Chernobyl Power Plant
On April 26, 1986, the Chernobyl nuclear power station, located in the Soviet Union near Pripyat in the Ukraine, suffered a major accident. This accident is considered as the most severe in the history of the nuclear power industry due to a huge release of radioactive substances that caused contamination of the surrounding area over the large areas of Belarus, Russia and the Ukraine. In addition to the former Soviet Union countries, the contamination by radioactivity was spread throughout the Northern Hemisphere, mainly across Europe. The variation of meteorological conditions and wind regimes during the period of release was a contributing factor. The activity of the multiple plumes from Chernobyl was measured even in Japan, Canada, and the United States. Based on reactions of the public authorities in the various countries, it was clear that they were not prepared to deal with an accident of this magnitude. In addition, there were technical and organizational deficiencies in emergency planning in almost all countries. Since the exposure at the Chernobyl site was very specific in nature, this event enchanted public apprehension all over the world about the risks associated with the use of nuclear energy. Thus, in the 21 years since the accident, the UN Agencies in cooperation with experts from many countries conducted different studies dedicated to the Chernobyl accident, its aftermath, and the lessons that can be learnt for future. Although, these studies include the numerous aspects associated with reactor safety and severe accident management, intervention criteria, emergency procedures, and communication, the international community put its efforts to evaluate a significant impact of ionizing radiation on human health and environment. Spread of contamination at large distances from the accident site caused not only serious physical, health, and environmental damage in the short term, but it also led to the long term consequences in terms of social, economic disruption, and psychological stress.
The explosion at the Chernobyl nuclear power plant, was obviously the most severe ever to have occurred in the history of the Soviet nuclear industry; therefore, there have been many efforts put by authorities and experts at the national level to explore and understand the accounts of the accident caused such a serious and enormous consequences on human society. Although there are still some uncertainties regarding the exact causes and events leading to the accident, the key factors are now known. For example, United Nations Scientific Committee on the Effects of Atomic Radiation, in its Report to the General Assembly, has reported that the Unit 4, one of the four reactors of the Chernobyl nuclear power station, was to be shutdown for routine maintenance on 25 April 1986. On that occasion, it was decided to carry out a test of the capability of the plant equipment to provide enough electrical power to operate the reactor core cooling system and emergency equipment during the transition period between a loss of main station electrical power supply and the start up of the emergency power supply provided by diesel engines.
Unfortunately, this test, which was to concern the non-nuclear part of the power plant, was carried out without a proper exchange of information and co-ordination between the team in charge of the test and the personnel in charge of the operation and safety of the nuclear reactor. Therefore, inadequate safety precautions were included in the test program and the operating personnel were not alerted to the nuclear safety implications and potential danger of the electrical test. This lack of co-ordination and awareness, resulting from an insufficient level of safety measures within the plant staff, led the operators to take a number of actions which deviated from established safety procedures and led to a potentially dangerous situation. This course of actions corresponded to the existence of significant drawbacks in the reactor design that made the plant potentially unstable and easily susceptible to loss of control in case of operational errors. The combination of these factors provoked a sudden and uncontrollable power surge that resulted in violent explosions and almost total destruction of the reactor. The consequences of this catastrophe were further worsened by the graphite moderator and other material fires that broke out in the building and contributed to a widespread release of radioactive materials to the environment. (UNSCEAR 2000, 454-456)
The release of radioactive materials to the atmosphere was extremely high in quantity, involving about 190.3 tonnes of radioactive product inventory existing in the reactor core (qtd. in Smith ). The release of radioactive materials, lasting for more than a week, consisted of a wide variety of radioactive substances such as gases, aerosols and fragmented nuclear fuel particles with different physical, chemical and biological properties. The most significant impact on people's health caused radioactive iodine - the isotope 131 and caesium 137 (UNISEF 27). This duration and the high altitude (about 1-2 km) reached by the release were largely due to the graphite fire which was very difficult to extinguish. For these reasons and frequent changes of wind direction during the release period, the area affected by the radioactive plume and the consequent deposition of radioactive substances on the ground was extremely large, contaminating the whole Northern Hemisphere, although only part of Europe had significant levels of contamination (Smith 14). According to the report commissioned by UNDP and UNICEF with the support of UN-OCHA and WHO, the pattern of contamination on the ground and in foodchains, however was very uneven in some areas, especially in the western part of the Soviet Union, due to the influence of rainfall during the passage of the plume. This irregularity in the pattern of deposition was particularly pronounced at large distances from the reactor site (26-27).
