Development of nondestructive elemental analysis system for Hayabusa2 samples using muonic X-rays

Osawa, Takahito; Nagasawa, Shunsaku*; Ninomiya, Kazuhiko*; Takahashi, Tadayuki*; Nakamura, Tomoki*; Wada, Taiga*; Taniguchi, Akihiro*; Umegaki, Izumi*; Kubo, Kenya*; Terada, Kentaro*; et al.

ACS Earth and Space Chemistry (Internet), 7(4), p.699 - 711, 2023/04

https://doi.org/10.1021/acsearthspacechem.2c00303

The concentrations of carbon and other major elements in asteroid samples provide very important information on the birth of life on the Earth and the solar-system evolution. Elemental analysis using muonic X-rays is one of the best analytical methods to determine the elemental composition of solid materials, and notably, is the only method to determine the concentration of light elements in bulk samples in a non-destructive manner. We developed a new analysis system using muonic X-rays to measure the concentrations of carbon and other major elements in precious and expectedly tiny samples recovered from the asteroid Ryugu by spacecraft Hayabusa2. Here we report the development process of the system in 4 stages and their system configurations, The analysis system is composed of a stainless-steel analysis chamber, an acrylic glove box for manipulating asteroid samples in a clean environment, and Ge semiconductor detectors arranged to surround the analysis chamber. The performance of the analysis system, including the background level, which is crucial for the measurement, was greatly improved from the first stage to the later ones. Our feasibility study showed that the latest model of our muonic X-ray analysis system is capable of determining the carbon concentration in Hayabusa2's sample model with an uncertainty of less than 10 percent in a 6-day measurement.

Design and actual performance of J-PARC 3 GeV rapid cycling synchrotron for high-intensity operation

Yamamoto, Kazami; Kinsho, Michikazu; Hayashi, Naoki; Saha, P. K.; Tamura, Fumihiko; Yamamoto, Masanobu; Tani, Norio; Takayanagi, Tomohiro; Kamiya, Junichiro; Shobuda, Yoshihiro; et al.

Journal of Nuclear Science and Technology, 59(9), p.1174 - 1205, 2022/09

https://doi.org/10.1080/00223131.2022.2038301

In the Japan Proton Accelerator Research Complex, the purpose of the 3 GeV rapid cycling synchrotron (RCS) is to accelerate a 1 MW, high-intensity proton beam. To achieve beam operation at a repetition rate of 25 Hz at high intensities, the RCS was elaborately designed. After starting the RCS operation, we carefully verified the validity of its design and made certain improvements to establish a reliable operation at higher power as possible. Consequently, we demonstrated beam operation at a high power, namely, 1 MW. We then summarized the design, actual performance, and improvements of the RCS to achieve a 1 MW beam.

Improvement construction for ground around High Active liquid Waste facility in Tokai Reprocessing Plant

Omori, Kazuki; Yamauchi, Sho; Yanagibashi, Futoshi; Sasaki, Shunichi; Wada, Takuya; Suzuki, Hisanori; Domura, Kazuyuki; Takeuchi, Kenji

Nihon Hozen Gakkai Dai-18-Kai Gakujutsu Koenkai Yoshishu, p.245 - 248, 2022/07

Tokai Reprocessing Plant (TRP), which is shifted to decommissioning stage, stores large amount of high-level radioactive liquid waste (HLLW). Although TRP is implementing vitrification of HLLW to reduce the risks related to HLLW storage, additional 20 years are required to complete vitrification of HLLW. Therefore, TRP is implementing safety countermeasure related to seismic resistance of HLLW storage facility as one of the top priorities. The results of the seismic evaluation indicate that although the facility itself is seismically resistant, there is a risk of insufficient binding force acting between the facility and the surrounding ground. Thus, replacement of the surrounding ground with concrete is performed. Since the countermeasures, to protect existing buries structure and coordinate with the other construction projects around the site, are required, the dedicated team was setup to handle the process and safety management of the concrete replacement construction.

Long-term density-dependent groundwater flow analysis and its effect on nuclide migration for safety assessment of high-level radioactive waste disposal with consideration of interaction between fractures and matrix of rock formation in coastal crystalline groundwater systems

Park, Y.-J.*; Sawada, Atsushi; Ozutsumi, Takenori*; Tanaka, Tatsuya*; Hashimoto, Shuji*; Morita, Yutaka*

Proceedings of 3rd International Conference on Discrete Fracture Network Engineering (DFNE 2022) (Internet), 8 Pages, 2022/00

Safety analysis for underground disposal facilities for high-level radioactive waste requires thorough understanding of long-term groundwater flow and nuclide migration processes in geologic media. In the coastal subsurface systems, groundwater flow is defined by the complex interactions between freshwater of meteoric origin and denser saline water from the sea. In addition, sea levels are expected to fluctuate significantly due to a transgression and regression of the sea over the millions of years for safety analysis. This study presents long-term evolution of groundwater environment such as salinity concentration and flow velocity with focus of the interaction between fractures and matrix blocks in regional and near-field scale analysis framework for groundwater flow and nuclide migration for underground disposal facilities in hypothetical fractured crystalline coastal systems.

