The stuff of fission
There is only enough nuclear fuel to last for another fifty years.
Supplies of uranium-235 available by extraction in line with today’s uranium prices will only last for fifty years. It should be noted that this is actually not as pessimistic as the estimates for availability of other minerals or fuels. However, uranium-235 lies elsewhere in abundance, albeit with increased extraction costs, which are ready for use once the market makes them economical. Uranium is overall a fairly common metal, about as common as tin or zinc.
Currently, uranium is extracted from rich ores, which are a far more concentrated source. This makes sense economically for the time being while they are available. However, there are other sources, such as granite and sedimentary rocks that contain uranium. Even coal contains uranium, which is usually released into the atmosphere in coal-fired power stations. It is estimated that the trace amounts of uranium present in the coal could provide more energy through fission than the coal itself through combustion. Of course, at present, burning the coal is cheaper than extracting uranium from it.
It is currently estimated, and indeed estimates are constantly increased in all mineral and fuel resources and new information becomes available, that supplies of uranium-235 from these conventional resources are sufficient for over 200 years at present consumption. However, there are less conventional sources, which can offer still more reserves of the isotope, such as phosphate deposits and especially seawater, provided the market makes the significantly increased prices economical.
But this is only the beginning. A nuclear fuel cycle relying exclusively on uranium-235 is doomed to a shorter life because it is only 0.7% of natural uranium. The key to extending the resource is to make use of uranium-238, which comprises the vast majority of natural uranium. In thermal reactors, this is limited because uranium-238 cannot be made to fission by thermal neutrons. It can, however, be bred into other isotopes, which are fissile. When spent fuel comes out of the reactor, it generally contains around 1% plutonium from just this plus a trace of minor actinides. Under the closed cycle, this resource is extracted and fabricated into MOX fuel. This helps to extend the resource further.
But the plans are bolder. The Generation IV forum focuses mostly on fast reactor technology, which is not only capable of burning uranium-238, but also every other isotope bred from it. A properly configured fast breeder reactor would be able to breed large amounts of fissile material from uranium-238 for use in other reactors; more than is actually consumed during reactor operation. With this and other technologies, this uranium-238 can be used to produce energy like uranium-235 is now, leading to complete use of the uranium resource. With this done, the yield increases by a factor of more than 60, giving us 12,000 years worth of energy from natural uranium.
Going further a field, there is thorium. All natural thorium is thorium-232, which can be bred into uranium-233. Since thorium is three times more abundant than uranium, we have in this actinide a resource to last more than 18,000 years.
So in total, the known reserves of potential nuclear fuel amounts to a 30,000 year supply of energy.
Nuclear proponents say that nuclear power gives a degree of energy security by replacing a proportion of foreign fossil fuel consumption. How can this be the case when many of the countries seeking energy security must import their raw uranium?
They key is in the miniscule quantities of raw uranium ore required to yield a given amount of energy compared to fossil fuels. If a gas fired power station is depending on imports of natural gas, then its continued operation requires a constant supply. Should the exporter decide to cut off the supply, then continued production is in great jeopardy. If a nuclear power station is depending on imports of uranium, then it will be able to continue functioning through many months of a potential uranium embargo. Nuclear power is not as sensitive to disruption in raw fuel supplies as fossil fuel power is.
With reprocessing, spent fuel may be recycled helping to mitigate the requirement for foreign imports in keeping the reactors operational. For example, the large plutonium reserves in Sellafield, created as the waste products mostly from nuclear energy and weapons development but also through reprocessing of spent fuel, is a major energy resource for the UK, if there was any will to make use of it. Leaving aside the fact that those who complain most about the buildup of plutonium seem most opposed to the productive disposal of it in reactors, hence not much provision has been made for this option, the reliability of Canada and Australia as uranium exporters, means this is the economically preferable solution at this time. But should the need to import become a greater liability, this option is there. Unlike with fossil fuel usage, nuclear waste can be recycled to produce more fuel.
Longer term, the adoption of fast breeder technology can reduce the need for imports almost entirely. Fast breeder reactors produce more fuel than they consume so a small initial investment of imported uranium can give a country almost full self-sufficiency in fuel supplies.
So although technically, many countries seeking energy security will need to import raw uranium (and thorium), nuclear power can give them a large degree of energy security compared to fossil fuels because,
- Reliability of the supply is not a critical factor in the short term.
- Reprocessing allows countries to mitigate the requirements for fresh ore.
- Breeder technology can eliminate the majority of the need to import ore.
Uranium needs to be enriched and this produces depleted uranium, which is then turned into ammunition for the battlefield.
If you have a problem with this, take it up with the Department of Defense. Depleted uranium is virtually entirely uranium-238, which is significantly less radioactive than uranium-235. It is also fertile and is an invaluable energy resource in the fast uranium cycle. In the mean time, if it really must be discarded, it is simple to turn it back into an ore and put it back into the original uranium mine, where it is less radioactive than the natural uranium.
Plutonium is the most toxic substance known to man.
We are unsure of where this myth started. It was no doubt something to do with the activists campaigning against nuclear power on the grounds that plutonium shares its name with the Roman god of the Underworld or similar emotional or religious arguments.
Plutonium is hardly the most toxic in any way. Chemically, it is a heavy metal and as such it is chemically toxic like lead or mercury, but it lies on the middle of the scale. Mercury and lead have a much greater chemical toxicity, both of which are in widespread use. Other chemicals like cyanides represent an even greater chemical hazard. In terms of radiotoxicity, plutonium isotopes are also unremarkable. They are alpha emitters with little or no gamma emission. The energy of the alpha particles is around 5 MeV, which is on the high end of the scale, but by no means the highest. Most notably radon gas, which is responsible for more than half of our total radiation dosage, has alpha particle energies in excess of 6 MeV. Plutonium isotopes are also considerably longer lived than radon isotopes or other alpha emitters of similar energies, meaning that their activity is lower. The decay chain take them to uranium isotopes, which are even less remarkable radiologically, with enormous half-lives and lower energy emissions.
The myth of plutonium being the most toxic substance known to man is one that is not supported by the facts. Chemically, it is insignificant and radiologically, there are many more common materials, to which we are constantly exposed, that are more hazardous.
Surplus plutonium recovered from nuclear weapons is not a valuable energy resource and it should not be treated as such.
Of all the things the grass roots anti-nuclear movement has said over the past few decades, this is, without a doubt, the most deranged. Weapons grade plutonium clearly represents a potential proliferation threat, evidenced by the fact that is was used previously to make a nuclear warhead. The best course of action for eliminating this threat is to destroy the plutonium permanently. The only way to destroy weapons grade plutonium is through neutron bombardment and there is no better source of cheap neutrons than a nuclear reactor. If the plutonium is to burn it in a reactor as the most effective way of preventing anyone from ever turning it into a nuclear weapon again, then it is not a great leap to suggest the energy produced be turned into useful electricity.
Suggestions that the plutonium should be immobilised and buried as high level waste, while effective, are incredibly and criminally wasteful. The dismantled warheads of the USA and Russia have yielded billions of dollars worth of energy in the form of plutonium and nations have repeatedly plunged regions into war for access to the equivalent in oil. When we have this resource sitting ready to be used within our own countries, it is callous and immoral to simply discard it as though it is worthless.