One of the main tasks of Chornobyl NPP shutdown stage is shutdown and partial dismantling of individual systems and components of power-generating units. The selected strategy of dismantling described in the Chornobyl NPP Decommissioning Programme specifies a capability at the shutdown stage to dismantle those systems and elements of the installation which are external relative to nuclear reactor and do not affect the safety and are not required for work at the subsequent decommissioning stages. Dismantling approach is from “clean’ equipment to “contaminated” in terms of its radioactivity.

Basic information: ChNPP Decommissioning

The strategy was selected based on the comprehensive analysis of the following factors:
• Ensuring safety of personnel, population and environment
• Availability of infrastructure for managing the dismantled equipment (intermediate storage facilities, stations for decontamination, size-reduction etc.)
• Availability of infrastructure for managing the radioactive waste (final storage facility for waste, facilities and plants for its processing)
• Sufficient funding for decommissioning activities
• Availability of required technologies and accessibility to them
• Prospects for further use of the site for other purposes

The systems and equipment that can be dismantled at the shutdown stage are specified in “The Chornobyl NPP Units 1, 2 and 3 Shutdown Programme”.

In 2008, the Kyiv Institute “Energoproject” completed the feasibility study to determine reasonability and desired time frames of equipment dismantling and processing. This report contains a brief description of fundamental solutions for dismantling of the Turbine Hall equipment, general description of the equipment and elements’ types and volumes to be dismantled, dismantling stages and expected duration, synopsis of operational activity in the course of dismantling and processing stage implementation, impact of implementation time frame on economic, radiological and social indicators.

For ChNPP the optimum option was recommended that foresees the following:
• The most prepared for dismantling equipment includes the systems, components and structures of the Turbine Hall Block “Г” that have been conditioned to the state when they can be dismantled and their radiation parameters enable to carry out the equipment dismantling without working time constraints for personnel;
• Activities with respect to dismantling of the Generation II Block “Г” are to be started immediately as it will lead to reduction of maintenance costs for safety of the building and the equipment inside it as well as due to continuous growth of radioactive waste disposal cost;
• All dismantling activities are to be carried out by contractors as such approach is economically more feasible.

Pursuant to Order of the Ministry of Emergencies of Ukraine dated 14.04.2014 No.382 “On Additional Actions to Implement National Target Environmental Program for Radioactive Waste Management”, the Chornobyl NPP developed an action plan for dismantling, size-reduction and decontamination of radioactively contaminated metal contained within the equipment and steel structures.

On November 14, 2012, a contract for “Dismantling, processing and release from regulatory control of Unit 1 Turbine Hall equipment and structures” was made.

As of now, 10,737 tons of equipment has been dismantled. 207 tons of this equipment have been disposed as RAW; 9,303 tons has been decontaminated and released from regulatory control; 1,164 tons are in the process of decontamination and release from regulatory control.

Basic information: Radioactive Material Management

Currently, pursuant to the National Programme of Chornobyl NPP Decommissioning and Shelter Transformation into an Environmentally Safe System the activities in terms of ChNPP Cooling Pond decommissioning are under way.

Chornobyl NPP Cooling Pond is an artificially created process basin of intended use.

The Cooling Pond is located on the right bank of the Prypiat River 1.5 km downstream of Chernihiv-Ovruch railway bridge (click here to view the map). It was commissioned in 1976 together with the ChNPP Unit 1. By the commissioning date this water body had been constructed as a bowl filled with water only up to half of the level. Following Units 3 and 4 commissioning in 1983, the Cooling Pond bowl was extended from 12.7 km² to 22,9 km² (the area is equal to the area of about 3,000 football pitches).

When the ChNPP worked in a power-generating mode the Cooling Pond was removing heat from the plant’s systems and equipment. Following the shutdown of the last ChNPP power-generating unit this water body stopped to ensure its functional purpose and its existing area multiply exceeds the required area.

Commencing in 1986, the scientific organizations conducted study of Cooling Pond's condition. In 2006, their study results were summarized in “Ecological Feasibility Report on the Cooling Pond Decommissioning and Determination of Initial Data for Feasibility Study”.

Based on this report data the Chornobyl NPP management with involvement of the government regulatory authorities and research institutions of Ukraine made a decision about development of Cooling Pond decommissioning feasibility study.

In February 2007, the ChNPP Scientific and Technical Council determined the following areas:
1. Providing the systems remaining in operation with service water (civil works project). Activities to implement the working design “SSE ChNPP. Service water supply system. Service water source (service water pond) with make-up pumping station” were completed within 2012-2014.
2. Development of Feasibility Study, Environmental Impact Assessment, Radiation and Environment Monitoring Programme (non-construction project).

Crucial factors that determined the necessity to decommission the ChNPP Cooling Pond are the following:
1. Significant operational costs.
2. Risks and expenses associated with high groundwater level at the site.

In 2009, the following document was elaborated: “Requirements for contents and structure of the ChNPP the Cooling Pond decommissioning FS (Feasibility Study) and EIA (Environmental Impact Assessment) data”. In 2013, these documents were completed and in 2014 the positive conclusions of state expert review conducted by the State Nuclear Regulatory Authority of Ukraine, the Ministry of Health of Ukraine, the Ministry of Ecology of Ukraine was obtained.

The Feasibility Study contains the assessment of Cooling Pond as-is condition and review of potentially possible decommissioning scenarios, analysis of the potentially possible consequences of water body transformation after the water drawdown, forecasts, potentially possible remediation strategies, assessment of the Cooling Pond decommissioning environmental impact and the established criteria for completion of the Cooling Pond decommissioning.

Based on the review of the scenario implementation advantages and disadvantages it was decided that the most reasonable one is a scenario of step-by-step drawdown with a feasibility to carry out remediation actions within the dried areas.

For a period of the Cooling Pond drawdown a Radiation and Environment Monitoring Programme (PREM) was developed.

In the second half-year of 2014 within the Cooling Pond pre-decommissioning activities the water level in the Prypiat River lowered significantly. That’s why it was impossible to take water for the Cooling Pond make-up. In October 2014, water drawdown started in the Cooling Pond.

Within a period from the drawdown start till the Cooling Pond decommissioning activities start, additional radiation situation monitoring was arranged to ensure radiation protection of the personnel.

Following the completion of activities in terms of preparation for the Radiation and Environment Monitoring Programme in August 2016, the SNRIU issued a permit for start of the ChNPP Cooling Pond decommissioning activities and the entire set of the envisaged within this Programme actions started.

In 2016 in the course of the drawdown, the Cooling Pond started to split into separate so-called “lakes” within its former area. In summer 2017, the dried area of the Cooling Pond made 42% of its entire previous area.

Project status:

Project was completed in August 2019. The criteria of work completion in terms of Cooling Pond decommissioning were achieved; these criteria had been established by Feasibility Study.
Water level of the wetland ecosystem is determined by the precipitation level, groundwater level and natural hydrological regime of the Prypiat River.

Equivalent dose rate around the drained areas is within the range of values specified in the design documentation. Due to the wind transport of the radioactive aerosols from the drained territory the changes in the radiation situation within the areas adjacent to Cooling Pond are within the range of the aerosol activity level of the Exclusion Zone surface layer of the atmosphere and dependant on natural and man-induced factors.

Vegetation cover is formed depending on physical and chemical properties of the soils within the drained area. Here, negative erosion processes that cause deterioration of the ecological and radiation conditions of the adjacent territories are not observed. ChNPP Cooling Pond area is transformed into the wetland ecosystem without degradation of the sanitary-and-epidemiological situation and there are no prerequisites for its deterioration.

Read more here: The IAEA Report based on project results