The Fukushima disaster reminded us of all the dangers associated with uranium-powered nuclear reactors. New news this month of Tepco’s ongoing battle to contain and cool the fuel rods shows how vigorous the uranium fission reactions are and how difficult they are to control. This level of energy is, of course, exactly why we use nuclear power – it’s incredibly efficient as a source of energy, it’s very low in emissions, and it has a commendable safety record.
This conversation – “nuclear good, but uranium dangerous” – regularly leads to a very good question: What about thorium? Thorium is two places in the same row or row of uranium in the periodic table. Elements of the same series have common characteristics. In the case of uranium and thorium, the crucial similarity is that both can absorb neutrons and convert them into fissile elements.
This means that thorium, like uranium, could be used as a fuel for nuclear reactors. And as proponents of the underdog fuel will be happy to tell you, more abundant than uranium in nature, thorium is non-fissile on its own (meaning reactions can be stopped if necessary), produces less radioactive waste, and generates more energy per ton.
Why on earth are we using uranium? As you may recall, research into the mechanization of nuclear reactions was initially driven not by the desire to generate energy, but by the desire to make bombs. The $ 2 billion Manhattan project that produced the atomic bomb sparked a global surge in nuclear research, largely funded by governments involved in the Cold War. And here we come to it: Thorium reactors don’t produce plutonium, which is what you need to make a nuclear weapon.
How ironic. The fact that thorium reactors could not produce fuel for nuclear weapons meant that better reactor fuel was running out. Today we would like to be able to clearly distinguish a country’s nuclear reactors from its weapons program.
Is There Hope for Thorium in the Post Cold War World? Maybe, but don’t go to your broker yet.
The uranium reactor
The typical nuclear fuel cycle begins with refined uranium ore, which consists primarily of U238 but contains 3% to 5% U235. The most naturally occurring uranium is U238, but this common isotope doesn’t split – this is the process by which the core splits and releases enormous amounts of energy. In contrast, the less common U235 is fissile. In order to produce reactor fuel, we therefore have to spend a lot of energy on the enrichment of yellowcake in order to increase its content of U235.
In the reactor, U235 begins to split and release high-energy neutrons. The U238 doesn’t just sit next to it, however; it transforms into other fissile elements. When an atom of U238 absorbs a neutron, it converts to short-lived U239, which quickly decays into neptunium-239 and then into plutonium-239, that beautiful, weapons-grade byproduct.
When the U235 content burns down to 0.3% the fuel is consumed but contains some very radioactive isotopes of americium, technetium and iodine, as well as plutonium. This waste fuel is highly radioactive and the culprits – these massive isotopes – have a half-life of many thousands of years. As such, the waste must be stored for up to 10,000 years, protected from the environment and from anyone who for nefarious reasons wants to get the plutonium.
The thing about thorium
Thorium’s benefits begin the moment it is broken down and purified, as except for a trace of naturally occurring thorium, Th232 is the isotope that is useful in nuclear reactors. That’s a hell of a lot better than the 3% to 5% uranium that is in the form we need.
Then there is the safety side of thorium reactions. In contrast to U235, thorium is not fissile. That said, no matter how many thorium cores you pack together, they won’t split and explode on their own. However, if you want to split thorium nuclei apart, it’s easy: you just throw neutrons at them. Then when you need the reaction to stop, just turn off the neutron source and the whole process will simply be completed.
This is how it works. When Th232 absorbs a neutron, it becomes Th233, which is unstable and decays into protactinium-233 and then into U233. This is the same isotope of uranium that we are currently using in reactors as a nuclear fuel that is, by itself, fissile. Fortunately, it’s also relatively long-lived, which means that at this point in the cycle the irradiated fuel can be dumped from the reactor and the U233 separated from the remaining thorium. The uranium is then fed into another reactor on its own to generate energy.
The U233 does its thing, splitting up and releasing high-energy neutrons. But there is not a bunch of U238 next to it. Keep in mind that uranium reactors are the U238, which by absorbing some of these soaring neutrons, has been converted to U239, producing all of the highly radioactive waste products. Thorium is used to isolate the U233 and the result is far less highly radioactive, long-lived by-products. Thorium nuclear waste only remains radioactive for 500 years instead of 10,000, and there are 1,000 to 10,000 times less of it initially.
