Eruption of a volcano in the Pacific was also detected by slovak NPPs

19.01.2022
Možnosti zdieľania:
The pressure wave from the eruption of the Hunga Tonga volcano has reached us. The human body does not perceive such a pressure change, but sensitive instruments in nuclear power plants have detected it and reacted correctly.

The Hunga Tonga submarine volcano off the Tonga archipelago in the southwest Pacific Ocean exploded over the weekend. The eruption carried water vapour and volcanic ash up to a height of 20 km. It lasted for about eight minutes and its intense rumbling was also felt by residents from Fiji, 800 kilometres away. The pressure wave following the eruption of the volcano was recorded by all meteorological stations in Europe, including amateur ones. The sudden change in atmospheric pressure was also picked up by measurements at Slovak nuclear power plants. Sensors in the Bohunice NPP signalled changes in negative pressure in the hermetic zone of the primary circuit. The automation regulated the pressure drop at both Bohunice units to keep the negative pressure within the set limits.

This is how the eruption was detected by satellite:

A view from space of the eruption of the Hunga Tonga-Hunga Ha'apai volcano

The tsunami wave that followed the eruption also affected remote areas. Japan reported three-metre waves and warnings were also issued by coastal countries in Asia, the US states of Alaska and Hawaii. Although they expected manageable waves of about 60 centimetres in California, these eventually reached two metres and caused flooding. Volcanologists have warned that the eruptions could happen again. Volcanic ash dispersed into the atmosphere could also bring a slight cooling locally as it prevents the sun's rays from reaching the Earth's surface.

In both Bohunice and Mochovce

  • On Saturday 15 January at 20:28 in the evening, the operator at the joint control room in EBO entered in the eSOMS log the arrival of an alarm in the information system caused by a vacuum in the box and on board the main circulation pumps of Unit 3. There were similar reports at Unit 4. In both cases, the underpressure was regulated to nominal values by the automatic control system.
  • Approximately six hours later, the SD operator again noted a pressure change in the steam generator box. It was caused by a pressure wave from a volcanic eruption, which had a longer route and came to Slovakia from the opposite side of the Earth.
  • Comparable signalling was also reported by the Mochovce steam generators in the steam generator box of both units. There too, they were easily regulated by the automation of the ventilation systems that create the negative pressure in the rooms in question.
The graph shows the pressure changes in the hermetic zone of the primary circuit of Mochovce NPP Unit 1
This graph captures the negative pressure change in the hermetic zone of the primary circuit of Bohunice NPP Unit 3

Fourteen-hour trip

The pressure wave arrived in the Slovak Republic after 8 pm on Saturday evening and rocked the air pressure readings for over two hours. Recorded fluctuations reported a rapid pressure rise of about 1.5 hPa in 15 minutes followed by a rapid drop of about 2 hPa. The delayed wave coming from the opposite side of the planet mainly caused a drop in air pressure, which persisted for a longer period of time at some stations, according to the SHMÚ report.


The distance from the explosion site to Mochovce or Bohunice is approximately 17 thousand km as the crow flies. The pressure wave covered this distance from the moment of the explosion to us in more than 14 hours.

Hunga Tonga-Hunga Ha'apai

This is a volcanic island in the State Territory of Tonga about 30 km south of the submarine volcano Fonuafoʻou and 65 km north of the main island This is a volcanic island in the State Territory of Tonga about 30 km south of the submarine volcano Fonuafoʻou and 65 km north of the country's main island, Tongatapu. An eruption in 2009 merged the islands of Hunga Tonga and Hunga Haʻapai, and an eruption a few days ago separated them again and reduced their size. The volcano is part of the very active Tonga-Kermadek Islands volcanic arc. It is located approximately 100 km from a very active seismic area. The island arc was formed at the lithospheric plate boundary where the Pacific Plate underlies the Indo-Australian Plate.

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