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Journal Articles

The Concept of dose system for radiological protection

Hirayama, Hideo*; Nakashima, Hiroshi; Sanami, Toshiya*; Yamaguchi, Yasuhiro; Sato, Osamu*; Takagi, Shunji*; Suzuki, Toshikazu*; Iwai, Satoshi*

Nippon Genshiryoku Gakkai-Shi, 55(2), p.83 - 96, 2013/02

Since the accident at the Fukushima Daiichi Power Plant, units of radiation doses such as Sv have been frequently reported by newspapers. However, it is not exactly understood even by experts on nuclear engineering that there are two different concepts which are the protection quantity such as the effective dose related to a radiation health risk and the practical quantity such as ambient dose equivalents related to measurements. In this special issue, Radiological Protection Quantity, and Operational Quantity and Radiological Protection Quantity, explain the radiation protection dose system including the protection and practical quantities established by ICRP and ICRU. Relation between Dosimeters used at Fukushima etc. and Radiological Protection Quantity describes a method and its problems to measure radiations from Cs on surface and underground using survey meters and personal dosimeters, and convert the measured values to effective doses.

Journal Articles

The First (U-Th)/He thermochronology of pseudotachylyte from the Median Tectonic Line, southwest Japan

Yamada, Kunimi; Hanamuro, Takahiro; Tagami, Takahiro*; Shimada, Koji; Takagi, Hideo*; Yamada, Ryuji*; Umeda, Koji

Journal of Asian Earth Sciences, 45(2), p.17 - 23, 2012/02

 Times Cited Count:1 Percentile:95.02(Geosciences, Multidisciplinary)

no abstracts in English

Journal Articles

Estimation of the paleostress field from the 3-D orientation distribution of microcracks and their geothermal conditions in the Toki Granite, central Japan

Takagi, Hideo*; Miwa, Shigenori*; Yokomizo, Yoshiyuki*; Nishijima, Kei*; Enjoji, Mamoru*; Mizuno, Takashi; Amano, Kenji

Chishitsugaku Zasshi, 114(7), p.321 - 335, 2008/07

Based on the 3-D orientations of intracrystalline healed, sealed and open extension microcracks in quartz grains in the Late Cretaceous Toki Granite, we discuss the paleostress field and the history of microcracking combining the microthermometry of fluid inclusions in healed microcracks and sealing material identification in sealed microcracks. Twenty one oriented samples are collected mainly from the DH-15 core (240-1000 mabh) drilled by Japan Atomic Energy Agency (JAEA) and additionally from five outcrops in the Tono region. 3-D orientations of healed microcracks indicate the $$sigma$$$$_{rm Hmax}$$ orientation of N-S to NW-SE in almost all sites, whereas those of sealed and open microcracks indicate the dominant $$sigma$$$$_{rm Hmax}$$ orientation of E-W. Two or three orthogonal sets of microcracks are common in both healed and sealed microcracks. The formation of these sets can be attributed to the switch of principal stress axis due to stress release just after the crack formation. Healed microcracks probably reflect more regional paleostress field because of consistency of the orientations than the case of sealed and open microcracks that show rather scattering orientations. N-S to NW-SE trending healed microcracks are formed around 60 Ma on the basis of K-Ar biotite ages of the Toki Granite and formation temperature (c. 300-400$$^{circ}$$C) of fluid inclusions estimated from microthermometry in the case of intrusion depth (3.5 km=100 MPa) of the Toki Granite. Thus the $$sigma$$$$_{rm Hmax}$$ orientation trended NW-SE after the restoration of clockwise rotation of SW Japan at c. 15 Ma. Following the healed microcrack formation, E-W trending high-angle sealed microcracks filled with carbonate mineral are formed. Open microcracks presumably formed at near-surface at the last stage of sealed microcrack formation after c. 20 Ma before the Mizunami Group deposited unconformably on the granite.

