Development of a technique for evaluation of activity distribution in a low-level radioactive waste. Extraction of requirements for measurement system

In order to transport low-level radioactive waste as LSA (Low Specific Activity)-II material, it is required to prove there is no extreme uneven distribution of activity according to the IAEA Safety Standards Series Regulations for the Safe Transport of Radioactive Material' published in 1996. To prove activity is distributed throughout, a simple method is suggested in the IAEA Safety Guide as follows; differences of the specific activities between portions, which are defined one fifth or one tenth of the volume, are within a factor of less than 10. We have, then, started a study to develop a method to evaluate activity distribution of low-level radioactive waste. By the use of MCNP Monte Carlo code, correlation between the uncertainty and the filling rate of waste were estimated with respect to three types of measuring method. Requirements for measuring methods were discussed. (author)