Simulation of a gamma-ray imaging technique using detector response patterns

Kitayama, Yoshiharu; Nogami, Mitsuhiro*; Hitomi, Keitaro*

Japanese Journal of Applied Physics, 63(3), p.032005_1 - 032005_6, 2024/03

https://doi.org/10.35848/1347-4065/ad2d7a

We introduce a novel gamma-ray imaging technique that uses detector response patterns. This method employs multiple shielding cubes randomly positioned in a three-dimensional configuration. Within the volume defined by these cubes, a unique gamma-ray flux pattern is formed based on the incidence direction of the gamma rays. This pattern can be measured using the responses of several scintillator cubes. By pre-measuring the detector response pattern and incidence direction of the gamma rays, the incidence direction can be estimated using an unfolding technique. Simulations were performed using a Cs point source. Our results show that a 10 MBq Cs source, located 3 m away from the imager, can be imaged with an angular resolution close to 10. These findings suggest that our new method is comparable to existing gamma-ray imaging techniques. Potential applications of this imaging method include nuclear power plant decommissioning, nuclear medicine, security, and astronomy.

Estimation of the activity median aerodynamic diameter of plutonium particles using image analysis

Takasaki, Koji; Yasumune, Takashi; Yamaguchi, Yukako; Hashimoto, Makoto; Maeda, Koji; Kato, Masato

Journal of Nuclear Science and Technology, 60(11), p.1437 - 1446, 2023/11

https://doi.org/10.1080/00223131.2023.2196969

The aerodynamic radioactive median diameter (AMAD) is necessary information to assess the internal exposure. On June 6, 2017, at a plutonium handling facility in Oarai site of Japan Atomic Energy Agency (JAEA), during the inspection work of a storage container that contains nuclear fuel materials, accidental contamination occurred and five workers inhaled radioactive materials including plutonium. Some smear papers and an air sampling filter were measured with the imaging plate, and we conservatively estimated minimum AMADs for two cases, plutonium nitrate and plutonium dioxide. As a result of AMAD estimation, even excluding a giant particle of a smear sample, the minimum AMADs of plutonium nitrate from smear papers were 4.3 - 11.3 m and those of plutonium dioxide were 5.6 - 14.1 m. Also, the minimum AMAD of plutonium nitrate from an air sampling filter was 3.0 m and that of plutonium dioxide was 3.9 m.

Development of an areal density imaging for boron and other elements

Tsuchikawa, Yusuke; Kai, Tetsuya; Abe, Yuta; Oikawa, Kenichi; Parker, J. D.*; Shinohara, Takenao; Sato, Ikken

Journal of Physics; Conference Series, 2605, p.012022_1 - 012022_6, 2023/10

https://doi.org/10.1088/1742-6596/2605/1/012022

We developed a method to obtain the areal density distribution of boron, which has a large neutron cross section, by means of an energy resolved neutron imaging. Commonly in a measurement of elements with very high neutron sensitivity, the quantitative measurement becomes more difficult with the amount of element due to the neutron self-shielding effect. To avoid this effect, an energy-resolved method using known cross section data was attempted, and a quantitative imaging of such elements was demonstrated at the MLF of J-PARC. This presentation introduces a measurement of melted simulated-fuel assemblies obtained in the research of the Fukushima Daiichi Nuclear Power Plant after the severe accident. Energy-dependent neutron transmission rates of the samples were measured by a neutron imaging detector, and were analyzed to obtained the areal density of boron at each position.

Fundamental research of X-ray absorption imaging for elemental identification using a secondary target

Nakae, Masanori*; Matsuyama, Tsugufumi*; Murakami, Masashi; Yoshida, Yukihiko; Machida, Masahiko; Tsuji, Koichi*

Advances in X-Ray Chemical Analysis, Japan, 54, p.89 - 99, 2023/03

Fundamental research on X-ray absorption imaging for elemental identification was studied. A secondary target was applied to obtain X-ray absorption images above and below the X-ray absorption edge of the target element. X-rays from an X-ray tube were irradiated to the secondary target, where the characteristic X-rays were emitted that were irradiated to the sample. X-ray absorption images were acquired with an exposure time of a few seconds with an X-ray camera. In this technique, it is difficult to change the energy of X-rays as we want, however we can apply this technique for imaging the specific element. Metal foil sample composed of Al, Cu, and Ni was analyzed. To obtain an X-ray elemental image of Ni, two X-ray absorption images were taken using the X-rays above and below the Ni K-edge. X-rays of Cu K and Zn K were prepared by using Cu and Zn plates as the secondary target. Finally, the Ni elemental image was obtained by subtracting two images. Furthermore, the X-ray camera had a function of setting critical energies for imaging, thus it was demonstrated that an X-ray elemental image of Ni was obtained using a single secondary target without changing the secondary target.

