By Walter Sorochan Emeritus Professor San Diego State University
Posted June 30, 2015, Disclaimer The information displayed herein is intended to simplify the complexity of using thorium in place of uranium as energy in nuclear power plants.
The nuclear power plant disasters at Three Mile Island, Chernobyl and Fukushima have made all of us aware of the dangers inherent in using uranium to generate electricity. Overlooked in the heat of these catastrophes has been thorium, a safer alternative to uranium. The mass media has given no attention to thorium. But this may be changing as countries the world over are attempting to harness thorium as a safer substitute energy for uranium.
Purpose of article: Switching from uranium to thorium as our primarily energy fuel could lead to cheaper, safer and more sustainable nuclear power. If you haven't heard of thorium or this idea, you are not alone! This article looks into this well kept secret. Info all documented for quick reading.
There are skeptics who reject the argument that thorium may be safer than uranium. We do need more research on using thorium instead of uranium as an energy source in nuclear power plants and much of this research is now being done in Asia.
Nuclear energy may be complicated but we need to understand how it works before attempting to understand why thorium is a better source of energy than uranium.
What is nuclear power?
The word "nuclear" refers to the nucleus, or dense center of the atom. The illustration on the right [ not drawn to scale ] shows inside an atom that has a nucleus [ white ]in the middle, neutrons [ green ], protons [ brown ] and is surrounded by electrons[ yellow ].
In a nuclear power reactor, these nuclei are split into smaller parts through a process known as fission. A sub-atomic particle known as a neutron strikes the nucleus of an atom of suitable fuel (particular isotopes of the heavy elements uranium and plutonium) breaking it into its component parts. Each fission results in the release of energy in the form of electromagnetic radiation and kinetic energy in the fragments of the split nucleus. This effect is twofold; the release of energy will produce heat, and the release of neutrons, which can in turn fission other atoms.
In material that has typically been employed as nuclear fuel, this reaction occurs in a "chain reaction" and is self-sustaining. When this is occurring, the reactor can be said to be"'critical". In a fission weapon, a mass of plutonium or uranium in excess of critical is assembled very quickly, with a flood of neutrons from a device known as an "initiator". The release of energy is extremely rapid and results in a massive explosion.
In a nuclear power reactor, the reaction is far slower and more controlled - the heat produced can be harnessed to boil water to spin turbines for the generation of electricity and this has been in practice for decades. The use of nuclear reactors for power generation began on 27 June 1954 at the Obninsk power plant in the former Soviet Union and has continued in numerous countries to this day.
There are of course, some significant problems with nuclear power. Fission reactions will always result in the production of radioactive waste products which require secure storage and pose a health risk to humans and the environment. There is the possibility that the operators may lose control of the fission chain reaction resulting in an accidental release of this material (often referred to as a "meltdown"). There's also the concern that reactors may also be used for the production of material suitable for nuclear weapons.
The key difference between thorium and other nuclear fuels is that thorium cannot sustain a chain reaction on its own. Fissile fuels like uranium and plutonium are able to sustain a chain-reaction, yet fission can also be achieved in material like thorium that is not fissile but fertile - i.e. it can produce fissile material, if neutrons are provided from an outside source. Thorium chain reaction can be easily controlled whereas uranium is difficult.
How nuclear energy works.
Now that we have some insight into how minerals and elements change form and that some elements like uranium can cause toxic radiation by-products and how a nuclear uranium plant works, we can now begin to appreciate how thorium can be used to replace uranium in nuclear power plants.
Kirk Sorensen discuses in 10 minute U-tube presentation how thorium can be an alternative power supply to uranium:
So .... what is thorium?
Thorium: "is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder. In nature, virtually all thorium is found as thorium-232, and it decays by emitting an alpha particle, and has a half-life of about 14.05 billion years (other, trace-level isotopes of thorium are short-lived intermediates of decay chains). It is estimated to be about four times more abundant than uranium in the Earth's crust and is a by-product of the extraction of rare earths from monazite sands. Thorium was formerly used commonly as the light source in gas mantles and as an alloying material, but these applications have declined due to concerns about its radioactivity." Wiki: Thorium
Monazite, the most common and commercially most important thorium-bearing mineral, is widely distributed in nature. Monazite is chiefly obtained as a sand, which is separated from other sands by physical or mechanical means.
Why Thorium is better than uranium?
Thorium’s advantages start from the moment it is mined and purified, in that all but a trace of naturally occurring thorium is Th232, the isotope useful in nuclear reactors. This is much better than the 3 to 5% of uranium that comes in the form we need.
Then there’s the safety side of thorium reactions. Unlike U235, thorium is not fissile. That means no matter how many thorium nuclei you pack together, they will not on their own start splitting apart and exploding. If you want to make thorium nuclei split apart, though, it’s easy: you simply start throwing neutrons at them. Then, when you need the reaction to stop, simply turn off the source of neutrons and the whole process shuts down, simple as pie.
