|Fig. 1: This is a radiation map as a result of the Chernobyl explosion.  (Source: Wikimedia Commons)|
On March 9, 2011 an unfortunate event happened in Japan. A 9.0 earthquake hit Japan resulting in Tsunami. This horrifying natural disaster resulted in the death of over 14,000 citizens of Japan.  To make matters worse the earthquake caused a great deal of damage to the Fukushima Daiichi nuclear power plant. This resulted in a month-long emission of radioactive material into the atmosphere and ocean. As a result of this, areas within a 20 km radius of the Fukushima power plant were completely restricted during the month of the emissions.  The long-term effects of this tragic incident are still a bit unclear. However, in 1986 when the Chernobyl nuclear reactor exploded, it released 5% of its nuclear reactor core into the atmosphere. The explosion resulted in the diagnosis of 237 people with Acute Radiation Syndrome (ARS) and was later confirmed in 134 cases.  Of the 134 confirmed cases 28 people died as a result of ARS within a few weeks of the accident.  Nuclear-power plant accidents aren't very frequent, but when they happen they can be very terrible.
The primary fuel in a nuclear power plant is an isotope of uranium . This uranium undergoes fission produce the energy that is used to heat water and turn steam-driven turbine generators. The main problem that may occur when a nuclear plant acquires damage is that the nuclear core containing the uranium fuel and products from fission may become damaged and allow radioactive materials to escape into the atmosphere.  This can happen through a failing in the cooling system within the core. Elevated temperatures and cause the core and also the uranium fuel to melt; resulting in an explosion within the reactor. Thus, releasing the radioactive materials.
There are three ways to characterize radiation exposure. Those being total or partial body exposure, external contamination, and internal contamination.  Total or partial body exposure occurs when the external source irradiates the body either to the skin or deeply into internal organs. External contamination occurs when the products of fission settle on human beings, and exposes the skin or organs.Internal contamination occurs when fission products are ingested, inhaled, or enter the body through wounds. This is the most common source of radiation exposure to populations around nuclear reactors. 
After the Chernobyl explosion an estimated 5 million people were exposed to radiation through internal contamination.  As seen in Fig. 1, the radiation emitted spread through a vast part of the Ukraine. These nuclear plant disasters can release a variety of different radioisotopes into the environment. During, Chernobyl incident an estimated 20 isotopes were released.  These included Np-239, I-131, Cs-137,and Pu-239. The health threat of these isotopes are dependent on a variety of factors. For example radioisotopes such as Np-239 with a very short half-life (58 hours), radioisotopes such as Pu-239 with a very long half- life (24,400 years), and radioisotopes such as Pu-238 that are not released in big amounts do no cause a large amount of internal or external contamination.  In the contrary, I-131 can be a major cause of death due to its prevalence in reactors and its characteristic to settle on the ground. I-131 can be consumed through contaminated foods such as vegetables, fruits, and groundwater, and also inhaled.  Upon its entrance to the body, the I-131 swiftly accumulates in the thyroid gland, and becomes the source of β radiation.
A big consequence of radiation exposure is DNA damage. The damaged DNA will be fully recovered, harmless, cause dysfunction, or cell death. The effect of radiation exposure is dependent on, as mentioned, exposure type, and also radiation type (γ or β) and radiation dosage absorbed and rate of absorption. A single dose of more than 1 Gy radiation, which is equivalent to one joule of radiation energy per kilogram of body mass, can cause acute radiation syndrome. This has not been seen in the general population near a nuclear-reactor accident.  As mentioned before, all 134 patients with confirmed acute radiation sickness at the Chernobyl incident were plant workers or with the emergency response team. Most short term deaths due to the radiation exposure is due to hematologic, gastrointestinal, or cutaneous sequelae.  The 134 that died through the Chernobyl incident had bone marrow depression, 19 possessed widespread radiation dermatitis, and 15 had severe gastrointestinal complications. Long-term risks include elevated cancer risks. Studies of children living near the Chernobyl plant correlate the increased the risk of thyroid cancer by a factor of 2 to 5 per 1 Gy of thyroid dose. 
Nuclear Power-plant accidents are not very frequent, but can be cause a large health threat. The rareness of these accidents make it hard for those working in the medical field to treat health defects caused by these accidents. There must be continued plans created to provided a quick response to a unfortunate nuclear plant accident.
© Mallik Antoine. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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