Prediction of stability constants for novel chelates design in minor actinides partitioning over lanthanides using density functional theory calculation

Kaneko, Masashi; Sasaki, Yuji; Wada, Eriko*; Nakase, Masahiko*; Takeshita, Kenji*

Chemistry Letters, 50(10), p.1765 - 1769, 2021/10

https://doi.org/10.1246/cl.210402

Density functional theory calculation is applied to predict the stability constants for Eu and Am complexes in aqueous solution for molecular modelling of novel separation agents for minor actinides over lanthanides. Logarithm of experimental stability constants correlates with calculated complex formation enthalpies with high reproducibility (R 0.98). Prediction of stability constants of novel chelates is demonstrated and indicates a potential availability of the derivatives of diethylenetriaminepentaacetic acid type chelate in acidic condition and enhancement of Am selectivity over Eu.

Study on dominant aspects of unprotected loss-of-flow to be evaluated in the initiating phase for a sodium-cooled fast reactor

Kawada, Kenichi; Suzuki, Toru*

Journal of Nuclear Science and Technology, 58(3), p.347 - 360, 2021/03

https://doi.org/10.1080/00223131.2020.1838964

SAS4A is presently the worldwide standard computer code for simulation of the initiating phase of the Core Disruptive Accident (CDA) in MOX-fueled Sodium-cooled Fast Reactors (SFR). In order to improve the capability of the computational code, SAS4A, to be applied to the safety assessment for SFRs, detailed investigations of physical phenomena under unprotected loss-of-flow (ULOF) conditions were conducted, and physical models to be developed and improved were identified using the Phenomena Identification and Ranking Table (PIRT) method. A fuel stub motion, in which the residual fuel pellets would move to the core central region after fuel pin disruption, was selected as one of the key phenomena to be simulated properly and a key concept of the fuel stub motion model was presented.

Validation study of SAS4A code for the unprotected loss-of-flow accident in an SFR

Ishida, Shinya; Kawada, Kenichi; Fukano, Yoshitaka

Mechanical Engineering Journal (Internet), 7(3), p.19-00523_1 - 19-00523_17, 2020/06

https://doi.org/10.1299/mej.19-00523

The Phenomena Identification and Ranking Table (PIRT) approach was applied to the validation of SAS4A code in order to indicate the reliability of SAS4A code sufficiently and objectively. Based on this approach, issue and objective were clarified, plant design and scenario were defined, FOM and key phenomena were selected, and the code validation test matrix was completed with the results of investigation about analysis models and test cases. The results of the test analysis corresponding to this matrix show that the SAS4A models required for the IP evaluation were sufficiently validated. Furthermore, the validation with this matrix is highly reliable, since this matrix represents the comprehensive validation that also considers the relation between physical phenomena. In this study, the reliability and validity of SAS4A code were significantly enhanced by using PIRT approach to the sufficient level for CDA analyses in SFR.

Anomalous small-angle X-ray scattering (ASAXS) study of irradiation-induced nanostructure change in Fe-ion beam irradiated oxide dispersion-strengthened (ODS) steel

Kumada, Takayuki; Oba, Yojiro; Motokawa, Ryuhei; Morooka, Satoshi; Tominaga, Aki; Tanida, Hajime; Shobu, Takahisa; Konno, Azusa; Owada, Kenji*; Ono, Naoko*; et al.

Journal of Nuclear Materials, 528, p.151890_1 - 151890_7, 2020/01

https://doi.org/10.1016/j.jnucmat.2019.151890

We have developed an anomalous small-angle X-ray scattering (ASAXS) diffractometer in SPring-8 to investigate irradiation-induced nanostructural change in ion-beam irradiated stainless steel. A thermally-aged MA956 stainless steel sample displays power-law scattering that follows the Porod law at the magnitude of scattering vector, Q, below 0.5 nm and an overlapped shoulder around 0.7 nm. After the ion-beam irradiation, the intensity of the shoulder remained unchanged, whereas that of the power-law scattering nearly doubled. This result indicates that none of the structural parameters of the Cr-rich nanoprecipitates, such as the number density, size, and interface roughness, were changed by the irradiation.

Validation study of initiating phase evaluation method for the core disruptive accident in an SFR

Ishida, Shinya; Kawada, Kenichi; Fukano, Yoshitaka

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 10 Pages, 2019/05

Core Disruptive Accident (CDA) has been considered as one of the important safety issues in the severe accident evaluation of Sodium-cooled Fast Reactor (SFR), and SAS4A code is developed for Initiating Phase (IP) of CDA. Phenomena Identification and Ranking Table (PIRT) approach was applied to the validation of SAS4A code in order to enhance its reliability in this study. SAS4A was validated in the following steps: (1) selection of the figure of merit (FOM) corresponding to Unprotected Loss Of Flow (ULOF) which is one of the most important and typical events in CDA, (2) identification of the phenomena involved in ULOF, (3) ranking the important phenomena, (4) development of the code validation test matrix, and (5) test analyses for validation corresponding to the test matrix. The reliability and validity of SAS4A code were significantly enhanced by this validation with PIRT approach.

Machine-learning guided discovery of a new thermoelectric material

Iwasaki, Yuma*; Takeuchi, Ichiro*; Stanev, V.*; Gilad Kusne, A.*; Ishida, Masahiko*; Kirihara, Akihiro*; Ihara, Kazuki*; Sawada, Ryoto*; Terashima, Koichi*; Someya, Hiroko*; et al.

Scientific Reports (Internet), 9, p.2751_1 - 2751_7, 2019/02

https://doi.org/10.1038/s41598-019-39278-z