Krško Nuclear Power Plant

Krško Nuclear Power Plant is a commercial nuclear generating station at Vrbina, in the City Municipality of Krško, southeastern Slovenia. It is operated by Nuklearna elektrarna Krško, commonly abbreviated as NEK, and is owned jointly by Slovenia's state-owned Gen Energija and Croatia's state-owned Hrvatska elektroprivreda. The plant originated as a Yugoslav energy project intended to strengthen electricity supply in the constituent republics of Slovenia and Croatia. Although the two republics initially contemplated building one nuclear station in each republic, that broader plan was abandoned, leaving Krško as a shared cross-border facility. The plant uses a two-loop Westinghouse pressurized-water reactor. Its rated thermal capacity is approximately 1,994 MWt and its electrical capacity is 696 MWe. The reactor uses enriched uranium fuel, demineralized water as moderator and coolant, and control rods containing silver, indium and cadmium alloys. Krško was connected to the electricity grid on October 2, 1981, and entered commercial operation on January 15, 1983. It began producing electricity before the related Angra I and Kori-2 projects on which its design was based were completed. The plant's sister facility is Angra I in Brazil. Krško has strategic importance for both national power systems. It supplies more than one-quarter of Slovenia's electricity and about 15 percent of Croatia's electricity, according to descriptions of the facility's output. Its ownership and operating arrangements have also made it a significant institution in Slovenian-Croatian relations. During the 1990s, disagreements over invoicing, electricity deliveries, operating costs and nuclear-waste responsibilities led to a prolonged dispute. Slovenia nationalized the operating company in 1998 and stopped electricity deliveries to Croatia. A bilateral settlement in January 2001 restored the principle of equal ownership and shared responsibility for nuclear waste. Joint management began in 2002, while electricity deliveries to Croatia resumed in 2003 after local opposition delayed the interconnection. The original operating lifetime was extended by 20 years in 2015, taking the planned operating horizon to 2043. In 2023, Slovenia and Croatia agreed to continue operation until 2043. Safety-related work has included seismic retrofitting following the 2011 Fukushima accident and inspections after earthquakes in the Zagreb and Petrinja regions in 2020. Those inspections reportedly found no damage; the plant was nevertheless shut down preventively for several days after the stronger Petrinja earthquake. Krško stores high-level spent fuel in its spent-fuel pool and plans onsite dry-storage capacity to support operation through the revised end date. Low-level radioactive waste is stored at the facility and in secondary repositories. Framatome received a contract in 2021 for a plant upgrade. Both countries have also discussed expansion: Croatian Prime Minister Andrej Plenković expressed support in 2022, while Slovenian Prime Minister Robert Golob proposed a public referendum concerning a possible second reactor or two-unit expansion. In 2024, the proposed concept was described as an expansion of up to 2,400 MWe, subject to public approval, technology selection and later investment decisions.

Krško was conceived in the early 1970s, when Yugoslavia identified the need for additional electricity generation in Slovenia and Croatia. The two republics had access to domestic uranium resources and considered proposals from Siemens and Westinghouse. Westinghouse won the competition with a pressurized-water-reactor design related to the Angra I project in Brazil. The project was managed by personnel from Slovenian and Croatian power companies together with representatives of the federal government in Belgrade. As engineering progressed, Westinghouse developed a newer related design for the Kori-2 project in South Korea. Krško nonetheless reached operation before both Kori-2 and Angra I. The reactor was connected to the grid in October 1981 and entered commercial service in January 1983. The original bilateral concept envisaged two nuclear stations, one in each republic, but disputes about financing and electricity prices caused that plan to be abandoned in 1987. The change left unresolved questions about ownership, electricity allocation and the location of radioactive-waste facilities. After the breakup of Yugoslavia, the plant remained a shared asset of Slovenia and Croatia, but its operating arrangements deteriorated. In 1997, ELES and NEK increased charges related to operation and decommissioning. HEP disputed the charges and stopped paying. Slovenia nationalized NEK in 1998 and suspended electricity deliveries to HEP, while HEP brought a counterclaim seeking compensation for the loss of supply. In January 2001, the two governments agreed on equal ownership, joint responsibility for nuclear waste and settlement of their mutual claims. Joint management was scheduled to begin in 2002. Electricity supply to Croatia was delayed by protests from local residents and was restored in 2003. HEP subsequently pursued additional legal claims, culminating in a 2015 ICSID award that granted more than €40 million in damages, interest and attorneys' fees. The plant's initial 40-year operating period was supplemented by a 20-year life extension agreement in 2015. Its safety program has included seismic assessment and retrofitting after the Fukushima disaster. Earthquake inspections following the 2020 Zagreb earthquake and the stronger Petrinja earthquake found no damage; the facility was temporarily shut down as a precaution after the latter event. Operational planning has increasingly focused on long-term fuel and waste management. Spent fuel is held in the spent-fuel pool, while onsite dry storage has been planned to support operation through 2043. Low-level waste is held at the station and in secondary repositories. In 2021, Framatome won a contract for an upgrade. Slovenia and Croatia agreed in 2023 to continue operation until 2043. Since 2022, political leaders in both countries have also discussed building another reactor or expanding the site. Slovenia has considered a referendum before a potential final investment decision, with a concept of up to 2,400 MWe under discussion in 2024.

