研究者詳細 - 吉橋　幸子

論文 - 吉橋　幸子

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Development of a Sealed Li target as an accelerator-driven neutron source for Boron neutron capture therapy at Nagoya University

Honda, S; Yoshihashi, S; Tomita, S; Tsuchida, K; Kiyanagi, Y; Tsurita, Y; Watanabe, K; Yamazaki, A; Uritani, A

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 1040 巻 2022年10月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Nagoya University is developing a Sealed lithium (Li) target based on a new concept for an accelerator-driven neutron source for Boron neutron capture therapy. The Sealed Li target is a thick Li target with the new concept of sealing Li with Ti foil and stopping protons within Li. The incident proton beam on the target is generated by the Proton-dynamitron (IBA) accelerator and has a maximum energy of 2.8 MeV and a current of 15 mA (heat input of 6.6 MW/m2). In this paper, a test sample made with a small amount of Li was prepared to evaluate the performance of the Sealed Li target. We called the test target. When irradiated with a heat input of 4.6 MW/m2, the Ti foil on the surface of the test target was not damaged, although some Li melted and a dent with the same shape as the beam diameter was formed. Furthermore, the heat removal performance of the test target was evaluated using simulation software and the finite element method. The maximum temperature of the target surface was 144.4 °C when a heat input of 5.0 MW/m2 was calculated. Assuming that the bondability between Ti foil and Li is poor, the calculation was carried out by simulating the presence of cavities at the Ti foil–Li interface. As a result, we suggested that the presence of than 2 mm diameter cavity at the interface between Ti foil and Li would melt the Ti foil and damage the target. In order to obtain the ideal result, it was necessary to further improve the adhesion between Ti foil and Li, but we were able to confirm the performance of the sealed Li target with a new concept.

DOI： 10.1016/j.nima.2022.167140

High heat removal technique for a lithium neutron generation target used for an accelerator-driven BNCT system

Yoshihashi, S; Tsuneyoshi, T; Tsuchida, K; Furuzawa, D; Honda, S; Watanabe, K; Yamazaki, A; Tsuji, Y; Hamaji, Y; Tokitani, M; Tamura, H; Sagara, A; Kiyanagi, Y; Uritani, A

JOURNAL OF INSTRUMENTATION 16 巻 ( 4 ) 2021年4月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Instrumentation

Accelerator-driven neutron sources have been developed worldwide for boron neutron capture therapy (BNCT) instead of nuclear reactors. Nagoya University is currently developing a compact DC accelerator driven BNCT system using a sealed lithium (Li) target. The target receives a high heat load by a proton beam, and the heat then requires efficient removal. This study developed a high-efficiency heat removal technique that uses V-shaped staggered ribs on the heat removal side of the flow channels. We performed experiments using an electron beam to confirm the technique performance. The results showed double the heat removal performance compared to the smooth surface channel. The value expected to sufficiently remove 6.6 MW/m2 of heat load provided by the proton beam at the Nagoya University neutron source for BNCT.

DOI： 10.1088/1748-0221/16/04/P04016

Neutron flux distributions in the Large Helical Device torus hall evaluated by an imaging plate technique in the first campaign of the deuterium plasma experiment Open Access

Kobayashi, M; Tanaka, T; Nishitani, T; Ogawa, K; Isobe, M; Motojima, G; Kato, A; Yoshihashi, S; Osakabe, M

NUCLEAR FUSION 59 巻 ( 12 ) 2019年12月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Nuclear Fusion

The global flux distributions for thermal, epithermal and fast neutrons in the torus hall of large fusion devices were experimentally evaluated for the first time in the Large Helical Device (LHD) using the activation foil method measured by the imaging plate and high-purity germanium detector. It turned out that the thermal neutrons were effectively absorbed by borated polyethylene blocks placed beneath the LHD. This should reduce the radioactivity of the floor and would be beneficial in maintaining a good environment for radiation workers. Uniform distributions of epithermal and fast neutrons were observed near the LHD. In particular, the significant decrease in fast neutron flux with increasing distance from the LHD, due to the fast energy loss of fast neutrons, was observed. The neutron flux distribution measurement, with rough energy discrimination based on the threshold energy of the neutron activation foil, allows us to estimate the spatial radiation dose rate, as well as the radioactivity in components in the torus hall. The prediction of the radioactivity in the concrete floor indicated that radioactive isotope 55Fe will be a dominant source of radioactivity in the concrete after the nine-year deuterium experiment campaign finishes.

