I thought most modern nations would be chomping at the bit for a more efficient form of nuclear energy; from what I've heard a Thorium reactor can produce more energy and expends less waste, so why have many developed nations gotten cold feet? I'm not sure if anyone can confirm this but I've also heard that Thorium has almost no risk of a catastrophic meltdown, I'm not sure if that's correct or not.
Thorium won't continue to react like Uranium. From what I have read, Thorium reactors would still need a small amount of Uranium. The reactor technology was an outgrowth of bomb-making. The technology needs to catch up.
Some governments fear Thorium because it is essentially a breeder reactor, and as such could relatively easily be modified to make plutonium for nuclear weapons. Personally, I do not think this concern is really justified, as any reactor can potentially be modified into a breeder reactor. There is also much more experience with uranium reactors, so power companies are more likely to choose uranium over a less tested technology.
It's not that anyone has gotten cold feet; it's that nobody's feet were warm to begin with. (Except possibly the US in the 1970's, where research into thorium molten salt reactors was shelved because it wasn't useful for making bombs. Which was and is the real reason for US nuclear research). Thorium doesn't necessarily produce more energy than any other form of nuclear fission, but thorium is especially suited to a form of reactor called a molten salt reactor (MSR). An MSR produces far, far less long-term waste than any solid-fuel reactor, but that's (mostly) a function of the fuel being liquid, rather than the fuel being thorium. It is entirely possible to build an MSR with uranium as fuel and get low-waste operation. A uranium fueled MSR would have more long-term waste than a thorium fueled MSR, but both would be far, far lower than today's solid fuel reactors. Correct. An MSR cannot melt down, because the fuel is already liquid in normal operation. You can't melt what's already melted. Further, the liquid fuel circulates at ambient pressure, which means there would be no explosion in the event of a pipe break. In a "normal" water-cooled, solid fuel reactor, the water must be under very high pressure to avoid boiling at reactor temperatures. That means that if a pipe breaks, the high-pressure water flashes to steam, and BOOM! Explosion, loss of coolant, reactor meltdown. Very dangerous stuff, but that can't happen if the fuel isn't under pressure and is already liquid, as in an MSR. This advantage is also true for any MSR using any fuel, including uranium. The advantages for thorium over uranium fuel in an MSR are: 1. Thorium is cheaper and more plentiful worldwide than uranium. 2. Thorium produces fewer "transuranic" waste products than uranium -- the long-term nasty stuff. 3. The fissile material in the core of a thorium fueled MSR is uranium-233, which is very difficult to make into a bomb. The fissile material in the core of a uranium fueled MSR is plutonium-239, which is very useful for making bombs. Regarding current developments, the Chinese have committed to building a demonstration LFTR (Liquid Fuel Thorium Reactor, pronounced "lifter") in the near future (using US research from the 1960's and 70's as their basis). Some parliamentarians in the UK have become strong advocates for thorium reactors, but it's too early to say if that will have an impact on UK nuclear policy. And a new US firm, Transatomic, has designed an MSR specifically designed to use spent nuclear fuel "waste" from conventional reactors as fuel. Some links: The Weinberg Foundation (UK advocacy group. Site updated frequently with MSR/thorium news.) Energy from Thorium (US advocacy group. This site used to be quite active, less so nowadays. But there is a ton of [mostly technical] info on site if you follow all the links. The forum is useful too.) Transatomic website.
Some (very fast-paced) video mashups about thorium reactors: Thorium in 5 minutes: [video=youtube;uK367T7h6ZY]http://www.youtube.com/watch?v=uK367T7h6ZY[/video] Thorium in 16 minutes: [video=youtube;WWUeBSoEnRk]http://www.youtube.com/watch?v=WWUeBSoEnRk[/video]
The interest in thorium reactors is certainly increasing, for example the Chinese are committed to develop and build a LFTR by 2017: http://www.telegraph.co.uk/finance/...ail-for-clean-nuclear-power-from-thorium.html
"Meltdown" is a function of power density, prior power history, and heat removal technology. Any power metal can used in a reactor without risk of "meltdown", if the system design has that as an objective. Traditional pressurized water reactors have high power densities because their based on the United States Naval Reactors shipboard designs. PWR reactors are more than safe enough when operated correctly. The Navy's run a hundred of them without serious accident. Countries ignore thorium as a power metal because it doesn't produce plutonium. It's really that simple. Thorium, Uranium, and Plutonium can all be used in fission reactors, the only necessity being the configuration of the design to accommodate the reactivity of the particular metal and isotope.
Another advantage is that the MSR operates at a higher working fluid temperature at low pressure. Since reactors are essentially Carnot cycle heat engines this means that more energy can end up as electricity instead of waste heat.