3D visualization of radioactive contamination using an integrated Radiation Imaging System (iRIS)

Sato, Yuki

Isotope News, (781), p.19 - 23, 2022/06

no abstracts in English

Measurement of void fraction distribution

Kureta, Masatoshi

Ryutai Keisokuho; Kaitei-Han, p.367 - 371, 2022/04

The Japan Society of Mechanical Engineers publishes a revised version of the technical document summarizing fluid measurement techniques. This article is part of the application section, and the main content is an introduction of application examples using advanced thermal-fluid measurement technology that is progressing remarkably. In the chapter "Void Fraction Distribution Measurement", the technology for visualizing and measuring the void fraction distribution with neutron beams for the two-phase flow of gas-liquid flowing inside the instrument is summarized. In the first half, the definition of void fraction, measurement by neutron transmission method, and basic principles of CT imaging technology were explained. In the second half, visualization and measurement results were shown in the order of two-dimensional and two-dimensional time changes of various multiphase flows, and three-dimensional and three-dimensional time changes.

Investigation of radioactive samples for neutron capture reaction measurements using energy-resolved neutron imaging

Segawa, Mariko; Toh, Yosuke; Kai, Tetsuya; Kimura, Atsushi; Nakamura, Shoji

Annals of Nuclear Energy, 167, p.108828_1 - 108828_5, 2022/03

https://doi.org/10.1016/j.anucene.2021.108828

The First application of a GdAlGaO:Ce single-crystal scintillator to neutron radiography

Isegawa, Kazuhisa; Setoyama, Daigo*; Kimura, Hidehiko*; Shinohara, Takenao

Journal of Imaging (Internet), 7(11), p.232_1 - 232_9, 2021/11

https://doi.org/10.3390/jimaging7110232

Neutron radiography is regarded as complementary to X-ray radiography in terms of transmittance through materials, but its spatial resolution is still insufficient. In order to achieve higher resolution in neutron imaging, several approaches have been adopted such as optical magnification and event centroiding, and the authors focused on modification of the scintillator in this paper. A GdAlGaO:Ce single-crystal scintillator was applied to neutron radiography for the first time and was achieved a spatial resolution of 10.5 micrometers. The results indicate that this material can be a powerful candidate for a new neutron scintillator providing a resolution in micrometer order by optimizing the optical system and increasing the scintillator luminosity.

Observation of Eu adsorption band in the CMPO/SiO-P column by neutron resonance absorption imaging

Miyazaki, Yasunori; Watanabe, So; Nakamura, Masahiro; Shibata, Atsuhiro; Nomura, Kazunori; Kai, Tetsuya; Parker, J. D.*

JPS Conference Proceedings (Internet), 33, p.011073_1 - 011073_7, 2021/03

https://doi.org/10.7566/JPSCP.33.011073

Neutron resonance absorption imaging was adapted to observe the Eu band adsorbed in the CMPO/SiO-P column for minor actinide recovery by extraction chromatography. Several wet columns were prepared by either light water or heavy water and compared with the dry column to evaluate the neutron transmission. The neutron transmission spectra showed that 45% was transmitted through the dry column while 20% and 40% were transmitted through the wet columns of light water and heavy water, respectively. The results indicated that heavy water is more applicable than light water to observe the Eu adsorption band in the CMPO/SiO-P column.

XAFS analysis of ruthenium in simulated iron phosphate radioactive waste glass

Okamoto, Yoshihiro; Kobayashi, Hidekazu; Shiwaku, Hideaki; Sasage, Kenichi; Hatakeyama, Kiyoshi*; Nagai, Takayuki

Journal of Non-Crystalline Solids, 551, p.120393_1 - 120393_8, 2021/01

https://doi.org/10.1016/j.jnoncrysol.2020.120393

The chemical state of ruthenium in simulated iron phosphate radioactive waste glass was investigated by conventional X-ray absorption fine structure (XAFS) and imaging XAFS analyses. The EXAFS analysis suggested that ruthenium was contained as glass phase when content of the waste components was less than 10wt.% in 30 mol%FeO-PO base glass. In other samples, crystalline RuO was predominant. According to the imaging XAFS analysis, RuO particles in all samples had length smaller than 50m. Aggregations of RuO, which are found in nuclear waste borosilicate glass, were not seen in any of the iron phosphate glass samples.