DOI： 10.1088/1741-4326/ab3d14

Measurement of neutron spectrum using activation method in deuterium plasma experiment at LHD Open Access

Tanaka, T; Yoshihashi, S; Kobayashi, M; Uritani, A; Watanabe, K; Yamazaki, A; Nishitani, T; Ogawa, K; Isobe, M

FUSION ENGINEERING AND DESIGN 146 巻頁： 496 - 499 2019年9月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Fusion Engineering and Design

In the Large Helical Device (LHD) of the National Institute for Fusion Science, the experiments using deuterium plasma were performed from March 2017. Neutrons with the energy of 2.45 MeV are generated by d (d, n) 3He reactions. The evaluation of the neutron flux in the torus hall as well as the LHD vessel is very important for designing the decommissioning of the LHD in the future, and the radiation shielding for workers and components around LHD. In this study, we performed the activation experiments using multiple activation foils to obtain a neutron spectrum in the vacuum vessel of the LHD. The reaction rate of each activation foil was generally consistent with the calculation result by MCNP6. As a result of the unfolding with SAND-II code, we experimentally obtained the neutron spectrum in the vacuum vessel of the LHD for the first time.

DOI： 10.1016/j.fusengdes.2019.01.005

Effect of neutron beam properties on dose distributions in a water phantom for boron neutron capture therapy Open Access

Ishikawa, A; Tanaka, H; Nakamura, S; Kumada, H; Sakurai, Y; Watanabe, K; Yoshihashi, S; Tanagami, Y; Uritani, A; Kiyanagi, Y

JOURNAL OF RADIATION RESEARCH 65 巻 ( 6 ) 頁： 765 - 775 2024年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of radiation research

From the viewpoints of the advantage depths (ADs), peak tumor dose and skin dose, we evaluated the effect on the dose distribution of neutron beam properties, namely the ratio between thermal and epithermal neutron fluxes (thermal/epithermal ratio), fast neutron component and γ-ray component. Several parameter surveys were conducted with respect to the beam properties of neutron sources for boron neutron capture therapy assuming boronophenylalanine as the boron agent using our dose calculation tool, called SiDE. The ADs decreased by 3% at a thermal/epithermal ratio of 20-30% compared with the current recommendation of 5%. The skin dose increased with the increasing thermal/epithermal ratio, reaching a restricted value of 14 Gyeq at a thermal/epithermal ratio of 48%. The fast neutron component was modified using two different models, namely the 'linear model', in which the fast neutron intensity decreases log-linearly with the increasing neutron energy, and the 'moderator thickness (MT) model', in which the fast neutron component is varied by adjusting the MT in a virtual beam shaping assembly. Although a higher fast neutron component indicated a higher skin dose, the increment was <10% at a fast neutron component of <1 × 10-12 Gy cm2 for both models. Furthermore, in the MT model, the epithermal neutron intensity at a fast neutron component of 6.8 × 10-13 Gy cm2 was 41% higher compared with that of 2 × 10-13 Gy cm2. The γ-ray component also caused no significant disadvantages up to several times larger compared with the current recommendation.

