Research Program to Investigate the Fundamental Chemistry of Technetium

Edelstein, Norman M. ; Burns, Carol J. ; Shuh, David D. ; Lukens, Wayne

Lawrence Berkeley National Laboratory

关键词: Leaching;    Research Programs;    Radioactive Wastes;    Radiolysis;    12 Management Of Radioactive Wastes, And Non-Radioactive Wastes From Nuclear Facilities;   

DOI  :  10.2172/829921
RP-ID  :  EMSP-60296--1999
RP-ID  :  829921

美国|英语

来源: UNT Digital Library

【 摘 要 】

Technetium (99Tc, half-life = 2.13x105 years, b-emitter) is one of the radionuclides of major concern for nuclear waste disposal. This concern is due to the long half-life of 99Tc, the ease with which pertechnetate, TcO4 -, migrates in the geosphere, and the corresponding regulatory considerations. The problem of mobility of pertechnetate in the environment is compounded by the fact that pertechnetate is the thermodynamically stable form of technetium in aerobic environments. These two factors present challenges for the safe, long term immobilization of technetium in waste forms. Because of the stability of pertechnetate, technetium has been assumed to exist as pertechnetate in the aqueous phase of nuclear waste tanks. However, recent studies indicate that a significant fraction of the technetium is in a different chemical form. This program addresses the fundamental solution chemistry of technetium in the waste tank environment, and in a second part, the stability of technetium in various waste forms. The chemistry of this element will be studied in aqueous solutions at high pH, with various added salts such as nitrate, nitrite, and organic complexants, and as a function of radiation dose, to determine whether radiolysis effects can reduce TcO4 -. A separate facet of this research is the search for chemical forms of technetium that may be thermodynamically and/or kinetically stable and may be incorporated in various waste forms for long term storage. This phase of the program will address the problem of the possible oxidation of lower valent technetium species in various waste form matrices and the subsequent leaching of the highly soluble TcO4 -.