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Journal Articles

Establishment of a $$^{241}$$Am gamma calibration field based on international standards and its conversion coefficients

Tsuji, Tomoya; Yoshitomi, Hiroshi; Kowatari, Munehiko*; Tanimura, Yoshihiko

Radiation Protection Dosimetry, 200(15), p.1416 - 1424, 2024/09

 Times Cited Count:0 Percentile:0.00(Environmental Sciences)

Journal Articles

Analysis of the relationship between ambient dose, ambient dose equivalent and effective dose in operational neutron spectra

Endo, Akira

Radiation Protection Dosimetry, 200(13), p.1266 - 1273, 2024/08

 Times Cited Count:0 Percentile:0.00(Environmental Sciences)

This study examines the relationship between ambient dose $$H^*$$, ambient dose equivalent $$H^*(10)$$, and effective dose for external neutron irradiation over 163 operational spectra from different workplaces. The results show that $$H^*$$ provides a reasonable estimate with a controlled margin, even if overestimated, to assess effective dose compared with $$H^*(10)$$, which can lead to a significant overestimation or underestimation of effective dose depending on the neutron spectra. The results highlight the limitations of $$H^*(10)$$ and the superiority of $$H^*$$ in estimating effective dose according to the requirements of the operational quantity, especially in environments with high-energy neutrons.

Journal Articles

Development of DynamicMC for PHITS Monte Carlo package

Watabe, Hiroshi*; Sato, Tatsuhiko; Yu, K. N.*; Zivkovic, M.*; Krstic, D.*; Nikezic, D.*; Kim, K. M.*; Yamaya, Taiga*; Kawachi, Naoki*; Tanaka, Hiroki*; et al.

Radiation Protection Dosimetry, 200(2), p.130 - 142, 2024/02

 Times Cited Count:1 Percentile:41.04(Environmental Sciences)

Previously, we have developed DynamicMC for modelling relative movement of ORNL phantom in a radiation field for MCNP. Using this software, 3-dimensional dose distributions in a phantom irradiated by a certain mono-energetic source can be deduced through its graphical user interface (GUI). In this study, we extended DynamicMC to be used in combination with the PHITS by providing it with a higher flexibility for dynamic movement for a less sophisticated anthropomorphic phantom. We anticipate that the present work and the developed open-source tools will be in the interest of nuclear radiation physics community for research and teaching purposes.

Journal Articles

Interlaboratory comparison of electron paramagnetic resonance tooth enamel dosimetry with investigations of the dose responses of the standard samples

Toyoda, Shin*; Inoue, Kazuhiko*; Yamaguchi, Ichiro*; Hoshi, Masaharu*; Hirota, Seiko*; Oka, Toshitaka; Shimazaki, Tatsuya*; Mizuno, Hideyuki*; Tani, Atsushi*; Yasuda, Hiroshi*; et al.

Radiation Protection Dosimetry, 199(14), p.1557 - 1564, 2023/09

 Times Cited Count:1 Percentile:41.04(Environmental Sciences)

Interlaboratory comparison studies are important for radiation dosimetry in order to demonstrate how the technique is universally available. The set of standard samples are examined in each participating laboratory in the present study. After a set of standard samples together with the samples with unknown doses, which were prepared in the same laboratory as the standard samples, are measured at a participating laboratory, those samples are sent to another participating laboratory for next measurement. There is some small difference observed in the sensitivity (the slope of the dose response line) of the standard samples while the differences in the obtained doses for the samples with unknown doses are rather systematic, implying that the difference is mostly due to the samples but not to measurements.

Journal Articles

Estimation of external dose for wild Japanese macaques captured in Fukushima prefecture; Decomposition of electron spin resonance spectrum

Mitsuyasu, Yusuke*; Oka, Toshitaka; Takahashi, Atsushi*; Kino, Yasushi*; Okutsu, Kenichi*; Sekine, Tsutomu*; Yamashita, Takuma*; Shimizu, Yoshinaka*; Chiba, Mirei*; Suzuki, Toshihiko*; et al.

Radiation Protection Dosimetry, 199(14), p.1620 - 1625, 2023/09

 Times Cited Count:0 Percentile:0.00(Environmental Sciences)

We have been conducting dose assessments for Japanese macaques captured in Fukushima to reveal radiobiological effects on the low-dose expose animals. To accurately determine the external exposure dose, it is desirable to examine the analysis of the CO$$_{2}^{-}$$ radical intensity. We examined ESR spectra of teeth of 10 macaques captured in Fukushima by two spectrum-decomposition algorithms.