DOI： 10.1093/jrr/rrae076

Simultaneous measurements for fast neutron flux and tritium production rate using pulse shape discrimination and single crystal CVD diamond detector Open Access

Kobayashi, MI; Yoshihashi, S; Ogawa, K; Isobe, M; Aso, T; Hara, M; Sangaroon, S; Tamaki, S; Murata, I; Toyama, S; Miwa, M; Matsuyama, S; Osakabe, M

NUCLEAR FUSION 64 巻 ( 6 ) 2024年6月

掲載種別：研究論文（学術雑誌）出版者・発行元：Nuclear Fusion

This paper presents the development of a simultaneous measurement method for fast neutron energy spectra and tritium production rates within mixed radiation fields using a single crystal chemical vapour deposition diamond detector combined with a lithium fluoride (LiF) foil. The method involves the separation of pulses with rectangular shapes and the determination of the depth position within the single crystal diamond (SCD) struck by fast neutrons or nuclear reaction products including recoil tritons from the LiF foil based on pulse width, extracting pulse events occurred at the specific bulk region and the surface region of the SCD. Subsequently, unfolding techniques were employed to analyse the energy deposition spectrum of pulses at the specific bulk region which are induced only by fast neutrons, allowing the deduction of the fast neutron energy spectrum. To evaluate the tritium production rate, the energy deposition spectrum of pulses from events occurring at the SCD surface facing the LiF foil was analysed. By estimating the energy deposition spectrum solely induced by fast neutrons striking the SCD surface and subtracting it from the energy deposition spectrum of events at the SCD surface, the contribution of energetic ions, such as recoil tritons generated by the 6Li(n,α)3H reaction in the LiF foil, was determined. The fast neutron flux and tritium production rate obtained through this study were consistent with particle transport calculations, demonstrating the successful development of a method suitable for performance testing of fusion reactor blankets.

DOI： 10.1088/1741-4326/ad3f2e

Estimation of nuclear properties in a deuteron-lithium target using JENDL/ DEU-2020 for IFMIF and similar irradiation facilities

Nishitani, T; Yoshihashi, S; Tanagami, Y; Amano, S; Uritani, A; Kwon, S; Kondo, K; Kumagai, K; Ochiai, K; Sato, S

FUSION ENGINEERING AND DESIGN 202 巻 2024年5月

掲載種別：研究論文（学術雑誌）出版者・発行元：Fusion Engineering and Design

An accelerator-based neutron source powered by deuteron–Li (d–Li) reactions is among the most promising neutron sources for fusion materials irradiation facilities, such as IFMIF, IFMIF-DONES, and A-FNS. The yield estimation of neutrons and other particles is critical to the design of these facilities. Presently, the McDelicious code is employed for the aforementioned yield estimations, although it is not an open code. Recently, a deuteron-induced reaction library, JENDL/DEU-2020, was released by the Japan Atomic Energy Agency. Thus, employing benchmark tests, such as the Particle and Heavy Ion Transport code System (PHITS) + JENDL/DEU-2020, Monte Carlo N-Particle + JENDL/DEU-2020, and McDelicious, we confirm that PHITS (or Monte Carlo N-Particle (MCNP)) + JENDL/DEU-2020 effectively reproduces the experimental data and McDelicious results. We apply PHITS + JENDL/DEU-2020 to the yield estimations of the neutron, gamma, and charged particles in a Li target and to the yield estimation of the charged particles in the target backplate for A-FNS. The estimated production rates of tritium and 7Be during the continuous operation using a deuteron beam of 40 MeV and 125 mA are 1.4 × 1016 atoms/s (2.3 g/FPY) and 5.9 × 1014 atoms/s (0.21 g/FPY), respectively, and the estimated production rates of He and H in the target backplate for A-FNS are 3.2 × 102 and 1.8 × 103 appm/FPY, respectively.

DOI： 10.1016/j.fusengdes.2024.114320

Application of a single crystal CVD diamond detector for fast neutron measurement in high dose and mixed radiation fields

Makoto I. Kobayashi, Sachiko Yoshihashi, Kunihiro Ogawa, Mitsutaka Isobe, Tsukasa Aso, Masanori Hara, Siriyaporn Sangaroon, Shingo Tamaki, Isao Murata, Masaki Osakabe

2024 IEEE International Conference on Consumer Electronics (ICCE) 頁： 1 - 4 2024年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IEEE

This paper presents the method to evaluate the fast neutron energy spectrum under mixed radiation field using the single crystal CVD diamond detector. The pulse shape discrimination based on the shape and width of the pulse was applied to extract the event in which fast neutron hits at a specific depth of the single crystal diamond. Unfolding of the measured energy deposition spectrum induced by extracted pulses could deduce the neutron energy spectrum. An experiment using 14.1 MeV mono-energetic neutron source demonstrated the reliable capability of this method to evaluate the neutron energy spectrum quantitatively.

