Dr. Tsubokura's Radiation Lecture Vol.107

Author: Masaharu Tsubokura PhD.

Editors: Akihiko Ozaki M.D.,PhD., Yuki Senoo

113. A small effect of external radiation exposure from trucks passing through roads

Following the nuclear disaster, the national and local governments have taken the lead in processing decontamination work and nuclear waste disposal in various areas in the Fukushima prefecture. Furthermore, the decontamination process for all residential areas in the prefecture except for the difficult-to-return zone was completed in March 2018. Currently, trucks have started to transport the soil and waste temporarily stored at storage sites and decontamination sites to interim storage facilities.

 For this reason, many trucks come and go every day to transport the waste in the Fukushima prefecture. While a few dozen trucks pass by the temporary storage sites in each town and village in the prefecture every day, hundreds pass by on the main roads, and thousands pass by closed to interim storage facilities on the roads that are closed, such as the Joban Expressway interchange. Recent investigation has shown that the air dose rate at major truck transit points temporarily doubled at max, when approximately 3,300 trucks (about 3% out of a daily total of 110,000 trucks) passed by transit points.

 Some people may be concerned about external radiation exposure caused by trucks. However, the time taken by trucks to pass one point on a road is only a second. Even if someone were to stand at a point which tens of thousands of trucks pass in a day, the level of radiation exposure that person would receive would be less than a hundredth of that of a single chest x-ray.

114. 50cm of soil can block more than 99% of radiation exposure

Following the Fukushima Daiichi nuclear disaster, the national and local governments have taken the lead in processing decontamination work and nuclear waste disposal in various areas in the Fukushima prefecture. Furthermore, the decontamination process for all residential areas in the prefecture except for the difficult-to-return zone was completed in March 2018. Currently, trucks have initiated transportation of the soil and waste temporarily stored at storage sites and decontamination sites to interim storage facilities.

 The soil delivered from decontamination sites is spread across the storage facility using heavy machinery and then compressed to reduce its volume.

As is the case with some temporary storage sites, several measures to reduce radiation—such as covering the site with soil and ensuring adequate distance between the storage sites—have been taken.

 Soil with a thickness of 10cm can block 74% of radiation exposure emitted from cesium-137 radiation, while 30cm and 50cm of soil can block 98% and more than 99%, respectively. Moreover, when the soil delivered from decontamination sites is covered with concrete, it can block radiation slightly more compared to when it is covered with more soil. Furthermore, the intensity of radiation exposure is inversely proportional to the square of the distance from the source. Therefore, the level of radiation exposure when you are standing 10 meters and 100 meters away from the source will be 1/100th and 1/10,000th of the level when you are standing 1 meter away from it.

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The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, 10th and 17th February 2019 was reproduced for MRIC Global under the author's permission.

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