DP RAO has started the transportation of the steam generators of the small units at the Kozloduy NPP

On two consecutive days - on December 21 and 22, 2023, the State Enterprise "Radioactive Waste" successfully implemented a complex pilot operation to unbox the 3rd unit and transport the first of a total of 24 steam generators* from the 440 megawatt units of the nuclear power plant, which are in the process of decommissioning.

The facility weighs 156 tons and is 11.5 m long and about 4.5 m in diameter. It was raised to a height of 12 m and transported through the Reactor Hall and then to the Engine Room (ER). The operation was led by the chief technologist of the specialized division "Decommissioning - 1-4 block" - Borislav Iliev. He talked about the challenges in its implementation: "The hatch through which the steam generator had to pass is 9x5 meters in size. This means that given the dimensions of the facility, it had to be removed at an angle of about 45 degrees. For this reason, it was important from an engineering point of view to calculate the length of the slings extremely precisely. This was done by the Engineering Assurance management team in the specialized division. There are a total of three hatches in the steam generator box through which we are about to remove the remaining 5 steam generators. This means that some of them have to be moved into the pit itself, which is also a challenge, but we have the right equipment delivered and I believe we will be successful."

After a strict dosimetric check, the steam generator is now located in a temporary storage area in the Machine Room. A permit has been issued by the Nuclear Regulatory Agency for the operation of the site and storage of 12 steam generators. By the end of next year, the boxes of the steam generators of units 3 and 4 must be completely vacated. In 2026, the fragmentation of these facilities will begin. During these two years, a workshop for dry fragmentation is to be built - a project that will be financed by the Kozloduy International Fund through the European Bank for Reconstruction and Development.

The steam generator relocation activities started from the 3rd unit with two foundations. First, large-scale decontamination via the Spider facility was completed there first. Secondly, according to the Decommissioning Program, it is planned to create a storage facility for the temporary storage of large-tonnage containers (80 tons) in the box of the steam generators of this block by 2030. They will store fragmented elements from the internal casing devices of the reactors and from the reactors themselves, and one container will be able to hold up to 20 tons of materials separated during dismantling. They are expected to remain there in storage for the next 50 years – until a deep geological disposal repository is built or until activities decline enough to meet the criteria for disposal at the National Radioactive Waste Repository. 

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*The steam generator is a basic element of the scheme for generating electricity from nuclear power plants. It is a heat exchange device for producing water vapor with a pressure above atmospheric at the expense of the heat of the primary coolant coming from the nuclear reactor. In the 440-megawatt units of the nuclear power plant, there are 6 steam generators for each reactor.