The Krško NPP, which was shut down in early October after the discovery of a leak in the primary circuit connection system pipeline, could restart in mid-November after repairs, according to operator Nuklearna elektrarna Krško (NEK). Following investigation and analysis, a decision was taken to replace the complete pipeline segment from the reactor vessel to the first valve. Work began after moving all 121 fuel elements from the reactor vessel to the used fuel pool.

The Krško plant is co-owned by Croatia’s Hrvatska elektroprivreda (HEP) and Slovenia's GEN Energija. Krsko NPP, located in Slovenia near the border with Croatia, generates some 40% of Slovenia's electricity output. The 696 MWe Westinghouse pressurised water reactor, which is some 100 kilometres from the Austrian border, is Slovenia's only NPP.

NEK said Westinghouse with the support of the domestic industry, had begun removing part of the pipeline. In parallel, replacement parts were being prepared. A mock-up was made to train specialised welders, which corresponds to the space next to the reactor vessel where they have to work. NEK noted that, to ensure safe, long-term and early restart it was decided to replace a second pipeline which had been subjected to the same conditions. The first pipeline has been successfully removed and preparations are underway to remove the second and install new pipeline segments.

The Slovenian Nuclear Safety Administration (UJV – Uprava za jedrsko varnost), which is overseeing the work, explained that, as a preventive measure, the identical branch of the safety injection system's pipeline on the other side of the reactor vessel is being replaced as well, although no coolant leak occurred there. UJV is supervising the work with the help of dedicated Technical Support Organisations (TSOs). Weekly meetings are held involving NPP staff, UJV and TSOs to discuss the repair work as well as safety and technical details. “If the repair works are properly carried out, all the required tests successfully executed, and the appropriate approvals gained from UJV and TSOs, the start-up of the NPP is presumably going to take place in November,” UJV noted.

Image: The Krško nuclear power plant was shut down in early October after the discovery of a leak in the primary circuit connection system pipeline