Investigations on distribution of radioactive substances owing to the Fukushima Daiichi Nuclear Power Station Accident in the fiscal year 2024 (Contract research)

Group for Fukushima Mapping Project

JAEA-Technology 2025-013, 206 Pages, 2026/03

JAEA-Technology-2025-013.pdf:34.64MB

This report presents results of the investigations on the distribution-mapping project of radioactive substances conducted in FY2024. Car-borne and walk surveys, a measurement using survey meters, and an unmanned helicopter survey were carried out to obtain air dose rate data on land to create their distribution maps, and temporal changes of those air dose rates were analyzed. In order to confirm the applicability of unmanned aircraft to monitoring in mountainous areas, a basic performance of unmanned aircraft was investigated in mountainous areas. Surveys on depth profile of radiocesium and in-situ measurements as for radiocesium deposition were performed. These measurement results were published on the WEB site. Based on these measurement results, effective half-lives of the temporal changes in the air dose rates and the deposition were evaluated. Using the Bayesian hierarchical modeling approach, we obtained maps that integrated air dose rate distribution data acquired through surveys such as car-borne and walk surveys. Radiation monitoring and analysis of environmental samples owing to the comprehensive radiation monitoring plan were carried out. Representative life patterns that can be expected after the return to the evacuation-designated restricted area were set, and the cumulative exposure doses were evaluated for the local governments and residents in the area. Score maps to classify the importance of the measurement points were created, and the temporal changes in the score were analyzed. A system to report the tritium concentration level in seawater to the Nuclear Regulation Authority was operated, and the variation of tritium concentration before and after the discharge of ALPS treated water to the ocean was analyzed. Monitoring data in coastal area performed owing to the comprehensive radiation monitoring plan until FY2024 was analyzed.

Data of radon measurement in underground facilities of Mizunami Underground Research Laboratory

Aoki, Katsunori; Yamanaka, Hiroki*; Watanabe, Kazuhiko*; Sugihara, Kozo

JAEA-Data/Code 2020-018, 45 Pages, 2021/02

JAEA-Data-Code-2020-018.pdf:4.54MB
JAEA-Data-Code-2020-018-appendix(DVD-ROM).zip:6.8MB

Mizunami Underground Research Laboratory (MIU) Project is pursued by Japan Atomic Energy Agency (JAEA) in the crystalline host rock (granite) as a part of geoscientific study of JAEA, and underground facilities of MIU are constructed down to 500m blow the ground surface. As small amount of Uranium is normally contained in granite, high concentration of radon is sometimes detected in the air of the underground facilities constructed in granitic rocks depending on their ventilation conditions. Radon concentrations in underground facilities of MIU have been measured according to the excavation progress of underground facilities or the change of ventilation system. It is recognized that the data obtained by the actual measurement of radon concentration in such underground facilities are rare and valuable. This repot summarizes the measured data from fiscal 2010 to fiscal 2020, together with the information of ventilation conditions and air temperature which affect radon concentrations in underground facilities. The variation of the equilibrium factors of radon is also examined with the actually measured data. As a result, it has been found that radon concentration in the drift is high in summer and low in winter according to the natural ventilation caused by the seasonal temperature difference between in and out of the underground facilities. Furthermore, the temporary increase in the equilibrium factor of radon in the drift at the start of ventilation is supposed to be due to the aerosol increase by the ventilation flow, such as the dust blown up.

Recent status of research activities for development of CTBT-related technologies in JAERI

Hirota, Naoki*; Hokida, Takanori; Inoue, Yoji; Kumata, Masahiro; Kurosawa, Yoshiaki; Miyamoto, Yutaka; Nakahara, Yoshinori; Oda, Tetsuzo; Shinohara, Nobuo; Uchikoshi, Takako*; et al.

JAERI-Review 2003-021, 68 Pages, 2003/08

JAERI-Review-2003-021.pdf:9.73MB

This report describes research activities of the R & D Group for Non-Proliferation Technology related to the Comprehensive Nuclear-Test-Ban Treaty (CTBT) verification regime. The main subjects of this report are (1) an overview of the CTBT verification regime, (2) preparation of the National Data Center for radionuclide data, (3) construction and operation of the radionuclide monitoring stations at Takasaki and Okinawa and the certified rarionuclide laboratory at Tokai in Japan. We have participated in an intercomparison test internationally organized for the certified laboratories and the test results are given here. Scientific application of the CTBT-related technologies to environmental researches is also depicted.

Development of methodology for evaluating ground motion parameters and information system under seismic emergency

Shibata, Katsuyuki; Ebisawa, Katsumi; Abe, Ichiro*; Kuno, Tetsuya; Hori, S.*; Oi, Masahiro*

Proceedings of 12th World Conference in Earthquake Engineering (CD-ROM), 8 Pages, 2000/01

no abstracts in English

Design of JRR-4 operation supporting system

Takahashi, Hiroki; ; Yamamoto, Kazuyoshi; Yoritsune, Tsutomu

JAERI-Conf 99-006, p.125 - 130, 1999/08

https://jopss.jaea.go.jp/pdfdata/JAERI-Conf-99-006.pdf

no abstracts in English

Measurement and control system for the ITER remote handling mock-up test

Oka, Kiyoshi; Kakudate, Satoshi; ; ; ; Tada, Eisuke; ; Shibanuma, Kiyoshi

Fusion Technology 1998, 2, p.1701 - 1704, 1998/00

no abstracts in English

Optimizing long-term monitoring of radiation air dose rates near the Fukushima Daiichi Nuclear Power Plant

Murakami, Haruko*; Sun, D.*; Oroza, C.*; Seki, Akiyuki; Mikami, Satoshi; Takemiya, Hiroshi; Saito, Kimiaki

no journal, , 

In this study, we have developed a methodology for optimizing the monitoring locations of radiation air dose rates. It is based on (1) a Gaussian mixture model to diversify locations across the key environmental controls that are known to influence cesium mobility and distributions, and (2) a Gaussian process model to capture the heterogeneity of radiation air dose rates across the domain.

JAEA's experience in the source term estimation for the Fukushima Daiichi Nuclear Power Plant accident using WSPEEDI

Terada, Hiroaki

no journal, ,