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International Atomic Energy Agency (IAEA) experts have been informed that 21 natural gas boilers have been installed at the industrial zone nearby the Zaporizhia NPP (ZNPP) as part of measures to provide additional heating during the winter, including for the nearby city of Energodar, according to IAEA Director General Rafael Mariano Grossi.

The IAEA Support & Assistance Mission to Zaporizhia (ISAMZ) team confirmed that the new gas boilers can provide an extra 57 MW of heating. In addition, all nine mobile diesel boilers at ZNPP have been in operation most days to generate the heating needed as the weather gets colder with the onset of winter.

The ISAMZ team have learned that the three large capacity diesel boilers located at the Zaporizhia Thermal Power Plant (ZTPP) and at the industrial zone are planned to be converted to natural gas within the next month. Additional heating is provided by units 4&5 at the plant, which are in hot shutdown producing the steam required for nuclear safety and security related activities, as well as by more than 50 mobile boilers located throughout the city of Energodar.

Russia took control of ZNPP in March 2022 as part of its special military operation in Ukraine. In October 2022, Russian President Vladimir Putin signed a decree formally transferring ZNPP to Russian jurisdiction under nuclear utility Rosenergoatom (part of Rosatom). A Russian Federal State Unitary Enterprise. Zaporizhia NPP was established by Rosenergoatom to operate the plant. However, Ukrainian nuclear utility Energoatom still claims ownership of the plant. 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. Units 1, 2, 3 and 6 are currently in cold shutdown but units 4&5 are needed to supply heat for vital safety operations.

“With the continuing precarious nuclear safety and security situation at the Zaporizhzhya nuclear power plant, the team will monitor closely the efforts taken to prepare for the difficult coldest months of the year,” Grossi said. “Our presence remains essential.” During the past week, the new team of IAEA experts who began their rotation at ZNPP heard explosions outside the plant on a near-daily basis, highlighting the dangers posed by an armed conflict in such close proximity to a NPP.

The team was informed of the maintenance activities under way. Pressure testing of unit 3’s steam generators – a necessary procedure following the closure of its reactor vessel, which had been left open for over 18 months – was completed successfully and sealing of the steam generators is being performed. ZNPP informed the IAEA experts that maintenance is being performed on the primary circuit this week, after which final pressure testing will be conducted.

ZNPP also informed the IAEA that maintenance of the number 1 safety train at unit 6 would take place in the near future. ZNPP reactors each have three separate and independent redundant systems – known as safety trains – comprising the units’ safety systems, which are normally in stand-by mode ready to activate if needed. Maintenance on the other two safety trains was conducted in October. The team was also informed that maintenance of the main unit transformers of units 1, 2 & 3 will begin this week, similar to that recently performed on the unit transformers of units 4, 5 & 6.

The IAEA has been concerned that some of the maintenance activities that have been carried out on the safety systems of the reactor units may have been incomplete, warranting additional maintenance. This was apparent in July and August after unit 4 was placed in hot shutdown following maintenance on its safety systems. However, after unit 4 was returned to cold shutdown in August due to a water leak in one of the steam generators, further maintenance was also required to clean the heat exchangers of the unit’s safety systems.

“As a result of the ongoing conflict, the ZNPP… has not been able to maintain a comprehensive systematic maintenance programme, especially due to the reduction of experienced maintenance staff,” Grossi noted. “Nuclear safety and security remain at risk the longer the plant has reduced levels of trained and experienced staff. It is not a sustainable situation .”

The IAEA team continues to perform daily walkdowns. During a visit to the main control room, emergency control room and electrical room of unit 3, the team confirmed the unit’s cold shutdown status. A walkdown of the emergency diesel generators of units 1&2 was also conducted and IAEA experts also visited the ZNPP cooling pond and cooling towers and confirmed the integrity of the isolation gates.

IAEA continues to stress that it needs access to all six turbine halls to assess safety but says experts at the site were prevented from visiting parts of the turbine hall of unit 1, after receiving similar restricted access to the turbine halls of units 1, 2&4 during walkdowns in October. During walkdowns of the site perimeter, the team did not observe any mines or explosives, including in areas where they had been previously observed.

Outside of the perimeter of the site, IAEA visited the three large diesel fuel storage tanks at the storage facility. This stored fuel is required to run the 20 emergency diesel generators at ZNPP for at least 10 days. The facility is also being used to supply fuel for the mobile diesel boilers. The team was informed of the amount of fuel in the tanks and observed the filling of trucks taking diesel fuel to the mobile boilers.

Regarding the water used at the site for reactor cooling and other nuclear safety and security functions, ZNPP confirmed that insulation of the 11 groundwater wells was ongoing. The wells feed approximately 250m3/h of cooling water to the sprinkler ponds for reactor cooling. Insulation works are planned to be completed by the end of November. The IAEA experts were also informed that the power supply for the pumps in the wells is provided by the essential electricity consumer outlets. In case of a loss of off-site power, IAEA experts were informed that the pumps from the wells can be powered through the two common emergency diesel generators, ensuring the availability of cooling water if all off-site power was lost.

The IAEA team at the site learned that a ZNPP emergency exercise is planned later in November. The last major exercise was conducted in November 2021, before the start of the conflict. IAEA said that, since then, there has been an unprecedented change in the number of the ZNPP staff which could impede the site’s ability to effectively respond to emergency situations. The Agency stresses the need for the ISAMZ team to be permitted to observe the upcoming exercise and to receive the lessons learned from the exercise.

IAEA continues to gather information on the status and condition of staff. This includes building an understanding of the training and licensing of operating staff under Russian Federation regulations. IAEA experts visited the ZNPP training centre and gathered more information regarding the number of trainers and their training processes.

In terms of regulatory functions at the site, IAEA was also informed that Russian nuclear regulator Rostekhnadzor is establishing a more permanent presence at ZNPP with the arrival at the site of the Head of ZNPP Nuclear & Radiation Safety Inspections. The team was informed that the aim is to provide constant supervision and regulatory control of the NPP, in accordance with Russian state laws and to give licences to the employees.

Image: A view units 4 & 5 at the Zaporizhia nuclear power plant

Date: Wednesday, 15 November 2023
Original article: neimagazine.com/news/newsiaea-monitors-maintenance-activities-at-zaporizhia-npp-11297138