Research about the long-term stability of TRU waste disposal system

Tanaka, M.*; Fujisawa, O.*; Okutsu, Kazuo*; Takamura, Hisashi*; Aoyagi, Takayoshi*

This research arranged the relation with the events (the events which happen to each part grade of disposal institution and change) produced to the characteristic in connection with low permeability and the disposal system of barrier material, such as permeability. The important events which can affect the long stability of the performance which barrier material has by that cause, and its relation were extracted. And, the physical-properties data acquisition of bentonite supposing the events considered to be generated to a disposal system in the future was carried out. The research result of this year is shown below. (1)About the events considered to affect permeability, "the present knowledge and the reseach result" and the "view of a design about a event" were arranged. And it divided and arranged the time of construction and operation, and after closure. Consequently, the subject required in order to check the long stability of TRU waste disposal system was able to be extracted. (2)In order for the research in the last year to estimate the self-seal nature of a bentonite, swelling pressure and the permeability at the time of the bentonite which generated the maximum swelling pressure under the restricted condition for Na-bentonite and Ca-bentonite 100% material re-swelling to the space produced after that were acquired. About this result, the view of effective bentonite dryness density was applied, and the self-seal performance of the assumed material (bentonite 70%, silica 30%) examined in TRU waste disposal concept examination document was evaluated. In order to check the validity of the evaluation in the last year, the self-seal performance check experiment was conducted about the silica mixture bentonite. Consequently, the soundness of a barrier system was able to be checked by the specification of H12 TRU report.