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Chernobyl Nuclear Accident

4. How are highly contaminated areas managed?

  • 4.1 What has been done to reduce exposure in contaminated areas?
  • 4.2 What has been done to confine the damaged reactor and nuclear waste?
  • 4.3 What is the future of the restricted access area surrounding the site?

4.1 What has been done to reduce exposure in contaminated areas?

The source document for this Digest states:

Countermeasures involved huge human, financial and scientific resources

The Soviet and, later, Commonwealth of Independent States (CIS) authorities introduced a wide range of short and long term environmental countermeasures to mitigate the accidents negative consequences. The countermeasures involved huge human, financial and scientific resources.

Decontamination of settlements in contaminated regions of the USSR during the first years after the Chernobyl accident was successful in reducing the external dose when its implementation was preceded by proper remediation assessment. However, the decontamination has produced a disposal problem due to the considerable amount of low level radioactive waste that was created. Secondary cross-contamination with radionuclides of cleaned up plots from surrounding areas has not been observed.

The most effective agricultural countermeasures in the early phase were exclusion of contaminated pasture grasses from animal diets and rejection of milk based on radiation monitoring data. Feeding animals with “clean” fodder was effectively performed in some affected countries. However, these countermeasures were only partially effective in reducing radioiodine intake via milk because of the lack of timely information about the accident and necessary responses, particularly for private farmers.

The greatest long term problem has been radiocaesium contamination of milk and meat. In the USSR and later in the CIS countries, this has been addressed by the treatment of land used for fodder crops, clean feeding and application of Cs-binders, such as Prussian blue, see FIG. 7, to animals that enabled most farming practices to continue in affected areas and resulted in a large dose reduction.

FIG. 7. Changes with time in the use of Prussian blue in the CIS countries (IAEA).

Application of agricultural countermeasures in the affected CIS countries substantially decreased since the middle of 1990s (to less extent in Belarus) because of economic problems. In a short time, this resulted in an increase of radionuclide content in plant and animal agricultural products.

In Western Europe, because of the high and prolonged uptake of radiocaesium in the affected extensive systems, a range of countermeasures are still being used for animal products from uplands and forests.

The following forest-related restrictions widely applied in the USSR and later in CIS countries and in Scandinavia have reduced human exposure due to residence in radioactively contaminated forests and use of forest products:

  • Restrictions on public and forest worker access as a countermeasure against external exposure;
  • Restricted harvesting of food products such as game, berries and mushrooms by the public that contributed to reduction of internal doses. In the CIS countries mushrooms are a staple of many diets and, therefore, this restriction has been particularly important;
  • Restricted collection of firewood by the public to prevent exposures in the home and garden when the wood is burned and the ash is disposed of or used as a fertilizer; and
  • Alteration of hunting practices aiming to avoid consumption of meat with high seasonal levels of radiocaesium.

Numerous countermeasures put in place in the months and years after the accident to protect water systems from transfers of radioactivity from contaminated soils were generally ineffective and expensive. The most effective countermeasure was the early restriction of drinking water and changing to alternative supplies. Restrictions on consumption of freshwater fish have also proved effective in Scandinavia and Germany, though in Belarus, Russia and Ukraine such restrictions may not always have been adhered to.

Source & ©: UN Chernobyl Forum
 Chernobyl’s Legacy: Health, Environmental and Socio-economic Impacts (2006)
Environmental Consequences: Forum Expert Group Report, What environmental countermeasures and remediation have been implemented?, p.27-29

4.2 What has been done to confine the damaged reactor and nuclear waste?

The source document for this Digest states:

The accidental destruction of Chernobyl’s Unit 4 reactor generated extensive radioactive contamination and a large amount of radioactive waste in the Unit, at the plant site and in the surrounding area. Construction of the Shelter between May and November 1986, aiming at environmental containment of the damaged reactor, reduced radiation levels on-site and prevented further release of radionuclides off-site.

Planned New Safe Confinement over the destroyed Chernobyl reactor
FIG. 9. Planned New Safe Confinement over the destroyed Chernobyl reactor

The Shelter was erected in a short period under conditions of severe radiation exposure to personnel. Measures taken to save construction time and to reduce the high dose rates inside the structure led to imperfections in the Shelter as well as to lack of comprehensive data on the stability of the damaged Unit 4 structures. In addition, structural elements of the Shelter have degraded due to moisture-induced corrosion during the nearly two decades since it was erected. The main potential hazard of the Shelter is a possible collapse of its top structures and release of radioactive dust into the environment.

To avoid the potential collapse of the Shelter, measures are planned to strengthen unstable structures. In addition, a New Safe Confinement (NSC) that should provide more than 100 years service life is planned as a cover over the existing Shelter, see Fig. 9.

The construction of the NSC is expected to allow for the dismantlement of the current Shelter, removal of highly radioactive Fuel Containing Mass (FCM) from Unit 4, and eventual decommissioning of the damaged reactor.

In the course of remediation activities both at the Chernobyl nuclear power plant site and in its vicinity, large volumes of radioactive waste were generated and placed in temporary near-surface waste storage and disposal facilities. Trench and landfill facilities were created from 1986 to 1987 in the Exclusion Zone at distances of 0.5 to 15 km from the reactor site with the intention to avoid the spread of dust, reduce the radiation levels, and enable better working conditions at Unit 4 and in its surroundings. These facilities were established without proper design documentation and engineered barriers and do not meet contemporary waste disposal safety requirements.

During the years following the accident large resources were expended to provide a systematic analysis and an acceptable strategy for management of existing radioactive waste. However, to date a broadly accepted strategy for radioactive waste management at the Chernobyl power plant site and the Exclusion Zone, and especially for high level and long lived waste, has not yet been developed.

More radioactive waste is potentially expected to be generated in Ukraine in the years to come during NSC construction, possible Shelter dismantling, FCM removal and decommissioning of Unit 4. This waste should be properly disposed of.

Source & ©: UN Chernobyl Forum
 Chernobyl’s Legacy: Health, Environmental and Socio-economic Impacts (2006)
What are the environmental aspects of dismantlement of the Shelter and of radioactive waste management?, p.30-31

4.3 What is the future of the restricted access area surrounding the site?

The source document for this Digest states:

Exclusion Zone in Ukraine

The overall plan for the long term development of the Exclusion Zone in Ukraine is to recover the affected areas, redefine the Exclusion Zone, and make the less affected areas available for limited use by the public. This will require well defined administrative controls on the nature of activities that may be performed in the particular areas. In some of them, restriction of food crops planting and cattle grazing, and use of only clean feed for cattle still may be needed for decades to come for radiological reasons. Accordingly, these resettled areas are best suited for an industrial use rather than an agricultural or residential area.

The future of the Exclusion Zone for the next hundred years and more is envisaged to be associated with the following activities:

  • Construction and operation of the NSC and relevant engineering infrastructure;
  • Defuelling, decommissioning and dismantling of Units 1, 2 and 3 of the nuclear power plant and the Shelter;
  • Construction of facilities for processing and management of radioactive waste, in particular a deep geological repository for high-activity and long lived radioactive material;
  • Development of natural reserves in the area that remains closed to human habitation; and
  • Maintenance of environmental monitoring and research activities.

Source & ©: UN Chernobyl Forum
 Chernobyl’s Legacy: Health, Environmental and Socio-economic Impacts (2006)
What is the future of the Chernobyl Exclusion Zone?, p.31-32

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