Decontamination of metals by melt refinings/slagging: An annotated bibliography

Abstract

As the number of nuclear installations undergoing decontamination and decommissioning (D&D) increases, current radioactive waste storage space is consumed and establishment of new waste storageJareas becomes increasingly difficult, the problem of handling and storing radioactive scrap metal (RSM) gains increasing importance in the DOE Environmental Restoration and Waste Management Program. To alleviate present and future waste storage problems, Westinghouse Idaho Nuclear Company (WlNCO) is managing a program for the recycling of RSM for beneficial use within the DOE complex. As part of that effort, Montana Tech has been awarded a contract to help optimize melting and refining technology for the recycling of stainless steel RSM. The scope of the Montana Tech program includes a literature survey, a decontaminating slag design study, small scale melting studies to determine optimum slag compositions for removal of radioactive contaminant surrogates, analysis of preferred melting techniques, and coordination of large sc_!e melting demonstrations (100-500 Ibs) to be conducted at selected facilities. The program will support recycling and decontaminating stainless steel RSM for use in waste canisters for Idaho Waste Immobilization Facility densified high level waste. This report is the result of the literature search conducted to establish a basis for experimental melt/slag program development. The program plan will be jointly developed by Montana Tech and WlNCO. There are a significant number of publications that include information on decontamination of radioactive scrap materials, e.g., a search of Chemical Abstracts alone shows over 350 publications. At this time approximately 280 publications have been identified that are related to the decontamination of metallic scrap. A large number of literature databases have been searched. Titles, abstracts, and publications have been recovered and reviewed. Information and experimental test results are summarized in Table 2.1. Summary of Large-Scale Ferrous Melt Consolidation/Refining Program, and Table 6.2. Melt/Slag Refining Test Work Results for Uranium and Plutonium Decontamination of Metals and Alloys. Test work (both bench scale and larger scale) results to date demonstrate that slagging decontamination of uranium and plutonium from steel and stainless steel is an effective treatment technology. Based on trends found in the literature, basic calcium-aluminum-silicato slags (with additives _uch as calcium fluoride, nickel oxide, ferric oxide) appear to be effective steel decontaminators. At this time, however, optimum decontaminating slag compositions for the steels cannot be specified based solely on the presently available literature data. At present it appears that removal of most radionuclides by slagging and volatilization holds good possibilities for the treatment of steel scrap. The same slagging/volatilization possibilities appear to exist for stainless steel, except for the specific elements that constitute stainless steel. Radionuclides of iron, cobalt, nicke...