DOI： 10.1109/icce59016.2024.10444274

Application of a Single-Crystal CVD Diamond Detector for Fast Neutron Measurement in High Dose and Mixed Radiation Fields

Kobayashi, MI; Yoshihashi, S; Ogawa, K; Isobe, M; Aso, T; Hara, M; Sangaroon, S; Kusaka, S; Tamaki, S; Murata, I; Toyama, S; Miwa, M; Matsuyama, S; Osakabe, M

IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT 73 巻 2024年

掲載種別：研究論文（学術雑誌）出版者・発行元：IEEE Transactions on Instrumentation and Measurement

This article presents the method to evaluate the fast neutron energy spectrum using the single-crystal chemical vapor deposition (CVD) diamond detector to be applicable on the radiation monitoring in advanced scientific/engineering systems usually characterized with mixed and high-dose radiation field. The pulse shape discrimination (PSD) based on the shape and the width of a pulse was applied to extract events, in which fast neutron hits at the specific depth of the single-crystal diamond. Unfolding of the measured spectrum for extracted pulses could deduce the neutron energy spectrum. Experiments using monoenergetic neutron sources demonstrated the reliable capability of this method to evaluate the neutron energy spectrum quantitatively.

DOI： 10.1109/TIM.2024.3481590

Precise thermoluminescence glow curve analysis of BeO ceramic plates with slow heating rates

Sasaki, E; Sugioka, N; Chang, WS; Matsumoto, S; Negishi, T; Nagasaka, K; Yoshihashi, S; Uritani, A; Watanabe, K; Okada, G; Koba, Y; Shinsho, K

JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS 34 巻 ( 31 ) 2023年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Materials Science: Materials in Electronics

The glow curve components and thermoluminescence (TL) parameters of BeO ceramics plates with high bioequivalence were analyzed using extremely slow heating rates. Thermalox 995 was used as the BeO ceramic plates, which is a material with a BeO content of 99.5% or higher. The size of the plates was 10 × 10 × 0.7 mm3 with a density of 2.85 g/cm3, and an effective atomic number of 7.13. A linear accelerator was used for irradiation of the BeO plates at 5 Gy of 6 MV X-rays. After irradiation, the TL glow curve was measured using an in-house developed measurement instrument; the TL intensity was recorded from 50 to 400 °C with heating rates of 0.133, 0.05, and 0.005 °C/s used in three patterns. General-order kinetics were used for the theoretical analysis, which takes recapture into account. After irradiation, post-annealing was performed in the range of 50 to 350 °C at 50 °C intervals, and component analysis of the glow curves was also performed. The TL parameters were calculated from glow curves measured up to a heating rate that was three orders of magnitude slower than that previously measured. The activation energy and frequency factor for the main glow component at low temperatures were 1.15 eV and 1.11 × 1011/s, respectively, while those for the main glow component at high temperatures were 1.74 eV and 8.65 × 1013/s. The glow peak for the BeO ceramic plates were also determined have a low TL intensity component in close proximity to these two glow components. Furthermore, an increase in TL efficiency was observed when the glow curve was measured using an extremely slow heating rate. This may be due to a change of the carriers from TL-inactive when the glow curve is measured with a fast heating rate to TL-active with a longer thermal excitation time.

