Development of a practical tritiated water monitor to supervise the discharge of treated water from Fukushima Daiichi Nuclear Power Plant

Sanada, Yukihisa; Oshikiri, Keisuke*; Kanno, Marina*; Abe, Tomohisa

Nuclear Instruments and Methods in Physics Research A, 1062, p.169208_1 - 169208_7, 2024/05

https://doi.org/10.1016/j.nima.2024.169208

As part of the decommissioning work at the Fukushima Daiichi Nuclear Power Plant (FDNPP), the release of stored treated water began in 2023. In this study, we developed a practical tritium monitor to continuously monitor the concentration of tritiated water, as confirmed by batch sampling measurements at the FDNPP. The monitor is arranged with a flow cell detector comprising inexpensive plastic scintillator pellets and incorporating simultaneous measurements by three detectors, a veto detector, and lead shielding to reduce the influence of environmental -rays. The system reached a detection limit of 911 Bq L-1 with a measurement time of 30 min, which is lower than the discharge standard for tritiated water of 1,500 Bq L-1. The system can also qualitatively distinguish the presence of disturbances due to interfering radionuclides other than tritium or background radiation using the -ray spectrum.

A study on improvements in accuracy of nuclear data measurements using -ray spectroscopic methods

Furutaka, Kazuyoshi

JNC TN8400 2000-028, 70 Pages, 2000/10

JNC-TN8400-2000-028.pdf:1.71MB

This report describes the study done by the author as a postdoctoral research associate at Japan Nuclear Cycle Development Institute. This report is divided into two parts: improvements in accuracy in determination of thermal neutron capture cross sections, and improvements in accuracy of photo-nuclear absorption cross section measurements using the HHS. (1)In the measurements of thermal neutron capture cross sections using an activation method, accuracies of the final results attained are limited by (1) accuracy of -ray peak detection efficiencies, and (2) accuracies of -ray emission probabilities. In this study; to determine thermal neutron capture cross sections more accurately, the following researches have been done using a newly developed three-dimensional coincidence measurement system: (1)accurate determination of -ray standard sources using a - coincidence method, for precise calibration of -ray peak detection efficiency, and (2) development of a - coincidence measurement system using a plastic scintillation detector as a -ray detector, for the determination of -ray emission probabilities of short-lived nuclides, and measurement of -ray emission probabilities of Tc nuclide using the coincidence system. (2)To transform radioactive nuclides with small thermal neutron capture cross sections, use of photonuclear absorption reaction has been suggested. In order to transform these nuclides efficiently using the reaction, one has to know detailed behavior of the photo-absorption cross sections. In this study, a Monte-Carlo simulation code has been used to create a standard set of -ray response functions of the high-resolution high-energy spectrometer (HHS), to enable reliable analyses of the data obtained by the spectrometer.

None

PNC TJ1603 97-002, 66 Pages, 1997/03

PNC-TJ1603-97-002.pdf:1.7MB

no abstracts in English

Investigation of plasma facing components in JT-60U operation

*; Ando, Toshiro; ; Arai, Takashi; Neyatani, Yuzuru; Yoshino, Ryuji; Tsuji, Shunji; Yagyu, Junichi; Kaminaga, Atsushi; ; et al.

Journal of Nuclear Materials, 220-222, p.390 - 394, 1995/00

https://doi.org/10.1016/0022-3115(94)00638-5

no abstracts in English

None

; ; Komatsuzaki, Kenji;

PNC TN8520 93-002, 191 Pages, 1993/03

PNC-TN8520-93-002.pdf:4.47MB

None

Eye lens dosimetry for workers at Fukushima Daiichi Nuclear Power Station, 4; Evaluation of eye lens dose based on the beta-ray spectrometry

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

no journal, , 

no abstracts in English

Challenge toward extensive corrosion prevention in PCV system under the influence of // radiation, 3; Effects of - and -ray radiation on corrosion; Electrochemical investigations using sealed beta source

Sato, Tomonori; Kato, Chiaki; Sato, Nobuaki*; Hata, Kuniki; Watanabe, Yutaka*

no journal, , 

Primary containment vessel in Fukushima Daiichi Nuclear Power Station is exposed to the corrosive environment under irradiation. Especially, the materials nearby the fuel debris will be exposed not only to gamma-ray but also to alpha- and beta-rays. However, the limited data were reported for the corrosion evaluations under the direct irradiation of alpha- and beta-rays. So, the electrochemical investigations were performed using sealed beta-ray source (Sr-90) in this study. As a result, it was confirmed that the polarization resistance of carbon steel decreased and the corrosion potential of stainless steel increased by beta-ray irradiation.

Development of an omnidirectional detector for beta & gamma-ray imaging with fractal geometry

Torii, Tatsuo; Sasaki, Miyuki; Sanada, Yukihisa

no journal, , 

For the purpose of 3D radiation imaging in decommissioning and environment, we have developed a radiation detector with a self-similar fractal shape, Sierpinski's tetrahedron shape. This detector consists of a tetrahedral radiation sensor as a unit and 16 GAGG scintillators arranged in a Sierpinski tetrahedron shape with heavy metal filling between the sensors, enabling efficient measurement of radiation incident from any direction as a whole detector. The total count rate of the 16 scintillators is almost the same for the incident direction, but the count rate of each scintillator can be used to identify the incident direction of radiation. In this presentation, we will report on the progress of this development project.