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Takamizawa, Hisashi; Nishiyama, Yutaka
Journal of Pressure Vessel Technology, 143(5), p.051502_1 - 051502_8, 2021/10
Times Cited Count：3 Percentile：30.36(Engineering, Mechanical)no abstracts in English
Takamizawa, Hisashi; Ito, Hiroto; Nishiyama, Yutaka
Journal of Nuclear Materials, 479, p.533 - 541, 2016/10
Times Cited Count：6 Percentile：49.29(Materials Science, Multidisciplinary)To understand neutron irradiation embrittlement in high fluence regions, statistical analysis using the Bayesian nonparametric (BNP) method was performed for the Japanese surveillance and material test reactor irradiation database. The BNP method is essentially expressed as an infinite summation of normal distributions, with input data being subdivided into clusters with identical statistical parameters (such as mean and standard deviation) for each cluster to estimate shifts in ductile-to-brittle transition temperature (DBTT). Clusters typically depend on chemical compositions, irradiation conditions, and the irradiation embrittlement. Specific variables contributing to the irradiation embrittlement include the content of Cu, Ni, P, Si, and Mn in the pressure vessel, neutron flux, neutron fluence, and irradiation temperatures. It was found through numerous examinations that the measured shifts of DBTT correlated well with calculated ones. Data associated with the same materials were subdivided into the same clusters even if neutron fluences were significantly disparate among the results. This indicates that slowly developing or late-onset embrittlement mechanisms were not evident in the present study.
Takamizawa, Hisashi; Nishiyama, Yutaka
Proceedings of 2016 ASME Pressure Vessels and Piping Conference (PVP 2016) (Internet), 5 Pages, 2016/07
It has been accepted that neutron irradiation embrittlement of reactor pressure vessel is caused by irradiation-induced formation of solute clusters (SCs) and matrix damages (MDs). In the present study, to analyze the contribution of chemical composition contained in SCs to irradiation embrittlement at high fluence region, statistical analysis using the Bayesian nonparametric (BNP) method was performed for Japanese PWR surveillance data. The significance of P, Si and Mn contents, which are not necessarily included in embrittlement correlations unlike the Cu and Ni content, was evaluated. The BNP method can learn the complexity of the statistical model itself from the input data and infer the predicted data with individual probability distribution of predict condition. The result suggested that irradiation embrittlement was most affected by the Si content at high fluence region.
Matsumoto, Taro; Kishimoto, Yasuaki; Li, J.
Journal of Plasma and Fusion Research SERIES, Vol.6, p.597 - 600, 2004/00
no abstracts in English
Sumiyama, Morio*
JNC TJ8400 2000-009, 138 Pages, 2000/02
To evaluate corrosion behavior of carbon steel, a candidate materials of overpack, buried in soil for a long time, the water pipes buried in freshwater clay for a long time we digged out and the soil environment and the corrosion weight loss of pipes have been researched. From the results, a corrosion model (an empirical equation), an oxygen reduction reaction rate-determing step type, of carbon steel buried in soil was introduced. The corrosion data of under ground pipe collected by the Japan Community Gas Associations was used to increase reliability of the corrosion model equation. These data are one of researches of corrosion behavior of carbon steel buried in soil for a long time studied by at home and abroad. 38 samples buried freshwater clay were selected in 171 samples. With estimating the corrosion velocities and the soil environment factors of the above data, the maximum depth of pit corrosion was calculated by the statistical method of the extreme values using the area of overpack as the recurrent time. The correlation between the soil environment factors and the corrosion weight loss was obtained by the correlation analysis. The corrosion model of the maximum depth of pit corrosion at 0.99 of cumulative probability was compared between the under ground pipe data and the above data. On the reference data and the above data, the corrosion model equation; H = aY
was compared with the maximum depth of pit corrosion at 0.99 cumulative probability. The data of water pipes and community gas pipes at 0.99 cumulative probability showed the reasonable values when these data were compared with the reference data. So that the model was proved as a good corrosion model m the neutral low dissolved oxygen environment.
