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Scheduled overhaul in the Krško Nuclear Power Plant

After 18 months of safe and stable non-stop operations, a scheduled overhaul will take place at Krško Nuclear Power Plant (NE Krško) from 1 October to 2 November.

In addition to fuel element replacement that will see the replacement of 56 of the 121 fuel elements, extensive maintenance works and certain technological improvements or upgrades will be implemented, thereby further ensuring a high-level of nuclear and radiation safety. The assemblies of the DG1 diesel generator will be replaced, including an overhaul of the turbine-driven auxiliary feedwater pump and a regular cleaning and examination of the U-tubes of both steam generators will also take place. Important improvements during this year’s overhaul include the replacement of the high-pressure turbine, thus increasing the power plant’s electrical capacity by about 10 Mwe, and the upgrade of the power plant’s seismic instrumentation. The process of mechanical improvement of voltage conditions at the connections of the primary coolant piping system and the safety injection on the reactor pressure vessel to prevent and reduce the occurrence of stress corrosion on the appertaining bi-metallic welds is also very important.

The safety upgrade programme arising from the industry’s practice and administrative requirements following the Fukushima accident is practically completed. The construction of a dry storage facility for spent fuel remains open, but is in the final phase. The dry storage facility presents a transition to a 'passive' storage of nuclear fuel, which does not require active components for cooling.

Despite the revocation of the COVID-19 pandemic, NE Krško is prepared for a possible repeated outbreak of the pandemic, as occurred during the previous overhaul. Increased stock of protective equipment and self-testing kits are available, while regular disinfection of facilities is also taking place. A COVID-19 testing site is organised at the power plant’s car park and the healthcare service offers additional support.

The Slovenian Nuclear Safety Administration carefully monitors all overhaul activities with an emphasis on ensuring nuclear and radiation security during the shut-down of the power plant. The inspection service and colleagues from the Slovenian Nuclear Safety Administration will be present at NE Krško throughout the 2022 overhaul. Experts from national and international authorised organisations will provide expert assistance in the supervision. The power plant will again produce electric energy after the authorised organisations and the Slovenian Nuclear Safety Administration confirm that all works have been done accordingly, all tests were successful and nuclear security has been provided. With these measures, the power plant’s minimum impact on the environment will have been ensured.

The next overhaul is scheduled for spring 2024.