An International Atomic Energy Agency (IAEA) Safety Aspects of Long Term Operation (Salto) team of experts on 15 July completed a review of long term operational safety at the Kozloduy NPP in Bulgaria. The mission was requested by the Bulgarian Nuclear Regulatory Authority (BNRA).

Kozloduy NPP, Bulgaria’s only nuclear power plant, has two VVER-1000 pressurised-water reactor units in operation with an installed power of approximately 1000 MWe each. Unit 5 went into commercial operation in 1987 and unit 6 in 1991. The nine-member Salto team focused on aspects essential to safe Long Term Operation (LTO). The operation licences of the two units have been extended until 2027 and 2029, respectively. Units 1-4 (VVER-440s) were shut down as a condition for Bulgaria’s accession to the European Union and are being decommissioned. The team comprised experts from the Czech Republic, Slovakia, Spain, and the United Arab Emirates, and three IAEA staff members.

During the 6-15 July mission, the team reviewed preparedness, organisation and programmes related to LTO based on the relevant IAEA safety standards. The review team found plant staff to be professional, open and receptive to suggestions for improvement. “The team observed that the operator is implementing measures for safe LTO,” said team leader and IAEA Nuclear Safety Officer Gabor Petofi. “Most ageing management and LTO activities already meet IAEA safety standards. The Salto team encourages the plant to further improve its LTO related performance and to address the mission’s findings.”

It mission identified good practices that will be shared with the nuclear industry globally, including:

  • The plant implements comprehensive annual visual inspections of civil structures to identify ageing effects at a very early stage.
  • The plant cooperates with technical universities and high schools to support future staffing needs for the long term operation period.
  • The plant uses comprehensive information systems to monitor and evaluate the risk of loss of tacit knowledge. Tacit knowledge is non-recorded, non-formalised knowledge, for example, experiences and insights by long-standing plant workers. This strategy ensures the preservation of this important resource for LTO.

The team also provided recommendations and suggestions to support the operator in further enhancing safe LTO including:

  • Fully complete implementation of the equipment qualification programme to confirm reliable safety performance.
  • Complete an ageing management review for all of the NPP’s mechanical structures, systems and components to effectively manage ageing effects.
  • Fully implement ageing management programmes to monitor the condition of low voltage cables and to verify whether important cables are still reliable.

The plant management expressed a determination to address the areas identified for improvement and announced that it would continue cooperation with the IAEA in implementing safe LTO and ask the Government of Bulgaria to request a SALTO follow-up mission in 2023. “We appreciate the IAEA’s support to our plant in ageing management and for safe LTO,” said Nasko Mihov, CEO of Kozloduy NPP. “The results of this mission will help us continue improving our activities for safe LTO in compliance with IAEA safety standards.”