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Journal Articles

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

Times Cited Count：2 Percentile：30.99(Instruments & Instrumentation)

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 $^{2}$ Bq/cm $^{3}$ 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.

Journal Articles

Results of whole body counting for JAEA staff members engaged in the emergency radiological monitoring for the Fukushima nuclear disaster

Takada, Chie; Kurihara, Osamu*; Kanai, Katsuta; Nakagawa, Takahiro; Tsujimura, Norio; Momose, Takumaro

NIRS-M-252, p.3 - 11, 2013/03

http://repo.nirs.go.jp/dspace/bitstream/918273645/330/1/nirs_m_252.pdf

A massive earthquake and tsunami on March 11, 2011 resulted in an enormous amount of release of radioactivity to the environment. On the day after the earthquake occurrence, Japan Atomic Energy Agency (JAEA) started emergency radiological monitoring. The measurements with whole body counter (WBC) for the staff members who had returned from Fukushima started at the end of March. The measured activity of $^{131}$ I due to inhalation for emergency staff varied from LLD to 7 kBq, which corresponded to a range of estimated initial intakes of 1 to 60 kBq when extrapolated back to the date on which the staff started the operation in Fukushima. The measured activity of $^{134}$ Cs and $^{137}$ Cs were both in the ranges of LLD - 3 kBq. The range of initial intake of $^{137}$ Cs to $^{131}$ I was 11 when taking a median from all the measurements. The maximum committed effective dose of 0.8 mSv was recorded for a worker, a member of the 2nd monitoring team dispatched from March 13 to 14.

Journal Articles

Measurements of $^{131}$ I in the thyroids of employees involved in the Fukushima Daiichi Nuclear Power Station accident

Kurihara, Osamu*; Kanai, Katsuta; Nakagawa, Takahiro; Takada, Chie; Tsujimura, Norio; Momose, Takumaro; Furuta, Sadaaki

Journal of Nuclear Science and Technology, 50(2), p.122 - 129, 2013/02

https://doi.org/10.1080/00223131.2013.757449

Times Cited Count：6 Percentile：43.8(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Verification analysis of thermoluminescent albedo neutron dosimetry at MOX fuel facilities

Nakagawa, Takahiro; Takada, Chie; Tsujimura, Norio

Radiation Protection Dosimetry, 146(1-3), p.140 - 143, 2011/07

https://doi.org/10.1093/rpd/ncr138

Times Cited Count：0 Percentile：0.01(Environmental Sciences)

Radiation workers engaging in the fabrication of MOX fuels are exposed to neutrons, and hence thermoluminescent albedo dosemeters (TLAD) need to be used at JAEA-NCL. Because estimating the doses using TLADs are susceptible to the neutron energy spectrum, the authors have issued TLADs incorporating Solid-State Nuclear Tracks Detectors (SSNTDs) to selected workers who are routinely exposed to neutrons and been analyzing the relationship between the SSNTD and the TLAD (T/Rf) over the past 6 years. Consequently, the / $_{rm f}$ in each year was 10-20 (3.363 mm $^{-2}$ )/(mSv $^{137}$ Cs eq.), which is smaller than the data during 1991-1993, although the neutron spectra had not changed compared with that of the early 1990s. This decrease of the / $_{rm f}$ implies that the ratio of work carried out nearby the gloveboxes to total work decreased.

In late years, Electronic Personal Dosemeter (EPD) has been widely used because of its useful specifications: indicating measurement values on site, lower detect limits than glass badge. However, an investigation of its response characteristic is difficult to perform using actual low dose rate -ray. The investigation needs sheildings of a entire irradiation room for reducing natural radiation. In this study, at the compact irradiation system with low dose rate which National Institute of Advanced Industrial Science and technology developed, -ray of $^{137}$ Cs below 0.1Sv/h were irradiated to two models of EPD with recording function. Integrated dose and standard deviation for EPD were analyzed to investigate response characteristics for low dose rate radiation.

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

Results of whole body counting for JAEA staff members engaged in the emergency radiological monitoring for the Fukushima nuclear disaster

Measurements of $^{131}$ I in the thyroids of employees involved in the Fukushima Daiichi Nuclear Power Station accident

Verification analysis of thermoluminescent albedo neutron dosimetry at MOX fuel facilities

Study on phantoms for field-testing of personal neutron dosemeters in more realistic exposure condition

Neutron monitoring around the MOX facilities using TLD

Current activities for acute medical management of radiation emergency victims in Nuclear Fuel Cycle Engineering Lab., JAEA

Neutron monitoring at the boundaries of control areas in MOX facilities with TLD

Study on source term for emergency action plan on a criticality accident

Relationship between induced activity of indium and count rates of a survey meter for screening personnel exposed in a criticality accident

Individual dose analysis of non-uniform body and extremity exposures during glove box operations

Radiation control for extremity in Tokai Reprocessing plant, 1; TLD ring type dosemeter

Internal radioactivity measurements of workers at Fukushima Dai-ichi Nuclear Power Plant

Whole-body measurements for people living in Fukushima prefecture

Study of the individual exposure control using cloud-system direct ion storage dosimeter

Study on method of measuring children under 4 years old with the standing-type whole-body counters

Special monitoring for the persons working at central building in Tokai Reprocessing Plant

Ways of maintenance management for whole-body counters applicable to nuclear hazard

Investigations of personal dose characteristics involved Fukushima Daiichi reactor accident, 4; Field test, 2; Response of the personal dosemeter on the phantoms and result of a measurement of the ambient dose and the energy spectrum of rays

Investigation of electronic personal dosemeters response in the -ray field with low dose rate