Tests of membrane-sorption decontamination of the reservoir cascade of the Techa river

Abstract

Results are reported from a comprehensive test, under real conditions, of technology for removal of 90 Sr from the waters of the Techa reservoir cascade. This technology includes stages of preliminary decontamination, ion exchange softening with desorption and carbonate precipitation of hardening salts and 90 Sr from the desorbates, sorption cleanup on natural zeolites, and concentration of the strontium-containing carbonate precipitates. After the precipitates are removed, the solutions are reused in the desorption stage. The quality of the decontaminated water meets all the requirements for discharge into open drainage network in terms of all indicators. (The specific activity of 90 Sr is 3-5 Bq/liter in the filtrates.) The 90 Sr is concentrated by a factor of about 900 as solid radioactive waste in the form of a sediment with a moisture content of 50% and by about 1700 as air-dried solids. As a preliminary estimate, the operating cost of decontaminating 1 m 3 of water in the V-11 reservoir is 200 rubles.Decontaminating the cascade of water reservoirs along the Techa River is an important part of the radiation ecological rehabilitation of the area surrounding the Industrial Associacion Mayak industrial zone, which has been polluted by radioactive material from the Soviet nuclear program. The main difficulty is the large scale of the pollution, which occurred during the 1950s through the 1980s [1,2].The cascade of reservoirs of the Techa River consists of four successive artificially created reservoirs (V-3, -4, -10, and -11), which are delimited by dams, and two bypass canals. Low level radioactive and nonradioactive industrial effluents were dumped into reservoirs V-3 and V-4, which were originally ponds in the valley of the old channel of the Techa. Reservoirs V-10 and V-11 were created in 1956 and 1963 in the old channel of the Techa to catch water from reservoirs V-3 and V-4. At present, the water from all these reservoirs is classified as low-level liquid radioactive waste. In addition, the salt content, including hardening salts, is considerably higher than the natural salt background level for lakes in the Urals region. Thus, it is forbidden to discharge the water into the open drainage (hydrographic) network without removing the 90 Sr, 137 Cs, and salts to the level prescribed by the existing standards. The basic problem is to decontaminate reservoirs V-10 and V-11,

Radioactive Waste Management by Membrane Technique

“…Activated carbon/hollow fiber (water purifier) Ceramic hollow fiber membrane 90Sr Actual water contaminated by radionuclides from the Techa reservoir cascade; 90Sr was concentrated by a factor of 900 (Rudenko and Khan 2005). RO/ md Toray Tr60 and Tr70, Filmtec SW30, Ceramic or metallic ultrafiltration membrane with chelating polymers, membrane distillation(md) not specified Strontium, barium, zirconium, iodine, cesium Stock solutions including nonradioactive elements; Iodide, iodate, cesium and barium were removed with efficiencies, 85, 40, 75-90 and 85% (Shatalov et al 2008). RO/nanofiltration and enhanced "seeded" ultrafiltration 137Cs, 60Co, 85Sr Low and medium level liquid radioactive waste, not specified; based on various membrane separation results, they proposed RO/ultrafiltration/microfilter/membrane distillation hybrid process (Sato et al 2011).…”