IAEA Concludes Long-Term Safety Review of Slovenia’s Krško Nuclear Power Plant

Initially licensed for a 40-year operational period, Krško NPP received regulatory approval in 2023 to extend its operation by an additional 20 years, setting the new expiration date at 2043.

The International Atomic Energy Agency (IAEA) has successfully concluded a ten-day Safety Aspects of Long Term Operation (SALTO) review mission at the Krško Nuclear Power Plant (NPP) in Slovenia, affirming the plant’s commitment to high safety standards and its preparedness for long-term operation (LTO) through 2043.

Background of Krško Nuclear Power Plant

Located about 70 kilometers east of Slovenia’s capital, Ljubljana, and 40 kilometers northwest of Zagreb, Croatia’s capital, the Krško NPP is the sole nuclear reactor operating in Slovenia. Commissioned in 1983, it features a single pressurized-water reactor with a net output of 700 megawatts electric (MW(e)). The plant is co-owned by Slovenia and Croatia and plays a critical role in the energy security of both nations.

Initially licensed for a 40-year operational period, Krško NPP received regulatory approval in 2023 to extend its operation by an additional 20 years, setting the new expiration date at 2043. This extension is contingent on maintaining rigorous safety measures and effective ageing management programmes.

Purpose and Scope of the Review

The IAEA SALTO mission, conducted between 12 and 22 May 2025, followed a preliminary pre-SALTO mission held in 2021. It was requested by the plant’s operator, Nuklearna Elektrarna Krško (NEK), as part of its ongoing efforts to align with international safety standards.

A team of 12 experts—including members from Canada, the Czech Republic, France, Hungary, IAEA staff, and observers from Sweden and the Nuclear Energy Agency—engaged in detailed assessments of Krško NPP’s organization, safety procedures, and technical readiness for long-term operation. The review included document inspections, structured interviews with staff, and site walkdowns to observe the condition and management of safety-critical systems.

Commendations and Highlights

The IAEA team acknowledged significant advancements made by NEK in establishing a robust framework for long-term safety. Martin Marchena, team leader and IAEA Nuclear Safety Officer, praised the plant’s staff for their professionalism and readiness to go beyond established safety requirements.

Key areas of good performance included:

• Virtual Walkdown System: Krško’s innovative 360-degree “Virtual Walkdown” tool enables staff to visually inspect and monitor equipment using high-resolution photos linked with maintenance and design data. This enhances real-time decision-making and supports proactive ageing management.

• Equipment Qualification Programme: The plant has developed a comprehensive and regularly updated equipment qualification programme that ensures critical components can perform their safety functions under expected operational and environmental conditions.

• Reactor Pressure Vessel Management: The approach to managing the ageing of the reactor pressure vessel is structured, documented, and aligned with international best practices, showcasing a deep commitment to equipment longevity and performance.

Recommendations for Further Improvement

Despite its strengths, the review team identified opportunities for Krško to enhance its systems further. These include:

• Establishing a systematic oversight mechanism for the LTO programme to ensure continuous improvement and accountability.

• Better documentation of scope-setting methodologies used to determine which systems, structures, and components (SSCs) fall under ageing management.

• Completing and formalizing the management of ageing in electrical and instrumentation and control (I&C) systems, which are essential to plant operation and safety.

These recommendations aim to ensure that Krško not only maintains but strengthens its alignment with IAEA’s rigorous safety standards over the coming decades.

Commitment from Plant Management

Gorazd Pfeifer, President of NEK’s Management Board, welcomed the IAEA mission’s findings and emphasized the value of external, expert assessments. “We appreciate the IAEA's support in our LTO preparations,” Pfeifer stated. “Their experience helps us better identify our strengths and pinpoint areas for development. The mission outcomes will directly inform our efforts to improve operational safety and regulatory compliance.”

Next Steps

At the conclusion of the review, the IAEA delivered a draft report to NEK and the Slovenian Nuclear Safety Administration (SNSA). Both organizations have been invited to provide factual feedback before a finalized version is issued within three months. The final report will also be shared with the Slovenian Government to reinforce transparency and public assurance regarding nuclear safety.

Regional and Global Implications

As Slovenia’s only nuclear facility and a joint venture with Croatia, Krško NPP is strategically vital. The review findings not only bolster regional energy cooperation but also serve as a model of best practices for other ageing nuclear plants globally. The IAEA’s sharing of Krško’s successful programmes—like the Virtual Walkdown and equipment qualification strategies—aims to elevate safety performance across the international nuclear community.