NUCLEAR+FUSION+-+Vince

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=**Nuclear Fusion **= = **Definition:** = Nuclear fusion is the process in which 2 or more atomic nuclei join together to form a single heavier nucleus. It is one of the most promising options for generating large amounts of carbon-free energy in the future.

__ **How it works:** __ The theory of nuclear fusion: Nuclear fusion generates energy by combining 2 light atomic nuclei into a single heavier atom. When light nuclei fuses, they will release a huge sum of energy, because the mass of the combination will be less than the sum of the masses of the individual nuclei. The loss of mass, as a result, changes into energy and is released. It can be explained by the concept of **mass defect**, which implicates that any reactions in which there is a decrease of mass, is a source of energy.

To get energy from fusion, gas from a combination of types of hydrogen – deuterium and tritium – is heated to very high temperatures (100 million degrees Celsius). One way to achieve these conditions is a method called ‘magnetic confinement' – controlling the hot gas (known as a plasma) with strong magnets. The most promising device for this is the ‘tokamak', a Russian word for a ring-shaped magnetic chamber.

"Magnetic confinement is the approach that Culham and many other laboratories are researching to provide energy from fusion. A plasma of light atomic nuclei is heated and confined in a circular bottle known as a // tokamak //, where it is controlled with strong magnetic fields." "In a magnetic fusion device, the maximum fusion power is achieved using deuterium and tritium. These fuse to produce helium and high-speed neutrons, releasing 17.6MeV (megaelectron volts) of energy per reaction. This is approximately 10,000,000 times more energy than is released in a typical chemical reaction. A commercial fusion power station will use the energy carried by the neutrons to generate electricity. The neutrons will be slowed down by a blanket of denser material surrounding the machine, and the heat this provides will be converted into steam to drive turbines and put power on to the grid." --> source from Culham Centre for Fusion Energy (** http://www.ccfe.ac.uk/) **




 * __Natural Occurance of nuclear fusion:__**
 * The power that fuels the sun and the stars is nuclear fusion. **

__**Advantages: **__

The world needs new, cleaner ways to supply our increasing energy demand, as concerns grow over climate change and declining supplies of fossil fuels. Power stations using fusion would have a number of advantages:
 * // No carbon emissions. // The only by-products of fusion reactions are small amounts of helium, which is an inert gas that will not add to atmospheric pollution.
 * // Abundant fuels. // Deuterium can be extracted from water and tritium is produced from lithium, which is found in the earth's crust. Fuel supplies will therefore last for millions of years.
 * // Energy efficiency. // One kilogram of fusion fuel can provide the same amount of energy as 10 million kilograms of fossil fuel.
 * // No long-lived radioactive waste. // Only plant components become radioactive and these will be safe to recycle or dispose of conventionally within 100 years.
 * // Safety. // The small amounts of fuel used in fusion devices (about the weight of a postage stamp at any one time) means that a large-scale nuclear accident is not possible.
 * // Reliable power. // Fusion power plants should provide a baseload supply of large amounts of electricity, at costs that are estimated to be broadly similar to other energy sources.

__**Disadvantages**__: <span style="font-family: Arial,Helvetica,sans-serif; line-height: 18px;">Three parameters (plasma temperature, density and confinement time) need to be simultaneously achieved for sustained fusion to occur in a plasma. However, to create such a special condition, various confinement devices have to be used. The cost is huge and the project faces i <span style="color: #333333; font-family: Arial,Helvetica,sans-serif; font-size: 12px; line-height: 14px;">nsurmountable scientific and engineering challenges.

==__**<span style="color: #333333; font-family: Arial,Helvetica,sans-serif; font-size: 12px; line-height: 14px;">Conditions for a nuclear fusion reaction ****<span style="color: #333333; font-family: Arial,Helvetica,sans-serif; font-size: 14px; line-height: 14px;">: **__== <span style="color: #333333; font-family: Arial,Helvetica,sans-serif; font-size: 14px; font-weight: 900;">**Temperature**

Fusion reactions occur at a sufficient rate only at very high temperatures – when the positively charged plasma ions can overcome their natural repulsive forces. Typically, in JET(the Joint European Torus), over 100 million Kelvin is needed for the Deuterium-Tritium reaction to occur – other fusion reactions (e.g. D-D, D-He3) require even higher temperatures.

<span style="color: #333333; font-size: 14px; font-weight: 900; line-height: 19px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 10px; padding: 0px;">**Density**
The number of fusion reactions per unit volume is roughly proportional to the square of the density. Therefore the density of fuel ions must be sufficiently large for fusion reactions to take place at the required rate. The fusion power generated is reduced if the fuel is diluted by impurity atoms or by the accumulation of Helium ions from the fusion reaction itself. As fuel ions are burnt in the fusion process they must be replaced by new fuel and the Helium products (the “ash”) must be removed.

