Microbiological Transformations of Low- and Intermediate-Level Radioactive Wastes

Low-level and intermediate-level radioactive wastes (LILW) contain a variety of organic compounds (cellulose, chelating agents, plastics, ion exchange resins), inorganic compounds such as nitrate and sulfate. Microbial degradation of the organic constituents of the waste can result the production of gases such as CO2, CH4 and others. Radiolysis of plastics and rubber materials may not only result in the production of volatile toxic organic compounds but render the plastics more susceptible for biodegradation. An increase in microbial activity under appropriate conditions can alter the chemical speciation, solubility and sorption properties and thus could increase or decrease the concentrations of radionuclides in solution and affect their bioavailability and mobility in the environment. Although the physical, chemical, and geochemical processes affecting dissolution, precipitation, and mobilization of radionuclides have been extensively investigated, we have only limited information on the effects of microbial activity and the biochemical mechanisms which affect the stability and mobility of radionuclides. This study describes the various mechanisms of microbial transformations of U, Pu, Tc, Cs, Sr, I, 14C and 3H in wastes.