Ukraine's Zaporizhzhya Nuclear Power Plant (ZNPP) is transitioning its reactor unit 5 to cold from hot shutdown and intends to determine the cause of boron detected in a cooling circuit, still leaving one of the plant's six reactors in hot shutdown to produce steam and heating, Director General Rafael Mariano Grossi of the International Atomic Energy Agency (IAEA) said today.
The unit's transition to cold shutdown began yesterday and is expected to be completed later today, according to the ZNPP. Unit 4 will remain in hot shutdown. There are currently no plans to bring a second unit into hot shutdown to replace unit 5, the plant said.
Once in cold shutdown, the ZNPP will carry out tests to identify why low levels of boron were found in the secondary cooling circuit of one of the unit's steam generators.
The ZNPP informed the IAEA experts at the site that the boron concentration in the affected cooling circuit remained below the limits permitted by its technical specifications. In addition, no radioactivity has been detected in the secondary cooling circuit. Borated water is used in the primary coolant to help maintain nuclear safety.
The ZNPP decided to move the unit to cold shutdown after one of the three 17.4 megawatt diesel boilers located off-site started operating on 17 November, providing additional heating to the nearby town of Enerhodar, where many plant staff live.
The ZNPP had been keeping reactor units 4 and 5 in hot shutdown to provide heating and steam for nuclear safety purposes on site, as well as heating for Enerhodar. The IAEA continues to follow the ZNPP's progress to find an alternative source of steam generation. Ukraine's national regulator, the State Nuclear Regulatory Inspectorate of Ukraine (SNRIU), issued regulatory orders in June to limit the operation of all six units of the ZNPP to a cold shutdown state.
Separately, the IAEA experts on the site are continuing to gather information to fully understand the cause of the event that occurred last week which resulted in unit 6 losing power and relying on a diesel generator for 90 minutes.
Later this week, the IAEA team has been invited to observe the ZNPP's planned emergency exercise.
"We look forward to observing the emergency response exercise at the Zaporizhzhya Nuclear Power Plant from both the temporary emergency control centre and in the field," Director General Grossi said. "Emergency exercises are very important for nuclear safety, especially in these times of heightened risk caused by the conflict."
The IAEA team at the Rivne Nuclear Power Plant (NPP) last week observed an emergency exercise at that plant and today the IAEA team at the Chornobyl site observed an emergency drill at the radioactive liquid waste treatment plant.
The IAEA teams at the Khmelnitsky, Rivne and South Ukraine NPPs and the Chornobyl site report safe and secure operations of these nuclear facilities despite the continuation of the conflict.
