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.

Investigative report on the PVC bag burst in the contamination incident at Plutonium Fuel Research Facility; Radiolysis of organic materials and raising of internal pressure

Cause Investigation Team for the PFRF Contamination Incident

JAEA-Review 2017-038, 83 Pages, 2018/03

JAEA-Review-2017-038.pdf:11.37MB

The contaminated accident occurred at Plutonium Fuel Research Facility on June, 2017. The PVC bag packaging in a fuel storage container burst when a worker opened the lid, and a part of contents (uranium and plutonium) was spattered over the room. In order to clarify the cause of the burst, the Cause Unfolding Team collected information concerning characteristics of the contents from any past records and interview. And then we observed and analyzed the contents in a glove box. We also performed experiments on radiolysis of organic materials, degradation of PVC bag by radiation, and PVC bag burst. Based on fault tree analysis, finally we concluded that the main gas generation source was alpha radiolysis of the epoxy resin mixed with the fuel powder. We hope that the calculation procedures for the gas generation and the inner pressure transition described in this report can be useful reference for the management of fuel storage in other facilities.

Radiation measurement for safeguards environmental samples by imaging plate

Yasuda, Kenichiro; Sakurai, Satoshi; Gunji, Hideho; Usuda, Shigekazu

Journal of Nuclear Science and Technology, 39(Suppl.3), p.552 - 555, 2002/11

http://www.tandfonline.com/doi/abs/10.1080/00223131.2002.10875528

In order to contribute to the strengthened safeguards system based on the Program 93+2 of the IAEA, Japan Atomic Energy Research Institute (JAERI) constructed the CLEAR facility (Clean Laboratory for Environmental Analysis and Research) and is developing analytical technology for ultra trace amounts of nuclear materials in environmental samples. To avoid cross-contamination among the samples and contamination of the clean rooms, radioactive materials in the samples to be introduced into the CLEAR facility will be limited to a certain amount. For this purpose the authors have examined the feasibility of Imaging-plate method, which is a kind of autoradiography and is suitable for determination on distribution of low-level radioactivity in the samples. Preliminary examination with -ray (K-40), the linearity was obtained in the range of 0.01 - 0.2 Bq. The experiments with -ray (Sm-147) suggested the detection limit of 0.01 Bq, which was equivalent to 2 g of natural uranium. At the presentation, the results on actual environmental samples will be reported.

Theoretical analysis on phototimulated luminescence phenomenon of imaging plate

Kishimoto, Maki; Nakamura, Tatsuya; To, Kentaro; Sakasai, Kaoru; Katagiri, Masaki; Takahashi, Hiroyuki*; Nakazawa, Masaharu*

Nihon Genshiryoku Gakkai-Shi, 43(2), p.168 - 181, 2001/02

https://doi.org/10.3327/jaesj.43.168

no abstracts in English

Improvement of the technique for stack monitoring based on behavior analysis of natural radio-nuclides; The technique for reducing the value of the exhaust monitor's background

Izaki, Kenji; Noda, Kimio; ; Kashimuta, Yoshio*

JNC TN8410 2001-005, 30 Pages, 2001/01

JNC-TN8410-2001-005.pdf:0.62MB

Stack monitoring is the most important work in radiation control works. Exhaust monitors used for stack monitoring have the background (which is the counts by natural radio-nuclides) on normal condition, and the values of the background vary with the facilities. Therefore, if the value of background is high, it is difficult to estimate rapidly the radioactive concentration in the exhaust. In order to estimate rapidly the radioactive concentration in exhaust, we analyzed the behavior of natural radioactivity in the facilities and examine the technique fo reducing the value of the background. As a result of the examination, we found that it is possible to estimate rapidly if we change over the monitoring point to immediately after the HEPA filters on the exhaust duct. In this reports, the analyzed results of behavior of natural radio-nuclides in the facilities and the technique for reducing the values of the background are described. To reduce the value of the background has a major effect on not only rapidly estimating the radioactive density in the exhaust but also finding the unusual things on stack monitoring.

High-temperature operation of a radiation detector made of a type IIa diamond single crystal synthesized by a HP/HT method

Tanimura, Yoshihiko; Kaneko, Junichi; Katagiri, Masaki; Ikeda, Yujiro; Nishitani, Takeo; Takeuchi, Hiroshi; Iida, Toshiyuki*

Nuclear Instruments and Methods in Physics Research A, 443(2-3), p.325 - 330, 2000/04

https://doi.org/10.1016/S0168-9002(99)01048-7

no abstracts in English

Phoswich detection system applying optical techniques for actinide monitoring

Usuda, Shigekazu; Yasuda, Kenichiro

Proceedings of 5th International Conference on Nuclear and Radiochemistry (NRC5), 2, p.595 - 598, 2000/00

no abstracts in English

Decay properties of neutron-deficient actinide isotopes

Sakama, Minoru*; Tsukada, Kazuaki; Asai, Masato; Ichikawa, Shinichi; Oura, Yasuji*; Osa, Akihiko; Shibata, Michihiro*; Nishinaka, Ichiro; Nagame, Yuichiro; Ebihara, Mitsuru*; et al.

1st International Conference on the Chemistry and Physics of the Transactinide Elements; Extended Abstracts, 4 Pages, 1999/00

no abstracts in English

Radiation discrimination in phoswich detector system

Usuda, Shigekazu

Radioisotopes, 47(3), p.227 - 229, 1998/03

no abstracts in English

Development of Phoswich detectors for simultaneous counting of alpha particles and other radiations (Emitted from actinides)

Usuda, Shigekazu; Yasuda, Kenichiro; Sakurai, Satoshi

Applied Radiation and Isotopes, 49(9-11), p.1131 - 1134, 1998/00

https://doi.org/10.1016/S0969-8043(97)10033-1

no abstracts in English