JAEA Reports

Evaluation of containment failure probability due to ex-vessel steam explosions in LWR severe accidents

Moriyama, Kiyofumi; Takagi, Seiji*; Muramatsu, Ken; Nakamura, Hideo; Maruyama, Yu

JAEA-Research 2007-072, 54 Pages, 2007/11

JAEA-Research-2007-072.pdf:25.89MB

The containment failure probability due to ex-vessel steam explosions was evaluated for BWR and PWR model plants. A stratified Monte Carlo technique (Latin Hypercube Sampling (LHS)) was applied for the evaluation of steam explosion loads, in which a steam explosion simulation code JASMINE was used as a physics model. The evaluation was made for three scenarios: a steam explosion in the pedestal area or in the suppression pool of a BWR model plant with Mark-II containment, and in the reactor cavity of a PWR model plant. The scenario connecting the generation of steam explosion loads and the containment failure was assumed to be displacement of the reactor vessel and pipings, and failure at the penetration in the containment boundary. We evaluated the conditional containment failure probability (CCFP) based on the preconditions of failure of molten core retention within the reactor vessel, relocation of the core melt into the water pool without significant interference, and a strong triggering at the time of maximum premixed mass. The obtained mean and median values of the CCPF were 6.4E-2 (mean) and 3.9E-2 (median) for the BWR suppression pool case, 2.2E-3 (mean) and 2.8E-10 (median) for the BWR pedestal case, and 6.8E-2 (mean) and 1.4E-2 (median) for the PWR cavity case. The evaluation of CCFPs on the basis of core damage needs consideration of probabilities for the above-mentioned preconditions. Thus, the CCFPs per core damage should be lower than the values given above. The specific values of the probability were most dependent on the assumed range of melt flow rate and fragility curve that involved conservatism and uncertainty due to simplified scenarios and limited information. Additionally, the source term significance of the fine particles generated by steam explosions was discussed.

Journal Articles

Evaluation of containment failure probability by Ex-vessel steam explosion in Japanese LWR plants

Moriyama, Kiyofumi; Takagi, Seiji*; Muramatsu, Ken; Nakamura, Hideo; Maruyama, Yu*

Journal of Nuclear Science and Technology, 43(7), p.774 - 784, 2006/07

 Times Cited Count:12 Percentile:29.12(Nuclear Science & Technology)

The containment failure probability due to ex-vessel steam explosions was evaluated for Japanese BWR and PWR model plants. A stratified Monte Carlo technique (Latin Hypercube Sampling (LHS)) was applied for the evaluation of steam explosion loads, in which a steam explosion simulation code JASMINE was used as a physics model. The evaluation was made for three scenarios: a steam explosion in the pedestal area or in the suppression pool of a BWR model plant with a Mark-II containment, and in the reactor cavity of a PWR model plant. The scenario connecting the generation of steam explosion loads and the containment failure was assumed to be displacement of the reactor vessel and pipings, and failure at the penetration in the containment boundary. The mean conditional containment failure probabilities (CCFPs) were $$6.4times 10^{-2}$$ (mean) and $$3.9times 10^{-2}$$ (median) for the BWR suppression pool case, $$2.2times 10^{-3}$$ (mean) and $$2.8times 10^{-10}$$ (median) for the BWR pedestal case, and $$6.8times 10^{-2}$$ (mean) and $$1.4times 10^{-2}$$ (median) for the PWR cavity case. Note that the specific values of the probability are most dependent on assumed range of melt flow rates and on fragility curves that involve conservatism and uncertainty due to simplified scenarios and limited information. Also, note that these CCFPs were based on the preconditions of failure of accident termination within the reactor vessel, relocation of the core melt into the water pool at the place in question without significant interference, and a strong triggering ofa steam explosion with maximized premixed mass for the given premixing condition. The evaluation of CCFPs on the basis of core damage needs consideration of probabilities for these preconditions. Thus, the CCFPs per core damage should be lower than the values given above.

