B+-+Thorium+Reactor

Emily Young-On November 5, 2010. What is a Thorium Reactor?

Background Facts: The Chemistry Part:
 * Thorium is an actinide, a metallic element that is radioactive and belongs to the actinide series
 * Thorium is named after the Norse god of thunder, Thor
 * Usually, nuclear reactors use uranium-238 (it has a mass of 238 u) and an enriched form of uranium-235, making thorium reactors a relatively new idea
 * In some actinide elements, such as plutonium and uranium, the nuclei will spontaneously detonate when the atoms of those elements are closely compacted
 * Thorium reactors are also known as sub-critical reactors, which means that thorium is incapable of reacting on its own
 * Fertile- a substance that has the capacity to be transformed into a fissile substance
 * Fissile- a substance capable of undergoing fission
 * Fission- the splitting of a nucleus in an atom due to an excess of neutrons and resulting in the release of large amounts of energy (much of it in the form of heat)
 * Thorium is fertile and becomes fissile when its nucleus accepts a neutron. It then becomes protactinium-233, which is unstable and immediately decays to uranium-233. The thorium fuel cycle reaction goes something like this:


 * Thorium-232   ||    →    ||    Protactinium-233    ||    →    ||    Uranium-233    ||
 * (fertile)   ||    (absorption of neutron)    ||       ||    (decays)    ||    (fissile)    ||

Benefits of Thorium in Reactors: Extras: Sources Used: Jay, P. (2007, January 12). // Thorium comes clean? An alternative to uranium emerges //. Retrieved October 30, 2010, from  Dean, T. (2006, Issue 8). New age nuclear. // Cosmos // [online]. Retrieved October 29, 2010, from  World Nuclear Association. (2010). // Thorium //. Retrieved October 29, 2010, from  Wade, D. (2002). Sustainable nuclear energy. ©McGraw-Hill Companies. Retrieved November 1, 2010, from  Martin, R. (2009, December- 2010, January). Uranium Is So Last Century- Enter Thorium, the New Green Nuke. // Wired // [online]. Retrieved November 4, 2010, from < http://www.wired.com/magazine/2009/12/ff_new_nukes/> Hannich, T. (2009, December, 29). [Photograph]. Retrieved November7, 2010, from 
 * One reactor design that uses thorium in its solid form is the Accelerator-Driven System (ASD), proposed by the CERN physicist, Carlos Rubbia. The design is composed of a particle accelerator that fires protons at a lead spallation target, a target that releases neutrons or other particles when the nuclei of its atoms are struck by another particle moving at high speeds. In this reactor, the target releases neutrons. The neutrons collide with the nuclei of thorium-232, initiating the thorium fuel cycle.
 * Another thorium reactor design was actually developed in 1955 by nuclear physicist, Alvin Weinberg. He came up with the design that used thorium in its liquid form dissolved with fluoride salts. The mixture was poured into pipes to make up the centre, or core of the reactor. Should the core heat up to extreme temperatures as a result of the nuclear fission occurring in the core, the mixture would expand and flow over the top of the pipes to prevent a meltdown (radiation escaping).
 * When many nuclei undergo fission, the resulting radioactive material, uranium-233 among others, builds up in the reactor. When water is pumped past the hot material it becomes steam and turns a turbine, which generates electricity in a generator.
 * When fertile, thorium does not produce as many radioactive by-products (such as plutonium that may be used in the creation of nuclear weapons) as uranium and they do not release any greenhouse gases, making it an environmentally friendly energy source.
 * In comparison, the amount of time it would take for the by-products of a thorium-run nuclear reactor to lose their radioactivity to the amount of time it would take for the by-products of a uranium-run nuclear reactor to lose their radioactivity, the thorium-run nuclear reactor by-products would be radioactive for 5% of the amount of time that the uranium-run nuclear reactor by-products would be radioactive for.
 * The radioactive waste produced by uranium nuclear reactors would take 10,000 years to become safe, meaning that a new problem is created in having to build a structure to house all of the waste material that would last for twice as long as the pyramids have lasted to date. The radioactive material produced by a thorium reactor would last only 500 years and the end result of that radioactive material would be a substance roughly as radioactive as coal ash, a product of burning coal for energy.
 * Thorium reactors are able to use any other radioactive actinides as a source of neutrons, incinerating them and disposing of some hazardous radioactive material, such as old nuclear weapons.
 * While ASD thorium reactors sound like a great way to have the reactor turn on and off at the will of the operator, only small-scale tests have been performed using this method and there are still questions as to whether a larger, commercial-sized ASD thorium reactor would work as efficiently
 * Australia and India have the largest reserves of thorium in the world and India, especially, has been making efforts to seriously look into thorium as their primary source of nuclear energy fuel since they do not have readily accessible uranium
 * Weinberg’s thorium reactor was not a functional model until 1965. Unfortunately for him, by that time uranium reactors were already in use in United States and the U.S. nuclear program wanted the plutonium by-products of uranium to make bombs. For this reason, thorium is considered to be a “new” source of fuel for nuclear reactors, despite the idea being thought up over half a century ago .media type="youtube" key="CKWloASlLEg?fs=1" height="385" width="480"