For a few decades the debate has raged: are you pro or anti-nuclear power? While nuclear power is a fantastic source of energy it can be dangerous and produces waste that we are currently hard pressed to store. Movies such as 1979's 'The China Syndrome' have aided public fear of nuclear power once the new rubbed off in the 1960's. Since the Three Mile Island accident, there have been no new reactors built in the US. What if there were a new kind of reactor that was safer, cleaner, and used our stockpile of waste as fuel?
Lately there has been some press on the traveling wave reactor (TWR). A spinoff from a Bill Gates backed company called TerraPower is working with the design, but it's really nothing new. The TWR has been studied since the late 1950's and there are several articles in the literature that describe the theory of the units.
The principle of operation is to use depleted uranium and spent fuel that would traditionally be stashed away in a repository to fuel the reaction. The reaction starts with ~10% enriched uranium at one end of the fuel column. As a chain reaction takes place in the critical zone it converts material downstream into fissile material which is then the new critical zone. Basically the critical zone that is actually producing the power moves down the fuel column with time. This means if we were to look at a movie of where the power is produced through time we would see a soliton (wave that travels maintaining its shape) pass through the fuel column over a period of ~60 years.
The advantages of such a reactor include using depleted stocks of uranium and not producing material that could proliferate into atomic weapons. As with every process governed by the laws of physics there is no free lunch. Currently the reactor is a 'paper reactor'; no prototype has ever been built, though many have been run as numerical simulations. The unfortunate thing is reactors often don't live up to their numerical ideal models and that could push the TWR into the realm of being currently non-economical. While the units are smaller and safer they do produce less power and would require a significant investment to start building in an industry that is currently set in its ways.
In reality, the reactors sound fantastic, but I don't plan on seeing them anytime soon as the money for research, even energy related is just not there. To get a reactor from paper to common production takes decades and often includes unforeseen problems. Full scale reactors of the fission sort built in the early days had many kinks to work out. Some would startup and then mysteriously shutdown by themselves; it turns out this was xenon poisoning, something that was handled poorly in the reactor design. Other reactors such as the SL-1 were thought to be safe, but engineering flaws caused an accident and ended up impaling a man to the roof of the containment building with a control rod. It has taken decades to get the current reactor technology to where it is. While remaining optimistic about the TWR design, it is sadly not ready to swoop in and help us in the energy crisis.