18 nuclear power plants in the European Union are operating without a valid license, according to research conducted by Germany's Green Party.

This number doesn't include the 34 other illegal power plants in neighboring European countries that aren't part of the EU.

All operating illegal atomic reactors were never subject to an Environmental Impact Assessment (EIA).

Spiegel indicated that — should any reactor fail an EIA assessment — governments in those countries where reactors are operating may face serious consequences.

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There are 18 active nuclear power plants currently operating without a valid license in the European Union, according to a report seen by Business Insider.

Many of the power plants should have already been subject to an Environmental Impact Assessment (EIA), according to a report put together by Germany's Green Party member and nuclear expert Sylvia Kotting-Uhl.

An EIA aims to identify the environmental consequences of major projects, such as the construction of an airport, and has proposed some lesser damaging alternatives.

Some of the EU countries running the illegal power plants include the Netherlands, Bulgaria, Ukraine, Belgium, Finland, the UK, Sweden, and Switzerland.

The number does not take into account the 34 other illegal nuclear power plants in neighboring European countries that aren't part of the EU.

Read more: Chernobyl's 'sarcophagus,' which helped contain the spread of radiation, is being dismantled because it's teetering on collapse

If these power stations were to fail an EIA following the publication of this report, the EU countries in charge will be facing serious consequences, according to German publication the Spiegel.

In France alone, there are 58 pressurized water reactors, which produce over 70% of the country's electricity. Many of them are classified as "high-risk reactors" because they are more than 30 years old. The recommended operating age of a nuclear power plant is 40 years.

Should these specific reactors fail the EIA, France would most likely have to temporarily shut down the power plant concerned and buy electricity elsewhere — possibly even from Germany.

Read more: It looks like the Russians are trying to hide the truth about that nuclear accident in Nyonoksa

Another nuclear power plant at the Mühleberg site in Switzerland has also been classified as particularly dangerous by an Austrian environmental protection organization called "Global2000".

Not only is it a "high-risk reactor", but it's also the same power plant as Fukushima — the Japanese reactor which had a nuclear disaster in 2011.

"In the event of a rupture of the nearby dam and consequent flooding, all pumps of this power plant could fail. This would lead to a core meltdown, one similar to the one seen in Fukushima," the environmental protection organization wrote in a report.

The Mühleberg power plant will be shut down in December 2019.

The German government announced that it had no specific knowledge of "which European plants are currently operating without a (transboundary) EIA", according to the SPIEGEL.

The UN Committee responsible for these investigations is currently examining several nuclear reactors which are said to have been approved in Europe without an EIA.