutions for completing the neutralization experiments. This paper discusses our experience in defining appropriate size reduction equipment and presents our results of using the magnesia crucibles for hydrochloric acid neutralization; a logical precursor to introduction into glovebox enclosures.