Evaluation of exposure doses and reduction factor for sheltering for each nuclear site under each accident scenario (Contract research)

Hirouchi, Jun; Watanabe, Masatoshi*; Hayashi, Naho; Nagakubo, Azusa; Takahara, Shogo

JAEA-Research 2024-015, 114 Pages, 2025/03

JAEA-Research-2024-015.pdf:10.03MB

The public living in areas contaminated by nuclear accidents is exposed to radiation in the early phase and over the long term. Even under the same accident scenario, the exposure doses and the effectiveness of sheltering, which is one of the protective measures, vary depending on the meteorological condition and the surrounding environment. The exposure doses and sheltering effectiveness in the early phase are important information for the public and the national and local governments planning a nuclear emergency preparedness. In this report, we evaluate the exposure doses and sheltering effectiveness at sites with nuclear facilities in Japan using OSCAAR, one of the probabilistic risk assessment codes, for five accident scenarios: three scenarios from past severe accident studies; a scenario defined by the Nuclear Regulatory Authority; and a scenario assuming the Fukushima Daiichi Nuclear Power Station accident. The sheltering effectiveness differed by approximately 20% among the sites. This was due to the differences in wind speed among the sites.

Development of a DO/HO vapor generator for contrast-variation neutron scattering

Arima-Osonoi, Hiroshi*; Takata, Shinichi; Kasai, Satoshi*; Ouchi, Keiichi*; Morikawa, Toshiaki*; Miyata, Noboru*; Miyazaki, Tsukasa*; Aoki, Hiroyuki; Iwase, Hiroki*; Hiroi, Kosuke; et al.

Journal of Applied Crystallography, 56(6), p.1802 - 1812, 2023/12

https://doi.org/10.1107/S1600576723009780

New measurement system based on small-angle neutron scattering for structural analysis of light-responsive materials

Iwase, Hiroki*; Akamatsu, Masaaki*; Inamura, Yasuhiro; Sakaguchi, Yoshifumi*; Morikawa, Toshiaki*; Kasai, Satoshi*; Ouchi, Keiichi*; Kobayashi, Kazuki*; Sakai, Hideki*

Journal of Applied Crystallography, 56(1), p.110 - 115, 2023/02

https://doi.org/10.1107/S1600576722011104

With the increasing importance of light-responsive materials, it is vital to analyze the relationship between function and structural changes induced by light irradiation. Small-angle scattering (SAS) is effective for such structural analysis. However, quantitatively capturing local molecular structure formation and molecular reactions at a scale of less than 1 nm via SAS is difficult. In this study, to analyze the structure of non-equilibrium phenomena in light-responsive materials, a new sample environment has been developed for a time-of-flight small- and wide-angle neutron scattering instrument (TAIKAN), comprising a UV-Vis irradiation system, UV-Vis absorption measurement equipment and photodetector. Simultaneous measurement of small-angle neutron scattering and UV-Vis absorption was achieved. This system was used to demonstrate the in situ observation of UV-Vis irradiation-induced structural change of micelles formed by a light-responsive surfactant sample in an aqueous solution.

Gas-flow humidity control system for neutron reflectivity measurements

Arima-Osonoi, Hiroshi*; Miyata, Noboru*; Yoshida, Tessei*; Kasai, Satoshi*; Ouchi, Keiichi*; Zhang, S.*; Miyazaki, Tsukasa*; Aoki, Hiroyuki

Review of Scientific Instruments, 91(10), p.104103_1 - 104103_7, 2020/10

https://doi.org/10.1063/5.0021128

Cryogenic sample environments shared at the MLF, J-PARC

Kawamura, Seiko; Takahashi, Ryuta*; Ishikado, Motoyuki*; Yamauchi, Yasuhiro*; Nakamura, Masatoshi*; Ouchi, Keiichi*; Kira, Hiroshi*; Kambara, Wataru*; Aoyama, Kazuhiro*; Sakaguchi, Yoshifumi*; et al.

Journal of Neutron Research, 21(1-2), p.17 - 22, 2019/05

https://doi.org/10.3233/JNR-190106

The Cryogenics and Magnets group in the Sample Environment team is responsible for operation of cryostats and magnets for user's experiments at the MLF in J-PARC. We have introduced a top-loading He cryostat, a bottom-loading He cryostat, a dilution refrigerator insert and a superconducting magnet. The frequency of use of them dramatically becomes higher in these two years, as the beam power and the number of proposal increase. To respond such situation, we have made efforts to enhance performance of these equipment as follows. The He cryostat originally involves an operation software for automatic initial cooling down to the base temperature and automatic re-charge of He. Recently we made an additional program for automatic temperature control with only the sorb heater. Last year, a new outer vacuum chamber of the magnet with an oscillating radial collimator (ORC) was fabricated. The data quality was drastically improved by introducing this ORC so that the magnet can be used even for the inelastic neutron scattering experiments.

