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IAEA Concludes Long Term Operational Safety Review of Bulgaria’s Kozloduy Nuclear Power Plant

Kozloduy, Bulgaria

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

Kozloduy NPP, Bulgaria’s only nuclear power plant, has two pressurized-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 9-member SALTO team focused on aspects essential to safe Long Term Operation (LTO). The operation licenses of the two units have been extended until 2027 and 2029, respectively. Units 1 to 4 have been shut down and are being decommissioned.

During the 6-15 July mission, the SALTO team reviewed preparedness, organization 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.”

The team comprised experts from the Czech Republic, Slovakia, Spain, and the United Arab Emirates, and three IAEA staff members. It 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-formalized 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:

  • 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.

“We appreciate the IAEA’s support to our plant in ageing management and for safe LTO,” said Nasko Mihov, Chief Executive Officer (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.”

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.

The team provided a draft report to the plant management and to the Bulgarian Nuclear Regulatory Authority (BNRA) at the end of the mission. The plant management and BNRA will have an opportunity to make factual comments on the draft. The IAEA will submit a final report to the plant management, BNRA and the Bulgarian Government within three months.


General information about SALTO missions can be found on the IAEA Website. A SALTO peer review is a comprehensive safety review addressing strategy and key elements for the safe long term operation of nuclear power plants. They complement OSART missions, which are designed as a review of programmes and activities essential to operational safety. Neither SALTO nor OSART reviews are regulatory inspections, nor are they design reviews or substitutes for an exhaustive assessment of a plant's overall safety status.

LTO of nuclear power plants is defined as operation beyond an established time frame determined by the license term, the original plant design, relevant standards, or national regulations. As stated in IAEA safety standards, to maintain a plant’s fitness for service, consideration should be given to life limiting processes and features of systems, structures, and components (SSC), as well as to reasonably practicable safety upgrades to enhance the safety of the plant to a level approaching that of modern plants.

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