Skip to main content
Report this ad

Power for the people!

The hohlraum or target for lasers used to ignite fusion.
The hohlraum or target for lasers used to ignite fusion.
National Ignition Facility, Lawrence Livermore labs

Regardless of how wonderful new technological thingies might be, they do and will need power (in general, electrical power) to run. The issue of where that power will come from is complex. Currently, we in the US use a lot of coal to generate electricity, and the use of that coal is in some disfavor at present, because it produces carbon dioxide when it burns (although, let's also note that we use carbon dioxide when we breathe so it is probably wise not to get too worked up about that!). Alternative methods of generating electrical power that do not generate carbon dioxide are currently in favor.

Here in the mid-west there is a lot of interest in wind power, although this too has its problems. A recent story tells us that wind turbines in Minnesota are not working right now because it is too cold for them to turn - imagine that - too cold in Minnesota in January - sounds like someone did not think those turbines through too clearly. Solar power is good, although of course it does not work too well at night, and that means that it cannot serve to provide the electrical base load that we need. Hydroelectric power can be wonderful, but it requires an appropriate river (in general) and the creation of the needed dam on the river can be very harmful to the fish that live in the river. Which leaves nuclear power!

Nuclear power at present is generated using the heat that is produced when heavy atoms undergo a process called fission. Put simply, heavy atoms (typically certain Uranium isotopes) are split when they are impacted by neutrons of a certain energy. When the heavy atoms split, they leave behind two lighter atoms, a number of neutrons, and some energy. The energy is used, in most nuclear power plants, to heat water and turn it into steam. The steam drives turbines which generate electricity. Here in Eastern Iowa, we get some of our electricity from the Duane Arnold Nuclear Power Plant.

But nuclear fission is not the only possible way to generate power from nuclear processes. Power can also be obtained through the process of nuclear fusion. This process is what powers the sun. In nuclear fusion light elements (typically hydrogen, or its isotopes, deuterium and tritium) get combined in such a way as to form slightly heavier elements (typically, in the sun at its current age, helium). There is, and has been since the 1940's, a great deal of interest in generating power through nuclear fusion. However, this is a process that is fraught with challenges.

The key challenge with fusion is that you have to bring the two atoms (or more specifically, the nuclei of the two atoms) together with sufficient energy that they can fuse. This means you have to have a combination of high temperature and high pressure (although those terms are a bit imprecise in the context of fusion). There are a number of ways in which this can be done (or at any rate, attempted) and there has been some interesting progress recently on various of these methods.

The traditional approach to fusion has been to use a Tokamak approach. This uses a toroidal magnetic field to confine plasma, thus creating the needed pressure or confinement. The heating of the plasma can be done in several ways, but since the plasma is conductive, much of the heating is done by passing a current through the plasma. The JET facility in Europe uses this approach, and the ITER facility (also in Europe, currently under construction) will take this approach even further.

A second approach is to use laser beams to both heat and confine the plasma and there has been a recent breakthrough in this technique at the National Ignition Facility at the Lawrence Livermore Labs. Specifically for the first time they have been able to use all 192 lasers at the same time, and focus them on a small chamber called a hohlraum in a symmetrical manner. This is a big deal, because if the beams do not focus in this way, then there will not be enough confinement. Additionally they have been able to deliver a pretty large jolt of energy into the hohlraum - specifically one megajoule. That may not sound like much, but they delivered it over a time period of a few billionths of a second. So the rate of energy delivery is huge, and it is one critical step toward achieving power generation through fusion.

A third approach to fusion power is Polywell or Bussard fusion. This approach uses a combination of electrostatic and magnetic methods to confine the plasma. It is rather novel and unconventional, but appears to be promising also. Certainly, the US Navy is very interested in this approach (for reasons that may become obvious with a little thought) and we should have an idea within a couple of years as to whether this is a viable approach.

Regardless of which method of fusion eventually leads us to fusion power, it is good news that we seem to be making progress on so many fronts. Not to oversell fusion power, but if it does work out, it is not only carbon dioxide free, but also much less radioactive than nuclear fission.


Report this ad