Among a flurry of executive actions, Mr. Trump directed the nation’s nuclear safety regulator to speed up approvals for new reactors.

Trump has signed a spate of executive orders promoting oil, gas and coal that warm the planet when burned to produce electricity. Nuclear reactors generate electricity without emitting greenhouse gases. Trump said reactors are safe and clean, but did not mention climate benefits.

Shares of nuclear power companies surged Friday as President Donald Trump signed new executive orders aimed at boosting the industry.