Zeolite Study
Natural sorbents as barriers against migration of radionuclides from radioactive waste repositories
The radioactive wastes from the Nuclear Power Plant in Bulgaria, both low- and intermediate level and high-level wastes have to be safely disposed and isolated from the human environment. Natural inorganic sorbents are known to act as effective barriers against radionuclide migration from radioactive waste repository and could be used as a buffer, backfill and sealing material [1.2]. The natural bentonite is proposed as a buffer and backfill material in granitic rock repositories [3-5] and its performance is estimated in field tests in Stripa mine [6]. The excavations in clay repositories could be backfilled with crushed clay [7]. Ilite and kaolinite have been proposed for shafts backfilling [8].
Zeolites could be used as anadditives to the bentonite to increase the retention of cesium-137 [9]. Komarneni and Roy [10] reported that a barrier of a tailored made mixture 1:1 zeolites (clinoptilolite and mordenite or phillipsite) sorbs the radioactive isotopes of cesium, rubidium and strontium. The presence of sorptive minerals in the host rock and the surrounding geological structures increases the retention properties of the strata. The Boom clay contains smectite and vermiculite [7]. D.L.Bish et al [11] reported that the migration of cesium, strontium and barium from the proposed repository in Yucca Mountain decreases with the increase of clinoptilolite content in the tuff. The sorption properties of Bulgarian natural inorganic sorbents – zeolites, clays – vermiculite. bentonite, glauconite, etc., have been studied in our Department for many years.
The report focuses on the sorption properties of some minerals that could be used as a buffer, backfill and sealing material, or that their presence in the geological strata decreases the migration of radionuclides.
