The immediate catalyst is fear that uranium supply out of Russia might be disrupted. Thursday, a group of U.S. senators introduced a bill to ban imports of its uranium and on Monday Russian Deputy Prime Minister

Alexander Novak

said the country is considering banning uranium exports to the U.S. as part of its response to sanctions, according to Reuters.

Russia actually isn’t a major miner of uranium ore, the stuff that is extracted from the ground, with a market share of 6% in 2020, according to the World Nuclear Association.

Jonathan Hinze,

president of uranium market-research firm UxC, notes that the country typically uses up the uranium that it mines domestically for its own reactors. But it is a crucial supplier of secondary uranium, which includes so-called tailings from previously processed uranium that can be enriched. And Russia has by far the largest enrichment capacity, with about 43% of global operational and planned capacity located there, according to the World Nuclear Association—more than France, Germany, the Netherlands and the U.K. combined. A ban on imports of uranium ore from Russia will be manageable, but full sanctions on Rosatom, Russia’s nuclear energy company that also owns enrichment unit Tenex, would be far more disruptive.

One factor that helps keep uranium-ore demand down is the global oversupply of enrichment capacity. Much of that excess is in Russia, according to the World Nuclear Association. Enrichment can, to some extent, substitute for freshly mined uranium ore. If enrichment can be compared with an orange-squeezing machine, uranium ore out of the ground is akin to fresh oranges, whereas tailings, or previously processed uranium, can be thought of as half-squeezed ones with juice left in them.

Because Russia has plentiful and cheaper enrichment capacity, it is able to keep running depleted tailings through its system. Without that supply, remaining enrichment facilities could start requiring more ore—fresh oranges—to yield the same amount of enriched uranium. Whether sanctions are imposed or not, Western utilities could be more inclined to seek supply from elsewhere on future contracts to ensure security of supply. Andrew Wong, an analyst at RBC Capital Markets, said in a report that with sanctions, uranium demand in the U.S. could theoretically increase by 10 million to 15 million pounds annually, or about 30% of typical annual demand.

But that isn’t all. Russia’s invasion has boosted support for nuclear energy as Europe looks to wean its dependence on Russia’s natural gas without boosting greenhouse-gas emissions. Belgium recently postponed its nuclear-energy phaseout by 10 years. France last month announced plans to construct six new reactors, while U.K. Prime Minister Boris Johnson is pushing hard on speeding up the country’s nuclear-energy plans. Arthur Hyde, partner at resource-focused hedge-fund manager Segra Capital, notes that there has been a “tidal wave of sentiment shifting in favor of nuclear energy” that hasn’t been seen since the energy crisis of the 1970s.

It will be hard to shake off nuclear energy’s association with disasters, though. Three Mile Island, Chernobyl and Fukushima each held back the industry’s advancement. Russia’s attack on a nuclear-power plant in Ukraine was a reminder of such concerns. This could, however, be a rare moment when fresh geopolitical fears trump fading memories of those accidents.

Write to Jinjoo Lee at jinjoo.lee@wsj.com