The relevance of the characterization of radioactive waste generated in the various stages of the binding biological assay

It is important to reduce the quantity of radioactive waste and its storage period in order to obtain good results at wastes management. Radioactive wastes can be quantified estimating the residual activity of the different kinds of material used in the biological assays through the values of adsorption coefficients. The objective of this work is to characterize the solid radioactive waste determining the adsorption coefficients of different materials used in each stage of the assay of Binding with 3H. These values can be used for any other 3H essay. It was selected the Binding radioactive technique which is used to quantify the drug receptor interaction using 3H as radiolabeled [tyrosyl-3,5-3H] Angiotensine. The radioactive waste generated in each stage was characterized by indirect method using the beta counter and scintillation solution. The solid materials were: plastic pointer of 20 mul and 1000 mul, cells culture plates with 12 wells and glass vials. The evaluation of adsorption coefficient was possible segregating the material in each stage and cleaning it with the scintillation solution as carrier. Once known the coefficients, the material mass and the retention of 3H for each stage, it was possible to estimate the specific activities of them. The results demonstrated that in the first assay stage the materials presented specific activities higher than the value required by the CNEN legislation (74 Bq/kg for solid waste), indicating the need of special treatment for the materials only in this stage. Even comparing the results with the PROGER- CNEN program which established 2% as reference adsorption value most of materials could not be discharged immediately. The waste management by indirect method allowed determines the residual activities with enough accuracy based on the adsorption coefficient values and consequently reduces the storage material and costs. (author)