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Journal Articles

Report on social communication activities of Young Researchers Association and Students Association of JHPS; Chiba-shi Science Festa

Yamada, Ryohei; Kono, Takahiko; Nakajima, Junya; Hirouchi, Jun; Tsuji, Tomoya; Umeda, Masayuki; Igarashi, Yu*; Koike, Hiromi*

Hoken Butsuri (Internet), 56(1), p.32 - 38, 2021/03

no abstracts in English

JAEA Reports

Soundness survey of cooling tower of Utility Cooling Loop (UCL Cooling Tower) in JMTR

Oto, Tsutomu; Asano, Norikazu; Kawamata, Takanori; Yanai, Tomohiro; Nishimura, Arashi; Araki, Daisuke; Otsuka, Kaoru; Takabe, Yugo; Otsuka, Noriaki; Kojima, Keidai; et al.

JAEA-Review 2020-018, 66 Pages, 2020/11

JAEA-Review-2020-018.pdf:8.87MB

A collapse event of the cooling tower of secondary cooling system in the JMTR (Japan Materials Testing Reactor) was caused by the strong wind of Typhoon No.15 on September 9, 2019. The cause of the collapse of the cooling tower was investigated and analyzed. As the result, it was identified that four causes occurred in combination. Thus, the soundness of the cooling tower of Utility Cooling Loop (UCL cooling tower), which is a wooden cooling tower installed at the same period as the cooling tower of secondary cooling system, was investigated. The items of soundness survey are to grasp the operation conditions of the UCL cooling tower, to confirm the degradation of structural materials, the inspection items and inspection status of the UCL cooling tower, and to investigate the past meteorological data. As the results of soundness survey of the UCL cooling tower, the improvement of inspection items of the UCL cooling tower was carried out and the replacement and repair of the structural materials of the UCL cooling tower were planned for safe maintenance and management of this facility. And the renewal plan of new cooling tower was created to replace the existing UCL cooling tower. This report is summarized the soundness survey of the UCL cooling tower.

Journal Articles

A Knowledge-sharing activity on the environmental radiation monitoring results affected by the Fukushima-Daiichi Nuclear Power Plant Accident at Tokai-Oarai area in Ibaraki Prefecture

Nakano, Masanao; Hosomi, Kenji; Nishimura, Shusaku; Matsubara, Natsumi; Okura, Takehisa; Kuramochi, Akihiko; Kawasaki, Masatsugu; Takeuchi, Erina; Fujii, Yutaka*; Jinno, Tsukasa*; et al.

Hoken Butsuri (Internet), 55(2), p.102 - 109, 2020/06

After the Fukushima-Daiichi Nuclear Power Station (1F) Accident in March 2011, the increase was significantly observed in a part of the result of the environmental radiation monitoring in Ibaraki prefecture. "The review meeting of the environmental effect from 1F accident" was established to discuss technically the fluctuation of monitoring data. The review meeting collected the monitoring data from the four nuclear operators, and discussed a fluctuating trend, $$^{134}$$Cs/$$^{137}$$Cs activity ratio, and so on. In this report, the results of the dose rate and $$^{137}$$Cs in fallout, surface soil, flatfish and seabed sediment are introduced. Also the problem solving in the review meeting is introduced.

Journal Articles

Joint meeting of young researchers in the field of radiation protection and radiation biology

Kataoka, Noriaki*; Nakajima, Junya; Miwa, Kazuji; Hirota, Seiko*; Tsubota, Yoichi; Yamada, Ryohei; Fujimichi, Yuki*; Ishikawa, Junya*; Sunaoshi, Masaaki*

Hoken Butsuri (Internet), 54(2), p.140 - 145, 2019/06

It is the written report of the joint meeting of young researchers in the field of radiation protection and radiation biology.

Journal Articles

Design of HTTR-GT/H$$_{2}$$ test plant

Yan, X.; Sato, Hiroyuki; Sumita, Junya; Nomoto, Yasunobu*; Horii, Shoichi*; Imai, Yoshiyuki; Kasahara, Seiji; Suzuki, Koichi*; Iwatsuki, Jin; Terada, Atsuhiko; et al.

Nuclear Engineering and Design, 329, p.223 - 233, 2018/04

 Times Cited Count:10 Percentile:87.34(Nuclear Science & Technology)

The pre-licensing design of an HTGR cogeneration test plant to be coupled to JAEA's existing test reactor HTTR is presented. The plant is designed to demonstrate the system of JAEA commercial plant design GTHTR300C. With construction planned to be completed around 2025, the test plant is expected to be the first-of-a-kind nuclear system operating on two of the advanced energy conversion systems attractive for the HTGR closed cycle helium gas turbine for power generation and thermochemical iodine-sulfur water-splitting process for hydrogen production.

