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Kuno, Yoshio; Sasamoto, Hiroshi
Materials Research Society Symposium Proceedings, Vol.1124, p.581 - 586, 2009/00
Column experiments were carried out using an artificial fracture within the granite rock in order to investigate the migration behavior of bentonite colloids. A sufficient fraction of colloids was immobilized within the fractured granite in 10
M NaCl solution. In case of comparatively high ionic concentration, retardation of bentonite colloids is expected in the geological medium.
Oi, Takao; Inagaki, Manabu; Kawamura, Makoto; Ebashi, Takeshi
Materials Research Society Symposium Proceedings, Vol.1124, p.407 - 412, 2009/00
In the safety assessment of geological disposal system of radioactive waste, diverse apprehensions have been extracted from the viewpoint of the impact on the safety and the researches relating to those have been carried out strenuously. However, systematical investigation for presenting the relative importance of those has so far scarcely been conducted. The demonstration of the importance is critical issue to contribute the improvement of reliability of safety assessment. In this study, the following investigations were carried out with the goal of developing the systematic approach which can present the relative importance of the apprehensions: (1) Establishment of Total Assessment Work Frame [TAWF], (2) Establishment of the organaization procedure for evaluating the relative importance.
Tachi, Yukio; Seida, Yoshimi; Doi, Reisuke; Xia, X.*; Yui, Mikazu
Materials Research Society Symposium Proceedings, Vol.1124, p.573 - 579, 2009/00
Honda, Akira; Masuda, Kenta; Nakanishi, Hiroshi*; Fujita, Hideki*; Negishi, Kumi*
Materials Research Society Symposium Proceedings, Vol.1124, p.365 - 372, 2009/00
Yoshida, Yasushi*; Yoshikawa, Hideki
Materials Research Society Symposium Proceedings, Vol.1124, p.413 - 420, 2009/00
Ra is one of the important radionuclide for performance assessment of HLW. Concentration of Ra in groundwater is limited by an interaction with calcite. Incorporation of Ra can be evaluated by partition coefficient. In addition to this parameter, a number of surface layers which contribute ion substitution reaction is also necessary for calculation. Therefore experiments were carried out. As a result, a number of surface layers of calcite is estimated as 15to 44. Those values are consistent with estimated value in literature. With this number of layers, the migration analysis of 4n+2 series radionuclides were performed with reaction of calcite. This effect can be evaluated with partition coefficient. As a result, release rates of Ra was largest in their series on an outer surface of engineered barrier and about one order magnitude lower than that for radionuclide of highest release rate at the point of 100 m in rock.
Sugaya, Atsushi; Horiguchi, Kenichi; Tanaka, Kenji; Akutsu, Shigeru
Materials Research Society Symposium Proceedings, Vol.1124, p.373 - 378, 2009/00
Development work has been carried out on the cementation of phosphate waste form the Tokai Reprocessing Plant Solvent Waste Treatment Facility. The phosphate effluent consists of NaH
PO
at an approximate concentration of 440 g/
, with only very minor quantities of other species. Results are presented here from non-active trials that demonstrate that it is possible to encapsulate this effluent using blastfurnace slag or Super-Cement. It was found that to achieve a stable wasteform it was necessary to pre-treat the phosphate effluent with lime before encapsulation. The optimum pre-treatment and cement formulations were investigated. Compressive strengths of grouted waste simulant exceeding 10 MPa after 28 days curing with a waste loading exceeding 13wt% was achieved.
Yokoyama, Yutaka*; Mitsui, Hiroyuki*; Takahashi, Rieko*; Asano, Hidekazu*; Taniguchi, Naoki; Naito, Morimasa
Materials Research Society Symposium Proceedings, Vol.1124, p.463 - 471, 2009/00
In Japan, carbon steel is one of the candidate materials for the disposal container (overpack) for high-level radioactive waste (HLW). Overpack seals vitrified waste and is required to isolate it from contact with groundwater for 1,000 years in Japan's waste management program. Its integrity for 1,000 years is evaluated in consideration of mechanical strength and corrosion property. The corrosion property of base metal is evaluated along with the corrosion scenarios of carbon steel overpack presented by JNC. However, the corrosion behavior of the weld zone of overpack under repository conditions has not been investigated enough to evaluate its long term integrity. The weld zone may have a different microstructure and chemical composition from the base metal because of the influence of welding. Therefore, the corrosion property of the weld zone may differ from that of the base metal. In this study, to evaluate the corrosion property of the weld zone produced by TIG, MAG and EBW, the corrosion modes which had become the main concerns in the weld zone were extracted from the corrosion scenario of base metal, and four tests: passivation behavior, corrosion property under aerobic conditions, susceptibility to stress corrosion cracking, and corrosion property and possibility of hydrogen embrittlement under anaerobic conditions, were examined.
