Biosphere assessment data set and flux-to-dose conversion factors of radionuclides specific for TRU waste geological disposal

Suzuki, Yuji*; Kato, Tomoko ; Makino, Hitoshi ; Oi, Takao 

The project to establish a technical basis for HLW disposal in Japan (H12) has used "reference biosphere" methodology. The radiation dose which was an index as a basis of the safety assessment was calculated. (In fact, the flux-to-dose conversion factors were calculated as coefficient reduced flux of radionuclide caused by geological disposal to radiation dose in biosphere.) And then, ICRP has introduced the new system for radiological protection in the publication 60 published in 1990. New regulations in Japan have been issued in 2001 and it defines new dose conversion factors of ingestion and inhalation as effective dose coefficients based on the publication 60. And so, nuclides for biosphere assessment of HLW disposal, the flux-to-dose conversion factors for biosphere assessment were calculated based on the new regulations. On the other hands, recent safety assessment on a waste of geological disposal equivalent in radioactive waste containing transuranic (TRU) nuclide was carried out the safety assessment based on the biosphere assessment model constructed by the methodology other than the reference biosphere. "Co-disposal concept" disposed of by also juxtaposing TRU waste with geological disposal site of high-level radioactive waste, was examined the geological disposal of TRU waste, and the consistency of models and assessment system in the geological disposal of HLW and TRU waste would have been required. Moreover, the environmental conditions in future various biosphere based on climatic change are considered, the importance of discussion considering the variation of the biosphere system has been indicated. The data set for appropriate models that should be considered in geological disposal safety assessment of TRU waste was also set, and flux-to-dose conversion factors were calculated for the new regulation based on the same concept and models as HLW disposal.