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Effect of Calcium Silicate Hydrate Precipitates at Cementitious and Bentonite Material Interface on Long-Term Engineered Barrier System Performance in TRU Waste Disposal Facilities

Published online by Cambridge University Press:  15 February 2011

Susumu Kurosawa ,
Hiroyuki Sakamoto ,
Kiyofumi Nitta ,
Chiya Numako ,
Kazuko Haga ,
Masahito Shibata ,
Tsutomu Sato ,
Toshiyuki Nakazawa  and
Hitoshi Owada
Susumu Kurosawa
Affiliation:
EBS Technology Research Project, Radioactive Waste Management Funding and Research Center (RWMC), 1-15-7, Tsukishima, Chuo-ku, Tokyo, 104-0052, Japan
Hiroyuki Sakamoto
Affiliation:
Solution Department, Taiheiyo Consultant Co., Ltd., 2-4-2, Ohsaku, Sakura-shi, Chiba, 285-8655, Japan
Kiyofumi Nitta
Affiliation:
Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1, Oho, Tsukuba-shi, Ibaraki, 305-0801, Japan
Chiya Numako
Affiliation:
Faculty of Integrated Arts and Sciences, The University of Tokushima, 1-1, Minami-josanjima, Tokushima, 770-8502, Japan
Kazuko Haga
Affiliation:
Solution Department, Taiheiyo Consultant Co., Ltd., 3-8-5, Misaki-cho, Chiyoda-ku, Tokyo, 101-0061, Japan
Masahito Shibata
Affiliation:
Solution Department, Taiheiyo Consultant Co., Ltd., 2-4-2, Ohsaku, Sakura-shi, Chiba, 285-8655, Japan
Tsutomu Sato
Affiliation:
Laboratory of Enviromental Geology, Graduate School of Engineering, Hokkaido University, Kita 8 Nishi 5, Sapporo, Hokkaido, 060-8628, Japan
Toshiyuki Nakazawa
Affiliation:
Naka Energy Research Laboratory, Mitsubishi Materials Corporation, 1002-14, Mukohyama, Naka-shi, Ibaraki, 311-0102, Japan
Hitoshi Owada
Affiliation:
EBS Technology Research Project, Radioactive Waste Management Funding and Research Center (RWMC), 1-15-7, Tsukishima, Chuo-ku, Tokyo, 104-0052, Japan
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Abstract

Chemical conditions and mass transport properties of engineered barrier systems in TRU waste facilities would change with time due to the interaction of cement/bentonite materials. (‘TRU waste’ is one of categories of the radioactive wastes and contains a significant amount of alpha-emitting transuranic nuclides. In some countries, these wastes are classified into the Intermediate Level Waste (ILW).) Previous numerical model analyses to assess the long-term performance of engineered barrier systems in TRU waste repositories predicted to form Calcium Silicate Hydrate (C-S-H) species at the interface between the cementitious and bentonite materials. If C-S-H precipitates in the bentonite side of the boundary, mass transport in the bentonite buffer decreases and mineralogical alterations are expected to be restricted for a long period. The evidence of C-S-H precipitation in the bentonite side, however, still has not been identified in the former experimental studies. To improve the reliability of numerical analyses, immersion experiments were performed using contact samples of cementitious and bentonite materials, and X-ray absorption fine structure (XAFS) analysis was carried out to detect C-S-H precipitation at the contacting interface. Precipitation of C-S-H was confirmed from the obtained XAFS spectra. This result is one of the evidences to show the validity of the current numerical model analyses, which suggests that the bentonite buffer performance as an engineered barrier would be kept over a long period.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1193: Scientific Basis for Nuclear Waste Management XXXIII , 2009 , 489
Copyright
Copyright © Materials Research Society 2009

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