1. 2021Framatome upgrade contract

   Framatome won a contract to upgrade the facility.

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2. 2015Twenty-year life extension agreed

   The operating period was extended by 20 years beyond the initial 40-year lifetime.

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3. 2003Electricity deliveries to Croatia resume

   After delays linked to local protests, the plant was connected to Croatia's supply arrangements.

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4. 2001Bilateral ownership settlement

   Slovenia and Croatia agreed on equal ownership, shared nuclear-waste responsibility and the handling of mutual claims.

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5. 1987Second-plant plan abandoned

   The original plan for another nuclear plant was abandoned amid disagreements over funding and electricity pricing.

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6. 1983Commercial operation begins

   Krško entered commercial operation on January 15.

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7. 1981Grid connection

   The plant was connected to the electricity grid on October 2.

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8. 1975Westinghouse selected

   Westinghouse was selected to supply the pressurized-water-reactor technology for the Krško project.

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9. 1970Bilateral nuclear-power concept emerges

   Slovenia and Croatia, then constituent republics of Yugoslavia, developed plans for additional nuclear generation and contemplated one plant in each republic.

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10. Planned end of extended operating period

    The extended operating horizon is planned to run through 2043.

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A strategic, jointly owned baseload electricity generator and a central component of the Slovenian and Croatian power systems.

• Nuclear-generated electricityElectricity generation1983

  Krško produces baseload electricity using a two-loop Westinghouse pressurized-water reactor. The unit has a rated electrical capacity of 696 MWe and supplies both Slovenian and Croatian power systems. Its output represents more than one-quarter of Slovenia's electricity and approximately 15 percent of Croatia's electricity, according to reference descriptions of the plant.

• Spent-fuel and radioactive-waste managementNuclear-facility operations

  The facility manages spent nuclear fuel and radioactive waste generated by reactor operations. High-level spent fuel is stored in the spent-fuel pool, with onsite dry storage planned to support the extended operating period. Low-level waste is stored at the plant and in secondary repositories.

• 2024Possible two-unit expansion put to public referendumStrategy

  Slovenian and Croatian officials have discussed expanding the site to address future electricity demand and energy-security concerns.

  What changed. Slovenia advanced plans for a referendum on a possible expansion of up to 2,400 MWe, subject to technology selection and publication of key documents.

  Aftermath. A final investment decision was discussed for 2028, with construction potentially beginning in 2032 if the project receives approval.

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• 2023Operation extended to 2043Strategy

  The plant remains important to the electricity systems of both owner countries.

  What changed. Slovenia and Croatia agreed to continue operation through 2043.

  Aftermath. The agreement reinforced the long-term operating plan and the need for additional waste-storage capacity.

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• 2021Plant upgrade awarded to FramatomeOther

  The facility required continuing modernization and safety-related investment during its extended operating period.

  What changed. Framatome won a contract to upgrade the plant.

  Aftermath. The contract supported the plant's continued operation and modernization program.

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• 2015Operating-life extensionStrategy

  The original operating period was approaching its planned 40-year limit.

  What changed. The owners agreed to extend operation by 20 years.

  Aftermath. The planned operating horizon moved to 2043, subject to regulatory and safety requirements.

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• 2001Settlement restores shared governanceStrategy

  Slovenia and Croatia had been in dispute over ownership, electricity deliveries, charges and responsibility for nuclear waste after Slovenia suspended deliveries to HEP.

  What changed. The governments agreed to equal ownership, joint waste responsibility and a framework for resolving mutual claims, with joint management to begin in 2002.

  Aftermath. Electricity deliveries to Croatia resumed in 2003 after a delay caused by local protests, although later litigation continued.

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• 2024Slovenia advances referendum discussion on possible Krško expansion

  Slovenian Prime Minister Robert Golob committed to a referendum concerning a possible expansion of Krško by up to two additional units with combined capacity of as much as 2,400 MWe. The proposal remained conditional on publication of key documents, technology selection and subsequent investment decisions.

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• 2023Slovenia and Croatia agree to continue operation through 2043

  The two owner countries agreed to extend the plant's operating period to 2043, consistent with the life-extension framework adopted earlier.

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• 2021Framatome wins plant-upgrade contract

  French nuclear-services company Framatome was selected for an upgrade contract connected with the operating plant.

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• 2015International arbitration awards damages to HEP in electricity-supply dispute

  The International Centre for Settlement of Investment Disputes ruled in favor of Hrvatska elektroprivreda in its dispute with the Slovenian side over the period when electricity from Krško was not supplied to Croatia. The award reportedly exceeded €40 million including damages, interest and legal costs.

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• 2008Coolant-leak incident triggers European radiological information alert

  A small leak in a cooling circuit led to a safe shutdown to hot zero-power mode and notification through the European Community Urgent Radiological Information Exchange. Slovenian authorities reported no radioactive release or harm to workers, residents or the environment. The incident also drew attention because Croatian authorities were not directly informed at the outset.

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1. Krško Nuclear Power Plant
2. Nuklearna elektrarna Krško official English website