The dismantling of four VVER-440/B-230 reactors at Bulgaria’s Kozloduy NPP is enters a challenging phase this year with the removal of the steam generators, to which there is no direct access, according to Sergey Tsochev, Chairman of the State Enterprise Radioactive Waste (DP-RAO – Drzhavno Predpriyatne RadioAktivnii Otpadtsi).
The Soviet-built reactors were commissioned between 1974 and 1982 and closed between 2002 and 2006 as a condition for Bulgaria’s entry into the European Union.
Twelve of the total 24 steam generators, which are located in shafts around the reactors, have already been removed. However, these were easily accessible. The others, each weighing 160 tonnes, had to be dragged through holes. All circulation pumps that are subject to treatment have already been removed.
The plan is to dismantle a total of 1,900 tonnes of equipment from the controlled reactor area in 2025. Of these, 1,100 tonnes must be cut up. A total of 2,100 tonnes, including material from previous years, will be released.
Tsochev recalled that almost all metals from the closed units, after they are identified, found to be safe, and approved by the nuclear regulator, are sold at auctions on the Sofia Commodity Exchange. About 90% of the dismantled metals go to scrap. This brings in BGN500,000-1m ($293,000-585,000) a year.
To dismantle the four reactors, some €860m ($985m) has been spent so far. Nearly 40% is Bulgarian funding. The rest comes from the European Commission as compensation for the closure of the units.
Another challenge for DP RAO was the supply of sufficient reinforced concrete containers for waste subject to disposal in the planned National Repository for Low and Medium Radioactive Waste near the Kozloduy NPP. As a result, the company reconstructed one of the old buildings on the site of decommissioned reactors in order to produce 700 containers a year. According to Tsochev, these will also be needed for the transfer of the low and medium radioactive waste, now stored near Novi Han, to the new repository site. The Novi Han, which began operation in 1964, is intended for storage of low and intermediate level radioactive waste generated from industry, medicine, agriculture and research.
Construction of the repository was completed last year, but it has not yet been put into operation. At the moment, tests are being conducted on the condition of shafts, ventilation systems and other systems before asking the regional ministry for permission to begin operation. This is expected to be obtained by the end of 2025, and in parallel work will be carried out on the licensing of the site by the Nuclear Regulatory Agency.
This is a long process, explained Tsochev. He explained that the procedure provides for the first issuance of a permit from the nuclear regulator to operate the facility in line with stated conditions as well as regular reporting and control. Then an update of the safety assessment will be made, and the site will receive a 10-year licence.
