On May 11th in the afternoon, I went for a walk for some exercise. This time I just took my Air Counter with me and left my heavy survey meter at home.
At around 2.30 pm, my reading went up to 1.15μSv/h in the middle of a vegetable field. It is more or less the same as the 1.1μSv/h measured at the Okumamachi Fureai Park (only 4 km away from The Fukushima Daiichi plant) on the same day! Now this was a shock.
The following is the record on the dosimeter. I had started to measure the air dose rate from about 1 pm and at 2 pm had measured around 0.3μSv/h.
1.15μSv/h is the highest reading that I had had during the 1 1/2 years of use of this dosimeter.
As you can see it was just for a short while that I measured such a high dose rate. As I moved about I still had high readings. I presume that there was an air current that carried radioactive substances near the ground. 1.15μSv/h is the equivalent of 300.000 Bq/m2 of cesium in the soil.
According to the following map the spot was at altitude 25.5m, in an area with mostly vegetable patches where urbanization is restricted.
松戸駅 Matsudo station
測定地点 location of measurement
船橋駅 Funabashi station
江戸川河口 mouth of Edogawa river
The following spot was quite far away from the previous one. The altitude is about 14m lower. The readings are not much different.
Where do the radioactive substances come from? It could be radon but would it rise so much on a plateau? There are incineration plants and waste recycling centres of Funabashi city in Sanbanse near the mouth of the Edogawa River. They are 8 km south of where I measured. If the chimneys of these plants are high then I guess the emission could travel quite far. It wouldn’t be unnatural to think that the emissions would have an impact on the surrounding environment in a radius of 8-10 km. I shudder to think that there are plants that release radioactive gas of 1μSv/h everywhere though.
I do not like the idea of taking a walk in a place where I can measure more than 1μSv/h. This is a dose rate where I literally should be running away from.
So on May 11th I was irradiated. These days, every time I go out to the countryside I get irradiated. I am starting to have the feeling that I cannot live near Tokyo any more.