Development of an innovative n/ scintillation detection system for simple non-destructive measurements (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*

JAEA-Review 2025-046, 70 Pages, 2026/01

JAEA-Review-2025-046.pdf:5.46MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2023. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station (1F), Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2023, this report summarizes the research results of the "Development of an innovative n/ scintillation detection system for simple non-destructive measurements" conducted in FY2023. At 1F, removal of fuel debris from the primary containment vessel (PCV) is scheduled for FY2023, and a phased expansion of the removal scale is being considered in the future. As a solution to the above problem, this study will develop an innovative scintillation radiation detection system for screening and continuous monitoring during target sample removal. To develop a remote measurement system that contributes to in-vessel investigations for decommissioning of nuclear facilities such as 1F. More specifically, we will develop vertically integrated research into the following elemental technologies: (1) development of innovative high-performance scintillation materials for thermal neutron / gamma-ray discrimination (Tohoku University), (2) downsizing of censer and signal processing system (the University of Tokyo), (3) construction and characterization of various radiation fields (National Institute of Advanced Industrial Science and Technology), and (4) development of a simple non-destructive measurement system and hot cell demonstration test (JAEA). By vertically integrating elemental technologies, R&D on each research item planned in FY2023 was conducted to develop a detector that can discriminate gamma-ray and neutron radiation in environments exceeding 10 Gy/h and simultaneously identify the dose rate and nuclide of each in PCVs and in each acceptance cell.

Research and development of three-dimensional isolation system for sodium cooled fast reactor, 7; Development summary of three-dimensional isolation system

Watakabe, Tomoyoshi; Yamamoto, Tomohiko; Okamura, Shigeki; Miyazaki, Masashi; Miyagawa, Takayuki; Uchita, Masato*; Hirayama, Tomoyuki*; Somaki, Takahiro*; Yukawa, Masaki*; Fukasawa, Tsuyoshi*; et al.

Proceedings of the ASME 2024 Pressure Vessels & Piping Conference (PVP 2024) (Internet), 10 Pages, 2024/07

To secure the seismic safety of the thin-walled mechanical components and piping under a severe design earthquake level, employing a three-dimensional (3D) seismic isolation system has been planned in a sodium-cooled fast reactor. The development results of the 3D isolation system have been reported in previous papers so far. Its update is reported in Part 7 to Part 9. Part 7 describes the overview of the development, the test plan of the isolation system in the assembled state of each element, and the performance of individual isolation elements. In part 8, the performance of the isolation device that each element was assembled into was investigated through loading tests. Part 9 reports analytical studies by an analysis model validated based on the insight of the test results.

Resilient design in nuclear energy; Critical lessons from a cross-disciplinary analysis of the Fukushima Dai-ichi Nuclear accident

Ayoub, A.*; Wainwright, Haruko*; Sansavini, G.*; Gauntt, R.*; Saito, Kimiaki

iScience (Internet), 27(4), p.109485_1 - 109485_15, 2024/04

https://doi.org/10.1016/j.isci.2024.109485

Application of satellite remote sensing in geological environment investigation; Development of a geobotanical remote sensing method for estimating high water table areas in a humid warm-temperate region

Koide, Kaoru

JAEA-Research 2023-003, 101 Pages, 2023/06

JAEA-Research-2023-003.pdf:14.08MB

This study developed a geobotanical remote sensing method for estimating high water table areas such as groundwater discharge points using differences in the growth conditions of forest trees induced by moisture supply from groundwater in a humid warm-temperate forest area. A new vegetation index (VI) termed AgbNDVI (Added green band NDVI) was proposed to discriminate the differences. The AgbNDVI proved to be more sensitive to water stress on green vegetation than existing VIs: SAVI and EVI2, and possessed a strong linear correlation with the vegetation fraction. To validate the proposed method, a 23 km study area was selected in the Tono region of Gifu Prefecture, central Japan. The AgbNDVI values were calculated from atmospheric corrected SPOT HRV data. To correctly detect high VI points, the influence factors on tree growth were identified using the AgbNDVI values, DEM and forest type data; the study area was then divided into 555 segments according to combinations of the influence factors: elevation, slope gradient, slope aspect and forest type. Thresholds for detecting high VI points were defined for each segment based on a histogram of AgbNDVI values. By superimposing the high VI points on topographic and geologic maps, most of the high VI points are clearly located on the concave/convex slopes and near the geologic boundaries prone to groundwater runoff. In addition, field investigations support the correctness of the high VI points, because the growth increments and biomass of trees () are greater than at points other than the high VI points, and they are located around known groundwater seeps and in a high water table area. Consequently, the proposed method can be expected to provide useful information for characterizing hydrogeological structures by combining with conventional photo-geological interpretation.

Spattering behavior induced by cavitation bubble collapsing nearby gas-liquid interface

Kawashima, Hiroyuki; Kurosawa, Takuma*; Teshigawara, Makoto; Naoe, Takashi; Tanaka, Nobuatsu*; Futakawa, Masatoshi; Kogawa, Hiroyuki

Advanced Experimental Mechanics, 7, p.43 - 48, 2022/08

https://doi.org/10.11395/aem.7.0_43

Laser cutting is expected for reducing the volume of radioactive components by taking account of radioactive levels. The scattering of radioactive dust such as fume and spatter, which is generated throughout the laser cutting process, gets to be a major issue for practical usage in cutting highly radioactive substances. One of driving forces of the spatter is likely to be attributed to the cavitation bubble collapsing caused by rapid thermal loading due to laser irradiation. In order to elucidate the mechanism of spattering, the technique of spark discharge in water was availed to generate the cavitation bubble. The growth and collapse behaviors influenced by the interaction between a free surface and bubbles resulting the spattering phenomena are observed by using an ultra-high-speed video camera, and the numerical simulation was carried out as well.