Journal Articles

Improvement of estimation of $$^{131}$$I concentrations in the air using data measured by monitoring posts applied by determination of passing-through time of plume using noble gas counts

Yamada, Junya; Hashimoto, Makoto; Seya, Natsumi; Haba, Risa; Muto, Yasunobu; Shimizu, Takehiko; Takasaki, Koji; Yokoyama, Sumi*; Shimo, Michikuni*

Hoken Butsuri, 52(1), p.5 - 12, 2017/03

The purpose of this study is to improve a quick method for estimation of $$^{131}$$I concentrations in the air using data measured by monitoring posts in case that a nuclear disaster occurs. In this method, $$^{131}$$I concentrations were estimated by multiplying $$^{131}$$I count rates of cloud-shine measured with NaI (Tl) detector by concentration conversion factor. A previous study suggested that it was difficult to determine passing-through time of plume from temporal change of $$^{131}$$I count rates or dose rate. Our study applies the method for estimating passing-through time of plume from temporal change of noble gas counts. The $$^{131}$$I concentrations in the air at Oarai center, Japan Atomic Energy Agency resulting from the accident at the Fukushima Daiichi Nuclear Power Plant were estimated by proposal technique. The result of comparison of this method with sampling method for $$^{131}$$I concentrations in the air were within factor 3.

Journal Articles

HTTR-GT/H$$_{2}$$ test plant; System design

Yan, X.; Sato, Hiroyuki; Sumita, Junya; Nomoto, Yasunobu; Horii, Shoichi; Imai, Yoshiyuki; Kasahara, Seiji; Suzuki, Koichi*; Iwatsuki, Jin; Terada, Atsuhiko; et al.

Proceedings of 8th International Topical Meeting on High Temperature Reactor Technology (HTR 2016) (CD-ROM), p.827 - 836, 2016/11

Pre-licensing basic design for a cogenerating HTGR test plant system is presented. The plant to be coupled to existing 30 MWt 950$$^{circ}$$C test reactor HTTR is intended as a system technology demonstrator for GTHTR300C plant design. More specifically the test plant of HTTR-GT/H$$_{2}$$ aims to (1)demonstrate the licensability of the GTHTR300C for electricity production by gas turbine and hydrogen cogeneration by thermochemical process and (2) confirm the operation control and safety of such cogeneration system. With construction and operation completion by 2025, the test plant is expected to be the first of a kind HTGR-powered cogeneration plant operating on the two advanced energy conversion systems of closed cycle helium gas turbine for power generation and thermochemical iodine-sulfur water-splitting process for hydrogen production.

Journal Articles

Calculation of conversion factor for estimation of $$^{131}$$I concentrations in the air from pulse-height distribution observed by NaI(Tl) detector in monitoring posts

Yamada, Junya; Hashimoto, Makoto; Seya, Natsumi; Haba, Risa; Muto, Yasunobu; Shimizu, Takehiko; Takasaki, Koji; Yokoyama, Sumi*; Shimo, Michikuni*

Radioisotopes, 65(10), p.403 - 408, 2016/10

The purpose of this study is to develop a quick method for estimation of $$^{131}$$I concentrations in the air using data measured by monitoring posts. In this method, $$^{131}$$I concentrations were estimated by multiplying $$^{131}$$I count rates at the full-energy peak measured with a NaI(Tl) detector by a concentration conversion factor. The concentration conversion factor for monitoring posts in JAEA Oarai Center was calculated with an EGS5 Monte Carlo code. As a result, the concentration conversion factor for an infinite-air-source was 25.7 Bq/m$$^{3}$$/cps.

