Upgrade of the small-angle neutron scattering diffractometer SANS-J at JRR-3

Kumada, Takayuki; Motokawa, Ryuhei; Oba, Yojiro; Nakagawa, Hiroshi; Sekine, Yurina; Micheau, C.; Ueda, Yuki; Sugita, Tsuyoshi; Birumachi, Atsushi; Sasaki, Miki; et al.

Journal of Applied Crystallography, 56(6), p.1776 - 1783, 2023/12

https://doi.org/10.1107/S1600576723009731

The combination of the existing position-sensitive photomultiplier and the 3He main detector with focusing devices, and the newly installed front detectors in SANS-J at JRR-3 covers small-angle neutron scattering signals in the range of the magnitude of the scattering vector Q from 0.002 to 6 nm-1 gaplessly with three standard device layouts. The installation of the front detector and a graphical user interface system largely improved the usability of SANS-J.

Debris-simulated core analysis under fuel procurement constraints in new STACY experiments

Araki, Shohei; Gunji, Satoshi; Arakaki, Yu; Yoshikawa, Tomoki; Murakami, Takahiko; Kobayashi, Fuyumi; Izawa, Kazuhiko; Suyama, Kenya

Proceedings of 12th International Conference on Nuclear Criticality Safety (ICNC2023) (Internet), 8 Pages, 2023/10

New experiments simulating fuel debris in the new criticality assembly, STACY, are designed to contribute to the validation of criticality calculations for criticality control of the fuel debris in the Fukushima Daiichi Nuclear Power Plant accident. In the new STACY experiment, a two-region core consisting of a driver region and a test region was investigated in order to configure a debris-simulated core with under-moderation condition (lattice pitch 1.27-cm) having the constraint of available fuel rod number. The test region with a 1.27-cm lattice pitch is surrounded by the driver region, in which fuel rods are arranged in a checkerboard pattern on a 1.27-cm lattice plate, with a 1.80-cm lattice pitch. Neutron spectra and sensitivity were calculated by using MCNP6 and ENDF/B-VII. The core which has a 1717 test region with 373 fuel rods is the largest two-region core under the constraint. It was found that the core which has a 1717 test region can simulate the neutron spectra of under-moderation condition in a 1313 region inside the test region with the root-mean square percentage error of less than 5%. It was also confirmed that the sensitivity of Si and Ca (n,) reactions when the concrete simulant, was loaded could be simulated.

Development of local exhaust device for vinyl-bag work

Local Exhaust Device Development Team in Analysis Section

JAEA-Technology 2023-015, 19 Pages, 2023/08

JAEA-Technology-2023-015.pdf:1.45MB

In the analytical laboratory of Tokai Reprocessing Plant, samples for operation and facility maintenance are analyzed in glove-box. Analytical reagents and equipment are carried inside the glove-box, and radioactive wastes generated through the analytical work are carried out using plastic bag (vinyl-bag) attached to the glove-box. The work carrying in and out from the glove-box is called as bag-in and bag-out. During these works, if the vinyl-bag is damaged, radioactive materials inside the glove-box may be leaked out and radioactive materials contaminate the vinyl-bag surface and the work area. In addition to that, if the radioactive contamination floats into the air, air in the work area may be contaminated. In this study, actual situation of the vinyl-bag work, specifications, and features of a local exhaust device for glove exchange work, which is an existing local exhaust device for gloves with a similar installation structure to vinyl-bags, have been investigated. Then, local exhaust device for vinyl-bag work have been developed. The developed local exhaust device has the same dimensions and shape as worktable that are conventionally used for vinyl-bag work. Also, a hood, HEPA filter, and exhaust blower, which are main components of the exhaust device for glove exchange work, are installed inside of this worktable. As a result, it has been confirmed that the developed local exhaust device is effective to prevent air contamination in vinyl-bag work without increasing the work procedures, manpower, and work time.

