Introduction
The explosion of the Chernobyl reactor remains one of the greatest and most iconic nuclear disasters of the 20th century. The incident allows us to examine the dangers of nuclear power. Chernobyl had profound effects on the surrounding ecology and public health, with consequences of radiation being felt to this day. Using the principles of time, distance, and shielding, this paper will seek to determine the extent of radiation exposure caused by the Chernobyl disaster.
Time
Emergency workers were exposed to direct radiation for prolonged periods. Helicopter pilots hovered over the reactor for several minutes, making several flights a day. On-ground workers were forced to work in shifts of several hours. People conducting operations within direct exposure to the reactor were officially limited to working in short shifts but considerably exceeded exposure times. Furthermore, even when off-duty, the laborers were exposed to the irradiated atmosphere in the plant area. The official death toll for Chernobyl workers stood at 56 but is estimated to be in the thousands (SFASUEM, 2016).
The population in the nearby area was continuously exposed to radiation. While residential centers within the 30-km exclusion zone were evacuated quickly, the further one lived from the plant; the later an evacuation order was issued. Some villages only 4km from the plant were only evacuated after three days, resulting in citizens receiving a 130mSv radiation dose (Drozdovitch et al., 2011). Models suggest that significant radioactive isotope deposition could be measured in both urban and rural environments up to seven years after the disaster, similar to that of atomic weapon testing. Minor effective doses will be noticeable within a range of up to 1000km well into the 21st century (Jacob et al., 1996).
Distance
Approximately 24,000 people within 15km of the plant received an average of 450 mSv before evacuation. The total radiation released is considered to be 5200 PBq (World Nuclear Association, 2016). The contamination spread to significant distances from the incident site throughout the Soviet Union and Europe. The radioactive cloud spread through Ukraine, Belarus, reaching as far as Sweden and Western Europe (SFASUEM, 2016).
Heavy radioactive particles were mostly found within a 100km zone of Chernobyl while the wind carried smaller particles. The 30-km zone around the reactor was severely contaminated with cesium-137 ground deposits exceeding 1,500 kBq/m2 while territories 500km away ranged in the 200-600 kBq/m2 (OECD Nuclear Energy Agency, 1995). The ratio of radioactive isotopes in the atmosphere and deposited into the ground differs based on distance and velocity. In combination with time-related factors, public health exposure to radiation significantly exceeded established limits.
Shielding
At the time of the explosion, citizens in the surrounding areas had no effective warning or protection. Shielding factors that can be considered are residential buildings made from construction materials such as concrete or wood (Drozdovitch et al., 2011). Workers participating in liquidating the disaster received little to no effective protection. They were exposed directly to radioactive fire and fumes. Often secondary workers such as medical staff treating Chernobyl liquidators received as much as ten mSv (Stanford University, n.d.).
Temporary steel and the concrete sarcophagus was constructed over the reactor in the months following the disaster. However, it was significantly unstable and leaking. The radiation fuel inside the reactor exceeded 20MCi (Borovoi, 1996). Therefore, the shielding available to the population and disaster workers at the time and in the aftermath of the disaster was mostly unreliable.
References
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Drozdovitch, V., Khrouch, V., Maceika, E., Zvonova, I., Vlasov, O., Bratilova, A., … Bouville, A. (2011). Reconstruction of radiation doses in a case-control study of thyroid cancer following the Chernobyl accident. Health Physics, 99(1), 1-16. Web.
Jacob, P., Roth, P., Golikov, V., Balonov, M., Erkin, V., Likhtariov, I., Garger, E. & Kashparov, V. (1996). Exposures from external radiation and from inhalation of resuspended material. In A. Karaoglou, G. Desmet, G.N. Kelly, & H. G. Menzel (Eds.), The radiological consequences of the Chernobyl accident (pp. 251–260). Brussels, Belgium: European Commission.
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SFASUEM. (2016). National geographic documentary 2014 what really happened at Chernobyl full documentary hd 1 [Video file]. Web.
Stanford University. (n.d.). Ionizing radiation and terrorist incidents: Important points for the patient and you. Web.
World Nuclear Association. (2016). Nuclear radiation and health effects. Web.