Correlation of container exposure rates with radioisotopic inventory of waste

The Radioactive Waste Management Department (GRR) at the Nuclear and Energy Research Institute (IPEN) develops methods for determining the radioactive inventory of waste packages and waste streams. These methods involve radioanalysis of waste samples, gamma scanning of waste drums and calculations. The determination of the radioisotopic content of nuclear waste is a basic step in the waste characterization process and is essential in the treatment, in the transportation, and in the disposal of the waste. While radiochemical analysis of the wastes yields the most accurate results, an expedite method based on the measurement of exposure rates around waste packages can provide good approximations when previous information on gamma emitters present are available. Results of exposure rates can be used as a quick check of content in waste drum consignment and as an initial estimate of activity of fresh waste packages. The point-kernel source method is used to correlate exposure rate measurement results with gamma emission rate. Exposure rates calculated with this method are compared with results of measurements of drums containing spent ion-exchange resin replaced from the IEA-R1 research reactor water treatment system. (author)