Green Education: Green 101

Classic Challenges in Fusion Energy

Fusion energy was first “rediscovered” during the 1950′s, when scientists first realized its great potential as a replacement for fission energy. But while considered as one of the most promising sources of clean and safe energy, it is by far currently the alternative energy source that is least expected to be commercially viable.

That is because aside from the construction of the complex fusion reactor, researchers also have to face the basic process of initiating a fusion reaction, something that cannot be done as easily as ordinary stars do. Here on Earth, we must adhere to a set of very specific and complex conditions (which would definitely cost lots of money to fully control), before fusion can be achieved.

And if the ultimate objective is to economically produce a net amount of usable energy, we must also be able to overcome all of these 5 hurdles:

1. Fusion Reaction Energy Requirement – Stars are capable of initiating fusion reactions easily because they could simply use the extreme gravitational pressure levels of its own core. Because we cannot replicate the same pressure levels inside a star, we are left with the only other way, and that is by instilling raw energy into an atom. Initiating a deuterium-tritium (D-T) reaction, would require the activation energy of around 40,000 electron volts for each single pair of deuterium and tritium atoms.
2. Fusion Fuel Confinement – after delivering such high energy to the fusion fuel, it would eventually heat up wildly and turn into the energetic fourth state of matter, plasma. Keeping something in plasma form is very difficult because it loses a great deal of energy once it touches something with a slightly lower temperature. One way to confine the plasma fuel is via magnetic confinement, and today scientists usually use a tokamak (donut) shaped vessel to create the needed confining magnetic field. This is one of the easier hurdles to overcome technically, since it does not involve the inclusion of too many elements and variables.
3. Sustainable fusion energy output – Finally, after getting the reactor up and running, the next challenge is to keep the fusion reactions stable and steady. The energy that was released during the initial fusion reaction must be used to energize the next batch of atoms, which would then fuse, passing the energy to the next set, and so on, creating a self-sustaining fusion energy production cycle. This has been quite difficult to achieve even today though. In fact, just achieving a break-even reaction for a considerably long period of time can already be considered as a historical milestone. Additionally, other energy requirements, such as the energy required to power other systems in the reactor, is also taken into account for this challenge.
4. Elimination of extra neutrons – One of the important “risks” that an economically viable fusion reactor must face is the production of extra neutrons during a fusion reaction. Unlike in standard nuclear fission reactors, the amount of “shooting” neutrons that is produced in fusion reactions is theoretically 100 times greater. Since it is impossible to confine neutrons using electrostatic or magnetic fields, it would inevitably go through the vessel material, displacing the atoms within it, and eventually lowering the structural integrity of the entire structure over time. Tungsten is currently the best material of choice in creating a confinement vessel that could resist the atom displacement caused by the runaway neutrons.

While solutions have already been developed for each of these challenges, the current status of fusion research today is still swamped with many other new hurdles. One particular problem is fusion energy’s changing level of economic feasibility in the face of other currently developing alternative energy technologies.

Photo credits: Some rights reserved by etee via Flickr.

Source: TheEnvironmentalBlog