Precautions of capacitor inspection and its treatment based on the PCB Special Measures Law

Ono, Ayato; Takayanagi, Tomohiro; Sugita, Moe; Ueno, Tomoaki*; Horino, Koki*; Yamamoto, Kazami; Kinsho, Michikazu

JAEA-Technology 2022-036, 31 Pages, 2023/03

JAEA-Technology-2022-036.pdf:8.77MB

In the Japan Atomic Energy Agency (JAEA), many electrical facilities such as power receiving equipment and power supply units are installed in experimental facilities such as the Nuclear Science Research Institute (NSRI) and the Japan Proton Accelerator Research Complex (J-PARC). However, some facilities have been in operation for more than half a century since they were manufactured, some have already been closed or deactivated, and others are still in operation while replacing parts and taking other aging measures. In these facilities, materials that were used because of their excellent properties at the time of manufacture are now designated as hazardous substances and require special management when disposed of. One of them is polychlorinated biphenyl (PCB). PCB were used in a very wide range of fields because of their stability against heat, high electrical insulation, and chemical resistance. However, it was found that PCB have persistent properties and may cause damage to human health and the living environment, and the government has enacted the "Act on Special Measures for Promotion of Proper Treatment of PCB Wastes (PCB Special Measures Law)" to promote reliable and proper disposal. JAEA has almost completed the excavation survey of high-concentration PCB waste and is in the process of excavating low-concentration PCB waste. However, there are still new relevant items to be discovered. This report summarizes and reports the knowledge necessary for identifying PCB waste and points to be noted when handling capacitors, etc., based on examples of actual disassembly and investigation work conducted on power supply units and other electrical equipment, such as capacitors attached to power supply units, etc.

Research on factor analysis and technical process for achieving denuclearization; Denuclearization of South Africa

Tazaki, Makiko; Kimura, Takashi; Shimizu, Ryo; Tamai, Hiroshi; Nakatani, Takayoshi; Suda, Kazunori

JAEA-Review 2022-056, 54 Pages, 2023/01

JAEA-Review-2022-056.pdf:1.86MB

As part of the "Research on Factor Analysis and Technical Processes for Achieving Denuclearization" South Africa's nuclear development and denuclearization cases were investigated then analyzed from seven denuclearization factors namely (1) motivation for nuclear development, (2) internal and external situations at the time of denuclearization decision, (3) progress of nuclear development, (4) effects of sanctions, (5) incentives for denuclearization, (6) international framework for denuclearization, (7) denuclearization and verification methods. At the same time, characteristics of its denuclearization and lessons learned from the denuclearization were also analyzed. South Africa shifted its nuclear activities from research and development of "peaceful nuclear detonation" in the 1970s to developing "limited nuclear deterrence" and finally to manufacturing "transportable nuclear weapons" in the late 1980s. By then, it had completed producing six nuclear explosive devices using highly enriched uranium. However, in 1989, along with the abolition of the apartheid policy, South Africa decided denuclearization and dismantled its nuclear explosive devices and related facilities. Upon completion of dismantlement, it joined the Treaty on the Non- Proliferation of Nuclear Weapons and concluded a Comprehensive Safeguards Agreement (CSA) with the International Atomic Energy Agency (IAEA). The South Africa has remained one of the rare countries that has continued to the peaceful use nuclear energy, and its voluntary denuclearization is considered as a good example of denuclearization in the future.

High-pressure neutron experiments at PLANET in J-PARC using the six-axis multi-anvil press ATSUHIME

Hattori, Takanori

Yukuatsu Gijutsu, 61(7), p.29 - 35, 2022/07

As an example of the application of hydraulic technology, the 6-axis type multi-anvil press "ATSUHIME" in the J-PARC ultra-high pressure neutron diffractometer PLANET and the research on hydrogen in the Earth's core using them are introduced.

Guideline and cautionary points for accelerator system maintenance

Ono, Ayato; Takayanagi, Tomohiro; Sugita, Moe; Ueno, Tomoaki*; Horino, Koki*; Yamamoto, Kazami; Kinsho, Michikazu

