Asian Journal of Microbiology, Biotechnology & Environmental Sciences Paper

THE IMMOBILIZATION OF THE ASH RESIDUE PRODUCED AS A RESULT OF PROCESSING RADIOACTIVE ION-EXCHANGE RESINS IN A LEAD MELT

S.N. SKOMOROKHOVA, A.N. NIKOLAEV, R.SH. ASKHADULLIN, E.M. TRIFANOVA AND I.V. SITNIKOV

Abstract

The process of thermal destruction of the spent ion-exchange resins (IER) in a lead melt followed by immobilization of the ash residue in a water-resistant compound was tested in order to substantiate the technology of management of liquid radioactive waste (LRAW) of ion-exchange resins. A simulated composition of the spent IER of nuclear power plants was used for the process development. It was prepared on the basis of KU-2-8 and AB-17 ion-exchange resins by transition to corresponding salt forms (Na+, NO3-, K+, NH4+ and ВО33-- forms) using standard techniques. The weight of the simulated IER was reduced down to 90%wt. with the production of an ash residue – a dispersed material of black color that was slightly soluble in water and a mixture of acids. This reduction has been achieved at the optimum process parameters using pilot equipment. Fe, Ni, Pb, Na, К, etc. with the concentration from 0.4% wt. to 10.4% wt. represented chemical composition of the main metal components of the soluble part of the ash residue. The composition was determined by the atom-emission method (“Optima 7000DV” instrument with ICP with the detection limit of 10-4%wt.). Recipes of mineral-like compounds were developed, and a number of candidate samples of mineral-like compounds were fabricated on the basis of the studies of physical and chemical properties and structure of alkali-slag cement materials that had been carried out earlier. These compounds contained up to 45-46 %wt. of the ash residue. The fabricated samples meet the regulatory requirements stated in Standards and Regulations (SP)-019-15 and feature high engineering quality parameters (mechanical strength is 14-31 MPa, a water resistance, which is measured by 137Cs leaching rate, is <1×10−3 g/cm2´day, waterproofness is >>>5 MPa after a water storage for 90 days). These characteristics prove that the conditioned product of the ash residue immobilization – an alkali-slag compound - is suitable for long-term storage. The total reduction of the IER pulp by 13.5 times by volume and by 6.2 times by weight has been achieved as a result of the IER processing and the ash immobilization into a water-resistant compound.