The International Atomic Energy Agency (IAEA) in its latest update on the Zaporizhia NPP (ZNPP) said the plant had been reconnected to its only remaining main 750 kilovolt (kV) power line on 10 August ending the second outage of this power line on that day. The IAEA team on site were informed that the disconnection occurred 5.5 km from the open switchyard on the southern bank of the river due to the activation of an overcurrent protection system.

During the outage, ZNPP relied on a single remaining 330 kV power line for the external electricity needed for reactor cooling and other essential nuclear safety and security functions. There was no loss of off-site power and no need to use the emergency diesel generators. IAEA said the plant’s external power situation , nevertheless, remains highly vulnerable, underlining the precarious nuclear safety and security situation at the site.

ZNPP has been experiencing major off-site power problems since the conflict began in early 2022, exacerbating the nuclear safety and security risks facing the site currently located on the frontline.

“The repeated power line cuts underline the continuing precarious nuclear safety and security situation at the plant,” Director General Grossi said.

ZNPP has meanwhile transferred reactor unit 4 to cold shutdown following the detection of a water leak at one of its four steam generators located in the containment building. At the end of July, unit 4 had been transferred to hot shutdown to replace unit five which was put into cold shutdown for necessary maintenance.

IAEA said maintenance activities were underway, including inspection and testing of the safety systems which protect the reactor and its fuel; and cleaning of the heat exchanger. However, the IAEA team requested more complete information regarding the full scope of maintenance activities planned to be conducted on Unit 5, given the limited availability of spare parts and significantly reduced maintenance staff available at ZNPP.

As one of the plant’s six units is required to be in hot shutdown to generate steam for various nuclear safety purposes, unit 6 was subsequently put into hot shutdown to continue steam generation, replacing unit 4. Unit 6 had been in cold shutdown since 21 April, to enable inspection and maintenance of the safety systems. Prior to its transfer to hot shutdown, ZNPP completed this work and all tests of the safety systems before starting the transition. The IAEA team on the site closely monitored the operations for the transition between the shutdown states of units 4 and 6.

The IAEA continues to strongly encourage 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.

The availability of cooling water remains relatively stable at ZNPP, despite destruction of the Khakhovka dam in June, which has effectively drained the Khakhovka reservoir previously used to support plant cooling. IAEA said, while the height of the ZNPP cooling pond continues to drop by about 1cm a day, the height of the discharge channel from the neighbouring Zaporizhia Thermal Power Plant (ZTPP) is regularly being topped up by pumping water from the ZTPP inlet channel.

IAEA experts have been conducting multiple walkdowns in different parts of the site. These included a visit to the dry used fuel storage facility, where they were able to verify the integrity of the fuel casks stored there. The team also visited the unit 2 main control room, emergency control room and other safety-related rooms. They did not observe any mines or unusual objects in these areas. However, in the turbine hall of unit 2, the team noted the presence of a number of military trucks parked in an area reserved for vehicle maintenance.

The IAEA experts visited one of the fresh fuel storage facilities and confirmed that the fresh fuel was safely and securely stored. Following the IAEA experts’ visit to the unit 3 and unit 4 rooftops the previous week, the team continued to request access to conduct walkdowns on the rooftops of the other four units.

Access to the unit 3&4 roofs came just after a successful ninth rotation of teams at the plant with IAEA experts once again crossing the front line as the teams departed and arrived at the plant. On the night before the rotation the team reported hearing a series of detonations in the vicinity of the plant. The team was informed by the ZNPP that there was no impact on the site, the neighbouring industrial area or the city of Enerhodar as a result of these detonations.

Additionally, the IAEA experts recently performed radiation monitoring of the cooling pond area and the areas inside the site perimeter during the walkdowns. The measurements data are uploaded by the IAEA to the IAEA’s International Radiation Monitoring Information System (IRMIS). All radiation levels were normal.

Russian nuclear regulator Rostekhnadzor also supervised routine testing of safety systems at ZNPP. The inspectors supervised the conduct of comprehensive tests with the launch of mechanisms to ensure integrity of the safety systems at units 1 and 4. Rostechnadzor said no deficiencies affecting safety had been identified.

ZNPP reported that from the start of August it had launched a programme for employees to visit health resorts in the Crimea and the Rostov Region. “Employees of ZNPP EO JSC can apply for sanatorium treatment and rehabilitation and recreational activities for themselves and their family members, namely spouses and children under the age of 18,” the plant website announced. “As part of the spa treatment and rehabilitation programmes for August and September, Crimean sanatoriums are available for booking… Also, additional medical services are available to employees of ZNPP in medical institutions of Crimea and the Rostov region. All full-time employees of EO ZNPP JSC are provided with voluntary medical insurance through SOGAZ JSC.”

Image courtesy of Rosatom