Nuclear plant workers suffer internal radiation exposure after visiting Fukushima


Cooler King
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The government has discovered thousands of cases of workers at nuclear power plants outside Fukushima Prefecture suffering from internal exposure to radiation after they visited the prefecture, the head of the Nuclear and Industrial Safety Agency said.
Most of the workers who had internal exposure to radiation visited Fukushima after the nuclear crisis broke out following the March 11 quake and tsunami, and apparently inhaled radioactive substances scattered by hydrogen explosions at the Fukushima No. 1 Nuclear Power Plant.
The revelation has prompted local municipalities in Fukushima to consider checking residents' internal exposure to radiation.
Nobuaki Terasaka, head of the Nuclear and Industrial Safety Agency, told the House of Representatives Budget Committee on May 16 that there were a total of 4,956 cases of workers suffering from internal exposure to radiation at nuclear power plants in the country excluding the Fukushima No. 1 Nuclear Power Plant, and 4,766 of them involved workers originally from Fukushima who had visited the prefecture after the nuclear crisis. Terasaka revealed the data in his response to a question from Mito Kakizawa, a lawmaker from Your Party.
The Nuclear and Industrial Safety Agency said it received the data from power companies across the country that measured the workers' internal exposure to radiation with "whole-body counters" and recorded levels of 1,500 counts per minute (cpm) or higher. In 1,193 cases, workers had internal exposure to radiation of more than 10,000 cpm. Those workers had apparently returned to their homes near the Fukushima No. 1 Nuclear Power Plant or had moved to other nuclear power plants from the Fukushima No. 1 and 2 nuclear power plants.

Now, what are 'counts per minute', and can we convert them to an absorbed dose? A counts per minute reading is a measure of radioactivity. It is the amount of photons a geiger counter is able to detect after entering the gm tube of the device (calibrated to Cs-137). Each photon is presumed to have arisen from the decay of a radioactive isotope.

Although the 'counts per minute' value tries hard to indicate the amount of disintegrations per minute coming from a radioactive source, the two terms should not be confused. Most geiger counters have limitations, and will not detect all disintegrations taking place from a source, but will give you a good idea of the radioactivity originating in air, or coming from an object.

Nuclear disintegrations taking place within an atom are tied to the definition of the Becquerel. One becquerel = one disintegration per second. 60 counts per minute, theoretically, indicates 1 Becquerel of activity.

The readings mentioned in the article above stated a range of 1,500 to 10,000 cpm. Thus, they are reading between 25 to 166 becquerel of activity (assuming whole body), per person. The exact isotopes that NISA equipment is sensitive to is not mentioned in the article, but is also probably rated for Cesium.

Radiation Safety Philippines

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