Development of an continuous air monitor for the measurement of highly radioactive alpha-emitting particulates (-aerosols) under high humidity environment

Tsubota, Yoichi; Honda, Fumiya; Tokonami, Shinji*; Tamakuma, Yuki*; Nakagawa, Takahiro; Ikeda, Atsushi

Nuclear Instruments and Methods in Physics Research A, 1030, p.166475_1 - 166475_7, 2022/05

https://doi.org/10.1016/j.nima.2022.166475

In the long-lasting decommissioning of the Fukushima Daiichi Nuclear Power Station (1F), the dismantling of nuclear fuel debris (NFD) remaining in the damaged reactors is an unavoidable but significant issue with many technical difficulties. The dismantling is presumed to involve mechanical cutting, generating significant concentrations of particulates containing -radionuclides (-aerosols) that pose significant health risk upon inhalation. In order to minimize the radiation exposure of workers with -aerosols during the dismantling/decommissioning process at 1F, it is essential to monitor the concentration of -aerosols at the point of initial generation, i.e. inside the primary containment vessels (PCV) of the damaged reactors. Toward this end, an monitoring system for -aerosols ( alpha air monitor: IAAM) was developed and its technical performance was investigated under the conditions expected for the actual environments at 1F. IAAM was confirmed to fulfill four technical requirements: (1) steady operation under high humidity, (2) operation without using filters, (3) capability of measuring a high counting rate of -radiation, and (4) selective measurement of -radiation even under high radiation background with /-rays. IAAM is capable of selectively measuring -aerosols with a concentration of 3.3 10 Bq/cm or higher without saturation under a high humid environment (100%-relative humidity) and under high background with /-radiation (up to 100 mSv/h of -radiation). These results demonstrate promising potential of IAAM to be utilized as a reliable monitoring system for -aerosols during the dismantling of NFD, as well as the whole long-lasting decommissioning of 1F.

Development of ion beam breeding technology in plants and creation of useful plant resources

Hase, Yoshihiro; Nozawa, Shigeki; Asami, Itsuo*; Tanogashira, Yuki*; Matsuo, Yoichi*; Kanazawa, Akira*; Honda, Kazushige*; Narumi, Issey*

JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 102, 2014/03

Development of ion beam breeding technology in plants and creation of useful plant resources

Hase, Yoshihiro; Nozawa, Shigeki; Okada, Tomoyuki*; Asami, Itsuo*; Nagatani, Takeshi*; Matsuo, Yoichi*; Kanazawa, Akira*; Honda, Kazushige*; Narumi, Issei

JAEA-Review 2011-043, JAEA Takasaki Annual Report 2010, P. 100, 2012/01

https://jopss.jaea.go.jp/pdfdata/JAEA-Review-2011-043.pdf

Effects of ion-beam irradiation on germination and growth of seedlings of redpepper "Hirosakizairai"

Tomikawa, Masaru*; Maeda, Tomoo*; Honda, Kazushige*; Saga, Koichi*; Ishikawa, Ryuji*; Akita, Yusuke; Nozawa, Shigeki; Narumi, Issei

no journal, , 

no abstracts in English

Expression of mutations in the M2 generation of red pepper "Hirosaki zairai" irradiated with ion beam

Sato, Yusuke*; Maeda, Tomoo*; Honda, Kazushige*; Saga, Koichi*; Ishikawa, Ryuji*; Akita, Yusuke; Yoshihara, Ryohei; Nozawa, Shigeki; Narumi, Issei

no journal, , 

no abstracts in English

Control of electronic and structural properties of epitaxial graphene on 3C-SiC/Si and its device applications

Fukidome, Hirokazu*; Kotsugi, Masato*; Okochi, Takuo*; Yoshigoe, Akitaka; Teraoka, Yuden; Enta, Yoshiharu*; Kinoshita, Toyohiko*; Suemitsu, Tetsuya*; Otsuji, Taiichi*; Suemitsu, Maki*

no journal, , 

Study on mutation with the use of carbon ion beam in Chinese yam and Japanese yam

