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Journal Articles

Comparative study on performance of various environmental radiation monitors

Tamakuma, Yuki*; Yamada, Ryohei; Suzuki, Takahito*; Kuroki, Tomohiro*; Saga, Rikiya*; Mizuno, Hiroyuki*; Sasaki, Hiroyuki*; Iwaoka, Kazuki*; Hosoda, Masahiro*; Tokonami, Shinji*

Radiation Protection Dosimetry, 184(3-4), p.307 - 310, 2019/10

 Times Cited Count:1 Percentile:17.09(Environmental Sciences)

After the Fukushima Daiichi Nuclear Power Plant accident, the radiation dose for first responders was not evaluated accurately due to lack of the monitoring data. It has been important to evaluate a radiation dose for workers in emergency response at a nuclear accident. In this study, a new device which can evaluate both of external and internal exposure doses was developed and the performance of various environmental radiation monitors including commercially available monitors were tested and compared from the viewpoint of an environmental monitoring at emergency situation. Background counts of the monitors and the ambient dose equivalent rate were measured in Fukushima Prefecture. The detection limit for beta particles was evaluated by the method of ISO11929. The sensitivity for gamma-rays of the dust monitor using a ZnS(Ag) and a plastic scintillator was high, but that of the external exposure monitor using a silicon photodiode with CsI(Tl) crystal was relatively low. The detection limit ranged 190-280 Bq m$$^{-3}$$ at 100 $$mu$$Sv h$$^{-1}$$, exceeding the detection limit of 100 Bq m$$^{-3}$$ in the minimum requirement by the National Regulation Authority in Japan. Use of the shielding with lead is necessary to achieve the minimum requirement. These results indicate that the dust monitor using a ZnS(Ag) scintillator and a plastic scintillator is suitable for the external exposure monitor and the developed internal exposure monitor is for the internal exposure monitor at emergency situation among the evaluated monitors. In the future study, the counting efficiency, the relative uncertainty and the performance of the detection for alpha particles will be evaluated, and it will be considered which type of a monitor is suitable after taking the portability into account.

Oral presentation

A Study of sediment movements in mountainous catchments by beryllium isotopes analysis

Ikemi, Hiroaki*; Pachri, H.*; Kokubu, Yoko; Mitani, Yasuhiro*; Kuroki, Takahito*

no journal, , 

One of issues in the comprehensive river-sediment management is to develop how to estimate a sediment production from a mountainous stream. In this study, beryllium isotopes of quartz extracted from sediment samples have been analyzed by JAEA-AMS-TONO to clarify a sediment dynamics in mountain streams. The sediment samples have been collected at four riverbeds and one hillslope in two different sub-catchments (A and B) of a Mesozoic granitic block located in the Umi-kawa river basin, Fukuoka. The sample of the catchment B shows a little bit higher value in $$^{10}$$Be-content than those of catchment A. This result indicates that the river sediment in the catchment B includes quartz grains that have been exposed on a ground surface for a long time compared with the catchment A. It is also possible that the river sediment in the catchments A contains more landslide materials because the landslide materials, which have come from a deeper part, might have a lower value in $$^{10}$$Be-content.

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