WASHINGTON (Reuters) - Uranium miner Energy Fuels said on Tuesday it has won federal approvals to expand operations at two mines in southeastern Utah, after years of challenges from conservation groups worried about radon gas emissions.

The Bureau of Land Management and the U.S. Forest Service last week approved the expansion of the company’s La Sal complex near the Manti-La Sal National Forest, as well as the Daneros mine, located just outside the former boundaries of the Bears Ears National Monument, the company said.

The Bears Ears Monument boundaries were redrawn by the Trump administration last year to shrink the protected area, which the White House said would restore local authority to much of the land but which tribes and environmentalists decried as an attack on public lands.

The approvals allow Energy Fuels to expand the La Sal complex, which consists of four former uranium/vanadium mines, drill up to 400 exploration holes and build more ventilation shafts, while requiring the company to provide details of how it manages the facility during suspended operations.

The BLM also allows the expansion of the Daneros uranium mine if it implements additional emission controls.

Neither mine is currently operating due to low prices of uranium. Energy Fuels spokesman Curtis Moore said the company is considering restarting the La Sal complex because of its vanadium resources, which are currently more valuable.

“We are evaluating the potential,” he told Reuters by email.

The Interior Department has placed both vanadium and uranium on a draft list of “critical minerals” deemed important for national security and which should be produced in higher quantities in the United States.

Vanadium is used in jet engines, steel and increasingly in high-capacity batteries used for renewable energy storage. Uranium is mainly used in nuclear power.

The idled Daneros mine had applied to the Bureau of Land Management for an expansion in July 2016. Ore from that mine would have been transported through the former Bears Ears monument to Energy Fuels’ mill near Blanding, on the former monument’s western border.

Energy Fuels sent a letter to the Interior Department last year requesting that the monument be reduced to accommodate its operations. But the company said the Daneros mine is now unlikely to restart without a major market shift.

“In order to restart mining at the Daneros Project, we’ll need higher uranium prices,” Moore said.