Journal Articles

Evaluation of fracture toughness of fine-grained isotropic graphites for HTGR

Yamada, Teruaki*; Matsushima, Yuki*; Kuroda, Masatoshi*; Sumita, Junya; Shibata, Taiju; Fujita, Ichiro*; Sawa, Kazuhiro

Nuclear Engineering and Design, 271, p.323 - 326, 2014/05

 Times Cited Count:5 Percentile:43.74(Nuclear Science & Technology)

In order to investigate the effects of the experimental methodology and the notch angle on the fracture toughness of the fine-grained isotropic nuclear graphites IG-110 and IG-430, the three-point-bending test, which has been recently proposed as the methodology to evaluate the fracture toughness of graphite for high temperature gas-cooled reactors (HTGRs), was performed using two types of the specimens with different notch angles. The results obtained in this study could be summarized as follows: (1) The values of the fracture toughness of IG-110 and IG-430 measured in this study were 0.890 MPa m$$^{1/2}$$ and 1.031 MPa m$$^{1/2}$$, respectively. It was also found that the value of the fracture toughness of IG-110 was nearly equal to or smaller than the values obtained by the other method reported previously. (2) The values of the fracture toughness of the fine-grained isotropic graphites were not affected between the notch angles introduced by the incisive razor blade. (3) The ratio of the tensile strengths of IG-110 and IG-430 was estimated from Griffith Theory using the experimental data obtained in this study. The estimated strength ratio was in good agreement with the strength ratio obtained from the supplier's data.

JAEA Reports

Survey of radiation protection creiteria following the accident at the Fukushima Dai-ichi Nuclear Power Plant

Yamada, Katsunori; Fujii, Katsutoshi; Kanda, Hiroshi; Higashi, Daisuke; Kobayashi, Toshiaki; Nakagawa, Masahiro; Fukami, Tomoyo; Yoshida, Keisuke; Ueno, Yumi; Nakajima, Junya; et al.

JAEA-Review 2013-033, 51 Pages, 2013/12

JAEA-Review-2013-033.pdf:2.73MB

After the accident at Fukushima Dai-ichi Nuclear Power Plant, various numerical criteria relevant to radiation protection were defined. We surveyed these criteria through internet. As a result of survey, the following 13 items were identified: (1) criteria for taking stable iodine tablets, (2) criteria for the screening of surface contamination, (3) evacuation area, sheltering area, etc., (4) activity concentrations in food, drinking water, etc., (5) dose limit for radiation workers engaged in emergency work, (6) guideline levels of radioactive substances in bathing areas, (7) criteria for use of school buildings and schoolyards, (8) restriction on planting rice, (9) acceptable activity concentrations in feedstuff, (10) acceptable activity concentrations in compost, (11) criteria for export containers and ships, (12) criteria for contaminated waste, (13) standards for radiation workers engaged in decontamination work. In this report, the basis of and issues on these criteria are summarized.

JAEA Reports

Environmental radiation monitoring resulting from the accident at the Fukushima Daiichi Nuclear Power Plant, conducted by Oarai Research and Development Center, JAEA; Results of ambient gamma-ray dose rate, atmospheric radioactivity and meteorological observation

Yamada, Junya; Seya, Natsumi; Haba, Risa; Muto, Yasunobu; Numari, Hideyuki*; Sato, Naomitsu*; Nemoto, Koji*; Takasaki, Hiroichi*; Shimizu, Takehiko; Takasaki, Koji

JAEA-Data/Code 2013-006, 100 Pages, 2013/06

JAEA-Data-Code-2013-006.pdf:12.04MB

This report presents the results of emergency radiation monitoring, including ambient $$gamma$$-ray dose rate, atmospheric radioactivity, meteorological observation and estimation of internal exposure resulting from the accident at the Fukushima Daiichi Nuclear Power Plant triggered by the earthquake off the pacific coast of Tohoku on 11th March 2011, conducted by Oarai Research and Development Center (ORDC), Japan Atomic Energy Agency (JAEA) from March to May, 2011. ORDC is located in the central part of Ibaraki prefecture and approximately 130 km southwest of the Fukushima Daiichi Nuclear Power Plant. From around 15th to 21st March, 2011, the ambient $$gamma$$-ray dose rate increased and many radioactive nuclides were detected in the atmosphere.

Journal Articles

Evaluation of fracture toughness of fine-grained isotropic graphites for HTGR

Yamada, Teruaki*; Matsushima, Yuki*; Kuroda, Masatoshi*; Sumita, Junya; Shibata, Taiju; Fujita, Ichiro*; Sawa, Kazuhiro

Proceedings of 6th International Topical Meeting on High Temperature Reactor Technology (HTR 2012) (USB Flash Drive), 6 Pages, 2012/10

