Pressure vessel removal at Bohunice

Above: The reactor pressure vessel of Bohunice nuclear power plant has been removed (Photo credit: EBRD)

CONSTRUCTION OF BOHUNICE V1 BEGAN in 1972. The two VVER-440 V-230 reactors, supplied by Atomenergoexport of Russia and Skoda, were connected to the grid in 1978 and 1980. In 1976, construction started on two V-213 reactors (the V2 plant) built by Skoda and these began operation in 1984 and 1985. Atomenergoproekt designed all four units. Despite major upgrade work on the Bohunice V1 units, they were shut down in 2006 and 2008 as a condition of Slovakia’s accession to the European Union.

At the start of June the company completed a major step in the decommissioning programme when it transported the Unit 1 reactor pressure vessel from the reactor shaft to the pool where it will be dismantled. It is the first example of decommissioning a VVER-440 plant and was performed successfully despite the health and safety regulations in place to prevent the spread of coronavirus.

“This is a significant milestone in the process of decommissioning the V1 NPP in Jaslovske´ Bohunice. The operation was preceded by months of preparations, technical negotiations, design, production of handling equipment and approval of the necessary documentation by supervisory authorities,” says Toma´s? Klein, member of the Board of Directors of Javys, and director of the decommissioning division.

Transport of the reactor pressure vessel (RPV) began using a main crane in a reactor hall with a capacity of 250t, Javys notes. “The RPV was placed on a prepared platform in the pool of the wet fragmentation workplace and the transport was successfully completed.”

Javys began dismantling large-scale components from the primary circuit at the end of 2017 in cooperation with a consortium of Westinghouse Spain, Westinghouse Sweden and Slovak nuclear company VUJE.

“One of the main tasks of the project is the dismantling and fragmentation of RPVs and internal parts of reactors — the most radioactive parts of the power plant, whose radioactivity represents almost 100% of the total radioactivity of the power plant,” says Klein.

During 2018 and 2019 Javys prepared and won approval for project documentation, obtained permits for the construction of workplaces for the fragmentation of activated equipment and approval of nuclear and radiation safety documentation. After the pools for fragmentation of reactor pressure vessels and internal parts of reactors were built and approved, it began to transport of active components to them.

In the next step, the components will be dismantled remotely and the materials processed for safe storage or disposal. Project manager Tibor Rapant says: “Waste from dismantling activities will be safely stored or disposed of at the national radioactive waste repository and the Bohunice Interim Storage Facility.”

Decommissioning of Bohunice V1 is financed by the Bohunice International Decommissioning Support Fund, established in 2001, and carried out by Slovakia’s nuclear waste and decommissioning company Javys. Contributors to the fund include the European Commission, Austria, Denmark, France, Ireland, the Netherlands, Spain, Switzerland and the UK. The European Bank for Reconstruction and Development (EBRD) acts as fund manager.

The decommissioning fund finances and co-finances selected projects to support the decommissioning of Bohunice V1 and V2 in a safe, secure and cost-effective manner. It also supports new measures in the Slovak Republic to help minimise the impact of the closure of units 1 and 2 by improving the efficiency of energy supply and consumption. To date, the fund has received more than €650 million ($730m) and operations are on track to complete the decommissioning on target by 2025.