Characterization of the 32P solid and liquid wastes generated in the Hybridization assay

Some radioisotopes are frequently used in the biomedical research as an unsealed source generating solid and liquid wastes classified as Low Level Wastes (LLW), according to the Brazilian standards. The liquid and solid wastes should be segregated as recommended by the Comissao Nacional de Energia Nuclear - National Commission for Nuclear Energy (CNEN) standards. The LLW from research laboratories requires attention related to its management due to the easiness in unnecessarily increasing the storage amount. The characterization of the radioactive waste is very important in order to reduce the volume of waste and the storage period and to attain good results in the waste management. The quantification of the waste can be made by estimating the residual activity present in the different kinds of materials used in the biological assays through the values of adsorption coefficients of the radioisotopes. The objective of this work is to characterize the radioactive solid waste in the Hybridization assay using 32P through the activity values determined at each step of the experimental assay, considering the discharge threshold recommended by CNEN. The secondary aim is to establish the most appropriate management method by comparing the specific activities determined at the steps to the method that considers a rate of 2% as a safe hypothesis for any solid materials as well as the ten half-lives method. Radioactive Hybridization by Colony Blot technique was used to analyze the specific DNA sequence through radio labeled [α-32P] dCTP. The solid and liquid radioactive wastes were segregated into 4 steps and at each one the residual activity of different contaminated materials was indirectly measured by beta counter in the presence of scintillation liquid. The radioactivity present at the first and second steps resulted in specific activities higher than the discharge threshold established by CNEN (74Bq/kg for solid waste), indicating the necessity of storing the waste for decay. From this study it was possible to verify that the waste characterization by steps has potential to optimize the storage time and the amount of the storage radioactive wastes. (author)