We are working on building controlled fusion reactors but, so far, have been unable to overcome the technological problems in doing so. There have been some minor successes, but only on a microscopic scale.
One of the hard parts is maintaining the extremely high pressures and temperatures that are required to sustain a fusion reaction, in combination with being able to contain that reaction. The plasma state needed for the fusion reaction cannot be contained by anything mechanical, as it is too hot. In the Sun, this works because of the extreme mass present, causing enough gravity to sustain the pressure needed. On Earth, we can not use anywhere close to the Sun's mass, so we go with magnetic fields. Problem is, that in order to produce a magnetic field strong enough to hold the plasma, you often need super-conducting magnets, which require super-cold temperatures - yet that has to be sustained in close proximity to the ultra high temperature of the fusion reaction.
So far, the only successful fusion reactors we have are uncontrolled, i.e. Hydrogen Bombs. That would, of course, not do for a power reactor. It is interesting to note that the amount of energy required to initiate a fusion reaction is enormous - so enormous that Hydrogen Bombs actually use Atomic (fission) Bombs to set them off. That's part of the problem with controlled fusion reactions - the amount of energy required to initiate them.
No. Our reactors are fission reactors. We haven't yet mastered fusion reactors for power.
Yes, stars are fusion reactors.
Well, fusion bombs are, but fusion reactors should not be (if we can build them).
Nuclear fusion reactors do not exist yet as we don't know how to build them. All nuclear reactors are nuclear fission reactors.
In test reactors.
There are fission and fusion reactors. However, at present (2016) there is no commercial fusion reactor which can produce more energy than is required to operate it.
There are fuel pellets and laser beams inside fusion reactors. But note that we have not build a successful one. The technical problems are overwhelming at this point.
Zero, there are no practical fusion reactors. All existing prototype designs for fusion reactors take far more energy input to make them run than they generate.
I found the website K1 Project very helpful. They had several articles underneath their Learn/Energy tab which should answer any questions about nuclear fusion.
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Terry Kammash has written: 'Fusion reactor physics' -- subject(s): Fusion reactors
yes. If they ever perfect hydrogen fusion reactors, then maybe someone will have to come up with a clearer description, but until now, they are the same.