Climate scientists tell us that the world must drastically cut its fossil fuel use in the next 30 years to stave off a potentially catastrophic tipping point for the planet. Confronting this challenge is a moral issue, but it’s also a math problem—and a big part of the solution has to be nuclear power.

Today, more than 80% of the world’s energy comes from fossil fuels, which are used to generate electricity, to heat buildings and to power car and airplane engines. Worse for the planet, the consumption of fossil fuels is growing...