A Field Method for Validating Estimated 32P Activities in Solid Radioactive Waste

Abstract

Solid radioactive wastes containing 32 P are commonly generated as a byproduct of biomedical research and academic endeavours. The amount of radioactivity contained in these wastes is usually based on generalised mass balance calculations and intimate knowledge of the experiments performed But since most solid waste is actually incidental to the protocols conducted. activity estimates can be inaccurate. Hence, a rapid field test method to validate activity levels reported by generators would be useful: similar tests are regularly used for the validation of activities of wastes containing photon-emitting radionuclides. Although this methodology is not typically applied to wastes containing beta-emitting radionuclides, due to the significant potential for radiation attenuation by the solid waste material, the beta emission from 32 P is actually energetic enough readily to penetrate most paper, plastic and glass solid waste constituents. In this study, waste packages with variable predetermined amounts of 32 P were monitored at a set of pre-established points using standard portable survey instrumentation. A series of waste activity correction curves were developed and used as a basis for validating actual waste package activity content. The results of the study revealed that over 90% of the waste packages monitored exhibited significant discrepancies between the measured and reported activity content. Although the technique used in this study accurately indicated radioactive content over a wide range, it can be hampered by a significant probability of exhibiting false negative results. Nonetheless, the method can he used as a valuable tool for waste minimisation programmes when applied judiciously.