Leslie Dewan and Mark Massie are very patient people. They don’t exactly have a choice. When you’re trying to change the way the world gets its electricity, fast answers aren’t really part of the equation.

Their company, Transatomic Power, is about five years into its quest to reimagine the nuclear reactor. The work probably won’t pay off for many more years, as the small company navigates hardcore science and a shifting regulatory landscape. Oh, and there’s that silly startup stuff like making sure it has enough money to pay for those giant, world-changing plans.

Transatomic is part of a new wave of entrepreneurial interest in rethinking nuclear power, which many experts say will be a critical way to solve the carbon conundrum that threatens the planet’s climate.

“It’s such an exciting time to be a nuclear engineer. There’s so much interesting technological development going on; there’s so much work going on on the regulatory side, and there’s so many new people joining the field,’’ said Dewan, the company’s chief executive.

Transatomic Power is working on a modern version of reactor technology that dates to the 1960s. Known as a molten salt reactor, it uses a liquid chemical salt impregnated with radioactive fuel to produce the heat that generates steam and turns an electric turbine.

Most nuclear reactors today submerge their nuclear fuel in a bath of water. But that design only extracts about 4 percent of the available energy before components begin to break down, Transatomic says, which leaves piles of remaining radioactive waste for hundreds of thousands of years.

Transatomic says its molten salt reactor design is vastly more efficient, drawing about 96 percent of the energy from nuclear fuel. That means it could actually use today’s nuclear waste as fuel, reducing its dangerous lifespan to just hundreds of years while generating huge amounts of presently untapped power.

Transatomic is currently running a long series of experiments to determine whether the materials it would use will hold up to the stresses of the reactor environment. Once it finds out the expected lifetime of the metals, ceramics, and composites that could be employed, Transatomic will be better positioned to estimate the cost of a reactor.

And cost is a big consideration, even with huge societal benefits on the line.

“Advanced reactors will only matter if you can make them cheaper than coal, cheaper than fossil fuel sources,’’ Dewan said. “You want to make sure people have an economic incentive as well as an environmental incentive to build this carbon-free fuel source.’’

Curt Woodward can be reached at curt.woodward@globe.com. Follow him on Twitter @curtwoodward.