We are proud to announce the commissioning of Slovenia’s first used fuel dry storage facility at Krško Nuclear Power Plant in Slovenia. The owner and licensee of the plant, Nuklearna elektrarna Krško (NEK), received the operating license for the facility from the Slovenian Nuclear Safety Administration (SNSA) last October. Holtec placed the first HI-STORM FW system into storage on April 2, 2023, officially marking the facility’s commissioning. The first fuel loading campaign will consist of a total of sixteen HI-STORM FW casks placed in dry storage.

Dry Fuel Storage Building at NEK’s Krško Nuclear Power Plant in Slovenia Built and Commissioned by Holtec International

The facility is designed to withstand earthquake levels only encountered in high seismic regions of the world, such as California and the Western Pacific, although the seismic hazard at the site is not as high as those regions. In addition to the severe earthquake, the facility is designed to function under severe flood conditions and to attenuate the accreted dose from the facility to minuscule levels to protect public health and safety. A large safety-significant civil construction project by any measure, the Krško facility was built under the astute management of Holtec’s Civil Design & Construction Department with rigorous quality assurance controls and local supply chain management, primarily consisting of Slovenian, Croatian and Italian companies.

To ensure a large margin of structural safety, a seismically restrained version of the HI-STORM FW system was used for the project. The seismic restraint system uses a robust steel structure embedded within the thick concrete foundation of the storage building. The HI-STORM FW casks are qualified to a severe earthquake level that produces foundation pad accelerations 2.1 times higher than the earth’s gravity. Furthermore, the storage modules are also engineered to withstand impact from a military or commercial aircraft, exceeding the International Atomic Energy Agency’s (IAEA’s) guidance for operating nuclear power plants. The custom-engineered domed lid of the HI-STORM FW, unique to this project, is a Holtec innovation developed to engineer an impact-capable design. 

The Slovenian environmental permitting process for the facility, in accordance with EU rules, included a transboundary impact assessment in conjunction with neighboring countries. As part of the transboundary commenting process, it was decided to implement a non-intrusive leak-indication system to continuously monitor the welded multi-purpose canisters containing the fuel. The system monitors the temperature profile of the casks to detect potential depressurization. In fact, the HI-STORM FW system is designed and licensed as “leak-tight,” meaning a leak is not deemed credible by the regulatory authority. Thus, the monitoring system serves only as an additional safety measure. 

“Undoubtedly this project has been a pacesetter in terms of design and safety requirements, expanding the envelope of the types and severity of events normally considered for design of such a facility. Our success is a testament to the teamwork and ingenuity of the trans-national project team that executed the project. Holtec, NEK and our local partners stood together, committed to delivering the facility even through the pandemic and uncertain market conditions caused by Russia’s aggression in Ukraine. Commissioning of this facility was indispensable to support Krško’s continued generation of 24/7 clean nuclear power, which is critical to Slovenia’s clean energy aspirations,” says Holtec Senior Vice President of International Projects Dr. Rick Springman.