Joint environmental radiation survey by JAEA and KAERI around the Fukushima Daiichi Nuclear Power Plant; Performance of mobile gamma-ray spectrometry using backpack and carborne survey platforms

Ji, Y.-Y.*; Ochi, Kotaro; Hong, S. B.*; Nakama, Shigeo; Sanada, Yukihisa; Mikami, Satoshi

Health Physics, 121(6), p.613 - 620, 2021/12

https://doi.org/10.1097/HP.0000000000001471

According to the implementing arrangement between JAEA (Japan Atomic Energy Agency) and KAERI (Korea Atomic Energy Research Institute) in the field of the radiation protection and environmental radiation monitoring, the joint measurement has been conducted to assess the radioactive cesium deposition in the ground around the Fukushima Daiichi Nuclear Power Plants (FDNPP). First, mobile gamma-ray spectrometry using backpack survey platform was conducted to assess the distribution of dose rate around specific three survey sites. The carborne survey using gamma-ray spectrometers, as loading inside a vehicle, was successfully conducted to compare measured dose rates in routes from site to site and verify evaluation methods including the attenuation correction.

Calculation of low-energy electron antineutrino spectra emitted from nuclear reactors with consideration of fuel burn-up

Riyana, E. S.*; Suda, Shoya*; Ishibashi, Kenji*; Matsuura, Hideaki*; Katakura, Junichi*; Sun, G. M.*; Katano, Yoshiaki

Journal of Nuclear Science and Technology, 56(5), p.369 - 375, 2019/05

https://doi.org/10.1080/00223131.2017.1291370

Nuclear reactors produce a great number of electron antineutrinos mainly from beta-decay chains of fission products. Such neutrinos have energies mostly in MeV range. We are interested in neutrinos in a region of keV, since they may have information on fuel burn-up and may be detected in future with advanced measurement technology. We calculate reactor antineutrino spectra especially in the low energy region. In this work we present neutrino spectra from various reactors such as typical PWR reactor and others types of reactors for comparison. Our result shows the electron antineutrino flux in the low energy region increases with burn-up of nuclear fuel by accumulated nuclides with low Q values in beta decay.

Series studies on inter-comparison of radiation calibration fields and calibration techniques between KAERI and JAEA

Yoshitomi, Hiroshi; Tanimura, Yoshihiko*; Tatebe, Yosuke; Tsutsumi, Masahiro; Kawasaki, Katsuya; Kowatari, Munehiko; Yoshizawa, Michio; Shimizu, Shigeru*; Kim, J.-S.*; Lee, J.-G.*; et al.

Proceedings of 4th Asian and Oceanic Congress on Radiation Protection (AOCRP-4) (CD-ROM), 4 Pages, 2015/07

Study on fracture behavior of 2D-C/C composite for application to control rod of very high temperature reactor

Sumita, Junya; Fujita, Ichiro; Shibata, Taiju; Makita, Taiyo*; Takagi, Takashi*; Kunimoto, Eiji*; Sawa, Kazuhiro; Kim, W. J.*; Park, J. Y.*

IOP Conference Series; Materials Science and Engineering, 18(16), p.162010_1 - 162010_4, 2011/09

https://doi.org/10.1088/1757-899X/18/16/162010

For control rod element of Very High Temperature Reactor, carbon fiber reinforced carbon matrix composite (C/C composite) is one of the major candidate materials for its high strength and thermal stability. Since the crack propagation of the C/C composite is complicated, the fracture behavior is one of the most important subjects of the design methodology for the control rod with the C/C composite. In this study, in order to assess the Mode-II fracture behavior of the two-dimensional (2D-) C/C composite which has the layer structure of laminas composed of fibers and matrix, bending test with oxidized end notched flexure specimen was carried out. The interlaminar fracture toughness decreased with increasing the oxidation for the 2D-C/C composite. The oxidized matrix causes reduction of fracture toughness and the reduction ratio is dependent on the matrix type. The crack initiates at the boundary between fiber bundles and grows along them without breaking the fiber. It is thought that the cracks which were initiated at the interface between matrix and fiber were gathered into the voids in the boundary between fiber bundles, and then the crack grows up in the matrix.

Calibration standards in radiation protection dosimetry at the NSRI of JAEA

Saegusa, Jun; Shimizu, Shigeru; Yamaguchi, Yasuhiro; Kim, B.-H.*

Proceedings of 2006 Autumn Conference of the Korean Association for Radiation Protection, p.238 - 239, 2006/11

At the Nuclear Science Research Institute (NSRI) of Japan Atomic Energy Agency (JAEA), reference calibration fields of X-, -, -rays and neutrons have been provided in the Facility of Radiation Standards (FRS) for calibrating dosemeters used for radiation protection purpose. In this paper we overview these calibration fields and describe its position in the traceability and quality assurance system, present status of their utilization, and so forth.

