Contract for early Chernobyl dismantling work signed

05 August 2019

A contract has been signed between SSE Chernobyl NPP and construction company Ukrbudmontazh (UBM) for the creation of infrastructure for the early dismantling of the Shelter Object. This structure, widely known as the 'sarcophagus', was hastily constructed over the remains of the destroyed reactor of unit 4 in the weeks after the 1986 accident.

The interior of the NSC (Image: ChNPP)

The contract - worth more than UAH2 billion (USD78 million) - was signed on 29 July after UBM won a tender in March to carry out the work.

The Shelter Object still contains the molten core of the reactor and an estimated 200 tonnes of highly radioactive material. The stability of the structure has developed into one of the major risk factors at the site, and its potential collapse threatens to liberate more radioactive materials. A project to shore up the structure was completed in mid-2008, but at that time the maximum life of the stabilised structures was determined as the end of 2023.

A giant arched structure known as the New Safe Confinement (NSC) was constructed to enclose the damaged reactor and the Shelter Object to reduce the consequences of a collapse while also allowing the sarcophagus to be taken apart under controlled conditions.

SSE Chernobyl NPP (ChNPP) - the Ukrainian state company tasked with managing the Chernobyl plant - said UBM will carry out the work under the new contract in three stages. The first and second stages involve the inspection of the Shelter Object and design works. The completion of these two stages are required for the careful planning of the dismantling of the unstable structures, managing the large volumes of radioactive waste generated, and ensuring the maximum safety of workers.

The third stage of the work involves the procurement and installation of equipment for the dismantling and handling of the disassembled fragments, as well as early dismantling.

ChNPP said the third and final stage of work is the most complicated. "The work will be carried out under conditions of increased nuclear and radiation risk. Besides, the structures of the Shelter - built over 30 years ago - are free-standing and are only supported by the force of gravity," it said. "Such conditions, together with corrosion processes, make this facility extremely complicated to carry out work on. In order to complete this dismantling work, the contractor must simultaneously dismantle the Shelter whilst reinforcing it as the removal of each element increases the risk of its collapse."

The dismantled parts of the Shelter are to be remotely processed in the NSC Technological Building, where they will be cut, decontaminated, placed in transport containers and prepared for transportation for recycling or disposal.

Dismantling of the Shelter is "the next logical step following the work we have done over the past 12 years," according to ChNPP Acting Director General Sergei Kalashnyk. "This is our future, global scope of activities that must be completed."

Built at a cost of EUR1.5 billion (USD1.7 billion) and financed by 45 donor countries and institutions, the NSC was constructed in two halves near the accident site between 2010 and 2016, and was eventually slid into place over the damaged reactor in November 2016. It is the largest moveable land-based structure ever built, with a span of 257 metres, a length of 162m, a height of 108m and a total weight of over 36,000 tonnes equipped, including a crane system for future dismantling work.

The keys for the NSC were symbolically presented to the Ukrainian authorities last month.

Researched and written by World Nuclear News