Hydrogen dioxide-boosted acid elution of radionuclides from high level vitrified wastes

Abstract

• A wet chemical elution was used to extract radionuclides from nuclear waste glass. • H 2 O 2 largely enhanced the elution capability of HNO 3 under mild conditions. • The insoluble Zr was well extracted by H 2 SO 4 solution through coordination. • The PGMs were extracted using liquid Sn extraction under reductive heat-treatment. The extraction of radionuclides from high-level vitrified wastes (HLVWs) is of importance for eventual harmlessization of nuclear wastes by nuclear transmutation, but remains great challenges. Here, we showed an efficient elution method of various radionuclides from the simulated HLVWs with chemical durability using the mixed H 2 O 2 /HNO 3 solutions under mild conditions. The introduction of H 2 O 2 largely improved the elution capability of HNO 3 solution toward radionuclides contained in HLVWs. Most elements including glass main components (except the insoluble Si) and the simulated radionuclides (except for Zr and platinum group metals (PGMs: Pd, Ru, Rh)) were significantly leached from the HLVWs with the mixed solution of 1 ml H 2 O 2 /1 M HNO 3 at 90 °C for 5 h. The insoluble Zr and PGMs were further extracted by H 2 SO 4 solution and liquid tin extraction, respectively. Through optimization of the extraction conditions, the proposed wet chemical elution method and high temperature metallurgy to extract the elements from the HLVWs would open a new avenue to reduce the radioactivity and lifetime of the long-lived fission products (LLFPs) and minor actinides (MAs) in HLVWs through advanced nuclear transmutation in future. It also provides a feasible method for the reuse of some valuable radionuclides in HLVWs.