Journal Articles

Development of a method of evaluating PuO$$_{2}$$ particle diameters using an alpha-particle imaging detector

Morishita, Yuki; Sagawa, Naoki; Takada, Chie; Momose, Takumaro; Takasaki, Koji

Radiation Protection Dosimetry, 199(13), p.1376 - 1383, 2023/08

 Times Cited Count:1 Percentile:41.04(Environmental Sciences)

It is very important to evaluate the diameters (activity median aerodynamic diameter) of Plutonium dioxide (PuO$$_{2}$$) particles for internal exposure dose evaluation. In this study, a method of evaluating PuO$$_{2}$$ particle diameters using an alpha-particle imaging detector was developed. PuO$$_{2}$$ particles with different diameters were modeled by Monte Carlo simulation, and the change in the shape of the energy spectrum for each particle diameter was evaluated. Two different patterns were modeled, namely, the case of $$^{239}$$PuO$$_{2}$$ and the case of PuO$$_{2}$$ (including isotopic composition of Pu). Multiple regression analysis was performed to determine the PuO$$_{2}$$ particle diameter from the obtained parameters. The simulated diameters and the diameters obtained with the regression model were in good agreement. The advantage of using the alpha-particle imaging detector is to measure the alpha energy spectrum for individual particle, and this allows accurate measurement of particle diameter distribution.

Journal Articles

Estimation of inhomogeneous occupational exposure to the lens of the eyes and the extremities of radiation workers in a research accelerator facility

Kowatari, Munehiko*; Kubota, Takumi*; Yoshitomi, Hiroshi; Kunugita, Naoki*

Radiation Protection Dosimetry, 199(11), p.1239 - 1247, 2023/07

 Times Cited Count:0 Percentile:0.00(Environmental Sciences)

Journal Articles

Visualization software for radioactive contamination based on Compton camera: COMRIS

Sato, Yuki; Minemoto, Kojiro*; Nemoto, Makoto*

Radiation Protection Dosimetry, 199(8-9), p.1021 - 1028, 2023/06

 Times Cited Count:2 Percentile:65.72(Environmental Sciences)

Journal Articles

Dose measurement precision of an RPLD-based eye lens dosemeter applicable to the medical sector

Kowatari, Munehiko*; Nagamoto, Keisuke*; Nakagami, Koichi*; Yoshitomi, Hiroshi; Moritake, Takashi*; Kunugita, Naoki*

Radiation Protection Dosimetry, 198(17), p.1303 - 1312, 2022/10

 Times Cited Count:2 Percentile:38.50(Environmental Sciences)

Journal Articles

Crystal configuration dependence of CsI(Tl) scintillation detectors on environmental dose rate measurement

Tsuda, Shuichi; Saito, Kimiaki

Radiation Protection Dosimetry, 198(17), p.1283 - 1291, 2022/10

 Times Cited Count:0 Percentile:0.00(Environmental Sciences)

Spherical or cylindrical detectors superior to directional characteristic are commonly used to monitor dose rates in the environment to detect scattering gamma-rays emitted from radionuclides in soil or air. The authors have performed environmental dose rates measurements using various kinds of detectors to investigate the directional characteristics, and experimentally verified the variations in dose rates due to directional characteristics unique to each detector. Furthermore, a dose rate measured by a CsI(Tl) scintillation detector with cuboidal crystal agreed with that by a CsI(Tl) scintillation detector with cylindrical crystal. Simulations by PHITS under various CsI(Tl) crystal configurations revealed that there are certain aspect ratios of cuboidal CsI(Tl) crystal with less directional dependence. Since cubes are advantageous in terms of production cost, this result indicates the potential of CsI(Tl) scintillation detectors with cuboidal crystal for use in the environmental dose rate monitoring.

