Achievements and status of the STRAD project for radioactive liquid waste management

Arai, Yoichi; Watanabe, So; Nakahara, Masaumi; Funakoshi, Tomomasa; Hoshino, Takanori; Takahatake, Yoko; Sakamoto, Atsushi; Aihara, Haruka; Hasegawa, Kenta; Yoshida, Toshiki; et al.

Progress in Nuclear Science and Technology (Internet), 7, p.168 - 174, 2025/05

https://doi.org/10.15669/pnst.7.168

The Japan Atomic Energy Agency (JAEA) has been conducting a project named "Systematic Treatment of RAdioactive liquid waste for Decommissioning (STRAD)" project since 2018 for fundamental and practical studies for treating radioactive liquid wastes with complicated compositions. Fundamental studies have been conducted using genuine liquid wastes accumulated in a hot laboratory of the JAEA called the Chemical Processing Facility (CPF), and treatment procedures for all liquid wastes in CPF were successfully designed on the results obtained. As the next phase of the project, new fundamental and practical studies on primarily organic liquid wastes accumulated in different facilities of JAEA are in progress. This paper reviews the representative achievements of the STRAD project and introduces an overview of ongoing studies.

Establishment of a practical methodology for evaluating equieffective dose of individual patients based on RT-PHITS

Sato, Tatsuhiko; Furuta, Takuya; Sasaki, Hidetaka*; Watabe, Tadashi*

EJNMMI Physics (Internet), 12, p.28_1 - 28_16, 2025/03

https://doi.org/10.1186/s40658-025-00743-6

Multiple metamagnetic transitions in the helical antiferromagnet CeVGe

Jin, H.*; Choi, E. S.*; Wu, H.-C.*; Curro, N. J.*; Nawa, Kazuhiro*; Sato, Taku*; Kiyanagi, Ryoji; Ohara, Takashi; Klavins, P.*; Taufour, V.*

Physical Review B, 111(3), p.035103_1 - 035103_7, 2025/01

https://doi.org/10.1103/PhysRevB.111.035103

Effect of sea salt on the interaction between simulated corium and concrete

Sudo, Ayako; Sato, Takumi; Takano, Masahide

Journal of Nuclear Science and Technology, 9 Pages, 2025/00

https://doi.org/10.1080/00223131.2025.2456565

During the progression of the severe accident at the Fukushima Daiichi Nuclear Power Station, seawater flowed down and was predicted to react with molten corium and concrete. For the removal and storage of fuel debris, knowing the effects of seawater components on the characteristics of reaction products in the fuel debris is crucial. To understand changes in the microstructure of fuel debris, a reaction test was conducted by introducing sea salt to simulated corium and concrete under a temperature gradient. Among the components of sea salt, sulfur formed iron sulfide during metallic precipitation. Analysis of vaporized species indicated that most of Cl, some Na and K in the sea salt might volatilize during heating rather than react with simulated corium and concrete. Calcium and a small amount of Mg, Na, and K in the sea salt might be trapped in the silicate glass.

Separating urban heat island circulation and convective cells through dynamic mode decomposition

Sato, Takuto; Hino, Hideitsu*; Kusaka, Hiroyuki*

Atmospheric Science Letters, 25(12), p.e1279_1 - e1279_10, 2024/12

https://doi.org/10.1002/asl.1279

This study applies dynamic mode decomposition (DMD) to three-dimensional simulation results of urban heat island circulation (UHIC, which is horizontal circulation) and thermals (vertical convections). The aim of this study is to revisit how these phenomena coexist based on the characteristics of temporal changes in the flow field. We used DMD to obtain the dominant spatial patterns and information on temporal changes. One of the modes of horizontal wind, which does not change temporally (no oscillation or amplification), exhibits a spatial UHIC pattern. The unique feature of this UHIC mode is that there are small-scale striated structures (150-200 m) and large-scale convergence. The other modes are time-varying (oscillating and decaying) and represent smaller spatial-scale phenomena (150-250 m), such as thermals. The frequency of each mode takes various values, some of which are lower than the lifetime of thermals in accordance with the Deardorff convective scale (10 min). These low-frequency modes showed striated structures similar to that observed in the UHIC modes. These results suggest that UHIC and thermals deform each other through components that vary in long temporal scales.

Study on microwave power dependency of electron spin resonance spectrum of carbonate radicals in teeth

Iwami, Satone*; Yamashita, Takuma*; Mitsuyasu, Yusuke*; Ono, Kenta*; Oka, Toshitaka; Takahashi, Atsushi*; Kino, Yasushi*; Sekine, Tsutomu*; Shimizu, Yoshinaka*; Chiba, Mirei*; et al.

KEK Proceedings 2024-6, p.91 - 95, 2024/12

We aim to improve the detection limit of the ESR dosimetry method. In this study, the saturation behavior of each radical was investigated by varying the microwave power during ESR measurement. Based on the difference in spin relaxation time between carbonate radicals and native radicals, it is expected that the signal-to-noise ratio improves and the detection limit can be lowered when the microwave power is increased to 4.0 mW.

