“According to Zaporizhia NPP, the transition of the unit’s reactor installation to the “cold shutdown” mode began yesterday (Monday – ed.) and is expected to be completed today (Tuesday – ed.). The fourth power unit will remain in “hot shutdown” mode. At present, there are no plans to put the second power unit into “hot shutdown” mode to replace the fifth, the station reported,” the report notes. IAEA.
It is clarified that after the power unit is transferred to the “cold shutdown” mode, studies will be carried out at Zaporizhia NPP in order to identify the reasons for the detection of low boron content in the second cooling circuit of one of the steam generators of the power unit.
“ZNPP informed the IAEA experts who arrived on site that the concentration of boron in the affected cooling circuit did not exceed the limits allowed by technical specifications. In addition, no radioactivity was detected in the second cooling circuit,” the Agency explained. Borated water is used in the primary coolant of the reactor plant to ensure nuclear safety,” the IAEA added.
It is also clarified that IAEA experts continue to investigate the causes of the 90-minute power outage that occurred on November 16 at the sixth power unit.
The VVER-1000 reactor plants at the Zaporozhye NPP are double-circuit. In them, the circuits of the coolant (water) and the working fluid (water vapor) are separated. Accordingly, the coolant circuit is called the first, and the working fluid circuit is called the second.
Zaporozhye Nuclear Power Plant is located on the left bank of the Dnieper near the city of Energodar. This is the largest nuclear power plant in Europe in terms of the number of units and installed capacity – the station has six power units with a gigawatt capacity. In October 2022, the nuclear power plant became the property of Russia. IAEA experts have been working at the Zaporozhye NPP since September 1, 2022, after the first visit of the agency’s Director General Rafael Grossi to the site.