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.

Structural and compositional characteristics of Fukushima release particulate material from Units 1 and 3 elucidates release mechanisms, accident chronology and future decommissioning strategy

Martin, P. G.*; Jones, C. P.*; Bartlett, S.*; Ignatyev, K.*; Megson-Smith, D.*; Satou, Yukihiko; Cipiccia, S.*; Batey, D. J.*; Rau, C.*; Sueki, Keisuke*; et al.

Scientific Reports (Internet), 10, p.22056_1 - 22056_17, 2020/12

https://doi.org/10.1038/s41598-020-79169-2

Hydraulic tests using borehole PB-V01 in the Horonobe Underground Research Project

Samata, Yoichi; Iwata, Tatsuya*; Ishii, Eiichi

JAEA-Data/Code 2019-008, 19 Pages, 2019/09

JAEA-Data-Code-2019-008.pdf:2.82MB
JAEA-Data-Code-2019-008-appendix(CD-ROM).zip:1.38MB

In Horonobe Underground Research Laboratory Project, hydraulic tests for the excavation damaged zone have been performed in order to characterize the hydrological properties of the zone. In PB-V01 borehole, pore pressure observation started in October 2008, but the pore pressure is currently reduced by about 3 MPa compared to that time. In this report, in order to evaluate the influence that this pore pressure drop has on the permeability of the rock, the results of the in-situ permeability test using the long-term hydraulic pressure monitoring device installed in the same hole are summarized.

Wetting induced oxidation of Pt-based nano catalysts revealed by high energy resolution X-ray absorption spectroscopy

Cui, Y.-T.*; Harada, Yoshihisa*; Niwa, Hideharu*; Hatanaka, Tatsuya*; Nakamura, Naoki*; Ando, Masaki*; Yoshida, Toshihiko*; Ishii, Kenji*; Matsumura, Daiju; Oji, Hiroshi*; et al.

Scientific Reports (Internet), 7(1), p.1482_1 - 1482_8, 2017/05

https://doi.org/10.1038/s41598-017-00639-1

Replacement of the criticality accident alarm system in the Tokai Reprocessing Plant

Sanada, Yukihisa; Ishii, Masato*; Hasegawa, Ichiro; Kanazawa, Nobuyuki; Chikazawa, Tatsuya*; Momose, Takumaro

NEA/CSNI/R(2010)4 (Internet), p.351 - 370, 2010/11

https://www.oecd-nea.org/nsd/docs/2010/csni-r2010-4.pdf

A criticality accident alarm system (CAAS) was installed in the 1980s as part of criticality safety management at the Tokai Reprocessing Plant (TRP) to reduce the chance of workers being exposed to radiation in the rare case of a criticality accident. From a compliance point of view processing at TRP cannot take place without the criticality monitoring provided by the CAAS. This paper gives an overview of the process of the CAAS being replaced as part of aging management.

Progress of the ITER central solenoid model coil programme

Tsuji, Hiroshi; Okuno, Kiyoshi*; Thome, R.*; Salpietro, E.*; Egorov, S. A.*; Martovetsky, N.*; Ricci, M.*; Zanino, R.*; Zahn, G.*; Martinez, A.*; et al.

Nuclear Fusion, 41(5), p.645 - 651, 2001/05

https://doi.org/10.1088/0029-5515/41/5/319

no abstracts in English

Elucidation for production scenario of insoluble Cs particles from Unit 1 using multifaceted analysis

Satou, Yukihiko; Kobata, Masaaki; Okane, Tetsuo; Sueki, Keisuke*; Matsuo, Kazuki*; Ishii, Tatsuya*; Martin, P.*; Scott, T.*

no journal, , 

no abstracts in English

Chemical state of cesium in the insoluble radioactive particles emitted from Unit 1 of Fukushima Di-ichi Nuclear Power Station

Satou, Yukihiko; Kobata, Masaaki; Okane, Tetsuo; Yoshii, Kenji; Fukuda, Tatsuo; Kawasaki, Ikuto; Osaka, Masahiko; Owada, Kenji*; Sueki, Keisuke*; Ishii, Tatsuya*

no journal, , 

no abstracts in English

Evaluation on the denitration characteristics heated by the circular polarized microwave

Segawa, Tomoomi; Tanigawa, Masafumi; Kato, Yoshiyuki; Kawaguchi, Koichi; Ishii, Katsunori; Suzuki, Masahiro; Kitazawa, Toshihide*; Taguchi, Kenji*; Kashiwa, Tatsuya*

no journal, , 

For the purpose of improving the microwave heating denitration technology, the denitration characteristics of cobalt nitrate aqueous solutions as a simulated materials were analyzed and evaluated by using the microwave heating equipment whichi was controlled to circular polarized wave. Numerical simulation confirmed that the circular polarized wave controlled microwave irradiation uniformed the absorbed power distribution in the circumferential direction. Moreover, it was confirmed that the denitration proceeded uniformly even in the radial direction by the microwave heating denitration experiments of cobalt nitrate aqueous solutions. From these results, it was revealed that favorable heating and denitration characteristics can be obtained by the circularly polarized wave controlled microwave heating equipment.

Electromagnetic field analysis for the development of the microwave heating equipment capable of uniform heating of a metal nitrate aqueous solution and the metal oxide powder with circular polarization control

Segawa, Tomoomi; Tanigawa, Masafumi; Kato, Yoshiyuki; Kawaguchi, Koichi; Ishii, Katsunori; Suzuki, Masahiro; Kitazawa, Toshihide*; Kashiwa, Tatsuya*

no journal, , 

To improve the handling and sinterability of raw powder of a uranium and plutonium mixed oxide produced in the reprocessing process of spent fuels, the microwave heating equipment has been developed considering the microwave property of linear polarization and circularly polarization that contribute to the uniformization of the microwave heating denitration by JAEA. The electromagnetic field simulation analysis was carried out by the Finite-Difference Time-Domain method, and the experimental results were evaluated. An analysis model was developed based on the obtained physical property data which were measured by the cylindrical cavity resonator method. The liquid phase state, microwave was concentrated on the upper surface and bottom surface due to the high loss of the cobalt nitrate aqueous solution, while in the solid phase state, microwave energy was absorbed inside. The absorption electric power distribution became uniform in the circumferential direction.