DOI： 10.1007/s10854-023-11378-7

Measurement of 6Li burn-up reaction rate using a single crystal CVD diamond detector under fast neutron irradiation environment

Kobayashi, MI; Yoshihashi, S; Ogawa, K; Isobe, M; Miwa, M; Toyama, S; Matsuyama, S; Osakabe, M

FUSION ENGINEERING AND DESIGN 193 巻 2023年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Fusion Engineering and Design

The study aimed to develop a technique for measuring the 6Li burn-up rate using a single crystal diamond (SCD) detector (SDD) made by chemical vapor deposition (CVD) with a thin lithium fluoride foil. The method relied on pulse shape discrimination (PSD) to separate pulses by nuclear reaction products of 6Li from pulses due to fast neutrons and gamma-rays. By applying the PSD method, the rectangular shape pulses induced by events occurred at the specific depth positions of the SCD, i.e., the incident surface, the ballistic center region (BCR), and the rear surface, were extracted. Thereafter, pulses occurred each specific depth position of the SCD were discriminated according to the pulse width. Due to a short range of nuclear reaction products in the SCD, pulses at the incident surface should be induced by both fast neutrons and nuclear reaction products, although pulses at the BCR are caused by fast neutron only. The study demonstrated that quantitative measurements of nuclear reaction products in the 6Li burn-up reaction under fast neutron irradiation can be achieved using only one SDD by analyzing event rates at the incident surface and in the BCR region.

DOI： 10.1016/j.fusengdes.2023.113799

(12)光ファイバ型中性子検出器を用いた原子炉特性の計測

渡辺賢一, 吉橋幸子, 石川諒尚, 若林源一郎

近畿大学原子炉利用共同研究等経過報告書令和3年度頁： 61 - 64 2023年3月

Neutron/γ-ray discrimination based on the property and thickness controls of scintillators using Li glass and LiCAF (Ce) in a γ-ray field 査読有り

Kaburagi M., Shimazoe K., Terasaka Y., Tomita H., Yoshihashi S., Yamazaki A., Uritani A., Takahashi H.

Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 1046 巻 2023年1月

Neutron/y-ray discrimination based on the property and thickness controls of scintillators using Li glass and LiCAF (Ce) in a y-ray field 査読有り

Kaburagi Masaaki, Shimazoe Kenji, Terasaka Yuta, Tomita Hideki, Yoshihashi Sachiko, Yamazaki Atsushi, Uritani Akira, Takahashi Hiroyuki

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 1046 巻 2023年1月

Measurements of <i>γ</i>-rays and neutrons in BNCT irradiation field using thermoluminescent phosphor

Shinsho, K; Oh, R; Tanaka, M; Sugioka, N; Tanaka, H; Wakabayashi, G; Takata, T; Chang, WS; Matsumoto, S; Okada, G; Sugawara, S; Sasaki, E; Watanabe, K; Koba, Y; Nagasaka, K; Yoshihashi, S; Uritani, A; Negishi, T

JAPANESE JOURNAL OF APPLIED PHYSICS 62 巻 ( 1 ) 2023年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Boron neutron capture therapy (BNCT) is an innovative cancer therapy that selectively destroys only cancer cells by utilizing the reaction between boron agents, which selectively accumulate in cancer cells, and neutron beams. However, the irradiation field in BNCT is a mixture of multiple radiation types, making accurate dose evaluation difficult. For dose evaluation in cancer tissue, which is particularly important, it is essential to discriminate between neutrons and γ-rays mixed in the BNCT irradiation field and to measure them correctly. In this paper, we introduce a new method for selective measurement of neutrons and γ-rays using a thermoluminescent phosphor, which is expected to be a promising method for improving the accuracy of dose evaluations.

DOI： 10.35848/1347-4065/ac971e

Evaluation of heat removal performance of a sealed Li target for an accelerator-driven neutron source of Boron Neutron Capture Therapy at Nagoya University

Honda, S; Yoshihashi, S; Hamaji, Y; Shen, JJ; Tsuchida, K; Nishitani, T; Kiyanagi, Y; Tsurita, Y; Watanabe, K; Yamazaki, A; Uritani, A

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 1042 巻 2022年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

