|Fig. 1: Chernobyl power plant taken in Pripyat, Ukraine. (Source: Wikimedia Commons.)|
The fuel of a nuclear power plant undergoes fission to produce the energy that is used to heat water and therefore turn the steam-driven turbine generators. However, the fuel also creates radioactive fission products. In the case of an accident, the primary concern lies in the chance that the support structure of the fuel and fission products gets damaged and releases radioactive elements into the surrounding environment. This can happen if the core cooling system fails, in which case the reactor core and the fuel itself can melt. High temperatures and pressures can result in explosions within the reactor, thereby distributing the radioactive material. However, in most plants, the potential effects of a cooling-system failure are "minimized by surrounding the reactor core with a steel-walled vessel, which in turn is surrounded by an airtight, steel-reinforced concrete containment structure that is designed to contain the radioactive material indefinitely." 
During a nuclear core-melt accident, cooling capacity is lost in an operating nuclear reactor and melting of the reactor core. Inserting neutron-absorbing control rods can stop fission of uranium in a fuel. However, tremendous amounts of heat generated by radioactive decay must be discharged to prevent to core from melting. The most dramatic incidents occurred at operating commercial nuclear power plants, including: Three Mile Island, USA in 1979, Chernobyl, USSR in 1986, and Fukushima, Japan in 2011. 
Radiation exposure due to reactor accidents is characterized in three different ways: (1) total or partial body exposure due to close proximity to a radiation source, (2) external contamination, and (3) internal contamination. Total or partial body exposure can result when an external source irradiates the body either on the skin or in the organs. This difference is due to the radiation waves - beta radiation does not travel that long of a distance, and can result in the tissues, but high-energy gamma radiation can penetrate more deeply, resulting in damage to internal organs. External contamination results when the fission products settle on the body, thereby exposing the skin and internal organs. Internal contamination results when fission products are either ingested or inhaled, or when they enter the body via open wounds. The latter mechanism is the process by which large populations around a reactor accident get exposed to radiation. 
The Fukushima Nuclear Power Plant suffered several radiation accidents after The Great East Japan Earthquake in March of 2011. The earthquake and the tsunamis instigated the failure of the containment cooling system of the reactors, which led to a core meltdown and a hydrogen explosion within the reactors. The explosion of No. 1 reactor on March 12 left five people injured, while that of No. 3 left eleven people injured. On March 24, it was reported that three workers were exposed to radiation when laying cables in the radiator. 
Baum et al. investigated the psychophysiological impact of an environmental stressor by examining the nuclear accident of the Three Mile Island (TMI). In the study, TMI residents were compared to people living near an undamaged nuclear power plant, people living near a coal-fired power plant, and people living more than 20 miles from any power plant. Behavioral measures of stress were obtained. Results indicated that the residents of the Three Mile Island exhibited more symptoms of stress more than one year after the nuclear accident in comparison to people who did not live in those areas. 
With regards to the Chernobyl nuclear accident, the main hazard post-accident was due to radioiodine. A difference was found between children who were tested under the age of seven at the time of the accident and the rest of the population. In the later phase, whole-body exposure to radiocaesium was the main concern. Nonetheless, preventative measures was able to greatly reduce the risk of health effects. 
© Danielle Rasooly. 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.
 J. P. Christodouleas, "Short-Term and Long-Term Health Risks of Nuclear-Power-Plant Accidents." N. Engl. J. Med. 364, 2334 (2011).
 P. C. Burns, R. C. Ewing, and A. Navrotsky, "Nuclear Fuel in a Reactor Accident," Science 335, 1184 (2012).
 N. Morimura et al., "Emergency/Disaster Medical Support in the Restoration Project for the Fukushima Nuclear Power Plant Accident," Emerg. Med. J. 30, 997 (2013).
 A. L. Baum, R. J. Gatchel, and M. A. Schaeffer, "Emotional, Behavioral, and Physiological Effects of Chronic Stress at Three Mile Island," J. Consult. Clin. Psych. 51, 565 (1983).
 L. A. Ilyin et al., "Radiocontamination Patterns and Possible Health Consequences of the Accident at the Chernobyl Nuclear Power Station," J. Radiol. Prot. 10, 3 (1990).