Nuclear+fusion+-+Rajit

11.5 Presentations 11.4 Presentations =Nuclear Fusion =

  **What happens?** 

Nuclear fusion is the process by which like-charged nuclei merge to form a heavier nucleus. This change usually results in either the absorption or the release of an amount of energy. During Nuclear Fusion, two superheated atoms, usually deuterium and tritium (isotopes of hydrogen) are brought close together. Once this happens, the two atoms fuse together, releasing energy in the form of neutrons. However, there are many conditions for this fusion reaction:

Normally, in a nucleus, there are two types of forces at work. First, electrostatic force. This force is basically the force that causes positive nuclei to repel other positive nuclei and attract negative nuclei. The other type is nuclear force. This nuclear force attracts nucleons together, but only comes into effect once the nucleons are very close together. Therefore, in order for fusion to happen, the two like-charged nuclei must be extremely close together, less than a femtometer apart (0.0000000000000001m) :P This is done using magnetic fields and ion beams. **
 * 1. Distance**

2. Heat ** This reaction also requires the electrons to be superheated, such that the atoms are no longer in the gaseous state, but are instead plasma (more than a hundred million degrees celsius). Such extreme temperatures are reached by using microwaves and lasers.  **Example** (Facts & Figures)  One of the biggest examples of nuclear fusion is the sun. In the sun, the hydrogen atoms at the core is being squeezed together by the huge mass around it, which causes four hydrogen nuclei to combine into one helium nucleus. In this process energy is released. The extreme pressure at the core of the sun results in the temperature there being about 13,600,000°K. About 9.2 x 1037  (920,000,000,000,000,000,000,000,000,00 0,000,000,000) hydrogen nuclei are converted into helium nuclei every second, or about 4.4 x 109  kg of hydrogen per second. This reaction releases energy at a rate of 383 yottawatts per second (3.83 x 1026  W), or about 9.15 × 1010 megatons of TNT per second. Since the largest nuclear weapon ever exploded had a yield equal to about 50 megatons of TNT, this reaction is equal to 1.83 trillion such weapons each se cond.  In fact, thermonuclear bomb (fusion bombs) also use the same process. However, in a bomb it all happens at once in a huge chain reaction. The Sun doesn't blow up because of the enormous weight of the gases around it. This weight balances the pressure caused due to the energy created at the core. In the case that the amount of energy created decreases, the sun would begin to collapse which would in turn increase the pressure, balancing it out again. If the amount of energy increases, the pressure would cause the sun to expand a little, again balancing it.  <span style="color: #a30000; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 110%;"> The energy changes involved are as follows:
 * Energy Changes (involved)**

Nuclear Potential Energy --> Kinetic Energy --> Heat Energy --> Electrical Energy

This begins with the nuclear potential energy in the nuclei, which causes the nuclei to be attracted towards each other, creating kinetic energy. When these nuclei come close enough, the fusion reaction occurs, releasing heat energy. This energy is then captured and converted into electrical energy.

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;"> **Environmental Effects** The fusion fuel cycle does not involve the input of any radioactive material and it does not generate radioactive waste directly, only in the form of the intermediate fuel tritium. There is thus the freedom to reduce the radioactivity using suitable designs and materials. Fusion does not produce any greenhouse gases, and thus does not harm the environment in any way besides the electricity needed to power the support systems (cooling). These impacts are EXTREMELY small compared to the impact of fission or damming a river. <span style="color: #a30000; font-family: 'Trebuchet MS',Helvetica,sans-serif;"> ** Advantages ** <span style="color: #a30000; font-family: 'Trebuchet MS',Helvetica,sans-serif;">
 * <span style="color: #a30000; font-family: 'Trebuchet MS',Helvetica,sans-serif;">**Extremely large source of fuel (enough for millions to billions of years)**
 * <span style="color: #a30000; font-family: 'Trebuchet MS',Helvetica,sans-serif;">**Releases a lot of energy**
 * <span style="color: #a30000; font-family: 'Trebuchet MS',Helvetica,sans-serif;">**No emissions (no acid rain, global warming or ozone depletion** )
 * <span style="color: #a30000; font-family: 'Trebuchet MS',Helvetica,sans-serif;">**Minimal radioactive waste**
 * <span style="color: #a30000; font-family: 'Trebuchet MS',Helvetica,sans-serif;">**Much lower land use and environmental impact than other energy forms**
 * Disadvantages **
 * <span style="color: #a30000; font-family: 'Trebuchet MS',Helvetica,sans-serif;">**Cannot be done yet in a way that has a large enough energy gain. However, progress is being made. Hopes are to have an operational reactor by 2018.**