The European Commission and the European Nuclear Safety Regulators' Group (ENSREG) agreed on the criteria covered and the way controls will be done. In addition, they decided the starting day for the stress test in European nuclear power plants.

The stress tests are re-assessments of the safety margins of the EU nuclear power plants. Therefore, the European Commission and the European Nuclear Safety Regulators' Group (ENSREG), which represents the 27 independent national authorities responsible for nuclear safety, agreed on the scope and the modalities for a comprehensive risk and safety assessment of EU nuclear power plants. To guarantee the highest safety standards in the world, the EU draws the lessons from Fukushima and focuses in the tests on all sorts of natural disasters and includes also the effects of man-made accidents such as airplane crashes as well as terrorist or other malevolent attacks.

The European Council of 24 and 25 March 2011 stressed the need to fully draw the lessons from recent events related to the accident in Japan, and to provide all necessary information to the public. Following discussions with Member States recognising among others the need for confidentiality, all security-related aspects such as measures preventing terroristic attacks will be dealt separately.

With regard the stress test, from the 1 June onwards, nuclear power plants will be re-assessed in a three-step-process:

1. Pre-assessment by the nuclear power plant operators which answer the stress tests questionnaire, submitting supporting documents, studies and plans.
2. National Report drawn up by the national regulator checking whether answers of nuclear power plant operators are credible.
3. Peer reviews. Multinational teams will review the national reports. These teams will consist of seven people – one European Commission representative and six Members of the 27 national regulators. The exact composition of each team will be decided later. Teams can decide to inspect nuclear plants on the spot. 

The Commission is also in close contact with countries outside the EU and is working with them on re-assessing their nuclear power plants. These are in particular Switzerland, the Russian Federation, Ukraine and Armenia.