Zaporizhzhia: Unit 4 in hot shutdown, IAEA reports mines

The decision to switch unit 4 to hot shutdown was taken by the operators of the nuclear power plant, which has been under Russian military control since early March last year. When a unit is in hot shutdown it can provide the steam necessary for, as the IAEA has explained, "various nuclear safety purposes including the processing of radioactive waste collected in storage tanks".

The State Nuclear Regulatory Inspectorate of Ukraine issued regulatory orders last month for all six units to be placed in cold shutdown, given its situation on the frontline of the war, and the breaching of the dam that had helped ensure plentiful cooling water supplies. The Russian operators of the plant say such a move is not required from a "legal or technological point of view". The IAEA has urged investigation into whether an external boiler could be installed at the site to generate the steam required, so all units could be moved to cold shutdown.

In a brief statement issued on Tuesday, the Russian operators of the plant said: "In order to conduct a scheduled technical inspection of the equipment of power unit 5, the management of the Zaporizhzhia nuclear power plant decided to transfer it to the 'cold shutdown' state. And in order to provide steam for the station's own needs, the reactor plant of power unit 4 was transferred to the 'hot shutdown' state."

Meanwhile, in his latest update, the IAEA's Director General Rafael Mariano Grossi, said that the agency experts on the nuclear power plant site have seen some mines "located in a buffer zone between the site's internal and external perimeter barriers ... situated in a restricted area that operating plant personnel cannot access and were facing away from the site". The team did not see any within the inner site perimeter.

Grossi has had UN Security Council backing for his safety principles of not firing at or from the nuclear plant as well as not using it to store heavy military equipment. The team of IAEA experts at the site have carried out inspections and regular walkdowns and have not seen heavy military equipment. They are continuing to request access to the roofs of the reactors and turbine halls.

He said: "The IAEA has been aware of the previous placement of mines outside the site perimeter and also at particular places inside. Our team has raised this specific finding with the plant and they have been told that it is a military decision, and in an area controlled by military. But having such explosives on the site is inconsistent with the IAEA safety standards and nuclear security guidance and creates additional psychological pressure on plant staff - even if the IAEA’s initial assessment based on its own observations and the plant’s clarifications is that any detonation of these mines should not affect the site’s nuclear safety and security systems."

The IAEA team reported that the available water supply "remains relatively stable, with the water level decreasing by around 1 centimetre per day due to usage and evaporation and the site continues to have sufficient water for some months".

The IAEA now has teams stationed at all of Ukraine's nuclear power plants. The personnel at the Rivne, Khmelnitsky and South Ukraine plants will be rotated this week. Separately, the IAEA Support and Assistance Mission on the Safety and Security of Radioactive Sources in Ukraine arrived to carry out a mission to "assess the radiation safety and nuclear situation regarding radioactive sources in the country".