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Uchida, Shunsuke; Chimi, Yasuhiro; Kasahara, Shigeki; Hanawa, Satoshi; Okada, Hidetoshi*; Naito, Masanori*; Kojima, Masayoshi*; Kikura, Hiroshige*; Lister, D. H.*
Nuclear Engineering and Design, 341, p.112 - 123, 2019/01
Times Cited Count：5 Percentile：48.99(Nuclear Science & Technology)Improvement of plant reliability based on reliability-centered-maintenance (RCM) is going to be undertaken in NPPs. RCM is supported by risk-based maintenance (RBM). The combination of prediction and inspection is one of the key issues to promote RBM. Early prediction of IGSCC occurrence and its propagation should be confirmed throughout the entire plant systems which should be accomplished by inspections at the target locations followed by timely application of suitable countermeasures. From the inspections, accumulated data will be applied to confirm the accuracy of the code, to tune some uncertainties of the key data for prediction, and then, to increase their accuracy. The synergetic effects of prediction and inspection on application of effective and suitable countermeasures are expected. In the paper, the procedures for the combination of prediction and inspection are introduced.
Honda, Akira; Mihara, Morihiro; Kato, Hiroshige*
JNC TN8400 2004-020, 69 Pages, 2004/11
JNC-TN8400-2004-020.pdf:3.09MB
Cementitious materials will be used expensively in the TRU waste repository. The cementitious materials will keep the high pH condition (pH
12) in the pore water of repository and the surrounding environment for long period. Thus it is necessary to obtain the data measured under the high pH conditions for the performance assessment of the TRU waste repository. However the uumber of the available data are limited. On the other hand, iodine-129 is an important nuclide because of its long half-time and poorly-sorbing nature. Therefore the effective diffusion coefficients De and distribution coefficients Kd of iodine in both crystalline rock and sedimentary rock were estimated in this study. Granodiorite and sandstone were selected as an example of crystalline rock and that of sedimentary rock respectively. Through diffusion experiment were carried out in an argon atmosphere.The diffusivity of iodine in both type rocks saturated by synthetic cement pore water was reduced with increasing experimental period. The analysis of experimental results suggested that this phenomenon was caused by decrease of De values. For granodiorite, the De values obtained in this study using synthetic cement pore water were 2 orders of magnitude smaller than literature values which obtained at neutral pH. For sandstone, the De values using synthetic cement pore water were 1 - 2 orders smaller than literature values, however those using synthetic groundwater were consistent with literature values. SEM observation of sandstone after the diffusion experiment showed that the secondary mineral coated the surface of sandstone. These observation results suggested that decrease of De value in case of synthetic cement pore water was ascribed to the precipitation of secondary mineral.In this study, Kd values of iodine on sandstone were 1.7x10
- 3.0x10m
/kg in synthetic groundwater. However Kd values of other cases could not be estimated.
Kato, Hiroshige*; Mine, Tatsuya*; Mihara, Morihiro; Oi, Takao; Honda, Akira
JNC TN8400 2001-029, 63 Pages, 2002/01
JNC-TN8400-2001-029.pdf:1.81MB
Cementitious materials will be used for the TRU waste repository as a component of engineered barrier system. The distribution coefficients which represent the retardation of radionuclides migration for the cementitious materials would be one of the important parameter for the safety assessment. The much information of radionuclide sorption onto the cementitious materials has been accumulated through the study in the world. Therefore it is necessary to compile the information and Kd of the radionuclides reported in previous studies. In this report, the Kd of the important radionuclides, such as C, Ni, Se, Sr, Zr, Nb, Mo, Tc, Sn, I, Cs, Sm, Pb, Ra, Ac, Th, Pa, U, Np, Pu, Am, Cm, for the cementitious materials were compiled as the Sorption Database (SDB). For radionuclides to be sensitive to the redox potential, e.g. Se, Tc, Pa, U, Pu and Np, some Kds measured under the controlled atmosphere had been reported, and few Kds measured under the controlled redox potential had been reported. For Se, Mo, Sm, Cm and Ac, the distribution coefficients had not been reported, therefore distribution coefficients of Se and Mo for OPC (Ordinary Portland Cement) pastes were measured by batch sorption experiments and these data were added into the SDB.