The thorium leaders
Researchers have studied thorium-based fuel cycles for 50 years, but India is leading the way in commercialization. Given that India is home to a quarter of the world’s known thorium reserves and, in particular, there are no uranium resources available, it is not surprising that India plans to cover 30% of its electricity needs with thorium-based reactors by 2050.
In 2002, India’s nuclear regulator granted approval to build a 500-megawatt reactor for a rapid prototype electric prototype due for completion this year. In the next ten years, six more of these fast breeder reactors will be built that “grow” U233 and plutonium from thorium and uranium.
The design work for India’s first Advanced Heavy Water Reactor (AHWR) has largely been completed. This is a reactor that is mainly operated with thorium and has undergone a series of tests in the original replica. The biggest disadvantage at the moment is finding a suitable location for the plant, which will generate 300 MW of electricity. Indian officials say they plan to get the facility up and running by the end of the decade.
China is the other nation with a firm commitment to developing the thorium power. In early 2011, the Chinese Academy of Sciences launched an extensive research and development program on LFTR (Liquid Fluoride Thorium Reactor) technology using U233 grown in a liquid thorium salt blanket. This blanket of molten salt becomes less dense with increasing temperatures and slows down the reaction in a kind of built-in safety lock. This type of thorium reactor receives the most attention in the thorium world; China’s research program is in a race with similar, albeit smaller, programs in Japan, Russia, France, and the United States
There are at least seven types of reactors that can use thorium as a nuclear fuel, five of which have been commissioned at some point. Some were abandoned not for technical reasons, but because of a lack of interest or research funding (again to blame for the Cold War). So there are proven designs for thorium-based reactors that only require a certain amount of support.
Well, maybe quite a bit of support. One of the biggest challenges in developing a thorium reactor is finding a way to make the fuel economically. Thorium dioxide is expensive to make, in part because its melting point, at 3,300 ° C, is the highest of all oxides. The possibilities of creating the neutron barrier necessary to initiate the reaction depend regularly on uranium or plutonium and bring at least part of the problem full circle.
And while India is certainly working on thorium, not all of the eggs are in that basket. India has 20 uranium-based nuclear reactors already producing 4,385 MW of electricity and another six are under construction, 17 are planned and 40 are proposed. The country is receiving props for its interest in thorium as a native energy solution, but most of its nuclear money is still going into traditional uranium. China is in exactly the same situation – while it is fueling its efforts in the LFTR race, its big money is behind uranium reactors. China has only 15 reactors in operation, but 26 under construction, 51 planned and 120 proposed.
The bottom line
Thorium is three times more common in nature than uranium. Except for a trace, the world’s thorium exists as a useful isotope, which means it does not require enrichment. Thorium-based reactors are safer because the reaction can be easily stopped and operation does not have to take place under extreme pressures. Compared to uranium reactors, thorium reactors produce much less waste and the waste that is generated is much less radioactive and much shorter.
To top it off, thorium would also be the ideal solution to enable countries like Iran or North Korea to have nuclear power without worrying about whether their nuclear programs provide coverage for weapons development … a concern we only have for the moment are too familiar.
So should we go out and invest in thorium? Unfortunately, not. For one thing, there are very few investment vehicles. Most of the thorium research and development is carried out by national research groups. There is a public company called Lightbridge Corp. that is working on the development of thorium-based fuels. Lightbridge has the advantage of being a frontrunner in the region, but on the flip side, the lack of competition is a good sign that it’s just too early.
Had it not been for mankind’s seemingly insatiable desire to fight, thorium would have been the world’s nuclear fuel. Unfortunately, the Cold War pushed nuclear research towards uranium, and the momentum gained during those years has kept uranium well ahead of its lighter, more controllable, and abundant brother. There are numerous examples throughout history of inferior technology beating a superior competitor for market share, be it because of marketing or geopolitics. Once that stage is set, it’s nearly impossible for the runner-up to make a comeback. Do you remember Beta VCRs? Technically, they undoubtedly beat VHS, but VHS ‘marketing machine won the race and Beta fell into disuse. Thorium reactors aren’t quite the beta video recorders of the atomic world, but the challenge they face is pretty similar: getting the reigning champion off the field is darn hard.
Marin has an enviable track record in the uranium sector, with a current increase of nearly 1,600% since first recommending it to subscribers 39 months ago. Now he’s targeting a little-known company that has oil extraction technologies that could reward investors with similar profits.
Comments are closed.