About microspot

In Yokohama City, we have measured spatial radiation doses at approximately 4,300 facilities, such as nursery schools and elementary and junior high schools, but there is no problematic value in the radiation dose in the space where we usually live (minimum 0.01 μSv / h-maximum 0.21 μSv / h).
The current air dose in Yokohama City is a value that allows you to live a normal life with peace of mind.
However, there have been some places in the city that have been known nationwide and have locally high spatial radiation doses, which are described as so-called micro spots.

• September 21, 2011 "About measurement result of radiation dose in municipal nursery schools and municipal schools in Kohoku Ward" (PDF: 159KB)
• September 17, 2011 "Confirmation of places where radiation dose of higher value than the surrounding area was measured and future countermeasures" (PDF: 303KB)

• Results of measurement at municipal nursery schools (Kohoku Ward)

The so-called microspot is a radioactive material released by the hydrogen explosion that occurred in mid-March falls with rain and soaks in earth and sand, etc., repeatedly drying and depositing, resulting in a relatively high radioactivity concentration.
In general, it is said that under gutters and road gutters tend to become microspots.
The radiation dose of the microspot is related to the distance, and the air dose will be lower if it is slightly away, such as 50 cm or 1 m. In addition, frequent cleaning is effective for places where micro spots are likely to occur, such as the following.
If you are worried about daily cleaning of your home, please refer to the following website.

In Yokohama City, we measure places that are likely to become microspots, mainly in elementary and junior high schools and parks where children gather.

• A place for dust
• Rain gutters and their drains, around drains and manholes, dry traces of puddles, etc.

• Hotspot discovery / decontamination manual for private homes (outside site)(Japan Society of Radiation Safety Management)
• Guidelines for Response to Locally Contaminated Areas by Radioactive Materials (External Site)(Ministry of the Environment)