The Western European Nuclear Regulators Association (WENRA) says that although there are a number of alternative means of providing power in the event of a total loss of offsite power "war … can have unexpected and additional consequences” and the loss of two of the external power lines to Ukraine’s largest nuclear power plant “significantly weakens the robust electricity supply arrangements".

There are six units at Zaporozhe (Image: Energoatom)

The assessment by WENRA on the safety level at Zaporozhe concludes that even during the two days when three external power lines were down - there are four in total plus one standby line - cooling continued at the nuclear power plant.

"Furthermore, the availability of all the alternative means gave confidence that, even if all external power supply sources would have been lost, the situation would not have presented an immediate safety concern," it says.

WENRA said that "a fundamental function of nuclear power reactors is to ensure continuous cooling of the reactor cores and the spent fuel pools, which requires reliable and diverse sources of electrical power supply". If the offsite power is lost, the site would switch to emergency diesel generators (which is what happened at Chernobyl when it lost all external power).

There were also further backup options available - switching to house-load operation, where one of the six reactors at Zaporozhe provides the electricity to the whole site, and also the use of mobile diesel generators.

The organisation said that the current military conflict’s impact on Chernobyl and Zaporozhe showed it was "imperative to exercise the utmost restraint and vigilance to prevent any direct or indirect impact of military operations on the safety of all nuclear installations in the country".

It called for the two damaged 750 kV power lines of Zaporozhe to be promptly repaired and the physical integrity of the electrical power supply lines of all four Ukrainian nuclear power plants to be guaranteed. WENRA also says supplies of fuel and spare parts for on-site emergency diesel generators at all four Ukrainian plants should be guaranteed.

In its latest daily update, Ukrainian nuclear power plant operator Energoatom said that all four of its nuclear power plants were continuing to operate within safety limits.

In its update on the evening of 24 March, the International Atomic Energy Agency said it had been told by the State Nuclear Regulatory Inspectorate for Ukraine (SNRIU) that it did not expect the wildfires burning in the Chernobyl area to cause any significant radiological concern. This assessment was based on the experience of fires in previous years, because SNRIU said it could still not carry out radiation measurements in the exclusion zone.

Researched and written by World Nuclear News