Evaluation of indoor air dose rate based on Cs-137 depth distribution in surrounding artificially paved surfaces surveyed 10 years after the Fukushima Daiichi Nuclear Power Plant accident

Kobayashi, Hikaru*; Suto, Masahito*; Otsuki, Kentaro*; Yoshimura, Kazuya; Yoshida, Hiroko*

Japan Architectural Review (Internet), 6(1), p.e12353_1 - e12353_12, 2023/00

https://doi.org/10.1002/2475-8876.12353

(Copepoda) from a deep sediment-trap; Abundance and implications for ecological and biogeochemical studies

Ikenoue, Takahito*; Otosaka, Shigeyoshi*; Honda, Makio*; Kitamura, Minoru*; Mino, Yoshihisa*; Narita, Hisashi*; Kobayashi, Takuya

Frontiers in Marine Science (Internet), 9, p.884320_1 - 884320_11, 2022/05

https://doi.org/10.3389/fmars.2022.884320

We studied seasonal variations of the mesozooplankton swimmer community collected by a sediment trap moored at 873 m in the Kuroshio & Oyashio Transition region off the east coast of Japan from 5 August 2011 to 23 June 2013. The total flux of mesozooplankton swimmers varied between 0 and 11.1 individuals m-2 d-1, with a mean of 3.1 individuals m-2 d-1 during the sampling period. Among the Copepoda, Neocalanus cristatus was the most dominant taxon. The species composition of the swimmers closely reflected the mid-depth mesozooplankton of the Oyashio region. The fluxes of Neocalanus species reflected ontogenetic vertical migration, but may have been overestimates of active fluxes if they included dormant individuals that accidentally entered the sediment trap.

Radiological estimation and validation for the Accelerator-Based Boron Neutron Capture Therapy Facility at the Ibaraki Neutron Medical Research Center

Nakashima, Hiroshi; Nakamura, Takemi; Kobayashi, Hitoshi*; Tanaka, Susumu*; Kumada, Hiroaki*

NEA/NSC/R(2021)2 (Internet), p.142 - 151, 2021/12

Aiming of development of facilities for boron neutron capture therapy (BNCT) that can be installed in hospitals, an accelerator-based BNCT facility is being developed at the Ibaraki Neutron Medical Research Center under a collaboration among the Japan Atomic Energy Agency, the High Energy Accelerator Research Organization, the University of Tsukuba, and other institutions. It consists of a proton accelerator, having a maximum beam power of 80 kW, and a target, moderator, collimator and shield (TMCS) system. For the design concept, to satisfy the BNCT beam conditions and achieve a low activation, the radiation behavior in the TMCS system was simulated by the Monte Carlo method and this system configuration was optimized accordingly. In addition, the radiation estimation of the TMCS system was verified via several experiments and its applicability for BNCT was proved. This report reviews the estimation and validation studies for the development of the accelerator-based BNCT facility.

Result of seismic motion observation from ground surface to 500m depth at Mizunami Underground Research Laboratory and its detailed analysis

Matsui, Hiroya; Watanabe, Kazuhiko*; Mikake, Shinichiro; Niimi, Katsuyuki*; Kobayashi, Shinji*; Toguri, Satohito*

Dai-47-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (Internet), p.293 - 298, 2020/01

Japan Atomic Energy Agency has been observed seismic motions induced by earthquakes, at ground surface, galleries at 100m, 300m and 500m depth of Mizunami underground research laboratory for over 10 years. The results suggested that the amplitude of the seismic motion decreases with depth as the previous study on crystalline rock at Kamaishi mine indicated. Detailed analysis on the observed seismic motions shows that the Fourier amplitude and the phase difference of the earthquake occurred near epicenter correspond with the one calculated by one-dimensional multiple reflection theory.

Status of development on LaB filament arc-driven multi-cusp ion source for iBNCT

Shibata, Takanori*; Takagi, Akira*; Ikegami, Kiyoshi*; Sugimura, Takashi*; Nammo, Kesao*; Naito, Fujio*; Kobayashi, Hitoshi*; Kurihara, Toshikazu*; Honda, Yosuke*; Sato, Masaharu*; et al.

Proceedings of 15th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.385 - 387, 2018/10

Introduction to radiation physics; Third revised edition

Tada, Junichiro*; Nakashima, Hiroshi; Hayano, Ryugo*; Kobayashi, Hitoshi*; Asano, Yoshihiro*

Wakariyasui Hoshasen Butsurigaku; Kaitei 3-Han, 305 Pages, 2018/03

This book is an introduction to radiation physics. Under the concept of "linking physics of high school and radiation physics" for readers with high school graduation degree, we are doing simple commentary on the basis of qualitative explanation as much as possible. This book begins with "What is Radiation Physics", and consists of 12 chapters, including introductory special relativity, introductory quantum theory, structures of atoms and nuclei, radiations, radioactivity, interactions between radiation and matter, accelerators, radiation dose and so on.

