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# Nuclear Reactors

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Fusion Energy

### Fusion Energy

Credit: Robert Lopez
Source: CK-12 Foundation

When two light nuclei fuse into a heavier nucleus, energy is released. Long thought to be the next step in energy production, energy harvested from nuclear fusion has yet to be achieved due to several setbacks and the sheer difficulty inherent in fusion reactions.

#### Amazing But True

Credit: NASA
Source: commons.wikimedia.org/wiki/File:Sun_in_X-Ray.png

The sun is an example of a natural fusion reactor [Figure2]

• While fuel for nuclear fusion is virtually limitless, a viable method of efficiently harvesting energy for commercial use has yet to be found. One type of fusion reaction currently being researched is the following:

${^2 H} + {^3} H \rightarrow {^4 H}+n+17.6 \ MeV$

• Very large kinetic energies are needed to cause a fusion reaction between $^2 H$ and $^3 H$. One method to achieve these energies is by increasing the atom's kinetic energy by heating the system with temperatures around  $kT=10 \ keV$.
• The temperature that corresponds to the above relationship is on the order of $10^8 \ K$. Temperature of this scale, while usually only seen in stars, has been recently achieved in laboratory experiments. Despite 60 years of nuclear fusion research, scientists have a long way to go before finding a viable implementation of nuclear fusion. Currently, commercial power production using fusion is not expected till after 2050.

#### Explore More

Using the information provided above, answer the following questions.

1. The temperature listed is actually an overestimate of the temperature that is needed to produce a reaction. Why? (Hint: Think of possible quantum effects)
2. Why must the plasma being using in fusion experiments be prevented from contacting the walls of the container used?
3. Why are runaway reactions not a major concern in fusion reactors?

1. [1]^ Credit: Robert Lopez; Source: CK-12 Foundation; License: CC BY-NC 3.0
2. [2]^ Credit: NASA; Source: commons.wikimedia.org/wiki/File:Sun_in_X-Ray.png; License: CC BY-NC 3.0

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