In nuclear fusion the atoms are in a hot plasma and the temperature is >5000K for them to posses kinetic energy and overcome repulsion to fuse , this process generates some heat(which is equal to the mass defect).But how do we actually extract that given heat if the surroundings are already so hot ?
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$\begingroup$ Perhaps better posted on the Physics Stack. $\endgroup$– Solar MikeCommented Feb 13, 2023 at 7:58
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$\begingroup$ I thought of posting it in physics but the question seemed better on engineering because it involves a practical process rather than a theoretical concept. but sure! Thanks by the way and do i need to delete this question for posting it in physics ? @SolarMike $\endgroup$– Naveen VCommented Feb 13, 2023 at 8:02
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$\begingroup$ I think this question belongs here. I've thought of this question over time. I don't have an answer. It may be case of let's get a fusion reactor to work first & then when we see what it looks like & then we'll figure out how to extract useful energy out of it. $\endgroup$– FredCommented Feb 13, 2023 at 12:59
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$\begingroup$ A practical process that doesn't work yet $\endgroup$– Tiger GuyCommented Feb 13, 2023 at 14:57
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$\begingroup$ @TigerGuy yeah . In the distant future i can see it happening :) $\endgroup$– Naveen VCommented Feb 13, 2023 at 17:29
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2 Answers
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Most of the energy release in a fusion reaction is in the form of the kinetic energy of the reaction products plus a bit more in the form of radiative energy carried off by gamma rays. the kinetic energy of the reaction products is captured as heat in the part of the reactor known as the first wall, when the fast-moving products (helium nuclei) collide with the stuff from which the first wall is made (graphite, for example). The gamma rays also collide with the first wall and through a series of successive scattering events with nuclei inside the first wall they impart a bit more heat energy to the first wall as well. The heat from the first wall is then captured by heat transfer pipes that carry the heat out of the reactor and into a steam generator.
The plasma in which the fusion reactions occur must be confined in such a way that the plasma never comes into contact with the first wall, otherwise the fusion process will be immediately quenched and the reactor will shut itself down.
Since there is no material known which can stand up to fusion temperatures, the plasma confinement must be done either with magnetic fields or via inertial confinement.
Inertial confinement is the process in which the input energy required to trigger the fusion reaction is dumped into the fusion pellet so fast that the inertia of the pellet itself prevents it from escaping the reactor until the fusion process is finished. At that point, the input energy dump is over too which means the inertial confinement ceases and the energy (fast-moving helium nucleus plus gammas) streams freely out towards the first wall.
answered Feb 14, 2023 at 2:41
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$\begingroup$ is the heat released in the process equivalent to radiative energy from gamma rays ? how do they escape the inertial confinement ? thanks for the answer though ! $\endgroup$– Naveen VCommented Feb 14, 2023 at 3:48
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Given it's immature nature fusion reactors still in development/experimental stage, however the enormous temperatures aside the plasma density is quite low so thermal energy can be dissipated with conventional heat exchangers. So in theory a fusion reactor can power a Steam turbine. However engineers are more concerned with direct power, Because plasma dissociates electrons; attempts to siphon them to produce power directly by harnessing them in coils of conductive wire.
Other direct drive methods include ion pulse beams. Where Xrays and radiation are directed a beam of radiation thru a magnetic coil. Other high energy photovoltaic systems harness radiation similar to solar panels. THus fusion doesn't require moving mechanical parts to generate power in the classical sense.
