Development of -ray visualization survey meter in high gamma and neutron background environment

Tsubota, Yoichi; Kobayashi, Kenji; Ishii, Tatsuya; Hirato, Misaki; Shioya, Satoshi; Nakagawa, Takahiro

Radiation Protection Dosimetry, 200(16-18), p.1676 - 1680, 2024/11

https://doi.org/10.1093/rpd/ncae169

In the decommissioning of the Fukushima Daiichi Nuclear Power Station (FDNPS, 1F), workers are removing structures from inside the buildings, monitoring radioactive contamination, and decontaminating inside the buildings. For the measurement of contamination of suit surfaces of workers, we have developed a hand-held survey meter that can measure and visualize surface radioactive contamination of -nuclides in a high / -ray background environment. In order to selectively measure -nuclides, we designed and built a prototype hand-held survey meter for -rays, which consists of a thin-film ZnS:Ag scintillator, a multi-anode photomultiplier tube (MA-PMT), individual amplification and counting circuits for each channel of the MA-PMT. Based on the result of -ray counting, the developed device is capable of counting the -radiation beyond 2.110 cpm. In the -ray response test, there was no -ray response even when the detector was in close proximity to a high intensity source; The dose rate was estimated to be more than 1 Sv/h. In the future, we plan to reduce the weight and size of the device, as well as improve the usability of the device through actual testing in contaminated environments.

Evaluation of materials for developing a new individual dosemeter using electron spin resonance spectroscopy

Kitamura, Yoshimasa; Oka, Toshitaka; Seito, Hajime*; Yokozuka, Eri*; Nagasawa, Naotsugu*; Kitatsuji, Yoshihiro

Radiation Protection Dosimetry, 200(16-18), p.1660 - 1665, 2024/11

https://doi.org/10.1093/rpd/ncae194

In this work, we evaluated the applicability of hydroxyapatite, which is a main component of tooth enamel, as individual dosimeters that can detect from less than 1 Gy to several tens Gy. Commercially available hydroxyapatite was irradiated by Co gamma-ray up to 75 Gy and ESR spectrum of the irradiated sample was observed. The relationship between the intensity of produced carbonated radical and the absorbed dose shows a good linearity () from 0 to 75 Gy. The detection limit of this samples was estimated to be 99.7 mGy, and the radical intensity do not change for eight month from the irradiation. These results suggest that this sample can be used as a candidate of the individual dosimeter.

Establishment of a 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

https://doi.org/10.1093/rpd/ncae186

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

https://doi.org/10.1093/rpd/ncad278

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.

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

https://doi.org/10.1093/rpd/ncad150

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.

Development of a method of evaluating PuO 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

https://doi.org/10.1093/rpd/ncad186

It is very important to evaluate the diameters (activity median aerodynamic diameter) of Plutonium dioxide (PuO) particles for internal exposure dose evaluation. In this study, a method of evaluating PuO particle diameters using an alpha-particle imaging detector was developed. PuO 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 PuO and the case of PuO (including isotopic composition of Pu). Multiple regression analysis was performed to determine the PuO 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.

SUMRAY: R and Python codes for calculating cancer risk due to radiation exposure of a population

Sasaki, Michiya*; Furukawa, Kyoji*; Satoh, Daiki; Shimada, Kazumasa; Kudo, Shinichi*; Takagi, Shunji*; Takahara, Shogo; Kai, Michiaki*

Journal of Radiation Protection and Research, 48(2), p.90 - 99, 2023/06

https://doi.org/10.14407/jrpr.2022.00213

This paper reports on the calculation code that is the result of the activities of the "Task Group for Development of Cancer Risk Estimation Codes Associated with Radiation Exposure (FY2020-2021)" established by the Japan Health Physics Society. In order to promote research on the estimation of cancer risk associated with radiation exposure, the Task Group decided to disclose the source code, including the algorithm and parameters used in the calculations, and to release the code under a license that permits modification and redistribution of the code. The computational code was named SUMRAY and coded in two computer languages, that is R and Python. The code is capable of calculating the accumulated excess risk using Monte Carlo methods with a 95% confidence interval. The results of SUMRAY were compared with the results of the existing codes whose source code is not publicly available, under the same calculation conditions. From the results, it was found that they were in reasonable agreement within the confidence interval. It is expected that SUMRAY, an open-source software, will be used as a common basis for cancer risk estimation studies associated with radiation exposure.

MATXS multigroup file problem due to NJOY unresolved resonance processing

Konno, Chikara; Tada, Kenichi; Kwon, Saerom*

Proceedings of 14th International Conference on Radiation Shielding and 21st Topical Meeting of the Radiation Protection and Shielding Division (ICRS-14/RPSD 2022) (Internet), p.440 - 443, 2022/11

Neutron spectra inside a sphere of 1 m in radius, made of one natural isotope with unresolved resonance data, with an isotropic neutron source of 20 MeV at the center were calculated with the ANISN code and JENDL-4.0 MATXS file MATXSLIB-J40. Then unphysical neutron spectra produced in unresolved resonance data processing with the NJOY code were obtained. We examined its reasons and specified that unrealistic cross sections in dips between resonances caused the unphysical neutron spectra. We also demonstrated that this problem was solved by modifying NJOY.

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

https://doi.org/10.1093/rpd/ncac167

Influence of differences in model parameters observed in Europe and Japan, on the effective dose predicted by the European model for inhabited areas (ERMIN)

Hirouchi, Jun; Charnock, T.*

Proceedings of 14th International Conference on Radiation Shielding and 21st Topical Meeting of the Radiation Protection and Shielding Division (ICRS-14/RPSD 2022) (Internet), p.195 - 198, 2022/09

ERMIN (EuRopean Model for Inhabited Areas), which was compared and validated with other models by EMRAS II program, is a code that provides a module to two European nuclear accident decision support systems and calculates doses for people in inhabited areas contaminated by radionuclides. Parameters in ERMIN are principally based on observations after the Chernobyl accident. However, these parameters may differ among countries. In order to understand the uncertainty and variability of calculated doses when applying ERMIN elsewhere, it is important to investigate the degree of influence of each parameter on doses. Therefore, in this study, the parameters in Japan obtained by our literature surveys were compared with those used in ERMIN. We calculated doses using the values and uncertainties of those parameters and investigated the differences in doses and the influence of each parameter on doses. The results showed that the retention parameters, soil migration parameters, air exchange rate, and indoor deposition rate have a significant influence on the dose assessment.