Facility needs one reactor to generate steam for various nuclear safety purposes
Unit 4 at the Zaporizhzhia nuclear power station in Ukraine is being transferred from hot shutdown to cold shutdown following detection of a water leak at one of its four steam generators in the containment, International Atomic Energy Agency director-general Rafael Mariano Grossi said on Thursday (10 August).
Unit 4 will be placed in cold shutdown to determine the precise cause of the water leak and to carry out maintenance to repair the affected steam generator.
At the same time, over the next three days, staff will move Unit 6 to hot shutdown to continue steam production on site.
Unit 6 has been in cold shutdown since 21 April, to enable inspection and maintenance of the safety systems.
Staff at the six-unit station, on the frontline of fighting in southern Ukraine, have been carrying out maintenance on Unit 6 safety systems. This work and all tests of the safety systems were successfully completed before beginning the transition of Unit 6 to hot shutdown, the IAEA said.
The other units at Zaporizhzhia remain in cold shutdown.
Ukraine’s national nuclear regulator SNRIU has issued regulatory orders to limit the operation of all six units to a cold shutdown state.
The site uses the steam generated from one reactor unit in hot shutdown for various nuclear safety purposes including the processing of liquid radioactive waste collected in storage tanks.
IAEA Call On Safety
The IAEA is calling for the installation of an external source of process steam, which, from a nuclear safety perspective, would provide the safest longer-term solution for the steam needs at the site.
TeI IAEA also said that the 750kV Dniprovska power line disconnected twice on 10 August – first for approximately 12 hours until 13:37 and then again at 16:13 local time. It remained disconnected as of 19:00 local time on Thursday.
These disconnections of the power line mean that the station has had to rely on its only remaining off-site power line, the 330 kV backup line, to supply the electricity that is needed, for example, to perform safety functions such as pumping cooling water for the plant.
“There was no total loss of offsite power to the site and there was no need to use the emergency diesel generators,” the IAEA said.
ZNPP has been experiencing major offsite power problems since the conflict began in early 2022, exacerbating the nuclear safety and security risks facing the site currently located on the frontline.