Here’s how thorium works: When Th232 absorbs a neutron it becomes Th233, which is unstable and decays into protactinium-233 and then into U233. That’s the same uranium isotope we use in reactors now as a nuclear uranium fuel, the one that is fissile all on its own. Thankfully, it is also relatively long lived, which means at this point in the cycle that the irradiated fuel can be unloaded from the reactor and the U233 separated from the remaining thorium. The uranium is then fed into another reactor all on its own, to generate energy.
The U233does its thing, splitting apart and releasing high-energy neutrons. But there isn’t a pile of U238 sitting by. Remember, with uranium reactors it’s the U238, turned into U239 by absorbing some of those high-flying neutrons, that produces all the highly radioactive waste products. With thorium, the U233 is isolated and the result is far fewer highly radioactive, long-lived byproducts. Thorium nuclear waste only stays radioactive for 500 years, instead of 10,000, and there is 1,000 to 10,000 times less of it to start with.
Differences between thorium and uranium:
Thorium is much different than uranium when used as a nuclear fuel. Thorium is not fissile; meaning it cannot go critical and generate a nuclear chain reaction. This is referred to as thorium's safety valve by Sorensen. Thorium needs a spark or neutron driver to get it to start a reaction and get it to produce heat energy. It must undergo neutron bombardment to produce a by-product or radionuclide that can sustain a nuclear reaction. Thorium bombardment can be controlled. A thorium-fueled reactor must be jump-started with a fissile isotope such as uranium (U235) and/or plutonium (Pu239 or Pu241). Neutron bombardment of thorium results in this reaction: Th232 + Neutron = U233.
Uranium233 is a man-made fissile isotope with a half-life of 160,000 years, and is well-suited for use in nuclear reactors. After Th232 is converted, U233 can be unloaded and then fed to the core of another reactor to be used as fuel in a closed cycle.
Alternatively, U233 can be bred from thorium in an outer blanket [ protective shield ] surrounding a plutonium and/or uranium core, the U233 separated, and then fed back into the core. These are called "breeder reactors" because thorium is the fertile fuel that breeds a fissile radionuclide. Radioactive materials are recycled in thorium, so there is little waste left behind.
There are other significant advantages to the use of thorium in nuclear reactors. The raw material, thorium, is much more abundant than uranium and emits only low-level alpha particles. It has one isotope and therefore, does not require an enrichment cycle [ as uranium needs ] to be used as fuel. It is many times more energy efficient than uranium.
A thorium reactor produces no plutonium that can be made into atomic weapons and less longer-lived radionuclides than a uranium-based reactor. Because there is no chain reaction, there is no chance of a meltdown. Fissile means thorium cannot go "critical" and generate a nuclear chain reaction. But nuclear waste from past operations that contain fissile uranium and plutonium can be used as start-up fuel. Fulp: Thorium as energy fuel
That means thorium could be used to fuel nuclear reactors, just like uranium. Thorium is more abundant in nature than uranium, is not fissile on its own [ which means reactions can be stopped when necessary ], produces waste products that are less radioactive, and generates more energy per ton.
So why on earth are we using uranium? Research into the mechanization of nuclear reactions was initially driven not by the desire to make energy, but by the desire to make bombs. The $2-billion Manhattan Project that produced the atomic bomb sparked a worldwide surge in nuclear research, most of it funded by governments embroiled in the Cold War. And here we come to it: Thorium reactors do not produce plutonium , which is what you need to make a nuke.
Thorium is three times more abundant in nature than uranium. All but a trace of the world’s thorium exists as the useful isotope, which means it does not require enrichment. Thorium-based reactors are safer because the reaction can easily be stopped and because the operation does not have to take place under extreme pressures. Compared to uranium reactors, thorium reactors produce far less waste and the waste that is generated is much less radioactive and much shorter-lived.
To top it all off, thorium would also be the ideal solution for allowing countries like Iran or North Korea to have nuclear power without worrying whether their nuclear programs are a cover for developing weapons… a worry with which we are all too familiar at present. Katusa: thorium not uranium 2012
Fission occurs in thorium when atoms absorb a neutron to become a heavier isotope and quickly decay into an isotope of the element protactinium and then an isotope of uranium, which is fissioned when struck by an additional neutron. The number of neutrons produced is not sufficient for a self-sustained chain reaction.
A particle accelerator could be used to provide the necessary neutrons for fission to occur in thorium and a nuclear reactor making use of such an outside neutron source would be known as an 'accelerator driven system' (ADS).
The notion of the ADS is credited to Carlo Rubbia of the European Organization for Nuclear Research (CERN) joint winner of the 1984 Nobel Prize for Physics. The ADS would likely be far smaller than other reactors and if the accelerator were to be turned off, the nuclear reaction would cease, although it should be noted that even in a reactor which is not critical, the heat from the decay of materials can be significant and cooling is required.
In a thorium reactor, quantities of other fuels could be included, without the fuel being capable of sustaining a chain reaction, and thus the reactor could be used to provide energy from disposing of material such as plutonium from disassembled nuclear weapons. It's also possible to ensure that the reactors are designed in such a way that it is not possible to extract fissile material, which can be used to manufacture nuclear weapons.