Kawasaki, Michio*; Hatta, Yuki*; Senda, Mineo*; Suto, Hiroki*; Nozawa, Shigeki; Akita, Yusuke*; Hase, Yoshihiro; Narumi, Issey*

no journal, , 

no abstracts in English

Development of elemental technology for alpha-ray dust monitor for in-situ measurement of radioactive aerosol in dismantling and decommissioning

Tsubota, Yoichi; Honda, Fumiya; Nakagawa, Takahiro; Kawasaki, Takashi; Tamakuma, Yuki*; Tokonami, Shinji*; Momose, Takumaro

no journal, , 

A large number of radioactive aerosols, especially alpha particles, are expected to be generated during fuel debris retrieval on Fukushima - Daiichi (1F) site and decommissioning of nuclear fuel cycle facilities. In the case of conventional alpha dust monitor, silicon surface barrier detector (SSBD) is often used as a detector which has not so high limit of count rates. Moreover, SSBD is not suitable for high humidity environment. In this work, we developed a prototype of alpha dust monitor aiming at an in-situ measurement of high concentration of airborne alpha particles. Approx. 20M cpm of counting rate was achieved which was more than 10 times higher compared to a conventional alpha dust monitor using SSBD. For follow-up test, counting rate of prototype alpha dust monitor was smoothly followed with respect to the airborne concentration of alpha particles.

An In-situ alpha air monitor for the retrieval of fuel debris at the Fukushima Daiichi Nuclear Power Station

Honda, Fumiya; Tsubota, Yoichi; Tamakuma, Yuki*; Tokonami, Shinji*; Ikeda, Atsushi; Nakagawa, Takahiro

no journal, , 

A large number of radioactive aerosols, especially alpha particles, are expected to be generated during the fuel debris retrieval on the Fukushima Daiichi Nuclear Power Station. From the viewpoint of preventing contamination of the surrounding environment and the vicinity of the human-access area, it is important to measure the activity concentration of airborne radioactive substances inside the primary containment vessels (PCVs). In particular, it is necessary to monitor the concentration of particulates containing -nuclides (-aerosols), which have high effective dose coefficients upon inhalation. This presentation reports the development of an in-situ alpha air monitor (IAAM) for direct measurement of -aerosols by combining a flat-type flow path (FFP), an air heater, a ZnS scintillator, and a multi anode photomultiplier tube. The monitor should operate under high humidity with the maximum counting rate of approx. 2.110 cpm. To achieve the two requirements, the monitor was designed to keep the air sufficiently dry without overheating the detector, and to reduce the detection of coarse particles. This study also conducted a basic performance test using the developed IAAM with a modified FFP. As a result, we could keep the humidity of the air less than 30%RH by heating the inlet of the FFP to 80 C. In addition, by placing the FFP in a vertical position and installing a bend at the air intake port, coarse particles were reduced approx. 1/2-1/3. These achievements enable the monitor to measure -aerosols more precisely in the viewpoint of internal exposure assessment.

Improvement of pretreatment method for organically bound tritium analysis

Fujiwara, Kenso; Kuwata, Haruka*; Terashima, Motoki; Akata, Naofumi*

no journal, , 

The analysis method for organically bound tritium is summarized in the radioactivity measurement method series managed by the regulatory agency, but the pretreatment takes time. So far, joint research has investigated shortening the pretreatment, but the pretreatment still takes about a week, and speeding up is expected. This time, we investigated the relationship between the shape and weight of the sample and the time to reach a constant weight during freeze-drying. In the freeze-drying process, by increasing the surface area of the sample, the process that used to take about two days was shortened to about one day. In addition, with the aim of promoting efficient combustion, we attempted to accumulate data that would contribute to the control of combustion temperature by suggestive thermal analysis of organic matter samples.