Oskarshamn Nuclear Plant to Shut Down for Nine Days Due to Process Water Anomalies

Sweden's Oskarshamn nuclear power plant is scheduled for a temporary shutdown starting the night of December 11, 2025, lasting approximately nine days until December 20. The closure follows the detection of anomalies in the process water flowing from the reactor containment to the purification systems. Despite these irregularities, Uniper, the plant's operator, assured that the detected anomalies are small and remain well below established safety limits, indicating no immediate risk to safety.

This particular reactor is the largest in Sweden, with a production capacity of 1,400 MW. It had recently resumed operation after being offline for over six months due to repairs. Désirée Liljevall, press chief at Uniper, emphasized the need to investigate the root causes of the anomaly prior to the onset of winter, ensuring all potential issues are resolved. She also noted that the repair period often exceeds initial estimates, which underscores the caution exercised in the current shutdown.

The decision to halt operations has been officially communicated to the Nord Pool electricity market, with any potential changes to the restart date to be promptly relayed. Concurrently, another nuclear reactor at the Forsmark power plant remains offline undergoing a substantial revision, with its restart tentatively scheduled for December 14.

The measured approach reflects commitment to safety and reliability amid technical challenges. Uniper maintains transparency about the process and safety considerations, reassuring the public and electricity market stakeholders during this temporary interruption in nuclear power supply.