An accelerator-driven neutron source has been developed in Nagoya University for boron neutron capture therapy using a new concept of thick lithium (Li) target in which protons are stopped in a Li layer. A sealed Li target developed consists of a Li sheet placed on a copper (Cu) base plate equipped with water-cooled channels and a titanium (Ti) foil seal to cover Li surface. The proton beam injected into the target is produced through the proton–Dynamitron accelerator (IBA) with a maximum energy of 2.8 MeV and a current of 15 mA. The results of our previous study confirmed that the target was not damaged when irradiated with an acceleration energy of 1.8 MeV and a current of 0.5 mA (heat input of 4.6 MW/m2). To keep the soundness of the target up to 6–7 MW/m2, it is considered to be essential to improve the bonding between the Ti foil and Li interface, which will contribute the heat removal. It was suggested from our previous experiences that the bonding property may be improved by forming a Cu–Li alloy at the Ti–Li interface. In this paper, we evaluate the heat removal performance of a sealed Li target with Cu–Li alloy formation to improve the target durability. The sealed Li target was produced using a “Cu-coated pure Ti foil”, in which Cu was deposited on the surface of a Ti foil with a thickness of 0.2μm. The use of Cu-coated pure Ti foil actively forms Cu–Li alloys at the Ti–Li interface. For comparison, sealed Li targets were produced with pure Ti foil, and irradiation tests were conducted on each target. The heat removal performance was evaluated by electron beam irradiation using the active cooling teststand 2 (ACT2), a high heat flux test facility, and proton beam irradiation using the Dynamitron accelerator. We obtain a result that the Cu-coated pure Ti foil-sealed Li target has a heat removal capacity of 11 MW/m2, about five times higher than that of the pure Ti foil-sealed Li target. This confirmed that the Cu–Li alloy contributed to the improvement of the heat removal performance. For the proton beam irradiation test, a Cu-coated pure Ti foil target was produced and irradiated for 26 h at an acceleration energy of 1.8 MeV and an average current of 3.5 mA, where no neutrons were generated. The tests confirmed that the Cu-coated pure Ti foil target could withstand 26 h of irradiation at a heat input of 9.0 MW/m2. About anticipated degradation of the heat removal performance due to stopping the protons in the Li layer, no change was observed during this long irradiation test, in which 2.15 × 1024 protons were injected into the Li layer. Although further long-time irradiation test will be needed in the future, at present we have confirmed that there is no problem with stopping protons in the Li layer.

DOI： 10.1016/j.nima.2022.167414

γ-Ray measurements in boron neutron capture therapy using BeO ceramic thermoluminescence dosimeter

Tanaka, M; Oh, R; Sugioka, N; Tanaka, H; Takata, T; Wakabayashi, G; Sugawara, S; Watanabe, K; Uritani, A; Yoshihashi, S; Nagasaka, K; Okada, G; Negishi, T; Shinsho, K

JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS 33 巻 ( 25 ) 頁： 20271 - 20279 2022年9月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Materials Science: Materials in Electronics

In boron neutron capture therapy (BNCT), neutrons and γ-rays cause different biological effects, and it is necessary to discriminate between them for treatment planning and periodic inspections. Currently, the BeO powder thermoluminescence dosimeter (BeO powder TLD) is used for γ-ray dosimetry in mixed neutron and γ-ray fields due to the small capture cross section for neutrons, but correction is required because of the effects of neutron-induced activation. Besides, sales of BeO powder TLDs have been discontinued because the highly toxic BeO is readily dispersed when the detector is damaged. Therefore, the development of alternative replacement technologies for BeO powder TLDs that are not affected by neutrons is an important issue. In this study, we investigated the measurement of the γ-ray dose during BNCT using a BeO ceramic TLD, whereby the BeO was not released into the air. After 5, 15, 30, and 60 min of irradiation using the Kyoto University Research Reactor, the amount of thermoluminescence (TL) from the BeO ceramic TLD was shown to increase with irradiation time. In addition, the γ-ray dose, which was derived by converting the amount of TL to the dose, showed excellent proportionality to the irradiation time and was found to be comparable to the γ-ray dose measured with a BeO powder TLD. These results demonstrated that the BeO ceramic TLD can selectively measure only the γ-ray dose without influence by neutrons. Thus, our approach represents a new γ-ray dose measurement strategy that does not require correction for the contribution from thermal neutrons.