Journal Articles

Evaluation of ex-vessel steam explosion induced containment failure probability for Japanese BWR

Moriyama, Kiyofumi; Takagi, Seiji; Muramatsu, Ken; Nakamura, Hideo; Maruyama, Yu

Proceedings of 2005 International Congress on Advances in Nuclear Power Plants (ICAPP '05) (CD-ROM), 9 Pages, 2005/05

The containment failure probability due to ex-vessel steam explosions were evaluated for a BWR Mk-II model plant. The evaluation was made for two scenarios: a steam explosion in the pedestal area, or in the suppression pool. A probabilistic approach, Latin Hypercube Sampling (LHS), was applied for the evaluation of steam explosion loads, in which a steam explosion simulation code JASMINE was used as a physics model. The fragility curves connecting the steam explosion loads and containment failure were developed based on simplified assumptions on the containment failure scenarios. The mean conditional probabilities of containment failure per occurrence of a steam explosion were $$6.4times 10^{-2}$$ for suppression pool and $$2.2times 10^{-3}$$ for pedestal area. Note that the results depend on the assumed range of input parameters and fragility curves that involve conservatism and simplification.

Oral presentation

3-D directional distribution of microcracks in the Toki granite, and estimation of the paleostress field and geothermal condition

Miwa, Shigenori*; Takagi, Hideo*; Nishijima, Kei*; Yokomizo, Yoshiyuki*; Enjoji, Mamoru*; Mizuno, Takashi

no journal, , 

no abstracts in English

Oral presentation

(U-Th)/He dating of Taki pseudotachylyte, Ryoke granites

Yamada, Kunimi; Takagi, Hideo*; Tagami, Takahiro*; Danhara, Toru*

no journal, , 

Taki pseudotachylyte first found along the MTL was formed after mylonitization of the Hatai Tonalite under amphibolite to greenschist facies conditions, and had been post-dated by cataclasis. We dated some zircons from the mylonited Tonalite around the pseudotachylyte using the (U-Th)/He method, the age corresponds approximately to the FT ages of the pseudotachylyte, not the Tonalite. This suggests that the ambient temperature for generating the pseudotachylyte was higher than the closure temperature of ZHe, and this is consistent with cataclasis temperature. In this case we can not say the age of the pseudotachylyte, however, we can constrain something for the age and cooling-denudation history of this fault. Now we continue to date zircons from the pseudotachylyte.

Oral presentation

New (U-Th)/He dating systems and ages in Japan Atomic Energy Agency

Yamada, Kunimi; Hanamuro, Takahiro; Tagami, Takahiro*; Takagi, Hideo*; Shimada, Koji; Umeda, Koji; Iwano, Hideki*; Danhara, Toru*

no journal, , 

Japan Atomic Energy Agency have jointly set up the system of the (U-Th)/He dating in cooperation with Kyoto University and National Institute for Earth Sciences and Disaster Prevention. Through this two years, helium extraction machine using an electronically-cooled diode laser, micro crusible system using XRF bead sampler and uranium and thorium quantification procedure without artificial spikes are developed. Now we produce new ages of some age known samples. At the present stage, the accuracy and precision are roughly 20 and 10%, respectively, using the age standard zircon from the Fish Canyon Tuff (FC3). In the presentation, we will introduce our systems and the ages detailedly.

Oral presentation

(U-Th)/He dating of the Taki pseudotachylyte, Ryoke Granites

Yamada, Kunimi; Hanamuro, Takahiro; Tagami, Takahiro*; Shimada, Koji; Takagi, Hideo*; Iwano, Hideki*; Danhara, Toru*; Umeda, Koji

no journal, , 

no abstracts in English

Oral presentation

(U-Th)/He thermochronologic analysis of the Median Tectonic Line and associated pseudotachylyte

Yamada, Kunimi; Hanamuro, Takahiro; Tagami, Takahiro*; Shimada, Koji; Takagi, Hideo*; Iwano, Hideki*; Danhara, Toru*; Umeda, Koji

no journal, , 

no abstracts in English

Oral presentation

(U-Th)/He dating and its applications

Yamada, Kunimi; Hanamuro, Takahiro; Shimada, Koji; Umeda, Koji; Tagami, Takahiro*; Takagi, Hideo*; Yamada, Ryuji*

no journal, , 

no abstracts in English

Oral presentation

Determination of the shear direction using X-ray CT pictures

Iwamori, Akiyuki*; Takagi, Hideo*; Shimada, Koji; Asahi, Nobutaka*; Sugimori, Tatsuji*; Sasaki, Toshinori*; Aiyama, Kotaro*

no journal, , 

no abstracts in English

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