Overview of PHITS Ver.3.34 with particular focus on track-structure calculation

Ogawa, Tatsuhiko; Hirata, Yuho; Matsuya, Yusuke; Kai, Takeshi; Sato, Tatsuhiko; Iwamoto, Yosuke; Hashimoto, Shintaro; Furuta, Takuya; Abe, Shinichiro; Matsuda, Norihiro; et al.

EPJ Nuclear Sciences & Technologies (Internet), 10, p.13_1 - 13_8, 2024/11

https://doi.org/10.1051/epjn/2024012

The latest updates on PHITS, a versatile radiation transport code, focusing specifically on track-structure models are presented. Track structure calculations are methods used to simulate the movement of charged particles while explicitly considering each atomic reaction. Initially developed for radiation biology, these calculation methods aimed to analyze the radiation-induced damage to DNA and chromosomes. Several track-structure calculation models, including PHITS-ETS, PHITS-ETS for Si, PHITS-KURBUC, ETSART, and ITSART, have been developed and implemented to PHITS. These models allow users to study the behavior of various particles at the nano-scale across a wide range of materials. Furthermore, potential applications of track-structure calculations have also been proposed so far. This collection of track-structure calculation models, which encompasses diverse conditions, opens up new avenues for research in the field of radiation effects.

Development of a multi-scale meteorological Large-eddy simulation model for urban thermal environmental studies; The "City-LES" Model Version 2.0

Kusaka, Hiroyuki*; Ikeda, Ryosaku*; Sato, Takuto; Iizuka, Satoru*; Boku, Taisuke*

Journal of Advances in Modeling Earth Systems (Internet), 16(10), p.e2024MS004367_1 - e2024MS004367_38, 2024/10

https://doi.org/10.1029/2024MS004367

To bridge the gaps between meteorological large-eddy simulation (LES) models and computational fluid dynamics (CFD) models for microscale urban climate simulations, the present study has developed a meteorological LES model for urban areas. This model simulates urban climates across both mesoscale (city scale) and microscale (city-block scale). The paper offers an overview of this LES model, which distinguishes itself from standard numerical weather prediction models by resolving buildings and trees at the microscale simulations. It also differs from standard CFD models by accounting for atmospheric stratification and physical processes. Noteworthy features of this model include: (a) the calculation of long- and short-wave radiations in three dimensions, incorporating multiple reflections within urban canopy layers using the radiosity method, and accounting for building and tree shadows in the simulations; (b) the provision of various heat stress indices (Universal Thermal Climate Index, Wet Bulb Globe Temperature, MRT, THI); (c) the assessment of the efficacy of heat stress mitigation measures such as dry-mist spraying, roadside trees, cool pavements, and green/cool roofs strategies; (d) the capability to run on supercomputers, with the code parallelized in a three-dimensional manner, and the model can also run on a graphics processing unit cluster. Following the introduction of this model, the study confirms its basic performance through various numerical experiments, including simulations of thermals in the convective boundary layer, coherent structure of turbulence over urban canopy, and thermal environment and heat stress indices in urban districts. The model developed in this study is intended to serve as a community tool for addressing both fundamental and applied studies in urban climatology.

and study of biological effects on cancer cells in the presence of metallic materials during radiotherapy

Nagano, Takuya*; Matsuya, Yusuke; Kaida, Atsushi*; Nojima, Hitomi*; Furuta, Takuya; Sato, Kaoru; Yoshimura, Ryoichi*; Miura, Masahiko*

Journal of Radiation Research (Internet), 65(5), p.628 - 639, 2024/09

https://doi.org/10.1093/jrr/rrae062

In X-ray therapy, radiation regimen is planned to eliminate tumors while minimizing side effects on normal tissue. When irradiating the oral cavity, which includes dental metallic crowns, intense mucositis can occasionally be induced. However, the mechanism underlying the radiosensitization remains unclear. In this study, we investigated the radiosensitization mechanism using cell experiments and computational simulations. As a result, the enhancement ratio observed in the cell experiments was 1.2-1.4, which was found to be predominately attributed to local dose increase near metal. On the other hand, as a result of dose evaluation based on CT images as a preclinical test, it was found that the dose increase was underestimated due to the complex anatomical structure of the human body, and microscopic dose evaluation was necessary. This outcome contributes to the precise understanding of side effects on normal cells around metals.

MAAP code analysis for the in-vessel phase of Fukushima-Daiichi Nuclear Power Station Unit 1 and comparison of the results among Units 1 to 3

Sato, Ikken; Yoshikawa, Shinji; Yamashita, Takuya; Shimomura, Kenta; Cibula, M.*; Mizokami, Shinya*

Nuclear Engineering and Design, 422, p.113088_1 - 113088_24, 2024/06

https://doi.org/10.1016/j.nucengdes.2024.113088