New design of high power mercury target vessel of J-PARC

Wakui, Takashi; Wakai, Eiichi; Kogawa, Hiroyuki; Naoe, Takashi; Hanano, Kohei*; Haga, Katsuhiro; Shimada, Tsubasa*; Kanomata, Kenichi*

Materials Science Forum, 1024, p.145 - 150, 2021/03

https://doi.org/10.4028/www.scientific.net/MSF.1024.145

To realize a high beam power operation at the J-PARC, a mercury target vessel covered with water shroud was developed. In the first step, to realize an operation at 500 kW, the basic structure of the initial design was followed and the connection method between the mercury vessel and the water shroud was changed. Additionally, the operation at a beam power of 500 kW was realized in approximately eight months. In the second step, to realize the operation at 1 MW, the new structure in which only rear ends of vessels were connected was investigated. Cooling of the mercury vessel is used to reduce thermal stress and thick vessels of the water shroud are used to increase stiffness for the internal pressure; therefore, it was adopted. The stress in each vessel was lower than the allowable stress based on the pressure vessel code criteria prescribed in the Japan Industrial Standard, and confirmation was obtained that the operation with a beam power of 1 MW could be conducted.

Development of neutron transport calculation codes for 3-D hexagonal geometry, 2; Improvement and enhancement of the MINISTRI code

Sugino, Kazuteru; Takino, Kazuo

JAEA-Data/Code 2019-011, 110 Pages, 2020/01

JAEA-Data-Code-2019-011.pdf:3.37MB

A deterministic discrete ordinates method (SN method) transport calculation code for three-dimensional hexagonal geometry has been developed as the MINISTRI code (Ver. 7.0). MINISTRI is based on the triangle-mesh finite difference method, which can perform neutron transport calculations with high accuracy for cores of fast power reactors and assemblies of the Russian BFS critical facility. The present study has derived a proper scheme for remarkably improving the convergence of MINISTRI by investigating the issue of previous MINISTRI (Ver. 1.1), which sometimes plays a poor convergence performance in calculations for large-scale power reactor cores. The verification test of improved MINISTRI has been carried out for various cores by setting the reference result as the multi-group Monte-Carlo calculation with the same cross-sections as used in MINISTRI. As a result, it is found that the agreements are within 0.1% for eigenvalues and within 0.7% for power distributions. Thus, the satisfying accuracy of MINISTRI has been confirmed. In order to reduce the calculation time, the initial diffusion calculation scheme and the parallel processing have been implemented. As a result, the calculation time is reduced to the approximately one tenth compared with previous MINISTRI. Furthermore, adoption of the treatment of the anisotropic cell streaming effect, preparation of the perturbation calculation tool, implementation of the function for specification of the triangle-mesh-wise material and merging of the hexagonal-mesh calculation code MINIHEX have been carried out. Thus, the versatility of MINISTRI has been enhanced.

Evaluation growing and collapsing behaviors of cavitation bubbles under flowing condition

Kawamura, Shunsuke; Naoe, Takashi; Ikeda, Tsubasa*; Tanaka, Nobuatsu*; Futakawa, Masatoshi

Advanced Experimental Mechanics, 4, p.33 - 37, 2019/08

https://doi.org/10.11395/aem.4.0_33

A mercury enclosure vessel made of stainless steel is used as a spallation target in the pulsed spallation neutron source at J-PARC. It is severely damaged by the cavitation induced with pressure waves in association with the pulsed proton beam injection. A double-walled structure with a narrow mercury channel was adopted in the front end of the target vessel to reduce the cavitation damage. It has been experimentally demonstrated that the cavitation damage could be mitigated in the narrow channel but its mechanism has been unclarified yet. In this study, we investigated the cavitation from growing to collapsing through visualizing the spark-induced cavitation bubbles under flow field using a high-speed video camera. Furthermore, we measured the wall vibration due to the cavitation bubble collapse with changing flow velocity parametrically. It was found that the microjet collided perpendicular to the wall in the stagnant flow condition while it collided with an inclined angle from the perpendicular direction, suggesting that the collision pressure on the wall was reduced by flowing.

Analysis of maximum voltage transient of JT-60SA toroidal field coils in case of fast discharge

Novello, L.*; Cara, P.*; Coletti, A.*; Gaio, E.*; Maistrello, A.*; Matsukawa, Makoto; Philipps, G.*; Tomarchio, V.*; Yamauchi, Kunihito

IEEE Transactions on Applied Superconductivity, 26(2), p.4700507_1 - 4700507_7, 2016/03

https://doi.org/10.1109/TASC.2016.2521321

Exploring of peptides with affinity to HER2 from random peptide libraries using radioisotope; Random hexapeptide libraries with fixed amino acid sequence at 1 and 2 positions

Sasaki, Ichiro; Hanaoka, Hirofumi*; Yamada, Keiichi*; Watanabe, Shigeki; Sugo, Yumi; Ohshima, Yasuhiro; Suzuki, Hiroyuki; Ishioka, Noriko

Peptide Science 2014, p.257 - 260, 2015/03