WASHINGTON (AP) — The U.S. and its European allies are importing vast amounts of nuclear fuel and compounds from Russia, providing Moscow with hundreds of millions of dollars in badly needed revenue as it wages war on Ukraine.

The sales, which are legal and unsanctioned, have raised alarms from nonproliferation experts and elected officials who say the imports are helping to bankroll the development of Moscow's nuclear arsenal and are complicating efforts to curtail Russia's war-making abilities. The dependence on Russian nuclear products — used mostly to fuel civilian reactors — leaves the U.S. and its allies open to energy shortages if Russian President Vladimir Putin were to cut off supplies. The challenge is likely to grow more intense as those nations seek to boost production of emissions-free electricity to combat climate change.

"We have to give money to the people who make weapons? That's absurd," said Henry Sokolski, executive director of the Washington-based Nonproliferation Policy Education Center. "If there isn't a clear rule that prevents nuclear power providers from importing fuel from Russia — and it's cheaper to get it from there — why wouldn't they do it?"

Russia sold about $1.7 billion in nuclear products to firms in the U.S. and Europe, according to trade data and experts. The purchases occurred as the West has leveled stiff sanctions on Moscow over its 2022 invasion of Ukraine, blocking imports of such Russian staples as oil, gas, vodka and caviar.

The West has been reluctant to target Russia's nuclear exports, however, because they play key roles in keeping reactors humming. Russia supplied the U.S. nuclear industry with about 12% of its uranium last year, according to the U.S. Energy Information Administration. Europe reported getting about 17% of its uranium in 2022 from Russia.

Reliance on nuclear power is expected to grow as nations embrace alternatives to fossil fuels. Nuclear power plants produce no emissions, though experts warn that nuclear energy comes with the risk of reactor meltdowns and the challenge of how to safely store radioactive waste. There are about 60 reactors under construction around the world — 300 more are in the planning stages.

Many of the 30 countries generating nuclear energy in some 440 plants are importing radioactive materials from Russia's state-owned energy corporation Rosatom and its subsidiaries. Rosatom leads the world in uranium enrichment, and is ranked third in uranium production and fuel fabrication, according to its 2022 annual report.

Rosatom, which says it is building 33 new reactors in 10 counties, and its subsidiaries, exported around $2.2 billion worth of nuclear energy-related goods and materials last year, according to trade data analyzed by the Royal United Service Institute, a London-based think-tank. The institute said that figure is likely much larger because it is difficult to track such exports.

Rosatom's CEO Alexei Likhachyov told the Russian newspaper Izvestia the company's foreign business should total $200 billion over the next decade. That lucrative civilian business provides critical funds for Rosatom's other major responsibility: designing and producing Russia's atomic arsenal, experts say.

Ukrainian officials have pleaded with world leaders to sanction Rosatom to cut off one of Moscow's last significant funding streams and to punish Putin for launching the invasion. Ukrainian President Volodmyr Zelenskyy again pressed Western leaders to target Rosatom after Russian forces captured the Zaporizhzhia nuclear power plant. Rosatom is running the partially shutdown plant, and the International Atomic Energy Agency has repeatedly warned that a radiation leak at the Russian-occupied facility could be a major disaster.

"Ukraine does not understand why sanctions have not yet been introduced against Rosatom and its leadership," Zelenskyy said in May, "when representatives of this company continue to occupy Zaporizhzhia Nuclear Power Plant and put our general security at risk."

Nuclear energy advocates say the U.S. and some European countries would face difficulty in cutting off imports of Russian nuclear products. The U.S. nuclear energy industry, which largely outsources its fuel, produces about 20% of U.S. electricity.

The value of Russian nuclear fuel and products sent to the U.S. hit $871 million last year, up from $689 million in 2021 and $610 million in 2020, according to the U.S. Census Bureau. In terms of weight, U.S. imports of uranium products from Russia nearly doubled from 6.3 tons in 2020 to 12.5 tons in 2022, according to trade data from ImportGenius.

The reasons for that reliance goes back decades. The U.S. uranium industry took a beating following a 1993 nonproliferation deal that resulted in the importation of inexpensive weapons-grade uranium from Russia, experts say. The downturn accelerated after a worldwide drop in demand for nuclear fuel following the 2011 meltdown of three reactors at Japan's Fukushima Daiichi power plant.

American nuclear plants plants purchased 5% of their uranium from domestic suppliers in 2021, the last year for which official U.S. production data are available, according to the U.S. Energy Information Administration. The largest source of uranium for such plants was Kazakhstan, which contributed about 35% of the supply. A close Russian ally, Kazakhstan is the world's largest producer of uranium.

The Biden administration says it is trying to revive uranium mining and the production of nuclear fuel, and lawmakers have introduced legislation to speed up the process. This week, however, President Joe Biden announced the formation of a national monument to preserve land around Grand Canyon National Park that would prevent new uranium mining in the region.

"It is critical that we stop funding Russia's state-owned nuclear monopoly, Rosatom," said Sen. John Barrasso, the Wyoming Republican who introduced legislation earlier this year to fund America's nuclear fuel supply chain. "We also need to give America's nuclear fuel suppliers market certainty."

Europe is in a bind largely because it has 19 Russian-designed reactors in five countries that are fully dependent on Russian nuclear fuel. France also has a long history of relying on Russian-enriched uranium. In a report published in March, Greenpeace, citing the United Nations' Comtrade database, showed that French imports of enriched uranium from Russia increased from 110 tons in 2021 to 312 tons in 2022.

Europe spent nearly $828 million (almost €750 million) last year on Russian nuclear industry products — including fuel elements, nuclear reactors, and machinery — according to Eurostat, the EU's statistics office.

Some European nations are taking steps to wean themselves off Russian uranium. Early on in the Ukraine conflict, Sweden refused to purchase Russian nuclear fuel. Finland, which relies on Russian power at two out of its five reactors, scrapped a trouble-ridden deal with Rosatom to build a new nuclear power plant. Finnish energy company Fortum also announced an agreement with the U.S. Westinghouse Electric Company to supply fuel for two reactors after its contracts with Rosatom subsidiary Tvel expire over the next seven years.

The Czech Republic has sought to wean itself off Russian supplies completely and turned to Westinghouse and the French company Framatome for future shipments of fuel assemblies for its only nuclear power plant, currently supplied by Tvel, with the new supplies expected to begin in 2024. Slovakia and Bulgaria, two other countries that rely on Tvel for nuclear fuel, have also turned to different suppliers.

Despite the challenges, experts believe political pressure and questions over Russia's ability to cut off supplies will eventually spur much of Europe to abandon Rosatom. "Based on apparent prospects (of diversification of fuel supplies), it would be fair to say that Rosatom has lost the European market," said Vladimir Slivyak, co-chair of the Russian environmental group Ecodefense.

What remains unclear, Slivyak said, are how Hungary and France will address the issue. France has not expressed a willingness to shut off Russia's uranium spigot. Hungary, which maintains close ties to Russia, is fully dependent on Moscow to provide fuel for its four-reactor nuclear power plant. It has plans to expand that plant by two Rosatom reactors — a project that is financed by a 10 billion euro line of credit from a Russian bank.

Those reactors, experts said, will be fully reliant on Russian nuclear fuel for years, if not decades, to come.

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Litvinova reported from Tallinn, Estonia. Associated Press writers Courtney Bonnell in London, Jari Tanner in Helsinki and John Leicester in Paris contributed to this report.

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