In order to investigate the effects of the experimental methodology and the notch angle on the fracture toughness of the fine-grained isotropic nuclear graphites IG-110 and IG-430, the three-point-bending test, which has been recently proposed as the methodology to evaluate the fracture toughness of graphite for high temperature gas-cooled reactors (HTGRs), was performed using two types of the specimens with different notch angles. The results obtained in this study could be summarized as follows: (1) The values of the fracture toughness of IG-110 and IG-430 measured in this study were 0.890 (MPam$$^{1/2}$$) and 1.031 (MPam$$^{1/2}$$), respectively. It was also found that the value of the fracture toughness of IG-110 was nearly equal to or smaller than the values obtained by the other method reported previously. (2) The values of the fracture toughness of the fine-grained isotropic graphites were not affected between the notch angles introduced by the incisive razor blade. (3) The ratio of the tensile strengths of IG-110 and IG-430 was estimated from Griffith Theory using the experimental data obtained in this study. The estimated strength ratio was in good agreement with the strength ratio obtained from the supplier's data.

Oral presentation

Consideration of the rising count rate of the water monitor at rainfall time

Haba, Risa; Yamada, Junya; Seya, Natsumi; Muto, Yasunobu; Shimizu, Takehiko; Takasaki, Koji

no journal, , 

no abstracts in English

Oral presentation

Relation between a defference of an air diffusion for the year and a meteorological observation period at O-arai Centre, JAEA

Seya, Natsumi; Yamada, Junya; Haba, Risa; Muto, Yasunobu; Shimizu, Takehiko; Takasaki, Koji; Nemoto, Koji*; Sato, Naomitsu*

no journal, , 

no abstracts in English

Oral presentation

Environmental radiation monitoring in JAEA O-arai after Fukushima Daiichi NPP accident; Measuring results of monitoring post

Yamada, Junya; Seya, Natsumi; Haba, Risa; Muto, Yasunobu; Shimizu, Takehiko; Takasaki, Koji

no journal, , 

no abstracts in English

Oral presentation

Environmental radiation monitoring in JAEA O-arai after Fukushima Dai-ichi NPP accident; Estimation of radionuclide concentrations using Monte Carlo simulation

Yamada, Junya; Seya, Natsumi; Muto, Yasunobu; Shimizu, Takehiko; Takasaki, Koji

no journal, , 

no abstracts in English

Oral presentation

Regional contribution through the environmental monitoring which was conducted by JAEA Oarai, followed by the Fukushima Dai-ichi Nuclear Disaster

Muto, Yasunobu; Yamada, Junya; Seya, Natsumi; Shimizu, Takehiko; Takasaki, Koji; Nakajima, Akemi

no journal, , 

no abstracts in English

Oral presentation

Effect of notch-tip geometry on the fracture toughness of fine-grained isotropic graphite

Matsushima, Yuki*; Yamada, Teruaki*; Kuroda, Masatoshi*; Sumita, Junya; Shibata, Taiju; Sawa, Kazuhiro

no journal, , 

In order to investigate the effect of notch-tip geometry on the fracture toughness of fine-grained isotropic graphite ETU-10, three-point-bending fracture toughness tests have been performed by using two types of single-edge notched beam specimens with different notch angles of approximately 15$$^{circ}$$ and 30$$^{circ}$$. The values of the fracture toughness were calculated based on linear elastic fracture mechanics by using the maximum force which could be obtained by the load-displacement curve. As a result, the values of the fracture toughness of the specimens with the notch angles of approximately 15$$^{circ}$$ and 30$$^{circ}$$ were 0.933 MPa m$$^{1/2}$$and 0.926 MPa m$$^{1/2}$$, respectively. This suggested that the values of the fracture toughness were not affected between the notch angles. Further work has been ongoing to discuss the effect of the notch-tip geometry such as angle and root radius of notch in terms of finite element analysis.

Oral presentation

Wake effects on fast molecular transmission through a nanocapillary

Tsuchida, Hidetsugu*; Nakajima, Kaoru*; Yokoe, Junya*; Sugiyama, Motohiko*; Ota, Yushi*; Majima, Takuya*; Shibata, Hiromi*; Tomita, Shigeo*; Sasa, Kimikazu*; Hirata, Koichi*; et al.

no journal, , 

no abstracts in English

Oral presentation

Determination of concentration of radioiodine in plume resulting from the accident at the FDNPP by analysis of pulse-height distributions observed at monitoring posts using the EGS code system

Yamada, Junya; Seya, Natsumi; Haba, Risa; Muto, Yasunobu; Shimizu, Takehiko; Takasaki, Koji; Yokoyama, Sumi*; Shimo, Michikuni*

no journal, , 

no abstracts in English

27 (Records 1-20 displayed on this page)