Why do stars shine? And can we use this energy to our own advantage? In the context of mankind’s hunger for energy, we take a look at a new form of energy production: Nuclear Fusion. Go through the questions and answers in this feature to get a brief overview on how it works, what it’s risks are and when it will actually be ready for the mass market.
The idea of Nuclear Fusion is based on the concept of shining. Watch this video to get a brief impresson.
Source: Omega Matter/YouTube
In nuclear physics, nuclear fusion is a nuclear reaction in which two or more atomic nuclei collide at a very high speed and join to form a new type of atomic nucleus. During this process, mass is not conserved because some of the mass of the fusing nuclei is converted to photons(energy). Fusion is the process that powers active or “main sequence” stars.
The fusion of two nuclei with lower masses than iron(which, along with nickel, has the largest binding energyper nucleon) generally releases energy, while the fusion of nuclei heavier than iron absorbs energy. The opposite is true for the reverse process, nuclear fission. This means that fusion generally occurs for lighter elements only, and likewise, that fission normally occurs only for heavier elements. There are extreme astrophysical events that can lead to short periods of fusion with heavier nuclei. This is the process that gives rise to nucleosynthesis, the creation of the heavy elements during events such as supernovae.
To get a better impression on how nuclear fusion actually works, check out this video:
Source: Scientific American / YouTube
So, what can nuclear fusion do for us? Our energy future depends on this technology, says Michel Laberge. The plasma physicist runs a small company with a big idea for a new type of nuclear reactor that could produce clean, cheap energy. His secret recipe? High speeds, scorching temperatures and crushing pressure. In this hopeful TED-talk, he explains how nuclear fusion might be just around the corner.
In the magnetic approach, strong fields are developed in coils that are held in place mechanically by the reactor structure. Failure of this structure could release this tension and allow the magnet to “explode” outward. The severity of this event would be similar to any other industrial accident or an MRI machine quench/explosion, and could be effectively stopped with a containment building similar to those used in existing (fission) nuclear generators.
Most reactor designs rely on the use of liquid lithium as both a coolant and a method for converting stray neutrons from the reaction into tritium, which is fed back into the reactor as fuel. Lithium is highly flammable, and in the case of a fire it is possible that the lithium stored on-site could be burned up and escape. In this case the tritium contents of the lithium would be released into the atmosphere, posing a radiation risk. However, calculations suggest that at about 1 kg the total amount of tritium and other radioactive gases in a typical power plant would be so small that they would have diluted to legally acceptable limits by the time they blew as far as the plant’s perimeter fence.
The large flux of high-energy neutrons in a reactor will make the structural materials radioactive. The radioactive inventory at shut-down may be comparable to that of a fission reactor, but there are important differences.
The half-life of the radioisotopes produced by fusion tends to be less than those from fission, so that the inventory decreases more rapidly. Unlike fission reactors, whose waste remains radioactive for thousands of years, most of the radioactive material in a fusion reactor would be the reactor core itself, which would be dangerous for about 50 years, and low-level waste another 100.Although this waste will be considerably more radioactive during those 50 years than fission waste, the very short half-life makes the process very attractive, as the waste management is fairly straightforward. By 300 years the material would have the same radioactivity as coal ash.
In general terms, fusion reactors would create far less radioactive material than a fission reactor, the material it would create is less damaging biologically, and the radioactivity “burns off” within a time period that is well within existing engineering capabilities for safe long-term waste storage.
So, when will nuclear fusion finally conquer the energy market? In this video, the famous physicist Michio Kaku explains why we cannot say “no” to fossil fuels yet.