<span style="color: #333333; font-size: 14px; font-weight: 900; line-height: 19px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 10px; padding: 0px;">**Energy Confinement**
The Energy Confinement Time is a measure of how long the energy in the plasma is retained before being lost. It is officially defined as the ratio of the thermal energy contained in the plasma and the power input required to maintain these conditions.

And therefore, is it difficult to maintain a simultaneous plasma condition for the fusion.

(A magnetic fusion device)

__**Current research projects for nuclear fusion**__:
 * ===== **Culham Centre for Fusion Energy (CCFE)**: the UK's national laboratory for fusion research. CCFE (formerly known as UKAEA Culham) is based at Culham Science Centre in Oxfordshire, and is owned and operated by the United Kingdom Atomic Energy Authority. The 80-hectare site just south of Oxford was previously HMS Hornbill, a Fleet Air Arm airfield, before opening as a purpose-built fusion laboratory in 1960. Since then, Culham has made many major contributions to international fusion research and development. Today the UK fusion programme is centred on the innovative Mast (Mega Amp Spherical Tokamak) experiment and employs around 150 people. The programme is funded by the Engineering and Physical Science Research Council and the European Union under the EURATOM treaty. =====

=
**JET**: In 1978, the European Community (Euratom, along with Sweden and Switzerland) launched the Joint European Torus (JET) project in the UK. JET is the largest tokamak operating in the world today. A similar tokamak, JT-60, operates at the Naka Fusion Institute of Japan Atomic Energy Agency in Japan, but only JET has the facilities to use D-T fuel. JET has been very successful in operating remote handling techniques in a radioactive environment to modify the interior of the device and has shown that the remote handling maintenance of fusion devices is realistic. Further enhancements are planned at JET with a view to exceeding its fusion power record in future D-T experiments. ===== **KSTAR**:The KSTAR (Korean Superconducting Tokamak Reactor) at the National Fusion Research Institute in Daejeon produced its first plasma in mid-2008. The tokamak is the first to use Nb3Sn superconducting magnets, the same material to be used in the ITER project. Its first stage of development aims to achieve plasma pulses of up to 20 seconds by 2012. For the second phase of development (2013-2017), KSTAR will be upgraded to study pulses of up to 300 seconds. The device does not have tritium handling capabilities, so will not use D-T fuel.

__**Additional Information about nuclear fusion:**__ <span style="font-family: Arial,Helvetica,sans-serif; line-height: normal;"> <span style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: Arial,Helvetica,sans-serif; font-size: 10pt; line-height: 14pt; margin-bottom: 10px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; vertical-align: baseline;">Nobody has put the nuclear fusion technology into practice yet, but working reactors aren't actually that far off. Fusion reactors are now in experimental stages at several laboratories in the United States and around the world. <span style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: Arial,Helvetica,sans-serif; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; vertical-align: baseline;">Photo courtesy ITER <span style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: Arial,Helvetica,sans-serif; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; vertical-align: baseline;">**<span style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: Arial,Helvetica,sans-serif; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; vertical-align: baseline;">Proposed construction site of ITER fusion reactor plant at Cadarache, France. See more __<span style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; color: #005288; font-family: Arial,Helvetica,sans-serif; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; vertical-align: baseline;">[|nuclear power pictures] __. ** ||
 * < <span style="font-family: Arial,Helvetica,sans-serif;"><span style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; color: #005288; font-family: Arial,Helvetica,sans-serif; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; vertical-align: baseline;">[[image:http://static.howstuffworks.com/gif/fusion-reactor-1.jpg link="http://science.howstuffworks.com/nuclear-power-pictures.htm"]]

<span style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: Arial,Helvetica,sans-serif; font-size: 10pt; line-height: 14pt; margin-bottom: 10px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; vertical-align: baseline;">A consortium from the United States, Russia, Europe and Japan has proposed to build a fusion reactor called the International Thermonuclear Experimental Reactor (ITER) in Cadarache, France, to demonstrate the feasibility of using sustained fusion reactions for making electricity. <span style="border-bottom-width: 0px; border-color: initial; border-left-width: 0px; border-right-width: 0px; border-style: initial; border-top-width: 0px; font-family: Arial,Helvetica,sans-serif; font-size: 10pt; line-height: 14pt; margin-bottom: 10px; margin-left: 0px; margin-right: 0px; margin-top: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; vertical-align: baseline;">(source - http://science.howstuffworks.com/fusion-reactor.htm)

__** General source: **__
 * http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/fusion.html **
 * http://www.atomicarchive.com/Fusion/Fusion1.shtml **
 * http://www.ccfe.ac.uk/ **
 * http://www.jet.efda.org/fusion-basics/ **
 * http://www.world-nuclear.org/info/inf66.html **