The reactor pressure vessel has been removed from Bohunice V1 (Photo: EBRD)Slovakia’s nuclear and decommissioning company Jadrová a vyraovacia spoločnos (JAVYS) announced on 2 June that it had completed “one of the most complex operations of the Jaslovské Bohunice V1 decommissioning project”.

The reactor pressure vessel, which weighed 204 tons with suspension systems, had to be transported from the unit 1 reactor shaft to the wet fragmentation pool.

Construction of the Bohunice V1 plant began in 1972, with two VVER-440 V-230 reactors supplied by Atomenergoexport of Russia and Skoda. They 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. All were designed by Atomenergoproekt. Despite major upgrade work on the V1 units, they were shut down in 2006 and 2008 as a condition of Slovakia's accession to the European Union.

The decommissioning  Bohunice V1 by JAVYS is financed by the Bohunice International Decommissioning Support Fund, established in 2001. Contributors to the fund include the European Commission as well as Austria, Denmark, France, Ireland, the Netherlands, Spain, Switzerland and the UK. The European Bank for Reconstruction and Development (EBRD) acts as fund manager.

"This is a significant milestone in the process of decommissioning the V1 NPP in Jaslovské 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," said Tomáš Klein, member of the Board of Directors of JAVYS, as and director of the Decommissioning Division. It is the first example of decommissioning a VVER-440 plant.

The transport of the reactor pressure vessel began using a main crane in a reactor hall with a capacity of 250 tons, JAVYS said. “The RPV was placed on a prepared platform in the pool of the wet fragmentation workplace and the transport was successfully completed.”

The dismantling of large-scale components of the primary circuit was started by JAVYS 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," said Klein.

In 2018 and 2019, JAVYS completed preparation and approval of project documentation, obtaining permits for the construction of workplaces for the fragmentation of activated equipment and approval of documentation important from the point of view of nuclear and radiation safety. After the completion of the construction of pools for fragmentation of reactor pressure vessels and internal parts of reactors and their successful approval, transport of these active devices to the newly built pools began, JAVYS said.

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

The operation was performed successfully despite the current health and safety regulations in place to prevent the spread of the coronavirus pandemic. Work in Bohunice continued in recent weeks during emergency measures, which have now been revoked.

The EBRD said the decommissioning fund finances and co-finances selected projects to support the decommissioning of Bohunice V1 and V2 of the plant in a safe, secure and cost-effective manner. It also supports new measures in the Slovak energy sector 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.

Photo: The reactor pressure vessel has been removed from Bohunice V1 (Photo: EBRD)