Russian President Vladimir Putin. Germany and other EU countries are looking to sanction Russian nuclear energy.

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Germany, Poland and a few other EU nations are pushing for sanctions on Russian nuclear energy, as the bloc looks at new ways to hurt the Kremlin’s revenues amid Moscow’s invasion of Ukraine.

The 27 European nations have sanctioned Russian seaborne oil, coal and significantly cut purchases of natural gas from Moscow in the wake of its war with Ukraine. However, some nations believe it is time to do more.

“Across the EU, we must keep making ourselves independent from Russia,” Robert Habeck, the German economy and climate minister, said over the weekend.

“The nuclear sector is still outstanding. It is not justifiable that this area is still given preferential treatment. Nuclear technology is an extremely sensitive area, and Russia can no longer be seen as reliable partner within it,” he said.

In a document seen by CNBC, Poland and the Baltic States also called for sanctions on civil nuclear energy activities, as well as bans on diamond imports from Russia, on the provision of information and communication technology services to Russian state firms, and on oil imports on the Druzhba pipeline. These states are trying to ramp up pressure on the European Commission — the executive arm of the EU, which drafts sanctions proposals for the approval of various EU governments.

“Between March and December 2022, Russia exported just over $1 billion-worth of materials and technology of relevance to the nuclear energy sector,” the Royal United Services Institute, a think tank, said in a report in February.

“This trade included exports to members of NATO and the EU. In fact, not only has the value of Russian nuclear-related exports not shrunk since February 2022, the data reviewed by the author suggests that it may be expanding, with a handful of loyal customers still eager to do business with Russia’s nuclear sector,” the same report said.

According to data published by Europe’s statistics office Eurostat in 2021 — the year before Russia’s invasion of Ukraine — Moscow was the third biggest provider of uranium to the EU.

Ukrainian officials, as well as environmental groups, have previously criticized how the European Union has so far not curbed nuclear revenues for the Kremlin.

The EU has imposed 10 packages of sanctions on Russia in the 14 months since the invasion of Ukraine, and a further round of measures is being prepared.

Asked whether a new set of actions to target Russia would feature nuclear energy, a spokesperson for the European Commission said that the institution has no comment on ongoing confidential discussions.

“The preparations for the 11th package are ongoing,” the spokesperson said, “to have it all done and ready it takes time.”

The debate is always complex for the EU bloc, where any sanctions on Russia require a unanimous decision. Hungary and Bulgaria needed more time and persuasion during previous discussions, shrouding the whole process in uncertainty.

Further highlighting the complexity of the matter, Hungary announced in August that it would build two new nuclear reactors with the Russia state-owned firm Rosatom.

—CNBC’s Sophie Kiderlin contributed to this report.