Nuclear power provides 20 percent of America’s electricity, a fraction that is set to wane in the coming years: Since 2013, six of the nation’s nuclear reactors have shut down permanently, and 11 others are scheduled to be retired by 2025.

President Trump, who often talks about the benefits of nuclear power, has ordered the energy secretary, Rick Perry, to “prepare immediate steps” to stem the closing of reactors. But new trade barriers on nuclear fuel could further strain the industry.

“Maintaining all the elements of the domestic uranium fuel supply is in our national interest, and we urge the federal government to take appropriate action, without harming the fleet of nuclear reactors,” Maria G. Korsnick, head of the Nuclear Energy Institute, said in a statement.

The companies that requested the trade case asked that the Commerce Department limit imports so that 25 percent of the uranium used in the United States would be produced domestically. The companies argue that doing so would pose minimal burdens on nuclear power plants.

The companies that operate the plants dispute that idea, pointing to a recent study from NorthBridge Group, a consulting firm, that looked at the impact of such a quota, which would require domestic producers to expand their operations sharply in just a few years. Doing so would cost the nuclear power industry $500 million to $800 million per year, the study found, increasing the average cost of electricity from nuclear reactors by around 2 to 3 percent.

“We sympathize with the plight of uranium suppliers,” Ms. Korsnick said on Wednesday. “However, N.E.I. does not support the implementation of quotas as described in the petition. Potential remedies could put even more generating units at risk for premature closure.”

It is unclear what the Trump administration will ultimately propose with regard to imported uranium. If it determines that unfair trade practices are hurting domestic mining companies, the Commerce Department can recommend a broad range of remedies, from strict quotas to temporary tariffs. Such a decision would be expected to play out over several months, as the department continues its investigation and holds public hearings.