Airborne radiation in Fukushima forests down 74%

12 May 2018

Airborne radiation levels at 362 survey points in forest areas in Fukushima Prefecture averaged 0.23 microsievert per hour in fiscal 2017, down 74% from 0.91 microsievert in fiscal 2011 logged after the nuclear accident at Tokyo Electric Power Co.'s Fukushima Daiichi power plant, the prefectural government said on May 11 in a survey report.

The prefecture presented the results at a briefing in Fukushima city for people involved in the forestry industry. It has been continuously monitoring the level of airborne radiation in forests since the nuclear disaster.

According to the report, survey points with average radiation levels of less than 0.23 microsievert per hour, which is the target mainly for the national government's decontamination work, came to 226, accounting for 62% of overall points, in fiscal 2017, up from 42, 12%, in fiscal 2011.

Given the results, the prefecture's forestry planning section believes that the radiation dosage in the air has decreased at the same rate as the natural decay of radioactive cesium in forests. With radioactive cesium concentration in lumber seen to be lower in forests with lower radiation dosages, a section official said, "Forest areas eligible for logging are increasing year after year."

In a more detailed and wider survey for fiscal 2017 covering 1,300 points, including areas where evacuation orders after the nuclear accident have been lifted, radiation levels were on a downward trend across the prefecture, but remained high at survey points around the crippled plant. The highest level among all was 3.8 microsieverts per hour at a point in Iitate village, and the lowest came to 0.03 microsievert in the entire Minami-aizu district.

(Translated by Kyodo News)