Siemens Energy AG supervisory board chairman Joe Kaeser defended plans to continue doing business with Russia’s nuclear giant Rosatom Corp. in Hungary amid criticism that such deals help fill the Kremlin’s coffers.

Breaching the contracts, which were signed in 2019, could end up being very expensive, Kaeser told Welt am Sonntag.

“There are non-governmental organizations that demand that our management doesn’t comply with these valid contracts and is then possibly sued by an EU state for almost unlimited sums,” Kaeser said.

The controversy centers on two new power units for the Russian-built Paks 2 plant in Hungary, for which Siemens Energy is supplying safety technology. Construction started in August.

According to a recent Greenpeace report, European companies like Siemens Energy and France’s Framatome have contracts worth hundreds of millions of euros for Rosatom’s nuclear projects outside of Russia. Without these technology and knowledge transfers, many of the state giant’s new projects would grind to a halt.

Read more: The Manhattan Project to Wean the US Off Russian Uranium

The US and Europe are making efforts to wean themselves off Russian uranium but haven’t sanctioned nuclear technology, meaning Rosatom has operated as normal since Moscow’s full-scale invasion of Ukraine in February 2022.

The alternative for the Rosatom facility in Hungary “would be for the Chinese to step in and supply the controls for the nuclear power plant, which is much closer to Germany than Chernobyl was back then,” said Kaeser.

Rosatom is the world’s largest enricher of uranium, with 43% of total production capacity. That’s followed by Urenco Ltd., a UK-Dutch-German group, with a 31% share, China National Nuclear Corp. with 13%, and France’s Orano SA.

Germany phased out its last nuclear power plants this year, and government representatives have called for EU sanctions on Russian uranium from next year.

Kaeser added that he is “an avowed opponent” of today’s nuclear power technology, “because we are leaving hundreds of generations with waste that, in my view, simply cannot be stored responsibly. This is a moral dilemma.”