How to protect yourself?
Origin of Iodine-131
Nuclear power plants operate on the principle of nuclear fission, which is the process where heavy atomic nuclei (Uranium-235 or Plutonium-239) are split into smaller nuclei when bombarded by neutrons. This reaction releases a large amount of energy and also produces various radioactive elements, known as fission products, such as Cesium-137, Strontium-90, or Iodine-131.
In the event of an accident at a nuclear power plant, the release of iodine-131 into the atmosphere can have direct health consequences for exposed individuals. If inhaled or ingested, this radioactive element tends to accumulate in the thyroid gland, significantly increasing the risk of cancer in this hormone-producing organ.
Characteristics of Iodine-131
Iodine-131 is an artificial radionuclide that emits beta-negative (β-) electrons. Its radioactive half-life is 8 days, meaning it loses half of its activity every 8 days.
The main forms of radioactive iodine released during a discharge from a nuclear reactor include[1]:
- Molecular iodine (I2), present in a gaseous form,
- Organic iodine, commonly in the form of methyl iodide (ICH3), also gaseous,
- Particulate iodine (aerosols) with variable particle sizes (which can aggregate).
Pathways of contamination
Radioactive iodine released after a nuclear plant incident is emitted into the atmosphere either as a gas or as an aerosol.
Inhaling contaminated air mostly introduces gaseous iodine into the bloodstream, where it concentrates in the thyroid.
Iodine also contaminates the environment by getting absorbed by plants and subsequently entering animal products. Radioactive iodine in contaminated foods, such as milk, also accumulates in the thyroid.
Preventative measure: potassium Iodide
Potassium iodide is a compound that contains potassium and stable (non-radioactive) iodine. Taking potassium iodide preemptively saturates the thyroid gland with stable iodine, protecting it from potential exposure to radioactive iodine-131 during a nuclear incident. By preventing the uptake of I-131, potassium iodide reduces the risk of thyroid cancer.
Note: Potassium iodide does not protect against the effects of radiation from other fission products released into the atmosphere (e.g., Cesium-137). It should be used as a complement to evacuation, sheltering, and food safety measures.
When should you take potassium Iodide?
Potassium iodide should be taken when there is a high likelihood of exposure to significant amounts of iodine-131. It is most effective when taken before or immediately after exposure—ideally, before or as the radioactive cloud passes. However, it can still offer substantial protection if taken within three to four hours after exposure.
Follow health authority guidelines for when to start taking potassium iodide. At the same time, implement sheltering measures and ensure access to uncontaminated food and water.
Who should take potassium Iodide?
Adults under 40, children and pregnant and nursing women should take potassium iodide.
Adults over 40 should not take potassium iodide unless local health authorities say so, for example because a very high level of iodine-131 contamination is expected. Adults over 40 have a low risk of developing thyroid cancer after exposure to I-131, and are more likely to have allergic reactions to potassium iodide.
Breastfeeding women should stop breastfeeding as iodine-131 quickly passes into breast milk. However, if breast milk is the only available food source, breastfeeding should continue.
Usual dosage of potassium Iodide tablets[2]:
Government-issued potassium iodide tablets in the event of radiation exposure are usually dosed at 65mg or 130mg. Recommended daily dosages are:
- Infants (0–1 month, breastfed or not): 16mg (¼ of a 65mg tablet).
- Children (1 month to 3 years): 32mg (½ of a 65mg tablet).
- Children/adolescents (3 to 12 years): 65mg (one 65mg tablet).
- Adolescents from 12 years old and adults (including breastfeeding women): 130mg (two 65mg tablets).
How long should you take potassium Iodide?
Take potassium iodide as long as exposure to iodine-131 continues. Follow local health authority instructions.
Additional protective measure alongside Potassium Iodide
The CFO CBR filter canister [3] (large ABEK2 Hg SX P3 REACTOR NBC – Ref. OUVRY: 111001AA), used with a full-face mask, provides broad-spectrum protection, filtering both radioactive particles and radioactive iodine vapors.
Special case: zaporijia nuclear power plant
The Zaporijia nuclear power plant is located in Ukraine, in the Zaporijia oblast, near the city of Enerhodar, around 50 kilometers southwest of Zaporijia. It comprises six 1,000 MW VVER nuclear reactors and is near the frontline between Russian and Ukrainian forces. Ongoing fighting and bombardments present a constant threat to the safety and security of the installation, raising concerns that it could become an NRBCe weapon.
But what about the risk posed by iodine-131?
To assess the risk of a potential release of radioactive iodine from the Zaporijia plant, a detailed analysis of the reactors’ operating status is needed. When all reactors are in cold shutdown (as was the case on April 13, 2024, according to the IAEA[4]), the amount of radioactive iodine decreases rapidly due to its 8-day half-life. After 80 days, the remaining radioactive iodine is negligible, and taking potassium iodide is not necessary in the event of a radiological incident[5].
Bibliography:
[1] https://www.irsn.fr/sites/default/files/documents/larecherche/publications-documentation/fiches-radionucleides/I131SAN.pdf
[2] https://www.vidal.fr/medicaments/gammes/iodure-de-potassium-pharmacie-centrale-des-armees-40231.html
[3] https://ouvry.com/en/produit/abek2-p3-cbn-broad-spectrum-military-civil/
[4] https://www.iaea.org/newscenter/pressreleases/update-223-iaea-director-general-statement-on-situation-in-ukraine
[5] https://www.irsn.fr/savoir-comprendre/sante/ce-quil-faut-savoir-sur-comprimes-diode-stable