Ji, Y.-Y.*; Ochi, Kotaro; Hong, S. B.*; Nakama, Shigeo; Sanada, Yukihisa; Mikami, Satoshi
Radiation Physics and Chemistry, 179, p.109205_1 - 109205_11, 2021/02
In situ gamma-ray spectrometry using diverse survey platforms has been conducted in contaminated areas with several dose rate levels around the Fukushima Daiichi Nuclear Power Plant (FDNPP). Six survey sites, including two evacuation zones around the FDNPP, were selected for ground-based gamma-ray spectrometry using HPGe (high purity Ge) and LaBr(Ce) detectors to assess the radioactive cesium deposition in the ground. The diverse levels of radioactivity of Cs were then distributed to six survey sites from 30 to 3000 kBq m in the measurement period of October 2018. A method to directly calculate the depth profile using in situ measurement was introduced so as to have representation over a wide area, and the results were successfully compared with those of sample analysis at one point in the site.
Matsumura, Taichi; Nagaishi, Ryuji; Katakura, Junichi*; Suzuki, Masahide*
Radiation Physics and Chemistry, 166, p.108493_1 - 108493_9, 2020/01
In this work, when radiation sources of Cs, Sr and Y were assumed to be put in the front of a plain SUS304 plate as a typical material submerged in water, energy spectra of secondary photons and electrons at the front and back sides of plate were simulated with changing the thickness of plate, and spacing between the source and plate by using a Monte Carlo calculation code of PHITS. In the case of Cs gamma-ray (monochromatic 662 keV), the energy spectra at the front side was smaller than those at the back side due to the existence of plate. Then the dependence of spectra on the plate thickness was observed more clearly at the back side than at the front side. It was clearly shown how the energy spectra of photons and electrons varied with the incident radiation type, the spacing, and the thickness.
Kakitani, Kenta*; Kimata, Tetsuya*; Yamaki, Tetsuya*; Yamamoto, Shunya*; Matsumura, Daiju; Taguchi, Tomitsugu*; Terai, Takayuki*
Radiation Physics and Chemistry, 153, p.152 - 155, 2018/12
Seko, Noriaki*; Hoshina, Hiroyuki*; Kasai, Noboru*; Shibata, Takuya; Saiki, Seiichi*; Ueki, Yuji*
Radiation Physics and Chemistry, 143, p.33 - 37, 2018/02
Hirouchi, Jun; Takahara, Shogo; Iijima, Masashi; Watanabe, Masatoshi; Munakata, Masahiro
Radiation Physics and Chemistry, 140, p.127 - 131, 2017/11
Saegusa, Jun; Yanagisawa, Kayo; Hasumi, Atsushi; Shimizu, Takenori; Uchida, Yoshiaki*
Radiation Physics and Chemistry, 137, p.210 - 215, 2017/08
Following the Fukushima Daiichi Nuclear Power Plant (NPP) accident, large-scale radiation monitoring and environmental clean-up activities have been conducted throughout the Fukushima region. Outside air temperatures there reach 40C in summer and -20C in winter, which are beyond the quoted range of many radiation survey instruments. For the purpose, temperature performances of four types of portable Japanese survey instruments which are widely used in Fukushima were experimentally investigated with a temperature-controlled chamber.
Kitazawa, Sin-iti*; Wakai, Eiichi; Aoto, Kazumi
Radiation Physics and Chemistry, 127, p.264 - 268, 2016/10
The effects of annealing and double ion irradiation on nuclear structural materials were investigated using a novel, non-destructive, non-contact diagnostic method. A laser-induced and laser-detected surface acoustic wave (SAW) was adopted as a diagnostic system. The SAWs propagation velocity and the SAWs vibration velocity along the normal direction of the surface were measured to investigate mechanical properties of the substrates. Change of the shear modulus was detected in the annealed substrates. Non-linear effect on amplitude of the excited SAW was observed on the double ion irradiated materials. The potential of the SAW diagnostic system for assessing nuclear structural materials was demonstrated.
Yang, S.*; Katsumura, Yosuke*; Yamashita, Shinichi*; Matsuura, Chihiro*; Hiroishi, Daisuke*; Lertnaisat, P.*; Taguchi, Mitsumasa
Radiation Physics and Chemistry, 123, p.14 - 19, 2016/06
-radiolysis of boiling water has been investigated. The G-value of H evolution was found to be very sensitive to the purity of water. In high-purity water, both H and O gases were formed in the stoichiometric ratio of 2:1; a negligible amount of HO remained in the liquid phase. The G-values of H and O gas evolution depend on the dose rate: lower dose rates produce larger yields. To clarify the importance of the interface between liquid and gas phase for gas evolution, the gas evolution under Ar gas bubbling was measured. A large amount of H was detected, similar to the radiolysis of boiling water. The evolution of gas was enhanced in a 0.5 M NaCl aqueous solution. Deterministic chemical kinetics simulations elucidated the mechanism of radiolysis in boiling water.
