A back-up power line to Ukraine's Zaporizhzhya Nuclear Power Plant (ZNPP) has been restored, providing the plant with the external electricity it needs for reactor cooling and other essential safety functions, the International Atomic Energy Agency (IAEA) learnt at the site today.
Yesterday evening's restoration of a 330 kilovolt (kV) reserve line - which connects Europe's largest nuclear power plant to the Ukrainian network through the switchyard of a thermal power station in the nearby city of Enerhodar - enabled the ZNPP to shut down its last operating reactor early this morning. This reactor had over the past week provided the ZNPP with power after the facility was disconnected from the grid. With the line restoration, electricity needed for nuclear safety at the ZNPP once again comes from the external grid.
Director General Rafael Mariano Grossi welcomed the latest developments regarding the ZNPP's power status - which were also confirmed by Ukraine - but he stressed that the situation at the plant remained precarious after weeks of shelling in the area that damaged vital power infrastructure. Even with all the reactors in shutdown, power is still required for reactor cooling and other systems needed to maintain safety.
"Despite this damage, plant operators and engineers have been able to restore one of the reserve power lines, in very challenging circumstances, to provide the ZNPP with badly-needed external electricity," Director General Grossi said. "However, I remain gravely concerned about the situation at the plant, which remains in danger as long as any shelling continues. To address this serious situation, consultations have begun on the urgent need to establish a nuclear safety and security protection zone at the Zaporizhzhya Nuclear Power Plant (ZNPP)."
A secure off-site power supply from the grid and back-up power supply systems are essential for ensuring nuclear safety and preventing a nuclear accident, even when the reactors are no longer operating. This requirement is among the seven indispensable nuclear safety and security pillars that the Director General outlined at the beginning of the conflict.
IAEA experts present at the site of the ZNPP since 1 September - as part of the team led by Director General Grossi to establish the IAEA Support and Assistance Mission to Zaporizhzhya (ISAMZ) at the facility - were informed by senior Ukrainian plant staff that reactor unit 6 was shut down at 03:41am local time (02:41am CET). The other five units were already in cold shutdown and the plant is currently not providing any electricity to households, factories and others relying on it for their needs. The ZNPP is held by Russian forces since early March, but its Ukrainian staff are continuing to operate the plant.
In addition to the restored 330 kV line, work is under way to bring back other power lines. Reactor unit 6 had been providing power to the ZNPP since the plant was disconnected from the grid on 5 September. But operating a reactor at low power is not a sustainable solution for a longer period because it could over time damage key equipment of the nuclear power plant, such as electricity-producing turbines and pumps.
The ZNPP also has 20 emergency diesel generators available if needed, with supplies for at least 10 days of operation. There was no need to operate the generators during this operational change. Although the Enerhodar thermal power station remains down, the now restored power line provides the ZNPP with power from the Ukrainian grid transported through the station's switchyard.
As is the case for the five other reactor units, ZNPP operating staff plan to bring unit 6 to a cold shutdown state, which can take about 30 hours. The ZNPP will still need electricity for safety-related functions. However, in this state only power from one diesel generator per reactor is needed to maintain safety.
In a report on nuclear safety, security and safeguards in Ukraine that was issued on 6 September ahead of his briefing to the United Nations Security Council, Director General Grossi noted that the ZNPP on several occasions "lost, fully or partially, the off-site power supply as a result of military activities in the area". He recommended that off-site power supply line diversity and redundancy "should be re-established and available at any time, and that all military activities that may affect the power supply systems end."
