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Radiation air dose - Tsuzuki Ward   government office in Yokohama-shi, southern part greenery office, environmental science research institute (from the surface of the earth 0.5m in height and 1m) 

※This measurement was finished on March 21, 2012. Will please see page of radiation monitoring post (the west for Hodogaya Ward France) (surface of the earth 1m) in future.

1 measurement contents

 By method that followed "environmental γ (gamma) line assay with consecutive monitors", we continue atmospheric γ (gamma) dose of radioactivity in the roof (from the ground 23m) of environmental science research institute of 1, Takigashira, Isogo-ku and measure manual of Ministry of Education, Culture, Sports, Science and Technology from 1983 and, in Motoichi, announce the data as radiation monitoring post on homepage.
 → Please click this.
 As we measure radiation dose in 50cm in height and 1m in addition to this radiation monitoring post from the surface of the earth in city three spots (Tsuzuki Ward   government office, southern part greenery office, environmental science research institute) from June 13, 2011, we will tell about the data here.


2 measurement points

(1) Tsuzuki Ward   government office (Chigasakichuo, Tsuzuki-ku, Yokohama-shi)
(2) Southern greenery office (3, Kounandai, Kounan-ku, Yokohama-shi)
(3) Environmental science research institute (1, Takigashira, Isogo-ku, Yokohama-shi)


3 result of a measurement

 We assume the weekly measurement from September 11, 2011. In addition, we change model about measuring instrument.

[result of a measurement from September 11, 2011]

 From September 13 to December 27

  From January 6 to March 21

※We publish result of a measurement after the next day of the measurement.  

[result of a measurement from June 13, 2011 to September 10]

 From June 13 to June 26

 From June 27 to July 10

 From July 11 to July 24

 From July 25 to August 7

 From August 8 to August 21

 From August 22 to September 4

 From September 5 to September 10

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4 method for measurement

(1)  Measuring instrument

 In this investigation, we measure with facility measuring instrument which there is of carrying around in small size said to be the next survey meter. In addition, we change model of measuring instrument from September 11, 2011.
    Model name      Measuring instrument from September 11, 2011

            TCS-172B (product made in Hitachi Aloka Medical Corporation)

           Measuring instruments from June 13, 2011 to September 10

            TCS-161A (product made in Hitachi Aloka Medical Corporation)
    Detector     NaI(Tl) scintillation detector (φ 25.4mm *25.4mm)
    Measurement lines class    γ (gamma) line
    Measurement unit    Microsievert every hour [μSv/h]
    Dose rate measurement range 0.01-30μSv/h [μSv/h]
(2)  Method for measurement
 We carry out by method that followed "emergency environmental radiation monitoring guideline" by the Nuclear Safety Commission. We perform the measurement at three points of fixed points per one spot.
 Measurement height measures 4 directions at altitude of 50cm and 1m each from the surface of the earth and publishes the mean.
(3) The measurement period and the number of measurement
 We measured every day from June 13, 2011 to September 10, but are doing with the weekly measurement from September 11 to the end of December as there was not big change to the measurements for 3 months.


Point to keep in mind of 5 data

 Unevenness comes out to measurements even if we measured the same radiation by the measurement of radiation dose with survey meter. In addition, measurements of radiation change by wind or the rain even if they receive influence with geological feature of measurement point or neighboring buildings and measure at the same place.


Conversion of 6 grays and sievert

 [Gy/h] is credit indicating quantity of energy which radiation has in gray every hour. [Sv/h] is credit to express size of influence that radiation gives in the human body in sievert every hour.
[conversion table] When we assume 1 Gy = 1Sv

 1  Gy/h  Gray every hour  =  1  Sv/h  Sievert every hour
 1,000  mGy/h  Millimeters gray every hour  =  1,000  mSv/h  Millisievert every hour
 1.000,000  μGy/h  Microgray every hour  =  1 million  μSv/h  Microsievert every hour
 1 billion  nGy/h  Nanogray every hour  =  1 billion  nSv/h  Nanosievert every hour


Reference about 7 measurements

  Environmental Planning Bureau Environment Administration Division telephone 045-671-2499 (weekdays from 8:30 to 17:15) 



City of Yokohama, Environmental Planning Bureau environment Maintenance Division Environment Administration Division - June 14, 2011 Making - March 29, 2012 Update
Opinion, inquiry - ks-kankyokanri@city.yokohama.jp - telephone: 045-671-2499 - FAX: 045-681-2790
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