Though all nuclear reactors will produce waste products, a reactor fueled by thorium will produce far less long-lived waste products than one fueled by uranium or plutonium, with waste decaying to the same level of radioactivity as coal ashes after 500 years.
Thorium also produces more energy from the same amount of material compared to uranium.
"Two hundred tonnes of uranium can give you the same amount of energy you can get from one tonne of thorium," Rubbia told the BBC News in arecent interview.
Robert Hargraves and Ralph Moir explore the early days of decisions about selecting a nuclear power plant technology --- uranium vs thorium. Enrico Fermi argued that the uranium-plutonium breeder made more weapons faster in the Manhattan Project. Atomic physicist Edward Teller promoted the Thorium Liquid Fluoride Reactor Reduce [ LFTR ].
You can read their excellent article. Hargraves: Thorium reactors 2019 pdf
Beissmann Tim, "The thorium-powered car: Eight grams, one million miles," Car Advice, August 16, 2011. Beissmann: thorium driven care 2011
Bowersox Paul, "Irène Joliot-Curie and the Alchemists’ Dream," ANS Nuclear Cafe, September 30, 2011. Bowersox Alchemy
"Radioactive decay of atoms of the naturally-occurring, but slightly unstable element Thorium-232 (90 protons + 142 neutrons) spontaneously emitting an alpha particle (2 protons + 2 neutrons) to transform into an atom of Radium-228 (88 protons + 140 neutrons). No alchemy was required! In fact, it was later discovered that naturally-occurring, long-lived, heavy radioactive elements such as Thorium-232, Uranium-235, and Uranium-238 spontaneously transmute to many other unstable elements, on a pathway ending in stable, non-radioactive isotopes of the element Lead."
Chater James, "A history of nuclear power," Focus on Nuclear Power Generation, 2005. Chater: history nuclear power
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Dunlavey Joseph and Christopher Plummer, "Liquid-Flouride Thorium Reactor," Summer.2011. Dunlavey: Thorium Reactor 2011
Edwards Gordon, "URANIUM: Known Facts and Hidden Dangers," address at the World Uranium Hearings Salzburg, Austria, September 14, 1992. "Nuclear power is not a viable answer to our energy problems. We don't even need it for electricity. All you need for conventional electricity generation is to spin a wheel, and there's many ways of doing it: water power, wind power, geothermal power, etc."
Energy from Thorium, "Global New Energy Summit 2012." Global New Energy Summit 2012
Fissile: Unlike natural uranium, natural thorium contains only trace amounts of fissile material (such as 231 Th), which are insufficient to initiate a nuclear chain reaction. Fissile means it cannot go "critical" and generate a nuclear chain reaction. Thorium fuel cycle
Flibe Energy. Flibe Energy Flibe Energy, Inc. email@example.com 256-277-3542 4951 Century St. Huntsville, Alabama USA 35816
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"There are more than 400 nuclear reactors operating in various countries. A nuclear power station has 35-40 years of operating life. After that it must be dismantled and the area must be cleaned up (the decommissioning process). But so far, no nuclear power station has been completely decommissioned in the world. It has been estimated that decommissioning could last about 50 years and it would cost more than the construction cost."
Pentland William, "Is Thorium the Biggest Energy Breakthrough Since Fire? Possibly," Forbes, September 11, 2011. Pentland: Thorium energy breakthru' 2011
Rubbia Carlo, "Sub-critical Thorium reactors," CERN, Geneva, Switzerland. Rubbia: Thorium slice_pdf info
Sorensen Kirk, "Thinking Nuclear? Think Thorium," [ Thorium, a Readily Available and Slightly Radioactive Mineral, Could Provide the World with Safer, Clean Energy ] Machine Design, March 16, 2010. Sorensen: thorium machine design
Sorensen Kirk, "Thorium," Ted U-tube, April 22, 2011. Sorensen: thorium Ted Utube
Kirk Sorensen is founder of Flibe Energy and is an advocate for nuclear energy based on thorium and liquid-fluoride fuels. For five years he has authored the blog "Energy from Thorium" and helped grow an online community of thousands who support a renewed effort to develop thorium as an energy source. He is a 1999 graduate of Georgia Tech in aerospace engineering and is also a graduate student in nuclear engineering at the University of Tennessee. He has spoken publicly on thorium at the Manchester International Forum in 2009, at NASA's Green Energy Forum in 2008, and in several TechTalks at Google. He has been featured in Wired magazine, Machine Design magazine, the Economist, the UK Guardian and Telegraph newspapers, and on Russia Today. He also taught nuclear engineering at Tennessee Technological University as a guest lecturer. He is active in nonprofit advocacy organizations such as the Thorium Energy Alliance and the International Thorium Energy Organization. He is married and has four small children.
Thorium Energy Alliance [ John Kutsch director ], "T.E.A. Resources," TEA: thorium info 2012
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