There are several isotopes of radon with varying half lives....

There are several isotopes of radon with varying half lives. Naturally occuring thorium found in rare earth ores decays into radon-220 (also known as thoron). Radon-220 has a half life of only 55 seconds and none of its subsequent decay products are gases. What this means is that any radon released would have decayed within a few minutes and settled close to its source as radioactive dust. This dust then further decays into non-radioactive lead in a matter of hours. There is virtually no chance of any appreciable amount of radon-220 reaching even the perimeter of the plant.

Thorium-232 has a half life of 14 billion years. This means that in a year, if you take 1 tonne of thorium, less than 0.05 milligrams of that would have decayed and turned into radon. The planned capacity of the Gebeng plant is 22,000 tonnes per year, with thorium content claimed to be 0.16%. This comes to about 35 tonnes of thorium per year. There is some dispute about these numbers, so let?s be generous and take it as 100 tonnes. Assuming the unlikely scenario that a whole year?s supply of ore is left lying around exposed in the plant at any one time, we?re looking at less than 5 mg of radon being produced in a whole year. When dispersed into the air, given radon?s very short half life, this is negligible.

ALSO, the the radiation emitted are alpha particles;
1. Alpha radiation is not able to penetrate skin.

2. Alpha-emitting materials can be harmful to humans if the materials are inhaled, swallowed, or absorbed through open wounds.

3. A variety of instruments have been designed to measure alpha radiation. Special training in use of these instruments is essential for making accurate measurements.

4. A civil defense instrument (CD V-700) cannot detect the presence of radioactive materials that produce alpha radiation unless the radioactive materials also produce beta and/or gamma radiation.

5. Instruments cannot detect alpha radiation through even a thin layer of water, blood, dust, paper, or other material, because alpha radiation is not penetrating.

6. Alpha radiation travels a very short distance through air.

7. Alpha radiation is not able to penetrate turnout gear, clothing, or a cover on a probe. Turnout gear and dry clothing can keep alpha emitters off of the skin.
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