The license was issued after comprehensive tests were carried out to confirm that the facility was able to run in different operating modes at uprated power, and test results were thoroughly analyzed.

The unit was uprated with the input from Rusatom Service, a subsidiary of Russian nuclear corporation Rosatom. The uprate program included the replacement of the generator stator and upgrading of the reactor protection system and the steam separator. The process control system of the unit was also improved as part of the project.

The uprate program was financed by the Kozloduy nuclear power plant. A similar program is in progress at Kozloduy Unit 5.

The goal of the two uprate programs is to increase ‘clean power’ generation and cut greenhouse gas emissions in Bulgaria.

For reference: Kozloduy NPP has six nuclear power units. The shutdown of Units 1 to 4 with VVER-440 reactors was a requirement of the European Commission for Bulgaria’s accession to the European Union. Units 5 and 6 with VVER-1000 reactors were commissioned in 1988 and 1993 respectively. The uprate project was launched in the early 2010s with a view to extending service life and increasing power of the plant’s two operating units.