The idea to use thorium as a fuel for nuclear reactors is nothing new. It was there right at the beginning, when the idea to build nuclear power stations was first proposed. Now, decades later, news coming out of China is that thorium may be the green energy of the future, and Canada's Candu reactors are the best technology to harness that energy.
When plans were first drafted to build nuclear power plants after World War II, thorium was one of the possible fuels considered, and research into it continued in the United States up until 1973. The decision to go with uranium was not based on considerations about which would be the better long-term fuel for nuclear power, but on the fact that the Department of Defense needed plutonium for its nuclear weapons program.
In Canada, we had no plans to build nuclear weapons, but like everyone else, we still focused on uranium instead of thorium, and developed the Candu (Canadian Deuterium Uranium) reactor. The benefit of the CANDU 'heavy-water' design, though, was that it could use alternative fuels, such as recovered uranium, or a uranium-plutonium oxide mix called MOX fuel — thus it could take advantage of the availability of spent uranium fuel from other reactors and plutonium extracted from dismantled nuclear weapons.
The development of the Candu reactor wasn't the death of thorium power in Canada, though. In fact, the Candu reactor is proving to be the future of thorium power, as research has found that the it can use thorium as a fuel with only minor modifications.
There are specific advantages to using thorium as a nuclear fuel:
- It is abundant, with four times more available than uranium, and is readily accessible as tons of it has already been dug up while mining for rare-earth elements.
- It is safe, as it has far lower radioactivity than uranium. "A chunk of thorium is no more harmful than a bar of soap" states Richard Martin, in his book Superfuel. There is no chance of a nuclear meltdown, because nuclear chain reactions cannot be sustained in the fuel, so fission stops by default if an accident occurs.
- There are no byproducts from its use that can be used to manufacture weapons. Thorium reactors are cheaper to build, and the fuel is also cheaper, as thorium requires little to no processing to be used as a fuel. There is very little waste produced, and what waste there is becomes safe after a few hundred years, compared to the thousands of years that current fuels remain dangerous.
That's not to say there aren't potential downsides to using thorium. A primary concern is that thorium reactions require a 'primer' of some fissile material — such as plutonium or uranium-233 — to start, and thus it does not solve any problems regarding nuclear proliferation. However, the chain reactions can be maintained after that priming, and the reactors can be designed to make their own fissile materials to be used in other reactors — materials which will have no practical use to anyone wishing to make a bomb from them (something you can't do with uranium).
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Other concerns exist about long-lived radioactive byproducts, ongoing technical problems and whether or not thorium provides an economical solution to our energy needs. These claims have endured rebuttal and rebuke, of course, which have pointed out incorrect assumptions about the specific reactors and fuels to be used, and have provided some examples for perspective regarding radioactive byproducts.
Whether or not thorium is truly the nuclear fuel of the future will ultimately depend on a comparison of its advantages and disadvantages with those of the current nuclear fuels being used. With the CANDU reactor on the forefront of what could be a new thorium green-energy boom, Canada could take a leading role in the future of energy production.