Imai, Jun*
JNC TJ8400 2000-008, 196 Pages, 2000/02
JNC-TJ8400-2000-008.pdf:25.25MB
The objective of this research is to make clear long-term alteration processes of bentonite contacting with concrete under a repository condition for radioactive waste. The Uzu tunnel in yamagata prefecture in Japan, constructed during the term of December of 1963 to July 1967, was selected as an appropriate natural analogue: the tunnel wall was made of portland cement and which has been contacting with a bentonite bed during 
32 years. Sample analyses indicated that the original bentonite was Na
-type and it changed to Ca
-type in the range of a few millimeters from the contact. Although a Ca leaching was also observed from the concrete near the contact, neither transformation to zeolite nor to illite was recognized. On the other hand, sulfur increased and ettringite (3CaO 
Al
O
3CaSO
4 32HO) was recognized in the concrete within the depth about 30 mm from the contact.
Toida, Masaru*; Shiogama, Yukihiro*; Atsumi, Hiroyuki; Masumoto, Kazuhiko*; Yasui, Shingo*; Abe, Yasunori*; Furuichi, Mitsuaki*
JNC TJ7440 2000-006, 137 Pages, 2000/02
JNC-TJ7440-2000-006.pdf:3.55MB
no abstracts in English
Yui, Mikazu; Sasamoto, Hiroshi; Randolph C Arthu*
JNC TN8400 99-030, 201 Pages, 1999/07
According to the Japanese program for research and development of high level radioactive waste (HLW) disposal defined by Atomic Energy Commission (AEC), the second progress report (i.e., H-12 report) for performance assessment (PA) of HLW disposal is to be published by the Japan Nuclear Cycle Development Institute (JNC) and submitted to the Japanese government before the year 2,000 (AEC, 1997). This report presents the establishment of generic groundwater chemical compositions for the PA supporting the H-12 report. The following five hypothetical groundwaters are categorized for PA based on the results of the first progress report (i.e., H-3 report) and binaly statistical analyses of the screened groundwater dataset: (1)FRHP(Fresh-Reducing-High-pH) groundwater (2)FRLP(Fresh-Reducing-Low-pH) groundwater (3)SRHP(Saline-Reducing-High-pH) groundwater (4)SRLP(Saline-Reducing-Low-pH) groundwater (5)MRNP(Mixing-Reducing-Neutral-pH) groundwater. In order to define representative groundwater compositions for the PA for the H-12 report, JNC has established the representativeness of the above five hypothetical groundwaters by considering the results of multivariate statistical analyses, data reliability, evidence for geochemical controls on groundwater chemistry and exclusion criteria for potential repository sites in Japan. As a result, the following hypothetical reference groundwaters are selected for the performance assessment analysis in H-12 report, respectively: (1)Reference Case groundwater: FRHP groundwater, and (2)Alternative Geological Environment Case groundwater: SRHP groundwater. In addition, JNC has consulted with overseas experts on the concepts used in groundwater evolution modeling. This modeling effort has focussed on simulating equilibrium water-rock interactions to predict groundwater compositions resulting from reactions between initial water compositions and rock mineral assemblages. These discussions have centered on recommendations for developing ...
Kitabata, Hideyuki*; Chino, Masamichi
JAERI-Data/Code 99-012, 47 Pages, 1999/03
JAERI-Data-Code-99-012.pdf:2.82MB
no abstracts in English
Tsujimura, Norio; Momose, Takumaro; Shinohara, Kunihiko
PNC TN8410 96-036, 20 Pages, 1996/02
None
*; Nakamura, Hisashi; Kanazawa, Katsuo; Fujiki, Kazuo; *
Chuzo Kogaku, 68(8), p.644 - 649, 1996/00
no abstracts in English
Onizawa, Kunio; Suzuki, Masahide
IWG-LMNPP-95/5 (Vol. I), 0, p.279 - 293, 1995/00
no abstracts in English
Tsuji, Hirokazu; Miya, Kenzo*
Nucl. Eng. Des., 155, p.527 - 546, 1995/00
Times Cited Count：1 Percentile：16.76(Nuclear Science & Technology)no abstracts in English
Tsuji, Hirokazu; Miya, Kenzo*
Nucl. Eng. Des., 155, p.547 - 557, 1995/00
Times Cited Count：2 Percentile：28.65(Nuclear Science & Technology)no abstracts in English
Tsuji, Hirokazu; *; Tsukada, Takashi; Nakajima, Hajime
Journal of Nuclear Science and Technology, 30(12), p.1234 - 1242, 1993/12
Times Cited Count：3 Percentile：38.1(Nuclear Science & Technology)no abstracts in English
Tsuji, Hirokazu; *; Tsukada, Takashi; Nakajima, Hajime
JAERI-M 93-204, 24 Pages, 1993/10
no abstracts in English
