WM’04 conference, February 29-March 4, 2004, Tucson, AZ WM-4296 DEVELOPMENT OF RADIONUCLIDE INVENTORY DECLARATION METHODS USING SCALING FACTORS FOR THE KOREAN NPPS - SCOPE AND ACTIVITY DETERMINATION MEHTOD -

Regulations and guidelines for radionuclide waste disposal require detailed information about the characteristics of radioactive waste drums prior to transport to the disposal sites. So it is important to know the accurate radionuclide inventory of radioactive waste. However, estimation of radionuclide concentrations in the drummed radioactive waste is difficult and unreliable. In order to overcome this difficulty, scaling factor (SF) method has been used to assess the activities of radionuclides which could not be directly analyzed. A radioactive waste assay system has been operated at Korean nuclear power plant (KORI site) since 1996 and consolidated SF concept has played a dominant role in the determination of radionuclides concentrations. For corrosion product radionuclides, generic SFs were used due to the similar trend and better-characterized properties of Korean analyzed data compared to the worldwide database. For fission product and TRU radionuclides, it is not easy to use the generic SFs. Thus simple model reflecting the history of the operation of power plant and nuclear fuel condition is applied. However, some problems are remained to be resolved. For examples, disparity between the actual and ideal correlation pairs, uncertainty of analyzed sample values, inaccuracy in representativeness of derived SF values and so on. As a result, the SFs are somewhat dispersive. Therefore establishment of the assay system using more improved SFs is planned and progressed. In this paper, the scope of research is briefly introduced. For the selection of more reliable activity determination method, the accuracy of predicted SF values for each activity determination method is compared. From the comparison of each activity determination method, it is recommended that SF determination method should be changed from the arithmetic mean to the geometrical mean for more reliable estimation of radionuclide activity. Arithmetic mean method and geometric mean method are compared based on the data set in KORI system. As this study is progressed, more accurate and reliable prediction for the radionuclide inventory of radioactive waste based upon Korean analyzed database will be possible.