By Sonia Meetes, Cyber Era NG Special Correspondent, Switzerland

Ukraine’s Zaporizhzhya Nuclear Power Plant (ZNPP) lost the connection to its only remaining 330 kilovolt (kV) back-up power line for a second time this month, once again leaving the facility dependent on one single source of the external electricity it needs for reactor cooling and other key nuclear safety and security functions, IAEA Director-General Rafael Mariano Grossi has said.

The IAEA team stationed at the plant was informed that the power line was disconnected for more than 26 hours between Monday and Tuesday this week due to unspecified damage on the other side of the Dnipro River. It took place three weeks after another disconnection of the same line. In both instances, the ZNPP continued to receive electricity from its sole 750 kV line. Before the military conflict, Europe’s largest nuclear power plant (NPP) had four 750 kV and six 330 kV lines available.

“What once would have been unthinkable – a major nuclear power plant suffering repeated off-site power cuts – has become a frequent occurrence during this devastating war. The situation is clearly not getting any better in this regard. The nuclear safety and security situation at the Zaporizhzhya Nuclear Power Plant remains highly precarious,” Mr. Grossi said.

Underlining the persistent risks, the IAEA team has continued to hear explosions every day over the past week, although no damage to the ZNPP was reported.

The IAEA team members conducted walkdowns across the site as part of their activities to assess nuclear safety and security at the plant, including observing the testing of an emergency diesel generator (EDG) of reactor unit 4. In meetings with plant staff, they discussed other important topics, such as the modernization of control systems for the site’s EDGs as well as updated procedures related to the ZNPP’s radiation protection programme.

As a follow up to their visit last week to the cooling tower damaged by a major fire in August, the team members also discussed with the ZNPP how it will assess the extent of the damage, including the selection of an external contractor to carry out this work.

The IAEA teams present at the Khmelnytskyy, Rivne and South Ukraine NPPs and the Chornobyl site reported that nuclear safety and security is being maintained despite the effects of the ongoing conflict, including air raid alarms for several days over the past week.

At the South Ukraine NPP, the IAEA team was informed that reactor unit 1 was disconnected from the grid for about four hours on Tuesday evening due to a spurious signal to the unit’s protection systems without the reactor safety systems being activated. The root cause of the event is being investigated. The reactor – one of three at the plant – is again generating power for the grid.

At the request of Ukraine, an IAEA team is visiting six electrical substations in Ukraine this week, as part of the Agency’s work to assess the status of the electrical grid infrastructure essential to nuclear safety that began in September. During the visits, the team reviews the operational consequences of actual and potential damage to substations which supply off-site power to the country’s NPPs. 

Reliable access to off-site power is one of the Seven Indispensable Pillars for ensuring nuclear safety and security during an armed conflict outlined by Grossi two and a half years ago. The safety of operating NPPs is dependent on a stable grid connection, but the situation in this regard has become increasingly precarious in recent months.

The IAEA already has teams of staff stationed at all of Ukraine’s NPPs who contribute to maintaining nuclear safety and security during the military conflict.

The IAEA is continuing to implement its comprehensive programme of assistance in support of nuclear safety and security in Ukraine, including by delivering requested equipment. This week, two spectrometry systems enhancing the analytical capabilities of the hydrometeorological organizations of the Ukraine’s State Emergency Service were procured and delivered, funded by Switzerland. It was the 71st equipment delivery to Ukraine, totaling over 12.1 million euro since the start of the armed conflict.

In addition, the Agency has coordinated the delivery of the two static test benches from the Rivne NPP to the supplier for repair during an outage of reactor unit 2. The repair was funded by Norway. The repair should be completed by the end of April next year, when the repaired test benches will be returned to the plant to enable the unit’s restart. The equipment is used in the nuclear and other industries to stress test components, including hydraulic shock absorbers.