DOI： 10.1007/s10854-022-08843-0

Neutronics Analyses of the Radiation Field at the Accelerator-Based Neutron Source of Nagoya University for the BNCT Study Open Access

Nishitani, T; Yoshihashi, S; Tanagami, Y; Tsuchida, K; Honda, S; Yamazaki, A; Watanabe, K; Kiyanagi, Y; Uritani, A

JOURNAL OF NUCLEAR ENGINEERING 3 巻 ( 3 ) 頁： 222 - 232 2022年9月

掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Nuclear Engineering

The Nagoya University Accelerator-driven Neutron Source (NUANS) is an accelerator-based neutron source by 7Li(p,n)7Be reaction with a 2.8 MeV proton beam up to 15 mA. The fast neutrons are moderated and shaped to beam with a Beam Shaping Assembly (BSA). NUANS is aiming at the basic study of the Boron Neutron Capture Therapy (BNCT) such as an in vitro cell-based irradiation experiment using a water phantom. Moreover, the BSA is developed as a prototype of one for human treatment. We have evaluated the radiation field of NUANS by a Monte Carlo code PHITS. It is confirmed that the radiation characteristics at the BNCT outlet meet the requirement of IAEA TECDOC-1223. Additionally, the radiation field in the water phantom located just in front of the BSA outlet is calculated. In the in vitro irradiation experiment, the boron dose of 30 Gy-eq, which is the dose to kill tumor cells, is expected for 20 min of irradiation at the beam current of 15 mA.

DOI： 10.3390/jne3030012

Evaluation of Induced Radioactivity Generated during LHD Deuterium Plasma Experiments*) Open Access

Yoshihashi, S; Yamada, H; Kobayashi, M; Nishitani, T; Yamazaki, A; Isobe, M; Ogawa, K; Uritani, A

PLASMA AND FUSION RESEARCH 17 巻 ( 0 ) 頁： 2405096 - 2405096 2022年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人プラズマ・核融合学会

Neutrons are generated in a fusion plasma and induce various radionuclides via a nuclear reaction with fusion reactor materials. Evaluating the kinds of nuclide and the amount of induced radioactivity is important for decommissioning planning and regular maintenance. In this study, we verified a long-term prediction model of induced radioactivity in the large helical device (LHD) model by comparing induced radioactivity generated during deuterium plasma experiments in LHD with results calculated using a high-energy particle-induced radioactivity code. The metals employed for activation were SUS316L, Co, Mo, and Ni. During the deuterium plasma experiments, these materials were placed on an 8-O port of the LHD, and the induced radioactivity was measured weekly. To computed induced radioactivity using DCHAIN-SP, the neutron energy spectrum was computed using the LHD model with the Monte-Carlo simulation code PHITS. Although the calculated and measured radioactivity of 58Co and 54Mo agreed well, the calculated values of 60Co and 99Mo were underestimated. However, low-energy components could be improved by incorporating peripheral devices into the LHD model, resulting in more accurate radioactivity predictions

DOI： 10.1585/pfr.17.2405096

Development of a simple calculation tool of dose distributions in a phantom for boron neutron capture therapy Open Access

Ishikawa, A; Watanabe, K; Yoshihashi, S; Sakurai, Y; Kumada, H; Tanaka, H; Uritani, A; Kiyanagi, Y

JAPANESE JOURNAL OF APPLIED PHYSICS 61 巻 ( 7 ) 2022年7月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

A simple dose calculation tool, SiDE, was developed for dose evaluation in a water phantom for boron neutron capture therapy, which makes the calculation time much shorter compared with the conventional particle transportation Monte Carlo codes and is applicable to any type of incident neutron spectra to the phantom. As the SiDE can not only calculate quantitatively the dose distribution in the phantom but also output dose indexes such as advantage depth and peak tumor dose, a comparison between different boron neutron capture therapy neutron sources can be easily performed. Consistency with a Monte Carlo transportation code was verified through comparison with the conventional dose calculation with the Particle and Heavy Ion Transport Code System, and the calculation time was nearly 1/90 in the SiDE. The dose distributions for a reactor and accelerator-based neutron sources were compared, and the differences were found to be small although large differences existed between the incident spectra.

DOI： 10.35848/1347-4065/ac7273

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