[Dr. Scott W. Tinker] We looked at the benefits of nuclear. Mainly, high energy density and no carbon emissions. Now, let's look at the risks and ideas to reduce them. We'll start with spent fuel, also called nuclear waste. When nuclear fuel can no longer power the reactor, it still contains a huge amount of energy, heat, and radioactivity. Currently in the U.S., we cool that spent fuel in a pool for several years and store it for decades at the reactor site in large metal and concrete containers called dry casks. But it will be radioactive for much longer than that. We need a longer-term solution. For the French, they recycle the spent fuel, reuse part and current reactors, and store the rest for later use. In the future, we could see small modular reactors similar to those that run submarines. A few proposed models run long spent fuel making electricity while reducing waste. There are also proposed breeder reactors, which would burn completely through the fuel leaving almost no waste at all. Proliferation is another risk: that nuclear fuel or byproducts will be used to build a bomb. Today, security and complex technology have thwarted terrorists. Reality is, nations have and will continue to develop weapons using their nuclear energy programs. Minimizing proliferation requires diplomacy and cooperation and the sharing of safer technologies less conducive to building weapons. Finally, there's the risk of an accident. Nearly every power reactor in the world is held within the containment building; a massive structure of concrete and steel that's designed to contain the reactor if it were to overheat and protect it from outside forces. At Three Mile Island and even Fukushima, these containment buildings have proven remarkably resilient. Chernobyl, though, was one of just 11 reactors worldwide without containment. When the core melted, the whole facility caught fire and a cloud of radiation spread across all of Eastern Europe. It was our worst nuclear disaster by far. The World Health Organization estimates 4000 premature deaths caused because of it, and some estimates are even higher. Even with those, however, nuclear power is far less deadly per kilowatt hour than fossil fuels, and depending on how you count deaths from falls or material transport, it's safer than wind and solar too - it's surprising. Still, future reactors should be safer. These three designs are claimed to be passively safe, which means they cannot physically overheat. These two- thorium and fusion reactors- also produce much less waste, but they are decades away from commercial deployment. So that's what it comes down to. Nuclear has real risks, but so far the impacts of them- even among three notable accidents- have been small. And although some are still nervous, we can improve on the technology to make it safer still.