JOPSS - Search Results

Journal Articles

Establishing an evaluation method for the aging phenomenon by physical force in fuel debris

Suzuki, Seiya; Arai, Yoichi; Okamura, Nobuo; Watanabe, Masayuki

Journal of Nuclear Science and Technology, 60(7), p.839 - 848, 2023/07

https://doi.org/10.1080/00223131.2022.2159559

Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)

The fuel debris, consisting of nuclear fuel materials and reactor structural materials, generated in the accident of Fukushima Daiichi Nuclear Power Plant can become deteriorated like rocks under the changes of environmental temperature. Although the fuel debris have been cooled by water for 10 years, they are affected by seasonal and/or day-and-night temperature changes. Therefore, in evaluating the aging behavior of the fuel debris, it is essential to consider the changes in environmental temperature. Assuming that the fuel debris are deteriorated, radioactive substances that have recently undergone micronization could be eluted into the cooling water, and such condition may affect defueling methods. We focused on the effect of repeated changes in environmental temperature on the occurrence of cracks, and an accelerated test using simulated fuel debris was carried out. The length of the crack increases with increasing number of heat cycle; therefore, the fuel debris become brittle by stress caused by thermal expansion and contraction. In conclusion, it was confirmed that the mechanical deterioration of the fuel debris is similar to that of rocks or minerals, and it became possible to predict changes in the length of the crack in the simulated fuel debris and environmental model.

Journal Articles

Voltage drop analysis and leakage suppression design for mineral-insulated cables

Hirota, Noriaki; Shibata, Hiroshi; Takeuchi, Tomoaki; Otsuka, Noriaki; Tsuchiya, Kunihiko

Journal of Nuclear Science and Technology, 57(12), p.1276 - 1286, 2020/12

https://doi.org/10.1080/00223131.2020.1782280

Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)

The influence of materials of mineral-insulated (MI) cables on their electrical characteristics upon exposure to high-temperature conditions was examined via a transmission test, in the objective of achieving the stability of the potential distribution along the cable length. Occurrence of a voltage drop along the cable was confirmed for aluminum oxide (Al $_{2}$ O $_{3}$ ) and magnesium oxide (MgO), as insulating materials of the MI cable. A finite-element method (FEM)-based analysis was performed to evaluate the leakage in the potentials, which was found at the terminal end. Voltage drop yields by the transmission test and the analysis were in good agreement for the MI cable of Al $_{2}$ O $_{3}$ and MgO materials, which suggests the reproducibility of the magnitude relationship of the experimental results via the FEM analysis. To suppress the voltage drop, the same FEM analysis was conducted, the diameter of the core wires () and the distance between them () were varied. Considering the variation of , the potential distribution in the MI cable produced a minimum voltage drop corresponding to a ratio of 0.35, obtained by dividing with that of the insulating material (). In case of varying , a minimum voltage drop was l/ of 0.5.

Journal Articles

Recent activities in the field of reactor physics

Fukushima, Masahiro; Tojo, Masayuki*

Journal of Nuclear Science and Technology, 56(12), p.1061 - 1062, 2019/12

https://doi.org/10.1080/00223131.2019.1667925

Times Cited Count：0 Percentile：0.32(Nuclear Science & Technology)

Reactor Physics that treat the essentials of how fission nuclear reactors work fundamentally has important roles on safe operations and design studies of various types of nuclear reactors. From the latest activities in the field of reactor physics, this report summarizes some outstanding researches and developments published in scientific journals including the Journal of Nuclear Science and Technology.

Journal Articles

Release of radioactive materials from high active liquid waste in small-scale hot test for boiling accident in reprocessing plant

Yamane, Yuichi; Amano, Yuki; Tashiro, Shinsuke; Abe, Hitoshi; Uchiyama, Gunzo; Yoshida, Kazuo; Ishikawa, Jun

Journal of Nuclear Science and Technology, 53(6), p.783 - 789, 2016/06

https://doi.org/10.1080/00223131.2015.1072065

Times Cited Count：6 Percentile：43.41(Nuclear Science & Technology)

The release behavior of radioactive materials from high active liquid waste (HALW) has been experimentally investigated under boiling accident conditions. In the experiments using HALW obtained through laboratory scale reprocessing, release ratio was measured for the FP nuclides such as Ru, $^{99}$ Tc, Cs, Sr, Nd, Y, Mo, Rh and actinides such as $^{242}$ Cm, $^{241}$ Am. As a result, the release ratio was 0.20 for Ru and 1 $10^{-4}$ for the FP and Ac nuclides. Ru was released into the gas phase in the form of both mist and gas. For its released amount, weak dependency was found to the initial concentration in the test solution. The release ratio decreased with the initial concentration. For other FP nuclides and actinides as non-volatile, released into the gas phase in the form of mist, the released amount increased with the initial concentration. The release ratio of Ru and NOx concentration increased with temperature of the test solutions. They were released almost at the same temperature between 200 and 300 $^{circ}$ C. Size distribution of the mist and other particle was measured.

JAEA Reports

Experimental study on accelerator driven subcritical reactor, JAERI's nuclear research promotion program, H12-031 (Contract research)

Shiroya, Seiji*; Misawa, Tsuyoshi*; Unesaki, Hironobu*; Ichihara, Chihiro*; Kobayashi, Keiji*; Nakamura, Hiroshi*; Shin, Kazuo*; Imanishi, Nobutsugu*; Kanazawa, Satoshi*; Mori, Takamasa

JAERI-Tech 2004-025, 93 Pages, 2004/03

JAERI-Tech-2004-025.pdf:6.69MB

In view of the future plan of Research Reactor Institute, Kyoto University, the present study consisted of (1) the transmission experiments of high energy neutrons through materials, (2) experimental simulation of ADSR using the Kyoto University Critical Assembly(KUCA), and (3) conceptual neutronics design study on KUR type ADSR using the MCNP-X code. Through the present study, valuable knowledge on the basic nuclear characteristics of ADSR, which is indispensable to promote the study on ADSR, was obtained both theoretically and experimentally. For the realization of ADSR, it is considered to be necessary to accumulate results of research steadily. For this purpose, it is inevitable (1) to compile the more precise nuclear data for the wide energy range, (2) to establish experimental techniques for reactor physics study on ADSR including subcriticality measurement and absolute neutron flux measurement, and (3) to develop neutronics calculation tools which take into account the neutron generation process by the spallation reaction and the delayed neutron behavior.

JAEA Reports

Neutron data storage and retrieval system NESTOR2

Nakagawa, Tsuneo

JAERI-Data/Code 2003-016, 89 Pages, 2003/11

JAERI-Data-Code-2003-016.pdf:3.0MB

The data storage and retrieval system for neutron-induced reaction data NESTOR2 was developed. NESTOR2 was written in Fortran77, and can be used on workstations with UNIX and personal computers with Windows. Input data to NESTOR2 are those in EXFOR which are compiled and maintained under the international collaboration for nuclear data. By using the retrieval code, they can obtain lists of data index, numerical data and comment information and data files of numerical data. The present report explains the system and provides a user's manual of NESTOR2.

JAEA Reports