Saturday, August 13, 2011

1 Millisievert Internal Radiation from a Man in Minami Soma City

Minami Soma City, while waiting for the lifting of the "evacuation-ready zone" designation, tested the internal radiation exposure of the residents in the high-radiation area within the city using the whole body counter.

Over 1 millisievert internal radiation was found in a man in his 60's, but the rest of the residents tested less than 1 millisievert, and the mayor of the city is pleased with the result.

From Asahi Shinbun (8/13/2011):


Minami Soma City in Fukushima Prefecture tested the internal radiation exposure of the city's residents, and found one man in his 60's with more than 1 millisievert radiation. The result was announced by the City General Hospital on August 13. It is the first time that internal radiation of more than 1 millisievert has been detected in the survey of the city residents.


The whole body counter was used to evaluate the radiation exposure in the future from the ingested radionuclides such as radioactive cesium. Half life of cesium-137 in the body, taking into account the amount that will be expelled in urine and stools, is 9 days for children aged between 0 and 1, 89 days for people over 31. At this point, the amount of radioactive materials in the body is considered to have decreased significantly.


The survey was done on 569 people over the age of 16 who live in a high-radiation area in the city and 330 students aged between 6 and 15, who attended the elementary schools and junior high schools in the city at the time of the accident. According to the hospital, the man who has been found with 1.02 millisievert internal radiation stayed in the mountain on March 12 to secure water supply.

Kahoku Shinpo (local Fukushima paper) reports that the mayor of the city is pleased with the result, and thinks it will reassure the residents that it is safe to live in Minami Soma City:


Mayor Katsunobu Sakurai said "It is regrettable that one resident exceeded 1 millisievert. But the vast majority of the residents tested at the safe level. I believe the residents of the city can judge from the result that the city is safe to live and work."

And what is the result that made the mayor happy? According to Kahoku Nippo,


There was no one exceeded 20 millisieverts, the level at which a treatment may become necessary. 561 adults, 99% of the subjects, tested less than 0.5 millisievert; 7 adults tested between 0.5 and 1 millisievert (not exceeding 1 millisievert); 2 school children was found with radioactive cesium, but the rest tested below the detection limit.


Anonymous said...

This doesn't make sense. Saying "1 Millisievert" means nothing without a time period. It's like saying I was walking 60 kilometers. Is it per hour, per year, per day?

Anonymous said...

Kodama has already explained that Sv numbers are meaningless for internal exposure. Next they will say it's like 5 X-rays or a flight to NY or whatever.

Antony said...

The whole body counter isn't measuring much - just how much Cesium is in the body somewhere. However, Cesium is probably just a flag for other radionuclides that are probably present - Strontium-90, Plutonium, Uranium, and so on. Then there is the problem of where these are. If Plutonium and Uranium (etc.) particles are breathed in, they may lodge in the throat and lungs. Since they are very genotoxic, only very small amounts are likely to cause cancers in later years. The ICRP model figure of 100mSv - below which cancers are not supposed to occur - is almost certainly just plain wrong by 2 to 3 orders of magnitude - Chris Busby and the ECRR say 300-900 times - in the ability to predict cancers. The whole Fukushima health study just starting up now is based on the false reassurance of the ICRP/UNSCEAR model. Sorry, mayor, not much to be happy about.

Hélios said...

Hello, I'm translating this post and I think there is a mistake.

At the end:
"There was no one exceeded 20 millisieverts, the level at which a treatment may become necessary."

Is it 20 millisieverts or 20 microsieverts ?(the man in his 60's is just at 1 millisievert)

Please for an answer.

Have a nice weekend.

Anonymous said...

It was the correct translation.

The sentence started off by reminding the readers the condition for treatment.

I.e. the current rule in Japan is that if exposure is less than 20 msv no treatment is required. Meaning that anything less than 20msv is considered non-event. i.e. it is safe.

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