Stsatus of the ERL light source project

Hajima, Ryoichi; Kawata, Hiroshi*; Kasuga, Toshio*; Sato, Kotaro*; Nakamura, Norio*; Sakanaka, Shogo*; Kobayashi, Yukinori*

no journal, , 

no abstracts in English

Oxidation behavior and property change of nuclear grade C/C composite

Kim, W. J.*; Seo, M.-R.*; Park, J. Y.*; Sumita, Junya; Shibata, Taiju; Sawa, Kazuhiro

no journal, , 

Carbon-carbon (C/C) composites have been widely used for high-temperature structural applications because they possess excellent mechanical properties such as high specific strength and thermal shock resistance. In the nuclear industry, the composites have also been considered for plasma facing materials in fusion reactors and high-temperature structural parts in gas cooled reactors. In the high-temperature gas cooled reactor, the composites are being considered for the application of various high-temperature structural parts such as control rod components, core restraint belts, tie rods, upper plenum shroud, hot duct insulation cover sheets, and floor blocks. However, the carbon based materials are susceptible to oxidation at temperatures above 400 C. Therefore, the oxidation behavior and property degradation at high temperature under impure He or in air in case of accidental air ingress should be evaluated before the deployment of composites. In this study, the oxidation behavior of several nuclear-grade C/C composites was evaluated at various temperatures. Thermal and mechanical properties of the composites were also measured before and after oxidation. The oxidation experiments were performed in range of 500 to 1100 C under air or Ar atmosphere. Thermal diffusivity, flexural strength, tensile strength, and interlaminar shear strength of as-received and oxidized specimens were evaluated.

Development of information sharing requirements for regional nuclear transparency

Kawakubo, Yoko; Inoue, Naoko; Mongiello, R.*; Baldwin, G.*; Lee, N.-Y.*; Chung, J.*; Kwon, E.-H.*

no journal, , 

Nuclear transparency has been discussed in various contexts even within nuclear nonproliferation. Due to the wide range of the contexts, the similar discussions have been repeated. With this background, Japan Atomic Energy Agency (JAEA), US Sandia National Laboratories (SNL), Korean Institute of Nuclear Nonproliferation and Control (KINAC), and Korean Atomic Energy Research Institute (KAERI) initiated a new phase of study to develop "requirements" for information sharing framework (ISF) focusing on regional nonproliferation experts. The "requirements" in this study is defined as to implement Plan-Do-Check-Adjust (PDCA) cycle for each specific category of information to be shared. "Plan" should be made by defining seven essential elements of ISF. In "Do" stage, the participants will collect the information and initiate a sharing process. "Check" is to evaluate the effectiveness and efficiency of the ISF using the metrics and methodologies identified in "Plan". The feedback obtained from the "Check" will be reflected to the "Plan" for the second cycle, then the second cycle will be implemented. Because the nuclear transparency is a voluntary process, sustainability is a key challenge. "Requirements" were developed so that if the planning and implementation of ISF is carried out following the "requirements", ISF can automatically work in a sustainable and useful manner. This paper addresses the requirements for ISF that were developed by JAEA, SNL, KINAC, and KAERI, and demonstrates how they can work with showing the example planning.

Cooperation on radiation measurements for cross-border accidents, 2; Application of machine learning conversion method using monitoring data from Fukushima as teaching data

Sasaki, Miyuki; Sanada, Yukihisa; Lee, E.*; Joung, S.*; Ji, Y.-Y.*

no journal, , 

Since the Fukushima Daiichi Nuclear Power Plant accident, some types of radiation monitoring have been conducted in Japan. Walking surveys and unmanned helicopter surveys have been conducted around the FDNPP to the ambient dose equivalent rates (air dose rate). The airborne radiation survey (ARS) by unmanned helicopter has the advantage of measuring large areas including forests. However, ARS has lower measurement resolution than walking surveys. Sasaki et al. constructed an artificial neural network (ANN) to convert ARS data into air dose rates at 1 m above ground level using data accumulated after the accident (Ref). It has been reported that the conversion using ANNs can convert to values closer to those measured on the ground than the conventional method. Showing that the ANN constructed from the Fukushima experience can be applied to detectors other than the radiation detector used to construct the ANN will greatly contribute to the future development of ARS. In this study, we investigated how to apply radiation measurement data acquired with a detector different from the radiation detector used to acquire the training data to an ANN that has already been constructed.