Recalculation of activity concentration limits for an exempt material and activity limits for an exempt consignment prescribed in the IAEA Regulations for the Safe Transport of Radioactive Material by BRACCS code

IAEA Transport Regulations SSR-6 provides basic radionuclide values in Table 2 to classify packages to be used. In the table A1, A2, activity concentration limit for an exempt material (hereafter called “exemption concentration”) and activity limit for an exempt consignment (hereafter called “exemption value”) for each nuclide are given.The exemption concentrations and exemption values in the current SSR-6 are taken from the values given in the IAEA Basic Safety Standards (GSR Part 3). The scenarios underlying those values is found in the EC document RP-65.From recent needs to re-evaluate these values or to add new nuclides, we have developed the BRACCS code to calculate these values. In this study, recalculated results on exemption concentrations and exemption values will be reported. Reevaluation of A1 and A2 values was reported in PATRAM2016.In the early verification stage of the BRACCS code, calculation results for many nuclides could not reproduce those in SSR-6 even using the conditions in RP-65. Thus, the dose conversion coefficients for internal exposure, we used those in ICRP Publ. 68 (for worker) and ICRP Publ. 72 (for public), which were generally consistent with those used in the internal exposure scenario of RP-65. For the dose conversion coefficients for external exposures were reproduced based on the conditions available in RP-65. If the conversion coefficients were not sufficiently in detail, external exposures were calculated by MCNPX 2.6.0 code with assuming appropriate geometries. It is noted that the BRACCS code is also equipped with a function to select nuclear data given in ICRP Publication No.38 and No.107 for future calculation of all radionuclides.In order to justify above scenarios and geometries, we performed calculation of exemption limits for 387 nuclides listed in SSR-6. As shown in Fig. 1 and Fig. 2, calculated values are in good agreement with those in SSR-6 for most of the nuclides, demonstrating validity of recalculation by BRACCS. Together with the previously reported results on A1 and A2 values, calculation performance of the BRACCS code has been verified.