Ukraine’s Zaporizhzhia Nuclear Power Plant (ZNPP) has increased the number of reactors in hot shutdown to two units and has started operating mobile diesel boilers to generate more heating during the winter, including to the nearby town of Enerhodar, Mariano Grossi, Director General Rafael of the UN’s International Atomic Energy Agency (IAEA) said on Friday (20 October)
The ZNPP stopped producing electricity for the national grid in September last year. Since April of this year, Europe’s largest nuclear power plant (NPP) has kept five reactors in cold shutdown and just one in hot shutdown to generate steam to process liquid radioactive waste and for other safety-related functions.
Ahead of the upcoming winter months, however, it started transitioning a second reactor, unit 5, to hot shutdown last week, the IAEA said in a press release. “The reactor reached hot shutdown early on 16 October, joining unit 4 in this operational status. Both are now providing steam for the site and district heating to Enerhodar, where many plant staff live,” the UN agency said.
The IAEA has urged the ZNPP over many months to find an alternative source of steam generation. The plant has ordered an external steam generator to meet its requirements, which would allow all six reactor units to be placed in cold shutdown. However, the installation of this equipment is not expected to be completed until the first part of next year.
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.
The ZNPP separately informed the IAEA late last week that it had decided to close the reactor vessel of unit 3 – which had been left open and was being used as a reservoir of borated water in case it was needed. Borated water is used for cooling the nuclear fuel in the primary circuit of pressurised water reactors and the spent fuel stored in pools.
ZNPP has said that there is currently a sufficient supply of such water on site. The IAEA supports this decision of the ZNPP to close the unit 3 reactor as “it strengthens the defence in depth, improving the nuclear safety status of the unit,” the UN body said. The ZNPP has said it has no plans to put more than two reactors in a hot shutdown.
In response to water leaks in two steam generators of unit 6 earlier this month, the ZNPP has completed repairs successfully, with no further leaks detected. Planned maintenance work on part of the unit’s safety systems has begun. Nearby, the IAEA has noticed ongoing military activities, including explosions and sporadic machine gun fire.
Enerhodar experienced a power supply cut for over two hours on 18 October, with the cause remaining unclear. Prior to this, an electrical substation was damaged, leaving parts of the city without electricity and water. The IAEA conducted site walk-downs, finding no evidence of mines or explosives. They are also closely monitoring the staffing, training, and licensing of personnel at the plant under Russian Federation regulations.
While the IAEA gained access to the rooftop of unit 2 earlier, they continue to seek access to the rooftops of units 1, 5, and 6. Similarly, full access to all six turbine halls is required. Although they accessed all floors of the Unit 3 turbine hall, only partial access was granted to Unit 4 on 18 October.
Despite ongoing armed conflict, Ukraine’s other NPPs and the Chornobyl site operate safely and securely, according to the IAEA. The UN body rotated its teams at Chornobyl, Rivne, Khmelnytskyi and South Ukraine NPPs earlier this week.