Iwamatsu, Kazuhiro*; Muroya, Yusa*; Yamashita, Shinichi*; Kimura, Atsushi; Taguchi, Mitsumasa; Katsumura, Yosuke*
Radiation Physics and Chemistry, 119, p.213 - 217, 2016/02
A quick measurement system of a continuous absorption spectrum covering a wide range from 200 to 950 nm was constructed by employing an optical multi-channel detector. Ion beam pulse radiolysis with 12.5 MeV/u He, 18.3 MeV/u C and 17.5 MeV/u Ne ions were performed with the measurement system. Transient absorption spectrum of (SCN) was clearly observed in KSCN aqueous solutions within a few minutes in spite of their very small absorbance, demonstrating high sensitivity of 0.001-0.003 in absorbance in the range from 260 to 660 nm as well as short measurement time of a few minutes. Two different absorption peaks attributed to Br and Br were observed simultaneously in NaBr aqueous solutions, showing powerfulness of the measurement system in overviewing chemical kinetics under ion beam irradiation especially in not well investigated chemical systems.
Shibata, Takuya; Seko, Noriaki; Amada, Haruyo; Kasai, Noboru; Saiki, Seiichi; Hoshina, Hiroyuki; Ueki, Yuji
Radiation Physics and Chemistry, 119, p.247 - 252, 2016/02
Tsukuda, Satoshi*; Takahashi, Ryota*; Seki, Shuhei*; Sugimoto, Masaki; Idesaki, Akira; Yoshikawa, Masahito; Tanaka, Shunichiro*
Radiation Physics and Chemistry, 118, p.16 - 20, 2016/01
Polyvinylpyrrolidone (PVP)-Pt nanoparticles (NPs) hybrid nanowires were fabricated by high energy ion beam irradiation to PVP thin films including HPtCl. Single ion hitting caused crosslinking reactions of PVP and reduction of Pt ions within local cylindrical area along an ion trajectory (ion track); therefore, the PVP nanowires including Pt NPs were formed and isolated on Si substrate after wet-development procedure. The number of Pt NPs was easily controlled by the mixed ratio of PVP and HPtCl. However, increasing the amount of HPtCl led to decreasing the radial size and separation of the hybrid nanowires during the wet-development. Additional electron beam irradiation after ion beam improved separation of the nanowires and controlled radial sizes due to an increase in the density of crosslinking points inner the nanowires.
Kai, Takeshi; Yokoya, Akinari; Ukai, Masatoshi*; Fujii, Kentaro; Watanabe, Ritsuko
Radiation Physics and Chemistry, 115, p.1 - 5, 2015/10
Role of secondary electrons on DNA damage have not been understood sufficiently because there still exists a lack of study for thermalization process of an electron in liquid phase. We calculated thermalization lengths and spatial distributions of an electron in liquid water using cross sections for rotation and phonon excitations in a liquid phase. Obtained thermalization lengths are in good agreement with experimental results reported by literatures. Thermalization time was also estimated from time evolution of spatial distributions of the incident electron to be hundreds femtoseconds. From these results, we predict that thermalization and pre-hydration of electron might progress simultaneously. These electrons possibly cause damage in biological molecules in a cell. Particularly severe types of DNA damage consisting of proximately located multiple lesions are potentially induced by reaction of DNA with the thermalized electrons by dissociative electron transfer.
Kai, Takeshi; Yokoya, Akinari; Ukai, Masatoshi*; Watanabe, Ritsuko
Radiation Physics and Chemistry, 108, p.13 - 17, 2015/03
Role of secondary electrons on DNA damage have not been understood sufficiently because there still exists a lack of cross section of rotational and phonon excitation in the liquid phase for precise simulation of the electron behavior. We calculated cross sections, stopping powers, and energy loss rates for the excitations in liquid water. The values for rotation are less by three orders of magnitude than those in the gas phase, while the values for phonon are close to those reported for amorphous ice. Thermalization process has so far been estimated from an assumption that the energy loss rates do not depend strongly on the energy below 1 eV. However, we found that the energy loss rates depend significantly on the energy. This fact indicates that the thermalization time will be longer than the previously estimated time, and we predict that thermalization process strongly involve in subsequent hydrated and chemical processes. The data set provide here is expected to useful to make the role of the secondary electrons on DNA damage much clear.
Maeyama, Takuya*; Fukunishi, Nobuhisa*; Ishikawa, Kenichi*; Furuta, Takuya; Fukasaku, Kazuaki*; Takagi, Shu*; Noda, Shigeho*; Himeno, Ryutaro*; Fukuda, Shigekazu*
Radiation Physics and Chemistry, 107, p.7 - 11, 2015/02
We study the radiological characteristics of VIP polymer gel dosimeters under carbon beam irradiation with energy of 135 and 290 AMeV. To evaluate dose response of VIP polymer gels, the transverse relaxation rate R2 of the dosimeters measured by magnetic resonance imaging (MRI) as a function of linear energy transfer (LET), rather than penetration depth, as is usually done in previous reports. LET is evaluated by use of the particle transport simulation code PHITS. Our results reveal that the dose response decreases with increasing dose-averaged LET and that the response-LET relation also varies with incident carbon beam energy. The latter can be explained by taking into account the contribution from fragmentation products. Furthermore, as an application of the evaluated response-LET relation, we compare the measured and simulated R2 distribution in a VIP gel formed by heterogeneous irradiation and obtain agreement in overall distribution and range within an accuracy of 5% and 1-2 mm, respectively.
