Radionuclides and Physics

The accident at Chernobyl released ionizing radiation, a type of radiation that damages living tissues and causes DNA mutations in cells, which can lead to cancer and other health problems.

Ionizing radiation is released by atoms and has enough energy to remove tightly bound electrons from atoms, creating ions. The spontaneous atom disintegration is called radioactivity and the atoms that have the potential to disintegrate are called radionuclides.

There are two main types of radiation exposure: external, such as depositing on materials, and internal, such as entering the body or bloodstream. In the case of Chernobyl, the radionuclides from the disaster predominantly entered the body via ingestion or inhalation. Affected individuals were exposed to a range of radionuclides, including ¹³¹I, ¹⁰³Ru, and ¹⁴⁴Ce via external exposure and ¹³⁴Cs and ¹³⁷Cs via internal ingestion exposure.

Minor quantities of absorbed ionizing radiation can cause symptoms such as impaired tissue and organ function, radiation burns, and skin redness. When ionizing radiation accumulates in critical organs, such as iodine in the thyroid gland or strontium in bone marrow, prolonged exposure can be particularly dangerous. For example, the thyroid gland is responsible for regulating the body's metabolism, so if it is damaged by radiation, it can cause a wide range of health problems. Strontium-90 is chemically similar to calcium and cesium-137 is similar to potassium, so deficiencies in these vitamins can occur if they are absorbed.

In general, the medical theory states that if the body is exposed to radiation in low doses or over time, the risk of cancer and other health problems is reduced because the body's repair mechanisms have time to fix the mutations caused by radiation. These mutations are caused by ionizing radiation initiating carcinogenesis due to direct DNA damage or the formation of free radicals that induce DNA damage. However, exposure to high doses of radiation, even for a short period of time, can increase the risk of cancer. Even low doses of radiation, like those from pediatric CT scans, can increase cancer risk, especially when exposed at a young age. The severity of radiation sickness also increases with higher doses of radiation, with doses above 1000 mSv leading to long-term health effects like immune system impairment and gastrointestinal cancers. In the Chernobyl disaster, the highest radiation levels reached in the reaction building were 300,000 mSv/hr during the accident and 22 years after the explosion was 34,000 mSv/hr, but outside of the plant, radiation exposure was significantly less.

Given the drastic effects that radiation can have on the body, there is a major need to understand the effects of ionizing radiation from this disaster on the incidence of disease.