An Alpha imaging detector for on-site measurement of Plutonium and Neptunium

Morishita, Yuki; DiPrete, D. P.*; Deason, T.*; Nagaishi, Ryuji

Radiation Measurements, 181, p.107366_1 - 107366_8, 2025/02

https://doi.org/10.1016/j.radmeas.2024.107366

Nuclear fuel materials such as Plutonium (Pu) and Neptunium (Np) are produced as by-products of reprocessing operations, necessitating precise understanding of their contamination distribution within controlled areas for radiation protection. This study presents the development and application of an alpha particle imaging detector for on-site detection of Pu and Np contamination. The detector's performance was evaluated using various alpha sources, demonstrating promising energy resolution and spatial resolution. Subsequently, Pu and Np oxide samples were measured at the Savannah River National Laboratory, showing the detector's effectiveness in on-site applications. The detector enabled simultaneous measurement of radioactivity and energy spectrum of individual particles, facilitating rapid discrimination between Pu and Np. The imaging detector has potential for enhancing on-site detection of alpha nuclides in nuclear facilities, aiding in decontamination efforts and environmental monitoring.

Present and new operational quantities evaluated from photon spectrum measurements at workplaces in the research reactor and accelerator facility at the JAEA

Tanimura, Yoshihiko; Yoshitomi, Hiroshi; Nishino, Sho; Tsuji, Tomoya; Fukami, Tomoyo; Shinozuka, Tomoki; Oishi, Kohei; Ishii, Masato; Takamiya, Kei; Onuki, Takaya; et al.

Radiation Measurements, 176, p.107196_1 - 107196_6, 2024/08

https://doi.org/10.1016/j.radmeas.2024.107196

The ICRU has proposed to change the definitions of the operational quantities used for the area and individual monitoring for external exposure in the ICRU Report 95. As introducing the new operational quantities into the radiation monitoring may affect the dose assessment results using the present personal dosimeters, it is necessary to characterize the energy spectrum in the workplace and the energy dependency of the dosimeters to be used. In this work the photon spectra were measured using a NaI(Tl) scintillation detector or a LaBr(Ce) scintillation detector at the workplaces in the Japanese Research Reactor No.3 (JRR-3) and the Japan Proton Accelerator Research Complex (J-PARC) at Japan Atomic Energy Agency (JAEA). Then the present and new operational quantities were evaluated using the above mention spectra at the workplaces and compared each other.

Assessment of ambient dose equivalent rate distribution patterns in a forested-rugged terrain using field-measured and modeled dose equivalent rates

Yasumiishi, Misa*; Masoudi, P.*; Nishimura, Taku*; Ochi, Kotaro; Ye, X.*; Aldstadt, J.*; Komissarov, M.*

Radiation Measurements, 168, p.106978_1 - 106978_16, 2023/11

https://doi.org/10.1016/j.radmeas.2023.106978

In this study, we surveyed air dose rates using hand-held and backpack-type scintillators in a forest of deciduous and evergreen trees in Fukushima Prefecture, Japan. The effects of topographic features on air dose rates were examined using multivariate adaptive regression splines (MARS) against five selected topographic parameters. The air dose rates were distributed unevenly in the forest, and air dose rates varied by more than 1Sv/h as a function of time, likely owing to ground wetness etc. The effect of different topographic parameters varied between survey dates. The MARS model predictions with all topographic parameters yielded an R of 0.54 or higher. To discuss whether the effect of topography on air dose rates and soil contamination levels is consistent, air dose rates measured in the field were compared with those estimated from the depth profile of radiocesium in soil. Most air dose rates estimated from the soil samples were in the range of field measurements.

3D position and radioactivity estimation of radiation source by a simple directional radiation detector combined with structure from motion

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

Radiation Measurements, 142, p.106557_1 - 106557_6, 2021/03

https://doi.org/10.1016/j.radmeas.2021.106557

Measurements of the doses of eye lens for the workers of Fukushima Daiichi Nuclear Power Plant

Yokoyama, Sumi*; Ezaki, Iwao*; Tatsuzaki, Hideo*; Tachiki, Shuichi*; Hirao, Shigekazu*; Aoki, Katsunori; Tanimura, Yoshihiko; Hoshi, Katsuya; Yoshitomi, Hiroshi; Tsujimura, Norio

Radiation Measurements, 138, p.106399_1 - 106399_5, 2020/11

https://doi.org/10.1016/j.radmeas.2020.106399

Radon measurements with a compact, organic-scintillator-based alpha/beta spectrometer

