The second of four stages of the Chornobyl NPP’s decommissioning is currently underway, involving the final closure and decommissioning of the reactor units at Power Units Nos. 1, 2 and 3.

To date, the plant’s staff are preparing the premises in the conservation zones of the first-stage power units at the Chornobyl NPP: 94% of the physical work has already been completed on Power Unit No. 2, and 44% on Power Unit No. 1.

This work includes:

• decommissioning of systems and components located within the conservation zone premises;
• removal of thermal insulation and combustible materials from the conservation zone premises;
• removal of power, signalling and control cables;
• sealing of wall penetrations, installation and process openings at the boundary between the conservation zone premises and the control zones;
• installation of fire-resistant panels and mats at the points where wall penetrations and installation openings have been sealed, and on air ducts within the conservation zone.

The staff at the Chornobyl Nuclear Power Station are required to complete these works in full, in accordance with the work execution plans (WEPs), by December 2028.

“It has been decided to carry out this work ourselves, as part of routine operations and in accordance with the work execution plans drawn up by the Chornobyl NPP Engineering Centre,” said Maksym Protsenko, Head of the Chornobyl NPP Engineering Centre.

Work plans are also currently being drawn up for Power Unit No. 3. Physical work is scheduled to begin in 2027.

Once all the measures being carried out by Chornobyl NPP staff themselves have been implemented, in order to complete the final decommissioning and conservation of the reactor facilities, a contractor must implement the revised Final Decommissioning and Conservation (FDC) project, which provides for work to be carried out in two phases:

• refurbishment of the main building of power units No. 1 and No. 2;
• refurbishment of the main building of power unit No. 3.

As part of the refurbishment, the height of the central halls’ canopies is to be reduced by 12–16 metres. To this end, the metal structures of the canopies will be dismantled and a new roof covering installed. The dismantling of loading and unloading machinery and hoisting mechanisms is also planned.

Work during the final decommissioning and conservation phase of the reactor units is being carried out under a separate licence issued by the State Nuclear Regulatory Inspectorate on 31 March 2015.

In general, this stage involves carrying out key measures aimed at ensuring safety and preparing the reactor units for long-term controlled storage, in particular:

• the dismantling of systems and plant components external to the nuclear reactor which do not affect safety and will not be used in subsequent stages of decommissioning;
• strengthening the barriers that prevent the release of radioactive substances into the environment;
• the reliable preservation of plant components that are not subject to dismantling;
• the creation of conditions for the temporary controlled storage of radioactive substances remaining within the plant;
• the collection and conditioning of radioactive waste (RAW) generated during the works, and its transfer to specialised organisations for further management.

As a reminder, the first phase of the Chornobyl Nuclear Power Plant’s decommissioning was completed in 2015. At this stage, the power units were taken out of operation and a series of preparatory measures were carried out in anticipation of their decommissioning. The final stage of operation involved the removal of nuclear fuel and its transfer to the spent nuclear fuel storage facility, intended for long-term storage.

In accordance with the Chornobyl NPP decommissioning strategy, the third and fourth stages will involve the safe storage period of the reactor units, followed by their dismantling.

The safe storage stage involves a period during which the level of radioactivity is expected to decrease naturally to acceptable levels. It is planned to move to this stage in 2034, following verification of the safety of long-term storage of radioactive materials within the limits and for the duration specified in the nuclear facility decommissioning project.

During this period, the main tasks will be:

• the operation of systems and components necessary for the safe storage of radioactive substances remaining in the mothballed facilities;
• periodic inspections of the condition of the mothballed facilities.

During the next stage – the dismantling of the reactor units – systems and components subject to control as sources of ionising radiation will be dismantled and removed, and subsequently placed in radioactive waste repositories.

“This approach to the decommissioning of the Chornobyl NPP complies with national regulations and international standards,” emphasised Maksym Protsenko.

In parallel, throughout the entire decommissioning period for power units No. 1, No. 2 and No. 3, work is being carried out to dismantle equipment located outside the reactor buildings.