Kato, Hiroshige*; Sato, Mitsuyoshi*; Owada, Hitoshi*; Mihara, Morihiro;
JNC TN8430 2000-008, 53 Pages, 2000/05
Cementitious materials will be used in TRU waste disposal repository. In such cases, it is considered that the migration of alkaline leachates from cementitious materials, so called high pH plume, will cause dissolution of rock and precipitation of secondary minerals. In addition, the high pH plume will move along the flow of groundwater, so it is predicted that rock formation and components of high pH groundwater vary with time and space. However, time and spatial dependence of the variations of secondary minerals and groundwater components has not been clarified. In order to acquire the data of variations of secondary minerals and groundwater components, we carried out the rock alteration experiments with column method. The crushed granodiorite was filled into 4 meters length column (
3.7 cm) and artificial cement leachate (pH=13.3; Na=0,1 mol/l, K=0.1 mol/l, Ca=0.002 mol/l) was streamed at flow rates of 0.1 ml/min for 7 months at 80
C. As the result, secondary minerals confirmed on the rock were calcite and C-S-H at upstream of column and C-S-H at mid-downstream. The pH value of the fluid dominated by Na and K did not be decreased by reaction with the rock. In this study, the data relating to the effect of high pH plume on rock over the long term was acquired.
Mine, Tatsuya*; Mihara, Morihiro; Kato, Hiroshige*
JNC TN8430 99-012, 166 Pages, 1999/11
It is important to obtain the distribution coefficients of radio-elements on the bentonite under cementitious conditions in the geological disposal system of radioactive wastes. In-Diffusion experiments of Cs, Sr, Zr, Nb, Ni, Sn, Am, U, Np in Na-bentonite, Ca-bentonite, bentonite analcite mixture were carried out and the distribution coefficients were calculated. The experimental parameters were dry density (1200kg/m, 1600kg/m, 1800kg/m$^
) and synthetic solution type (distilled water, cementitous solution, cementitious solution+sea water, cementitous solution+sea water+nitrate). It was shown that the effects of the experimental parameters on the distribution coefficients on the most part of radio-elements used in this study were relatively small.
Mine, Tatsuya*; Mihara, Morihiro; Ito, Masaru; Kato, Hiroshige*
PNC TN8410 97-258, 57 Pages, 1997/06
None
Ara, Hiroshige*; Shinoda, Masao*; Iizuka, Yunosuke*
PNC TJ5060 86-002VOL3, 40 Pages, 1986/06
PNC-TJ5060-86-002VOL3.pdf:1.06MB
1.Objectives and Significance of Development of Equipments and Instruments for Underground Research Laboratories(URL) The second stage of R&D on HLW geological disposal includes geological survey, in-situ as well as laboratory tests and trial designing of the facility on a more concrete basis to promote the R&D program on HLW geological disposal. The second stage will call for numerous field investigations and tests. They can be summarized as follows: 1. Survey in search of potential sites for disposal (Wide-area Survey)2. Various tests to be conducted individually for the development of techniques for evaluating the performance of the natural barrier,ascertaining the performance of the engineered barrier and techniques for in-situ tests and construction works(Tests in Existing Caverns,Investigation on Groundwater Flow System) 3. Tests for developing,verifying and establishing an overall disposal technology by utilizing different techniques such as for survey,performance evaluation ,e
Ara, Hiroshige*; Fukumitsu, Kenji*; Iizuka, Yunosuke*; Ishii, Takashi*; Izumiya, Yasushi*; Imazu, Masanori*; Utsugida, Yoshizo*; Hasegawa, Makoto*; Maeda, Masaya*; Yabe, Yukio*; et al.
PNC TJ199 84-04VOL1, 20 Pages, 1984/03
PNC-TJ199-84-04VOL1.pdf:0.88MB
None
Onoda, Hiroshige*; Hanashima, Takayasu*; Takeda, Masayasu; Yanagihara, Hideto*
no journal, ,
no abstracts in English
