Radiation dose measurement status in the school grounds of Yokohama City School

About the school grounds of municipal schools Elementary school: Ground surface 50cm, junior high school: Measurement at a position of 1m above the surface

[Radiation measurement results of 491 schools in Municipal Elementary Schools and junior high schools] (Summary of measurement results from June to September) (PDF: 130KB)

（Ａ）　Measurer City of Yokohama, Fire Bureau

Type name RDS -30 (manufactured by Million Technology)
Detector Energy Compensation GM tube
Measurement line type γ (gamma) line
Measurement unit μSv/h
Dose rate measurement range 0.01 μSv / h to 100 mSv
Or 1 μrem/h to 10 μrem/h

（Ｂ）　Measurer Yokohama City School Pharmacists Association

Type name TCS-172B (manufactured by Hitachi Aloka Medical)
Detector Na I (TI) scintillation detector
Measurement line type γ (gamma) line
Measurement unit μSv/h
Dose rate measurement range 0.01 μSv / h to 30 mSv

[After Friday, August 12, with the cooperation of the Yokohama City School Pharmacists Association, the measuring instrument of (B) has been added to measure. ]

In general, the measured value of the GM count tube (A) is higher than that of the scintillation detector (B).
This is the difference in the mechanism of the device.
For example, scintillation detectors tend to have higher sensitivity to radiation in a certain direction, and GM tubes tend to have higher measurement values because they are sensitive to the radiation dose in the lateral direction.

In addition, we will guide you to the Tokyo Metropolitan Safety Research Center website for information on differences in measured values due to differences in equipment types.
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http://monitoring.tokyo-eiken.go.jp/radiation_measurement.html (external site)