An International Atomic Energy Agency (IAEA) team of experts yesterday completed a review of long term operational safety of the Krško Nuclear Power Plant (NPP) in Slovenia.
The Safety Aspects of Long Term Operation (SALTO) review mission was requested by the plant's operator, Nuklearna Elektrarna Krško (NEK). Krško NPP started commercial operation in 1983. It is the only reactor in Slovenia and is co-owned with neighbouring Croatia. Located approximately 70 kilometers east of Slovenia's capital Ljubljana, and 40 kilometres north-west of Croatia's capital Zagreb, Krško NPP is equipped with one pressurized-water reactor and has a net electrical output of 700 Megawatt electric (MW(e)). In 2023, the operating license of the NPP was extended from initially 40 years to 60 years until 2043.
During the ten-day mission that ended on 22 May, the team reviewed the plant's preparedness, organization and programmes for safe long term operation, which built upon an initial IAEA pre-SALTO mission held at the plant in 2021. The mission was conducted by a twelve-person team consisting of experts from Canada, the Czech Republic, France, Hungary, three IAEA staff members and four observers from France, Hungary, Sweden, and the Nuclear Energy Agency. During the review, the SALTO team held in-depth discussions with staff from the Krško NPP and conducted several site walkdowns.
The team noted the progress in measures taken by the operator to ensure safe LTO. "The professionalism, openness and receptiveness for improvements of plant staff to meet and move beyond the IAEA safety standards is commendable," said team leader and IAEA Nuclear Safety Officer Martin Marchena who noted that most ageing management and LTO activities were already in alignment with IAEA safety standards. "We encourage the plant to address the review findings and proceed with the implementation of all remaining activities for safe LTO", he added.
The team identified good performances that will be shared with the nuclear industry globally, including:
- Operating a 360-degree "Virtual Walkdown" application that allows staff to visually evaluate equipment through photos and associated design and maintenance data in support of ageing management activities.
- The comprehensive establishment, documentation and revalidation of the equipment qualification programme for LTO, which ensures that components can perform their intended safety functions under all conditions.
- Ageing management activities for the reactor pressure vessel are well-established and form a well-structured and comprehensive programme.
The team also provided suggestions to further improve safe LTO, for example:
- The plant should consider further developing a systematic approach for the oversight of the LTO programme.
- The plant should consider adequately documenting the methodology and results used for scope setting (the identification of relevant systems, structures and components) for ageing management.
- The plant should consider completing and fully documenting ageing management of electrical and instrumentation and control systems, structures and components (I&C SSCs).
The plant management expressed a determination to maintain the level of preparedness for safe LTO and further cooperate with the IAEA in this field.
"We appreciate the IAEA's support to our plant in ageing management and preparation for safe LTO," said Gorazd Pfeifer, President of the Krško management Board. "It is very important for us to get an external view on our business. The competencies and experience of the IAEA team enable us to effectively identify areas for improvement. The results of this mission will help us to improve our activities for safe LTO and to further align them with IAEA safety standards."
The team provided a draft report to the plant management and to the Slovenian Nuclear Safety Administration (SNSA), the country's nuclear regulatory authority, at the end of the mission. The plant management and SNSA will have an opportunity to make factual comments on the draft. A final report will be submitted to the plant management, SNSA and the Slovenian Government within three months.
Background
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.
