At this moment, every nuclear power plant on earth uses uranium as its fuel. But uranium has four big problems that are holding it back:
1) Uranium fuel creates the worst toxic waste possible, and this waste has to be stored securely for tens of thousands of years. Currently there are tens of thousands of tons of this waste stored non-securely around the United States.
2) The nuclear waste contains plutonium that can be turned into nuclear bombs, or the process of making the original U-235 fuel can just as easily produce U-235 for bombs.
3) Item 1 + Item 2 + the perception that uranium power plants can explode or leak = a public relations disaster for nuclear power, making it very hard to build new plants.
4) U-235 fuel is extremely expensive
But nuclear power has one big advantage: producing electricity with nuclear power produces no greenhouse gases. If we could replace coal-fired power plants with nuclear plants, it would be a big win.
We need alternatives to uranium fuel to make nuclear power work. This is a great article that shows one possible path - thorium:
The advantages of thorium are many:
But the book inspired him to pursue an intense study of nuclear energy over the next few years, during which he became convinced that thorium could solve the nuclear power industry's most intractable problems. After it has been used as fuel for power plants, the element leaves behind minuscule amounts of waste. And that waste needs to be stored for only a few hundred years, not a few hundred thousand like other nuclear byproducts. Because it's so plentiful in nature, it's virtually inexhaustible. It's also one of only a few substances that acts as a thermal breeder, in theory creating enough new fuel as it breaks down to sustain a high-temperature chain reaction indefinitely. And it would be virtually impossible for the byproducts of a thorium reactor to be used by terrorists or anyone else to make nuclear weapons.
Elswhere in the article the author points out that a year's worth of enriched uranium for a 1-gigawatt nuclear power plant costs $50 to $60 million, while thorium fuel costs only $10,000. That is another huge advantage.
You can learn more about thorium power here:
The other possibility is Fusion, as described in this inspiring TED talk:
The only problem with fusion is the timeline, given that we do not have a working prototype.