Factors affecting the effectiveness of sheltering in reducing internal exposure

Hirouchi, Jun; Takahara, Shogo; Komagamine, Hiroshi*; Watanabe, Masatoshi*; Munakata, Masahiro

Proceedings of Asian Symposium on Risk Assessment and Management 2017 (ASRAM 2017) (USB Flash Drive), 11 Pages, 2017/11

no abstracts in English

Survey on evacuation facilities in case of nuclear emergency in Shimane prefecture (Contract research)

Takahara, Shogo; Watanabe, Masatoshi; Oguri, Tomomi; Kimura, Masanori; Hirouchi, Jun; Munakata, Masahiro; Homma, Toshimitsu

JAEA-Data/Code 2016-016, 65 Pages, 2017/02

JAEA-Data-Code-2016-016.pdf:2.32MB

We surveyed on structural and material data on 22 facilities which are listed in local disaster management plan in Matsue city. These facilities can be divided into educational facilities, communal facilities and gymnastic hall. Height and floor-area of rooms, as well as window-area were collected as the structural data. We also collected information on constructional materials, and density of those. In addition, mass-thicknesses of the constructional materials were evaluated based on our surveys, and compared to the previous studies which were made in Japan, U.S., and European countries. Consequently, it was found that there is no significant difference of mass-thickness of constructional materials between the results of our surveys and the previous studies. However, for gymnastic hall, since thin metal plates are used for roofs, we can point out that the mass-thickness of roofs are much lower than those for other concrete facilities and clay tile roofing wooden houses.

Replacement of power supply for reactor control rod magnet of JRR-3

Kurumada, Osamu; Ikekame, Yoshinori; Ouchi, Satoshi; Sato, Masayuki; Kamiishi, Eigo; Wada, Shigeru

JAEA-Technology 2015-056, 35 Pages, 2016/03

JAEA-Technology-2015-056.pdf:29.49MB

The power supply for reactor control rod magnet of JRR-3 has been utilized for generating electromagnetic power of control rod coil and that was using more than 25 years. The power supply was required for provide to stabilize DC current. Therefore, we adopted series regulator method. Although, the power supply generate a high heat. Then, we decided to create switching regulator method in order to improve the aging and heat generation of the series regulator method. This paper reports the replacement of switching regulator method.

Measurement of air dose rates over a wide area around the Fukushima Dai-ichi Nuclear Power Plant through a series of car-borne surveys

Ando, Masaki; Nakahara, Yukio; Tsuda, Shuichi; Yoshida, Tadayoshi; Matsuda, Norihiro; Takahashi, Fumiaki; Mikami, Satoshi; Kinouchi, Nobuyuki; Sato, Tetsuro*; Tanigaki, Minoru*; et al.

Journal of Environmental Radioactivity, 139, p.266 - 280, 2015/01

https://doi.org/10.1016/j.jenvrad.2014.05.014

A series of car-borne surveys using the KURAMA and KURAMA-II systems was conducted in a wide area in eastern Japan from June 2011 to December 2012 to evaluate the distribution of air dose rates around the Fukushima Dai-ichi Nuclear Power Plant, and to determine the time-dependent trend of decrease in air dose rates. An automated data processing system was established, which enables analyses of large amounts of data obtained with the use of about 100 units of the measurement system in a short time. The initial data for studying the migration status of radioactive cesium was obtained in the first survey, followed by the other car-borne surveys having wider measurement ranges. Comparing the measured air dose rates obtained in each survey, it was found that the decreasing trend of air dose rates measured through car-borne surveys was larger than that expected from the physical decay of radioactive cesium and that measured using NaI (Tl) survey meters around the road.

Development of the JRR-3 data processing computer system

Ouchi, Satoshi; Suwa, Masayuki; Isaka, Koji; Ikekame, Yoshinori; Terakado, Yoshibumi

JAEA-Testing 2011-006, 43 Pages, 2012/02

JAEA-Testing-2011-006.pdf:2.9MB

JRR-3 has been utilized for various researches such as neutron irradiation experiment, neutron beam experiment and so on as a high performance research reactor with thermal power of 20 MW since the first criticality in March, 1990. Process data needed for JRR-3 operation such as temperatures, pressures, and flow rates, etc. had been processed by JRR-3 process computer system which consisted of several computer systems and several application softwares. The system needed complicated data administration and conservation. Also there was a problem in the administration of recording data. Data discrepancy among computers used in the system was taken place since the system was not so designed as to synchronize the process timing among the computers. Therefore, we developed a program to synchronize among all of the computers. This paper reports the development of data processing computer system.