Completion of solidification and stabilization for Pu nitrate solution to reduce potential risks at Tokai Reprocessing Plant

Mukai, Yasunobu; Nakamichi, Hideo; Kobayashi, Daisuke; Nishimura, Kazuaki; Fujisaku, Sakae; Tanaka, Hideki; Isomae, Hidemi; Nakamura, Hironobu; Kurita, Tsutomu; Iida, Masayoshi*; et al.

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 8 Pages, 2017/04

TRP has stored the plutonium in solution state for long-term since the last PCDF operation in 2007 was finished. After the great east Japan earthquake in 2011, JAEA had investigated the risk against potential hazard of these solutions which might lead to make hydrogen explosion and/or boiling of the solution accidents with the release of radioactive materials to the public when blackout. To reduce the risk for storing Pu solution (about 640 kg Pu), JAEA planned to perform the process operation for the solidification and stabilization of the solution by converted into MOX powder at PCDF in 2013. In order to perform PCDF operation without adaption of new safety regulation, JAEA conducted several safety measures such as emergency safety countermeasures, necessary security and safeguards (3S) measures with understanding of NRA. As a result, the PCDF operation had stared on 28th April, 2014, and successfully completed to convert MOX powder on 3rd August, 2016 for about 2 years as planned.

Study of beam loading compensation with comb-like structure at J-PARC linac

Futatsukawa, Kenta*; Kobayashi, Tetsuya*; Sato, Yoshikatsu; Shinozaki, Shinichi; Fang, Z.*; Fukui, Yuji*; Mizobata, Satoshi; Michizono, Shinichiro*

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.327 - 331, 2016/11

In the J-PARC linac, an intermediate-pulse with the comb-like structure is shaped by kicking an unwanted beam by the chopper cavity. Therefore, the cavities lying downstream of the RF-chopper have the beam loading with this beam shape. The present feedforward system which assumes the averaged beam current and not the comb-like beam was operated in the present LLRF, because the beam current in the linac was lower than the design value. However, it has been difficult that the required precision for the RF system is satisfied with increasing beam current. Thus, we performed the beam study of the beam loading compensation with the same shapes as the intermediate-pulses. The positive results for the cavities of SDTL and DTL with high Q values were obtained compared to the present system. On the other hand, when this compensation system was used in the case of ACS cavities, the neighbor modes were excited by the input RF. We have to improve the FF system for the operation against the real beam.

Long distant microscope observation of radiation damage (blistering); Laser reflection microscope

Kurihara, Toshikazu*; Kobayashi, Hitoshi*; Sugimura, Takashi*; Hirano, Koichiro

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.814 - 816, 2016/11

http://www.pasj.jp/web_publish/pasj2016/proceedings/PDF/TUP0/TUP003.pdf

A problem of irradiation damage is the one observed in each part of a component of particle accelerators; accelerating tubs, scrapers, monitors and neutron targets. In-situ observation by an actual proton accelerator is made our last target. We observed the radiation damage of the various materials used by particle accelerators. From the distant place the target which is in the high radiation area, we propose the method to get information from the catoptric light from the target using a laser as a light source. A principle of this observation method as well as generating process of blisterings and limitation of this method will be reported.

Work and safety managements for on-site installation, commissioning, tests by EU of quench protection circuits for JT-60SA

Yamauchi, Kunihito; Okano, Jun; Shimada, Katsuhiro; Omori, Yoshikazu; Terakado, Tsunehisa; Matsukawa, Makoto; Koide, Yoshihiko; Kobayashi, Kazuhiro; Ikeda, Yoshitaka; Fukumoto, Masahiro; et al.

JAEA-Technology 2015-053, 36 Pages, 2016/03

JAEA-Technology-2015-053.pdf:8.33MB

The superconducting Satellite Tokamak machine "JT-60SA" under construction in Naka Fusion Institute is an international collaborative project between Japan (JA) and Europe (EU). The contributions for this project are based on the supply of components, and thus European manufacturer shall conduct the installation, commissioning and tests on Naka site. This means that Japan Atomic Energy Agency (JAEA) had a quite difficult issue to manage the works by European workers and their safety although there is no direct contract. This report describes the approaches for the work and safety managements, which were agreed with EU after the tough negotiation, and then the completed on-site works for Quench Protection Circuits (QPC) as the first experience for EU in JT-60SA project. With the help of these approaches by JAEA, the EU works for QPC were successfully completed with no accident, and a great achievement was made for both EU and JA.