Journal Articles

Performance evaluation of commercial scintillation cocktails for low-level tritium counting by high-capacity liquid scintillation counter

Kuwata, Haruka*; Tazoe, Hirofumi*; Kranrod, C.*; Fujiwara, Kenso; Terashima, Motoki; Matsueda, Makoto; Hirao, Shigekazu*; Akata, Naofumi*

Radiation Protection Dosimetry, 198(13-15), p.1014 - 1018, 2022/09

 Times Cited Count:0 Percentile:0.00(Environmental Sciences)

Journal Articles

Cesium-rich microparticles runoff during rainfall; A Case study in the Takase River

Tatsuno, Takahiro*; Waki, Hiromichi*; Kakuma, Minato*; Nihei, Naoto*; Wada, Toshihiro*; Yoshimura, Kazuya; Nakanishi, Takahiro; Ote, Nobuhito*

Radiation Protection Dosimetry, 198(13-15), p.1052 - 1057, 2022/09

 Times Cited Count:2 Percentile:38.50(Environmental Sciences)

Journal Articles

Development of emergency monitoring system for alpha-particle-emitting radionuclides in the air

Hokama, Tomonori; Fujita, Hiroki; Nakano, Masanao; Iimoto, Takeshi*

Radiation Protection Dosimetry, 196(3-4), p.136 - 140, 2021/11

 Times Cited Count:0 Percentile:0.00(Environmental Sciences)

During the early phase of a nuclear accident, major radioactive materials are released into the environment, necessitating the prompt deployment of various protective actions to avoid or reduce radiation exposure. To implement these actions, the levels of radioactivity in the environment should be determined. However, the radioactivity concentrations of artificial alpha-particle-emitting radionuclides such as plutonium are difficult to measure in airborne samples, because they are interfered with natural radionuclides such as uranium decay products. Therefore, chemical separation is required to measure the concentrations. This study presents a new emergency monitoring system for airborne samples, which performs multiple-pulse time-interval analysis (MTA) without chemical separation. The system is used in conjunction with an alpha/beta-particle survey meter and adopted an analysis method focusing on the detected time interval of each particle. Its features are that a short time to output measurement result, easy handling and nondestructive. The estimated detection limit of the system was 9.5$$times$$10$$^{-2}$$ Bq m$$^{-3}$$. The MTA-based monitoring system could be useful in situations requiring prompt measurement and screening of samples.

Journal Articles

Analyses of $$H$$*(10) dose rates measured in environment contaminated by radioactive caesium; Correction of directional dependence of scintillation detectors

Tsuda, Shuichi; Tanigaki, Minoru*; Yoshida, Tadayoshi; Okumura, Ryo*; Saito, Kimiaki

Radiation Protection Dosimetry, 193(3-4), p.228 - 236, 2021/03

AA2020-0760.pdf:0.87MB

 Times Cited Count:3 Percentile:37.09(Environmental Sciences)

Environmental dose rate monitoring has been performed with various scintillation detectors since the Fukushima Dai-ichi Nuclear Power Plant accident. Gamma-rays from caesium isotopes deposited in soil enter radiation detectors in any direction, but directional dependence of the detectors used for dose rate measurements are not always uniform and the dose rates vary even if measurement takes place at the same place. To investigate the influence of crystal configurations on dose rate, dose rate measurements using several scintillation detectors with different crystal configurations were conducted. By measuring pulse height spectra and multiplying them with spectrum - dose conversion operators (G(E) function), dose rates were deduced and compared. It was found that the dose rates varied within approximately 25% among six detectors. To reduce the differences, the dose rate using G(E) functions determined in rotational geometry were obtained and applied instead. The revised dose rates agreed with one another within uncertainties, but this was not the case of scintillation detector with flat crystal shape, and it means this method could not compensate its strong directional dependence. These experimental results reveal that detectors with superior directional characteristics should be used for environmental dose rate measurement since the compensation of directional dependence using a G(E) function determined in rotational geometry is not always available.

Journal Articles

Methodology for simple spot measurement of equilibrium equivalent radon concentration

Sakoda, Akihiro; Ishimori, Yuu; Kanzaki, Norie; Tanaka, Hiroshi

Radiation Protection Dosimetry, 191(4), p.383 - 390, 2020/10

 Times Cited Count:1 Percentile:10.11(Environmental Sciences)

Estimation of the effective inhalation dose of short half-life radon progeny requires the quantification of radon equilibrium equivalent activity concentrations (EEC). The aim of the present study is to develop new methodology that focuses on spot measurements to determine EEC from single gross alpha counts and determine an optimized protocol. The core of the approach is to measure alpha particles over time when the radon progeny attached to the sampling filter are significantly disintegrated. The calibration curve of single counts to EEC is theoretically deduced and validated by a comparison test. The advantage of the present method is its minimal requirements, including the use of common instruments and simple sampling, alpha counting, and analysis procedures. This approach offers an option for radon practitioners working in a variety of fields, as well as the possibility for non-experts to easily measure EEC.

