Preparatory work for the next stage of decommissioning at the three surviving power units of the Chornobyl NPP should be completed by the end of 2028, according to the site’s operating organisation ChNPP.
The 1986 accident that destroyed unit four did not damage the other three units, which continued to operate for some years. These three units, with RBMK-1000 reactors, were shut down in 1991, 1996 and 2000. In addition, there are two almost completed power units on site, which are also being decommissioned.
The first stage of work was completed by 2015, when all units were shut down and nuclear fuel was unloaded and transferred to the used nuclear fuel storage facility. ChNPP said its personnel have completed 94% of the preparatory work for decommissioning unit 44% of the work at unit 1. Planning is underway for work at unit 3, with physical work planned to begin in 2027.
The work includes decommissioning of systems and components located in the conservation zone premises; removal of thermal insulation and flammable materials; dismantling power, signal and control cables; sealing of penetrations in walls, installation and technological openings at the border between the premises of the conservation zone and controlled areas; as well as installation of fire-resistant panels and mats in places where wall penetrations and installation openings are sealed and on air ducts inside the conservation zone.
“We decided to carry out this work using the station’s own personnel as part of current activities and in accordance with work plans developed by the Chernobyl NPP Engineering Centre,” said Centre head Maxim Protsenko.
Current work belongs to the second of four stages of decommissioning and represents the final shutdown and mothballing of the reactor installations of all here units. After completion of the current stage, contractors will carry out work that includes reducing the height of individual parts of power units by 12–16 metres, as well as dismantling unloading and loading machines and lifting mechanisms.
ChNPP added that key activities aimed at ensuring safety and preparing reactor plants for long-term controlled storage will also be carried out. These include:
- dismantling systems and plant elements outside the nuclear reactor;
- strengthening barriers to the release of radioactive substances;
- reliable preservation of installation elements that cannot be dismantled;
- creating conditions for temporary controlled storage of radioactive substances remaining within the installation;
- collection and conditioning of radioactive waste generated during the work and its transfer to specialised organisations for further management.
“The safe storage phase involves a period during which the level of radioactivity is expected to fall naturally to acceptable values. The transition to this stage is planned in 2034 after confirmation of the safety of long-term storage of radioactive materials within the limits and for the period determined by the project for decommissioning the nuclear installation,” ChNPP reported.
At the next stage – dismantling of reactor installations – the systems and components to be monitored as sources of ionising radiation will be dismantled and removed, and subsequently placed in radioactive waste storage facilities. “This approach to decommissioning the Chornobyl nuclear power plant complies with national regulatory requirements and international standards,” Protsenko said.
The situation at the fourth power unit, destroyed during the 1986 accident is different. In a matter of months, a shelter was built over the damaged power unit, which allowed the remaining units to continue operating. It still contains the molten reactor core and an estimated 200 tonnes of highly radioactive material. This shelter was not designed to last very long and is now covered by the New Safe Confinement with a design service life of about 100 years. It was damaged by a drone strike last year and work is currently underway to restore it to full design functionality before planned work can begin to secure and dismantle the original shelter.
