Krško nuclear power station shut down as a precaution after quake

Krško – The Krško Nuclear Power Station (NEK) was shut down as a precaution on Tuesday after a powerful 6.4-magnitude earthquake hit near the town of Petrinja, Croatia, shortly after midday. Such a shutdown is standard procedure in the event of a strong earthquake, NEK told the STA. NEK is located some 80 kilometres north-west of Petrinja.

NEK director Stane Rožman said the quake was strong enough to trigger a safe shutdown. The power station “is in safe mode without any consequences for the environment. All systems are functioning normally. We will conduct a systematic check of equipment and systems and plan a return to service within 24 hours.”

Leon Cizelj, the head of the reactor technology department at the Jožef Stefan Institute, wrote on Twitter that the tremor was well within safe limits.

He said peak ground acceleration, a measure of the earthquake’s amplitude, was between 0.02 and 0.05, whereas NEK is built to function normally up to an acceleration of 0.15.

Located in a seismically active area, the nuclear power station is built to withstand tremors significantly stronger than typical earthquakes in the region.

NEK was designed to safely shut down during magnitude 7 earthquakes, but nuclear experts say improvements and reinforcements made since then mean it could safely shut down even in the event of a magnitude 8 earthquake.

The epicentre of the earthquake, which was felt in large swathes of Slovenia, was 46 kilometres south of Croatia’s capital Zagreb near Petrinja, which was already the epicentre of a 5.2-magnitude earthquake on Monday.

Slovenia’s Nuclear Safety Administration told the STA it was in contact with NEK staff and announced it would carry out an inspection tomorrow at the latest.

It said that even if the facility is resistant to powerful tremors, its electricity network is a soft spot, so it is key to have own power supply.

NEK purchased a third diesel generator a few years ago, halving the probability of radioactive matter being emitted into the environment.

It said that after the 2011 Fukushima disaster, NEK purchased various additional equipment to be used if its installed equipment failed in major natural disasters.

The strongest earthquake in the Krško area was recorded in 1917, some 65 years before NEK was launched. Translated into current standards, it would be a tremor of about magnitude 8, the administration said.

The safety assurances however never convince regional authorities in Austria’s Carinthia, which today repeated their call for NEK’s closure.