Until we can manage to make renewable energy sources pay off, nuclear power is arguably (and feel free to argue this) one of the cleanest and safest methods of energy generation there is. One of the biggest problems is the dangerous spent fuel, but there may be a solution to that: particle accelerators.
Spent nuclear fuel contains dangerous radioactive components with half-lives of tens of thousands to millions of years, meaning that generally, it takes at least that long for the material to become safe for living things. This is an impossibly long time frame to plan around, but we don't have a choice: high level nuclear waste just gets buried, and we have to hope that nobody in the future ever gets curious, which is obviously a vain hope, since even right now, whenever we find something that's even just a few thousand years old buried in the ground and sealed up with dire warnings not to touch it, we bust right in and loot the place.
Anyway, the point is that trying to just forget about this stuff is not a viable solution: we need to deal with it. One way of mitigating the danger is through reprocessing to turn the used fuel into new fuel, which helps, but you're still left with a whole heap o' nastiness. Scientists at the Belgium nuclear research center SCK CEN have a different idea: just turn the bad stuff into less-bad stuff using a particle accelerator and a neutron source.
Here's how it would work: you'd have a nuclear reactor. Inside that nuclear reactor would be a neutron spallation source, which is a material that can produce lots of fast-moving neutrons when you hit it with high energy protons. To get those high energy protons, you attach a particle accelerator to the top of the reactor and turn it on. So now you have a nuclear reactor that can produce its own neutrons outside of the fuel, meaning that a.) it can produce power without going critical for inherent safety,* and b.) you can use the neutrons to transmute fuel waste into much safer fission products, with half lives of about 200 years instead of 200,000.
This type of reactor is called MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications), and the beautiful thing about it is that it produces power without risk of a meltdown while at the same time making spent nuclear fuel safer by several orders of magnitude. Belgium is currently working on a prototype that should be up and running by the early 2020s, and we can only hope that this will help to promote the idea of nuclear power as a cleaner, and safer, alternative source of energy.
SCK CEN, via WaveWatching
*The inherent safety comes from being able to switch off the particle accelerator and instantly stopping the reaction. Since the reaction depends on neutrons from the spallation source, the fuel itself cannot generate enough neutrons to make it to a chain reaction on its own, making a meltdown impossible.
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