Morishita, Yuki; Ye, Y.*; Mata, L.*; Pozzi, S. A.*; Kearfott, K. J.*

Radiation Measurements, 137, p.106428_1 - 106428_7, 2020/09

https://doi.org/10.1016/j.radmeas.2020.106428

We have developed a compact, organic-scintillator-based alpha/beta spectrometer for radon measurements and have characterized it using a unique, small radon chamber. The spectrometer is composed of a through-silicon via (TSV) silicon photomultiplier (or SiPM) and a 6 mm 6 mm 6 mm stilbene crystal cube. Analog signals from the SiPM are sent to a digitizer. The detector is housed in a light-tight box, with a stacked air filter installed in one side of the box to enable Rn gas to diffuse to the inside. We conducted one experiment with the spectrometer and an AlphaGUARD detector placed in a basement at the University of Michigan, and we conducted other experiments with both detectors placed in a small radon chamber together with Ra sources. By applying a pulse-shape-discrimination technique, we were able to separate the alpha and beta spectra simultaneously and clearly and to measure them quantitatively. We found two peaks in the measured alpha spectrum: a lower-energy peak due to Po and a higher-energy peak due to Po. We found a linear relation between the radon concentration y from AlphaGUARD and the counting rates from the stilbene-SiPM detector. The alpha/beta spectrometer is less than 10 mm thick, and we expect that it will be easy to increase the sensitivity with future device construction. Thus, this compact, organic-scintillator-based alpha/beta spectrometer shows promise for use in novel radon-detection systems.

Prototype test of a portable thyroid dose monitoring system using gamma-ray spectrometers

Nishino, Sho; Tanimura, Yoshihiko; Yoshitomi, Hiroshi; Takahashi, Masa

Radiation Measurements, 134, p.106292_1 - 106292_5, 2020/06

https://doi.org/10.1016/j.radmeas.2020.106292

In the situation of a severe nuclear accident, radioiodine monitoring in thyroid should be performed for a large number of people immediately after accident. The portable thyroid dose monitoring system which can be used in a high dose rate condition is in development. In this presentation, the result of performance test using prototype model will be described.

Eye lens dosimetry for workers at Fukushima Daiichi Nuclear Power Plant, 1; Laboratory study on the dosemeter position and the shielding effect of full face mask respirators

Hoshi, Katsuya; Yoshitomi, Hiroshi; Aoki, Katsunori; Tanimura, Yoshihiko; Tsujimura, Norio; Yokoyama, Sumi*

Radiation Measurements, 134, p.106304_1 - 106304_5, 2020/06

https://doi.org/10.1016/j.radmeas.2020.106304

In FY 2017, the Japanese Nuclear Regulatory Agency (NRA) established the Radiation Safety Research Promotion Fund for funding projects on nuclear safety regulation, and adopted the two-year research project entitled "Study on standard eye lens monitoring, suitable dose management and radiation protection for nuclear and medical workers". The study is a two-phase study: a laboratory study on the eye lens dosemeter's characteristics to photons, and a field study executed at actual workplaces at Fukushima Daiichi Nuclear Power Station. This paper summarizes the results of the first-phase study, which was designed to clarify the eye lens dosemeter positioning and the shielding effect of full face mask respirators used at the station. No marked difference was observed in readings of the dosemeters attached on the different positions on the head phantom. Two types of full face mask respirators provided insignificant shielding effect for photons of 83 keV to 662 keV.

Investigation of using a long-life electronic personal dosimeter for monitoring aviation doses of frequent flyers

Yasuda, Hiroshi*; Yajima, Kazuaki*; Sato, Tatsuhiko

Radiation Measurements, 134, p.106309_1 - 106309_4, 2020/06

https://doi.org/10.1016/j.radmeas.2020.106309

We have investigated an application of a recently developed electronic personal dosimeter (D-Shuttle) for aviation dosimetry. As results of measurements in four long-haul flights between Japan and Germany, the D-Shuttle indicated values were in the range of 25 to 30% of the total H(10) values estimated by a route-dose calculations program JISCARD EX. Though we need more measurements and analyses under different flight conditions to conclude, according to these results obtained so far, it would be possible to perform monitoring of the annual aviation doses of frequent flyers by using D-Shuttle on an individual basis.

Verification of dose estimation of Auger electrons emitted from Cu-64 using a combination of FNTD measurements and Monte Carlo simulations

Kusumoto, Tamon*; Matsuya, Yusuke; Baba, Kentaro*; Ogawara, Ryo*; Akselrod, M. S.*; Harrison, J.*; Fomenko, V.*; Kai, Takeshi; Ishikawa, Masayori*; Hasegawa, Sumitaka*; et al.

Radiation Measurements, 132, p.106256_1 - 106256_4, 2020/03

https://doi.org/10.1016/j.radmeas.2020.106256

Internal radiation therapy with Cu-64 concentrates energy deposition in tumor cells by virtue of released Auger electrons with low energy. In our previous study, we have attached the solutions at the surface of Fluorescent Nuclear Track Detector (FNTD) and succeeded in measuring the absorbed doses of Auger electrons registered in FNTD. However, because there are several types of radiation emitted from the source, i.e., beta rays, positron etc., the contribution degree of Auger electron to energy concentration remain uncertain. In this study, we quantitatively analyzed the spatial dose distribution in the FNTD based on Monte Carlo simulation with PHITS and GEANT4, and evaluated high dose deposited by Auger electrons. The dose distribution calculated by the PHITS code is exactly equivalent to that by Geant4. Also, the simulations are well agreement with experimental results. If the contribution of Auger electrons is ignored, the significantly high absorbed dose proximal to the source is not properly reduced. These findings demonstrate that Auger electrons work very effectively to kill cancer cells proximal to Cu-64 source while minimizing damage effects on normal cells distal to the source.