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# Nuclear Reactors

## The nuclear reaction occurs which boils water into steam, the steam is used to spin a turbine, and the turbine turns an electrical generator.

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Fusion Energy

### Fusion Energy

Credit: Robert Lopez
Source: CK-12 Foundation

When two lighter nuclei fuse into a heavier nucleus, energy is released. Long thought to be the next step in energy production, the idea of fusion energy has yet to be achieved due to several setbacks and the sheer difficulty consistent fusion reactions.

#### Amazing But True

Credit: NASA
Source: http://en.wikipedia.org/wiki/File:Sun_in_X-Ray.png

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

• The power that could be produced from the fusion of nuclei is of great value because of the abundance of fuel that is available. Even though fusion energy has been in the research phase for over 80 years, we have yet to develop the technology to make it a viable source of energy. One type of fusion reaction currently being researched is the following:

2H+3H4H+n+17.6 MeV\begin{align*}{^2 H} + {^3} H \rightarrow {^4 H}+n+17.6 \ MeV \end{align*}

• To cause a fusion reaction between 2H\begin{align*}^2 H\end{align*} and 3H\begin{align*}^3 H\end{align*}, very large kinetic energies are needed. One method to achieve these energies is by increasing the atom's kinetic energy through heating the system. Since a large number of particles have kinetic energies that are larger than the mean kinetic energy, a temperature that is approximately kT=10 keV\begin{align*}kT=10 \ keV\end{align*} is needed assuming the density is reasonably high.
• The temperature that corresponds to the above relationship is on the order of 108 K\begin{align*}10^8 \ K\end{align*}. Temperature of this scale while usually only seen in stars, has been recently achieved in laboratory experiments. Even though it has been over 60 years since the initial start of fusion research, there is a long way to go before it is viable. 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?

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