Most of the population of the Northern Hemisphere was exposed to the radiation from the Chernobyl accident. After several years calculations of data from all available sources it is now possible to classify the range of population exposed to radiation into three groups: “Liquidators,” people involved in the clean-up and recovery operation during emergency period and the years after the accident (Smith 11); “Evacuees,” an evacuated population from exclusion zone, a 30-km radius from the reactor (Smith 252); and .not evacuated people. The main doses of radiation are those of the thyroid due to external irradiation and inhalation and ingestion of radioactive iodine isotopes and those to the whole body due to external irradiation from and ingestion of radioactive cesium isotopes. According to calculations of various international experts, the situation for the different exposed groups is the following:
The study of UNSCEAR 2000 reports that more than 110,000 inhabitants, living mostly in the 30-km radius area around the accident site, were evacuated during the first few weeks following the accident. These people received significant doses both to the whole body and to the thyroid, although the distribution of those doses was variable among them and depended on their places around the accident site and the delays of their evacuation. . Many of them are continued to be exposed, although to a lesser extent after their evacuation (472-474).
Based on the data available from Chernobyl: Catastrophe and Consequences by Smith and Beresford, the number of liquidators reaches up to 858,000 (239). A small number, about 400, of plant staff, firemen, local police and medical aid personnel, were on the site during the accident and its immediate aftermath and received very high doses from a variety of sources (UNSCEAR 2000, 469). Among them were all those who developed acute radiation syndrome and required emergency medical treatment. The doses to these people ranged from a few grays to well above 20 grays to the whole body from external irradiation and comparable or even higher internal doses, in particular to the thyroid, from incorporation of radionuclides. A number of scientists, who periodically performed technical actions inside the destroyed reactor area during several years, accumulated over time doses of similar magnitude (The Chernobyl Forum: 2003-2005, 11-14).
People living in contaminated areas of the former Soviet Union make up about 270,000 people continue to live in contaminated areas with radiocaesium deposition levels in excess of 555 kilobecquerels per square meter [kBq/m2], where protection measures still continue to be required (UNSCEAR 2000, 475). Children in the Gomel region of Belarus appear to have received the highest thyroid doses with a range from negligible levels up to 40 sieverts and an average of about 1 sievert for children aged 0 to 7. Because of the control of food in those areas, most of the radiation exposure since the summer of 1986 is due to external irradiation from the radiocaesium activity deposited on the ground (UNISEF 37-41).
Radiation exposure of the Chernobyl nuclear power plant caused the millions of people to suffer from numerous health effects that can be described as deterministic and stochastic effects. Effects termed deterministic are those of early health effects in extremely high radiation. In most cases, the symptoms of deterministic effects result in death and severe health impairment. As for stochastic effects, as a rule, they are late health effects caused by the low level exposures. In addition to radiation caused effects, the Chernobyl accident led to severe psychological effects (Smith 16-17).
The acute health effects occurred among the plant personnel and the persons, who intervened in the emergency phase to fight fires, provide medical aid and immediate clean-up operations. According to research of International Atomic Energy Agency, a total of 28 people died as a consequence of the accident, and about 134 people suffered various degrees of radiation sickness. No members of the general public suffered these kinds of effects (14).
As for the late health effects there was a possible increase of cancer incidence. In the decade following the accident there has been a real and significant increase of carcinomas of the thyroid caused by radioactive iodine fallout among the children living in the contaminated regions and by excessive consumption of ionized milk. By 2002, more than 4000 thyroid cancer cases had been diagnosed in this group, and it is most likely that a large fraction of these thyroid cancers is attributable to radioiodine intake (The Chernobyl Forum: 2003-2005, 15-16). There are might also be some increase of thyroid cancers among the adults living in those regions. From the observed trend of the increase of thyroid cancers it is expected that the peak has not yet been reached and that this kind of cancer will still continue for some time to show an excess above its natural rate in the area.
On the other hand, the scientific and medical observation of the population has not revealed any increase in other cancers, as well as in leukemia, congenital abnormalities, adverse pregnancy outcomes or any other radiation caused disease that could be attributed to the Chernobyl accident. Large scientific and epidemiological research programs, some of them sponsored by international organizations such as the WHO and Greenpeace, are being conducted to provide further insight into possible future health effects. However, the population dose estimates generally tend to indicate that, with the exception of thyroid disease, it is unlikely that the exposure would lead to discernible radiation effects. In the case of the liquidators this forecast should be taken with some caution.