Journal Articles

Organ absorbed dose estimation reflecting specific organ masses with simple scaling of reference doses using the organ masses

Manabe, Kentaro; Koyama, Shuji*

Radiation Protection Dosimetry, 189(4), p.489 - 496, 2020/05

AA2019-0343.pdf:0.67MB

 Times Cited Count:1 Percentile:10.11(Environmental Sciences)

It is important for radiation protection in diagnostic nuclear medicine to estimate organ absorbed doses in consideration of person-specific parameters. This study proposes a straightforward method for estimating organ doses which reflect an individual organ masses by scaling the reference doses based on the reference human models using the inverse ratio of the individual masses to the reference organ masses. The method was tested for the administration cases of $$^{rm 99m}$$Tc-labelled colloids and $$^{123}$$I-labelled sodium iodine to confirm the effectiveness of the method. The discrepancies of the doses estimated by the method were sufficiently small in terms of solid organs.

Journal Articles

Conversion factor from dosemeter reading to air kerma for nuclear worker using anthropomorphic phantom for further conversion from air kerma to organ-absorbed dose

Furuta, Hiroshige*; Tsujimura, Norio; Nishide, Akemi*; Kudo, Shinichi*; Saigusa, Shin*

Radiation Protection Dosimetry, 189(3), p.371 - 383, 2020/05

 Times Cited Count:5 Percentile:47.80(Environmental Sciences)

Journal Articles

Experimental determination of anisotropic emission of neutrons from $$^{252}$$Cf neutron source with the spherical protection case

Kowatari, Munehiko; Nishino, Sho; Romallosa, K. M. D.*; Yoshitomi, Hiroshi; Tanimura, Yoshihiko; Oishi, Tetsuya

Radiation Protection Dosimetry, 189(4), p.436 - 443, 2020/05

 Times Cited Count:0 Percentile:0.00(Environmental Sciences)

The anisotropic emission of neutrons from a cylindrical X1 $$^{252}$$Cf source with the spherical external casing was experimentally determined. The influence of metal materials and shapes of the external casing to the anisotropy factor, $$F_{I}$$($$theta$$) was assessed by the Monte Carlo calculation, before performing the measurement. The results of the calculation result implied that light and spherical-shaped external casing decreases the anisotropic emission of neutrons from a cylindrical source and the nature of the material does not affect the anisotropic emission to a large extent. The experimental results obtained when a spherical-shaped aluminum protection case was employed also revealed that the anisotropy factor was close to 1.0 with a wide zenith angle range.

Journal Articles

A Remote continuous air monitoring system for measuring airborne alpha contamination

Morishita, Yuki; Usami, Hiroshi; Furuta, Yoshihiro; Aoki, Katsunori; Tsurudome, Koji; Hoshi, Katsuya; Torii, Tatsuo

Radiation Protection Dosimetry, 189(2), p.172 - 181, 2020/04

 Times Cited Count:0 Percentile:0.00(Environmental Sciences)

We developed a remote continuous air monitoring (RCAM) system. The RCAM system consisted of a personal air monitor and a robot. The personal air monitor (poCAMon, SARAD, Germany) had a 400 mm$$^{2}$$ ion-injected silicon detector and a membrane air filter with 25 mm-diameter. The personal air monitor provides the alpha energy spectra for any measurement time interval. Demonstration measurements were taken underground at the Mizunami Underground Research Laboratory (MIU) and at a poorly ventilated concrete building. The RCAM system was remotely operated and successfully measured the $$^{222}$$Rn progeny even though the relative humidity (RH) was almost 100%. In the measured alpha spectra, the peaks of $$^{218}$$Po (6.0 MeV alpha) and $$^{214}$$Po (7.7 MeV alpha) were clearly identified. Our developed monitor is promising for alpha dust monitoring in a high gamma-ray environment or contaminated areas where a worker cannot safely physically enter.

Journal Articles

Exposure inhomogeneity from $$^{241}$$Am and $$^{90}$$Sr/$$^{90}$$Y sources in terms of the eye lens monitoring in the nuclear facilities

Yoshitomi, Hiroshi; Kowatari, Munehiko

Radiation Protection Dosimetry, 188(2), p.191 - 198, 2020/02

 Times Cited Count:2 Percentile:20.42(Environmental Sciences)

170 (Records 1-20 displayed on this page)