JAEA-Technology 2021-044, 53 Pages, 2022/03

JAEA-Technology-2021-044.pdf:43.7MB

The 3-GeV rapid cycling synchrotron of Japan Proton Accelerator Research Complex (J-PARC) uses a large number of electromagnet power supplies in order to manipulate a high-intensity beam of 1 MW. These devices have been specially developed to meet the requirement to achieve acceleration of the 1-MW proton beams. Because J-PARC has been in operation for 10 years, we have to replace many parts and equipments due to failures caused by age-related deterioration. J-PARC accelerator system supplies the beams for many users, and we have to recover it as soon as possible when a trouble occurs. Therefore, if the trouble can be prevented before it happens, reduction of the user beam time can be minimized. Furthermore, it enables us to reduce additional work for operators. Maintenance is important to keep the equipments in a normal state, and makes it possible to extend the life of the equipments by detecting and maintaining the faulty parts and the aged deterioration parts at an early stage. Since all the devices requires the maintenance, there are a wide variety of maintenance methods. Some works are carried out by the J-PARC members, and some are performed by outsourcing. Ensuring safety and protecting workers are the most important issues in maintenance work. Therefore, J-PARC has rules for safety work. All workers in J-PARC have to learn and follow the rules. In addition, various ideas are being considered to enable safe and efficient work by devising ingenuity in each work. We also elaborate various ideas and processes for safe and efficient work according to the individual work conditions. In this report, we summarize the guideline and cautionary points during maintenance based on the actual case of maintenance and inspection work of the horizontal shift bump electromagnet power supply.

Development of semiconductor clover switch for short-circuit protection of Klystron for J-PARC accelerator

Ono, Ayato; Takayanagi, Tomohiro; Ueno, Tomoaki*; Horino, Koki*; Yamamoto, Kazami; Kinsho, Michikazu

Proceedings of 18th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.831 - 834, 2021/10

https://www.pasj.jp/web_publish/pasj2021/proceedings/PDF/THP0/THP015.pdf

The Ignitron is used in the clover device of the klystron power supply for RF acceleration in the J-PARC LINAC. However, this ignitron uses mercury, the use of which is restricted worldwide, and its production is expected to be discontinued in the future. Therefore, we designed a semiconductor clover switch for short-circuit protection of klystron using a MOS gate thyristor. We have manufactured an oval-type board module that realizes an operating output of 3 kV, 40 kA, and 50 s per board. For the control power supply to each board module assuming a high voltage of 120 kV, we adopted a self-power supply method that creates a control power supply with a high-voltage DCDC converter from the voltage shared and charged by each board module. It was possible to confirm the operating performance on a 1/4 scale (30 kV, 40 kA) against the voltage of the existing equipment (120 kV, 40 kA) by connecting ten oval board modules in series. The output test result will be reported.

Nondestructive quantitative analysis of difficult-to-measure radionuclides Pd and Tc

Toh, Yosuke; Segawa, Mariko; Maeda, Makoto; Tsuneyama, Masayuki*; Kimura, Atsushi; Nakamura, Shoji; Endo, Shunsuke; Ebihara, Mitsuru*

Analytical Chemistry, 93(28), p.9771 - 9777, 2021/07

https://doi.org/10.1021/acs.analchem.1c01233

Proposal of safe and secure maintenance method to realize long-term stable operation of electromagnet power supply

Ono, Ayato; Takayanagi, Tomohiro; Ueno, Tomoaki*; Horino, Koki*; Yamamoto, Kazami; Kinsho, Michikazu

JAEA-Technology 2021-005, 40 Pages, 2021/05

JAEA-Technology-2021-005.pdf:4.27MB

The 3-GeV rapid cycling synchrotron of Japan Proton Accelerator Research Complex (J-PARC) uses a large number of electromagnet power supplies in order to manipulate a high-intensity beam of 1 MW. These devices have been specially developed to meet the requirement to achieve acceleration of the 1-MW proton beams. State-of-the-art technologies are used to these devices. To achieve stable operation with few failures, and to prevent major troubles in the event of a failure, it is necessary to maintain the performance of the devices under the appropriate and accurate management strategy with an enough understanding of its characteristics. However, since the specification and function of each device is different respectively, and it is also produced by different manufacturer, we have to maintain adequately according to the structure, configuration and features of the apparatus. There are typically three major stages in the maintenance works. First, "Daily inspection" is constantly performed to monitor the status of the equipment during operation and check for any errors or abnormalities. Second, "Routine maintenance" is carried out weekly, monthly, or yearly to fix the errors, or to replace the parts that are deteriorated. Third, "Troubleshooting" is conducted to recover from sudden failures. In this report, we will introduce the specific contents of "Routine maintenance", "Daily inspection", and "trouble case" based on the experiences of the electromagnet power supply group. In particular, we will report the work management methods, including ideas for facilitating recovery work. We will also summarize the important points of a matter that does not depend on the configuration, structure, and characteristics of the equipment.