Caesium-137 (also Cs-137) has a half-life of approximately 30 years, which means that after a period of 30 years, the amount of Cs-137 will have halved due to radioactive decay. Due to its long half-life, caesium-137 is the most important nuclide in respect of long-term contamination and, without countering actions, the most significant nuclide for…

Iodine-131 (also I-131) has a half-life of approximately 8 days, which means that after 8 days, the quantity of I-131 will have halved due to radioactive decay. The absorption of iodine-131 by the body can be significantly reduced by saturating the thyroid gland with stable (not radioactive) iodine by the taking of potassium iodide tablets.…

Source term is the actual amount of radioactive substances released from an accident and the time period over which the release takes place.