Major international exercise on accident at European nuclear power plant

One of the world's largest international exercises on a serious nuclear emergency took place from 23 to 25 June 2025. The exercise was organised by the International Atomic Energy Agency (IAEA) in cooperation with ten international organisations and 76 countries. GeoSphere Austria has two key roles in such exercises and in the event of an emergency: Internationally, GeoSphere Austria is one of ten centres worldwide of the World Meteorological Organization (WMO) for nuclear emergency measures to calculate the dispersion of a nuclear cloud and advise the IAEA. Nationally, GeoSphere Austria is part of the National Crisis and Disaster Management Centre (SKKM) and supports the radiation protection authorities responsible in Austria. In order to assess the possible effects of a nuclear accident on Austria and the necessary measures to protect the population, emergency systems are operated in the Radiation Protection Department of the BMLUK, for which GeoSphere Austria regularly provides weather forecast data, among other things.

The scenario for the exercise was: an earthquake in Romania severely damages the nuclear power plant in Cernavodă and the cooling system fails. Significant amounts of radioactive material are released into the atmosphere and pose a massive threat to the immediate surroundings and, depending on the weather, to regions several hundred to over a thousand kilometres away.

At around 1000 kilometres, the distance from Austria to Cernavodă is of a similar order of magnitude to Chernobyl (super-GAU 1986).

ConVex-3 is the International Atomic Energy Agency's (IAEA) largest and most complex global exercise format. The emergency exercise took place together with a major national exercise in Romania.

The aim was to evaluate measures for responding to serious nuclear accidents and for emergency preparedness by states and international organisations, as well as to assess cooperation and identify areas for improvement.

76 countries worldwide took part in the exercise. Of these, 29 countries were actively involved with several hundred people. In addition to a wide variety of organisations and emergency services, including field hospitals and helicopters, experts in cyber security and public relations were also involved. Hacker attacks were simulated and a social media simulator generated true and false reports from the public, which had to be responded to immediately.

GeoSphere Austria has two key roles in such exercises and in the event of an emergency, both nationally and internationally:

At national level, there is a long-standing close co-operation with the Radiation Protection Department at the BMLUK. In Austria, the BMLUK participated in the CONVEX-3 exercise as the competent authority in cooperation with other federal ministries and GeoSphere Austria.

Internationally, GeoSphere Austria is one of ten meteorological centres worldwide for nuclear emergency response activities (Regional Specialized Meteorological Centre for nuclear Emergency Response Activities, RSMC ERA) of the World Meteorological Organization (WMO).

‘We support the IAEA during exercises and in an emergency with dispersion calculations and regular updates,’ explains Gerhard Wotawa, Director of the Climate and Environment Department at GeoSphere Austria and currently also Chairman of the WMO's Expert Team for Nuclear and Non-Nuclear Emergency Response (Expert Team ERA). ‘We use special meteorological dispersion models that allow us to make statements about the past and the future. After an accident at a nuclear power plant, we and the other centres calculate for the IAEA with regular updates where the radioactive cloud will move in the coming hours and days and what quantities of radioactivity will reach the ground. However, the models also work in reverse mode: if increased radioactivity is measured somewhere on Earth, we calculate where the radioactive cloud is coming from. On the one hand, this is used to monitor the Comprehensive Nuclear-Test-Ban Treaty (CTBT). On the other hand, the IAEA also investigates the cause of increased radioactivity levels in general.’

Translated with DeepL.com (free version)