Study of applicable limits on non-fixed surface contamination for the safe transport of radioactive materials

Munakata, Masahiro ; Tezuka, Hiroko*

We derived the applicable limits for surface contamination by using a model for radiation exposure based on an investigation of actual conditions of the transport in Japan. The dose limits for surface contamination were derived for each 415 nuclides which were included in the IAEA Safety Standard [IAEA, TS-R-1]. In the results, nuclide Ac-227 showed the maximum radiation dose on a package preparation and transport worker (Group A). Based on unit surface contamination (1 Bq/cm), it was 0.48 mSv/a while that of the model in TECDOC-1449 showed 9.20 mSv/a. If 0.3 mSv/a is used as a reference dose, the applicable surface contamination limit of Ac-227 becomes 0.63 Bq/cm in this model and 0.03 Bq/cm in the TECDOC model. The contamination limit of the TECDOC model is much lower than that of this model. For other radionuclides, the derived limits by this model have a safety margin of about 1 order of magnitude against to the applicable limits derived by the model in TECDOC-1449.