Example: Calculation of dose of ...

To estimate radiation dose from inhaling radioactive substances in the air, you need a concentration of radioactive substances in the air. Such data, however, are rarely announced.In question (3) mentioned above, the data presented by the Bureau of Labor and Industrial Affairs (http://www.sangyo-rodo.metro.tokyo.jp/) are used to calculate as follows.

Dose of radiation received (micro Sv) = Effective dose coefficient (the values in the chart below) x radioactive concentration (Bq/m3) x respiratory coefficient (22.2m3 a day here) x number of days

 

 

Iodine-131

Iodine-132

Cesium-137

Cesium-134

 

New-born baby (3 months)

0.072

0.0011

0.11

0.070

Infant(Age 1)

0.072

0.00096

0.010

0.063

Child (age 2-7)

0.037

0.00045

0.070

0.041

Adult

0.0074

0.000094

0.039

0.020



(Oral ingestionof particles (Type F); NIRS compiled the data based onICRP Database of Dose Coefficients: Workers and Members of the public, CD-ROM, 1998”)

The highest levels of radioactive concentration for Iodine-131, Iodine-132, Cesium-137 and Cesium-134 in the dust in the air in Tokyo were recorded from 10:00 to 11:00 hours on March 15 as being 241, 281, 60 and 64 Bq/m3., respectively.Thus, a rough estimate of the amount of radiation potentially received from inhaling 22.2m3 of air/h would be as follows.

Iodine-131: 0.0074 x 241 x 22.2 x 1/24 = 1.05 micro Sv. --- (1)

Iodine-132: 0.000094 x 281 x 22.2 x 1/24 = 0.0244 micro Sv. ---- (2)

Cesium-137: 0.039 x 60 x 22.2 x 1/24 = 2.16 micro Sv. ---- (3)

Cesium-134: 0.020 x 64 x 22.2 x 1/24 = 1.18 micro Sv. ---- (4)

Radiation dose in this hour = (1) + (2) + (3) + (4) = 5.01 micro Sv.

Repeat this calculation for all the hours and add them up. The above question (3) refers to the total of all values recorded from March 14 to April 11. Iodine vapor is not included.

With respect to children’s respiratory coefficients per day, the ICRP suggests (in publication 71) 2.86m3/day for a new born baby (3 months), 5.16m3/day for an infant (age 1), 8.72m3/day for a child (age 5), 15.3m3/day for a child (age 10) and 20.1 m3 for a child (age 15).

You can estimate your accumulated dose, to some extent, by combining the dose of radiation received from air dose, the dose from breathing in air containing radioactive substances and the radiation dose from the intake of food or water containing radioactive substances.