Radiation Physics and Chemistry, 104, p.84 - 87, 2014/11
The purpose of this study tries to apply the P-OSL to Japanese surface soil as retrospective dosimetry with ease physical separation. In this study, P-OSL instrument was developed originally. Performance of the instrument was tested using natural quartz extracted from Japanese surface soil and feldspar in mineral specimens. It was found that the signal from the feldspar decayed for 2-3 s and the signal from the quartz was measured over 50 s after the switch-off of the LED. By using mixture of the quartz and feldspar, the P-OSL protocol was improved to determine irradiation dose. Dose recovery test was conducted and then was successful to reconstruct irradiated dose by the P-OSL protocol with the pulse on-time of 4 s and the pulse off-time of 400 s.
Kimura, Atsushi; Nagasawa, Naotsugu; Taguchi, Mitsumasa
Radiation Physics and Chemistry, 103, p.216 - 221, 2014/10
Large quantities of polysaccharide-based biomass are ubiquitous on Earth, and they possess unique structures, distinctive properties, and offer the advantages of being non-toxic and biodegradable. Ionizing radiation is widely used as a convenient tool for the modification of the polysaccharides via decomposition, grafting, and cross-linking. Until now, radiation cross-linked materials have only been produced either from polysaccharide derivatives or using cross-linking reagents, as certain natural polysaccharides have poor solubility in water and organic solvents as well as low chemical reactivity. These limitations could possibly be circumvented by the use of room temperature ionic liquids (RTILs), which can cleave the hydrogen bonds of the polysaccharides to form solutions. In this study, we focus on the application of RTILs as "specific solvents for the dissolution of polysaccharides," and their use in establishing a "proper reaction field for radiation cross-linking." For the first time in this study, we have demonstrated the possibility of producing cellulose gels by -ray irradiation of cellulose in RTILs under humid conditions. The gel fraction could be controlled by adept regulation of following conditions: initial concentration of cellulose, irradiation temperature, water content, and the absorbed dose. The cellulose gel thus obtained had an electronic conductivity of 3.0 mS cm, showing great potential for applications in optoelectronic and medical devices.
Haema, K.*; Oyama, Tomoko; Kimura, Atsushi; Taguchi, Mitsumasa
Radiation Physics and Chemistry, 103, p.126 - 130, 2014/10
For biological and medical applications, radiation sterilization of gelatin was evaluated in terms of radiation stability. It was found that electron beam irradiation decomposed the gelatin and that the weight-averaged molar mass decreased by approximately 7-10% with sterilization doses in the range of 5-25 kGy. Also, we found that the hydrolysis rate in 37C water was affected by the irradiation. On the other hand, crosslinking was predominantly induced when the gelatin was irradiated in water solution and radiation-crosslinked (RX) gelatin hydrogel was fabricated. Using gel fraction and gel permeation chromatography analysis of the eluted sol, it was determined that the RX-gelatin hydrogel was stable for 7 days in water at 37C.
Kai, Takeshi; Yokoya, Akinari; Ukai, Masatoshi*; Fujii, Kentaro; Higuchi, Mariko; Watanabe, Ritsuko
Radiation Physics and Chemistry, 102, p.16 - 22, 2014/09
no abstracts in English
Yamashita, Shinichi*; Hiroki, Akihiro; Taguchi, Mitsumasa
Radiation Physics and Chemistry, 101, p.53 - 58, 2014/08
Idesaki, Akira; Uechi, Hiroki*; Hakura, Yoshihiko*; Kishi, Hajime*
Radiation Physics and Chemistry, 98, p.1 - 6, 2014/05
Effects of -ray irradiation on a cyanate ester/epoxy resin composed of dicyanate ester of bisphenol A (DCBA) and diglycidyl ether of bisphenol A (DGEBA) was investigated by changes in physicochemical and mechanical properties after the -ray irradiation with dose of 100 MGy as maximum at ambient temperature under vacuum. After the irradiation, gases of hydrogen, carbon monoxide and carbon dioxide were evolved, glass transition temperature decreased, and flexural strength also decreased. It was concluded that ether linkages bonded to cyanurate, isocyanurate and oxazolidinone structures are mainly decomposed by the irradiation. After 100 MGy irradiation, the flexural strength of DCBA/DGEBA was maintained more than 170 MPa which is 90% of initial value of 195 MPa.