In a preliminary version of a security chart in the Commission's report presented on Thursday, the Krško plant, active since 1981, was the only one to receive no security recommendations.

The warnings finally issued to NEK included the need to secure all measures for the prevention of the explosion of hydrogen and other combustible gases in the cases of serious accidents, to upgrade its filter ventilation system for the prevention of the spreading of radioactivity and to upgrade earthquake safety.

The plant was however also commended for a number of good practice measures, including for already having in place diesel generators to face power cuts or serious accidents.

The head of the Slovenian Nuclear Safety Administration Andrej Stritar told the STA in response that he was happy with the result, which was even more favourable than expected.

The safety administration and staff at the plant have been working hard, they however did not imagine they were the best in Europe, Stritar added, while announcing that focused and thorough work would also continue in the future.

He explained that additional efforts were invested into NEK after the Fukushima accident - which also prompted the EU study. A plan of investments and improvements until 2016 was adopted, with the tests showing that the Krško plant is on the right path.

NEK director Stane Rožman said he was happy that existing solutions are already adequate for facing the most improbable or hypothetical natural disaster scenarios.

He added that the management already had a clear idea on how the plant is to be upgraded in the coming five years.

The Commission report, which provides the first comprehensive security review for the 132 reactors active in 14 EU member states, established that all plants met high standards and none needed to be closed. However improvements, costing up to EUR 25bn, will be necessary in the coming years, the report adds.