THE BANKRUPTCY of Westinghouse, the venerable American nuclear-reactor maker now owned by Japan’s equally prestigious Toshiba, is a blow to two of the greatest names in global business — a devastating one. More important for the United States, and the planet, is what the debacle means for the future of nuclear energy, which still supplies 19.5 percent of this country’s electricity, all of it carbon-free.

Ideally, nuclear should be a part of the global solution to climate change. Deep cuts in carbon emissions “will require more intensive use” of nuclear as well as renewable energy, the Intergovernmental Panel on Climate Change noted in its 2014 assessment report. One reason France emits only a third as much CO2 per capita as the United States is that three-quarters of its electricity comes from nuclear. As always, though, the questions are about safety and cost; and, of course, legitimate concerns about the former drive up the latter.

Westinghouse thought it had come up with a new design that was both more reliable and, potentially, simpler to build. This AP1000 reactor, which relied less on electric-powered cooling pumps of the kind that failed so catastrophically at Fukushima, Japan, in 2011, promised to lead a renaissance in the U.S. nuclear industry, with potential for sales in emerging markets as well. Alas, Westinghouse still fell prey to the old bugaboos of the nuclear industry — delays and cost overruns. Now the four reactors that the company was building in the U.S. South are in limbo. The first of them will not come on line until 2019 at the earliest.

Even before this debacle, nuclear energy faced an uncertain future in the United States, due to what is otherwise a positive development for both the U.S. economy and the climate: the rise of cheap natural gas and wind energy, both of which proved more cost-effective as electricity sources in certain regions than nuclear. President Barack Obama’s Clean Power Plan would have aided nuclear utilities, but it has been blocked by the courts and may never go into effect if President Trump has his way.

Once billed as “too cheap to meter,” nuclear energy never quite lived up to its potential, either economically or environmentally. Yet nations that abandon it, as Germany did in the wake of Fukushima, add greatly to the costs and logistical challenges of meeting carbon-reduction goals. The United States should keep using nuclear energy during what is bound to be a long transition from the current energy mix to a completely renewable system, but it needs to rethink how best to do that. A carbon tax, undoubtedly, would help support the carbon-free industry. A long-term solution for radioactive waste disposal is also in order — specifically, using the Yucca Mountain site that has long since been determined to be safe, but has been blocked by politics. Government and the private sector need to support new reactor designs. If the United States lacks a robust nuclear industry, it may be less capable of influencing international policy on issues ranging from reactor safety to weapons proliferation. Maintaining a solvent, innovative nuclear industry would serve national security as well as the environment.