Radiation dose control from releases from “damaged” nuclear reactors

The recent nuclear crisis in Japan where four nuclear power reactors were damaged due to earthquake has raised questions with respect to the public exposures. In such accidental situations, the atmospheric releases from the damaged reactor core are mainly radio-nuclides in vapour form, such as of Iodine. Let us take an example of radioactive Iodine isotope, I-131.

The half-life - the time required for the radioactivity to reduce by one-half - for I-131 isotope is 8 days. Since the half life is considerably long, the isotope can travel long distances along the direction of the wind. On the way, the iodine isotope gets deposited on the soil, on water surfaces and on grass and “contaminates” them. Human consumption of such contaminated items results in radiation dose to the exposed population. Biologically, the thyroid hormone contains iodine in stable (not radioactive) form. If one is exposed to radioactive iodine, it will get uploaded into the thyroid and gets deposited there, giving radiation dose. Prophylaxis is a process where the thyroid is deliberately saturated by “stable” iodine and hence the uptake of “radioactive” iodine from the releases is minimized. A tablet of Potassium iodide/iodate (around 130 mg) is consumed, just before or just after the releases, for “blocking” the thyroid from radioactive iodine uptake.

In general, staying indoors, use of proper respirators and consumption of stable iodine tablets (if advised), reduces exposure of people from the atmospheric releases of radioactive isotopes/materials.

Public needs to be sensitized on this aspect for their protection.