An important effect of the accident, which has a bearing on health, is the appearance of a widespread status of psychological stress in the populations affected. The severity of this phenomenon, which is mostly observed in the contaminated regions of the former Soviet Union, appears to reflect the public fears about the unknowns of radiation spread and its effects, as well as its mistrust towards public authorities and official experts, and is certainly made worse by the disruption of the social networks and traditional ways of life provoked by the accident and its long-term consequences (Greenpeace 18-19). For instance, the number of psychological problems amongst the most affected population has increased due to evacuation and massive resettlement. In this case, people were forced to loose their jobs, social networks, leave their homes, and neighborhoods. It was more difficult for elderly people to adapt to the new environment, so in spite of the official restrictions on living in the contaminated zone from the reactor, most of these people return to their homes (qtd. in Smith 253).
The impact of the accident on agricultural practices, food production and use and other aspects of the environment has been and continues to be much more widespread than the direct health impact on humans.
Several techniques of soil treatment and decontamination to reduce the accumulation of radioactivity in agricultural produce and cow's milk and meat have been experimented with positive results in some cases. Nevertheless, within the former Soviet Union large areas of agricultural land are still excluded from use and are expected to continue to be so for a long time. In a much larger area, although agricultural production activities are carried out, the food produced is subjected to strict controls and restrictions of distribution and use (Smith 204).
A kind of environment where special problems were and continue to be experienced is the forest environment. Because of the high filtering characteristics of trees, deposition was often higher in forests than in other areas. An extreme case was the so-called "red forest" near to the Chernobyl site where the irradiation was so high as to kill the trees that had to be destroyed as radioactive waste. In more general terms, forests, being a source of timber, wild game, berries and mushrooms as well as a place for work and recreation, continue to be of concern in some areas and are expected to constitute a radiological problem for a long time (Smith 268-272).
Water bodies, such as rivers, lakes and reservoirs can be, if contaminated, an important source of human radiation exposure because of their uses for recreation, drinking and fishing. In the case of the Chernobyl accident this segment of the environment did not contribute significantly to the total radiation exposure. It was estimated that the component of the individual and collective doses that can be attributed to the water bodies and their products did not exceed 1 or 2 percent of the total exposure resulting from the accident (The Chernobyl Forum: 2003-2005, 24-25). The contamination of the water system has not posed a public health problem during the last decade. Nevertheless there are large quantities of radioactivity deposited in the catchment area of the system of water bodies in the contaminated regions around Chernobyl and there will continue to be for a long time a need for careful monitoring to ensure that washout from the catchment area will not contaminate drinking-water supplies (Smith 152-154).
The history of the modern industrial world has been affected on many occasions by catastrophes comparable or even more severe than the Chernobyl accident. However this accident, due not only to its severity but especially to the presence of ionizing radiation, had a significant impact on human society.
Not only it produced severe health consequences and physical and health damage in the short term, but, also, its long-term consequences in terms of social, economic disruption, psychological stress and damaged image of nuclear energy, are expected to be long standing. However, the international community has demonstrated a remarkable ability to understand and value the lessons that were drawn from this event. Now it is better prepared to cope with a challenge of this kind, if ever a severe nuclear accident should ever happen again.
List of Works Cited
Greenpeace. The Chernobyl Catastrophe Consequences on Human Health. Amsterdam: April, 2006.
International Atomic Energy Agency. The Chernobyl Forum: 2003-2005. Chernobyl's Legacy: Health, Environmental and Socio-Economic Impacts and Recommendations to the Governments of Belarus, the Russian Federation and Ukraine. Austria: IAEA, April, 2006
Smith, Jim, and Nicholas A. Beresford. Chernobyl: Catastrophe and Consequences. Chichester, UK: Springer Praxis Books, 2005.
United Nations Development Program and United Nations Children's Fund. The Human Consequences of the Chernobyl Nuclear Accident: A Strategy for Recovery. A Report Commissioned by UNDP and UNICEF with the support of UN-OCHA and WHO. New York: January, 2002.
United Nations Scientific Committee on the Effects of Atomic Radiation. Report to the General Assembly. Annex J: Exposures and Effects of the Chernobyl Accident. Volume 2. New York: UNSCEAR 2000.
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