Between nuclear fusion and nuclear fission, which produces more energy, and why – quora gas leak los angeles


First off is the difference between fusion and fission Nuclear fusion is taking two atoms and combining them in to one atom, while nuclear fission takes one atom and splits it into two atoms.… Both reactions involve the nucleus of an atom, and in both reactions, lots of energy are released. Other than that, the two reactions are pretty much opposite.

Fission is what is currently being used to produce clean energy, more so in the EU than in the US. Currently it uses continuous fission of Uranium (U-235). One must contend with decay of materials, fuel rods must be kept cool using hard water. Once Fuel Rods are spent, they must be disposed of carefully. There is a facility in Texas which stores the Nuclear waste deep underground. The Fukushima Daiichi Reactor in Japan is an example of just how dangerous Fission Reactors can be, in this instance it was caused by an earthquake.

Fusion puts out much more electricity, instead of the possibility of making a Fusion reactor just a year ago many were thinking it might take another 30 years before a Fusion Reactor would be ready for the Electrical Grid. But a project collaboration between MIT and the Commonwealth Fusion Systems (a private company), have come up with new materials to make magnets much more powerful, they believe they can have a Fusion Reactor on line within 15 years.

Until now every fusion experiment has operated on an energy deficit, making it useless as a form of electricity generation. Fusion works on the basic concept of forging lighter elements together to form heavier ones. When hydrogen atoms are squeezed hard enough, they fuse together to make helium, liberating vast amounts of energy in the process. However, this process produces net energy only at extreme temperatures of hundreds of millions of degrees Celsius – hotter than the center of the sun and far too hot for any solid material to withstand.

To get around this, scientists use powerful magnetic fields to hold in place the hot plasma – a gaseous soup of subatomic particles – to stop it from coming into contact with any part of the doughnut-shaped chamber. However a newly available superconducting material – a steel tape coated with a compound called yttrium-barium-copper oxide, or YBCO – has allowed scientists to produce smaller, more powerful magnets. And this potentially reduces the amount of energy that needs to be put in to get the fusion reaction off the ground.

The planned fusion experiment, called Sparc, is set to be far smaller – about 1/65th of the volume – than that of the International Thermonuclear Experimental Reactor project, an international collaboration currently being constructed in France.

The experimental reactor is designed to produce about 100MW of heat. While it will not turn that heat into electricity, it will produce, in pulses of about 10 seconds, as much power as is used by a small city. The scientists anticipate the output would be more than twice the power used to heat the plasma, achieving the ultimate technical milestone: positive net energy from fusion. For information on the International Thermonuclear Experimental Reactor in France, see this link: After 60 years, is nuclear fusion finally poised to deliver?

At the current time in the history of the universe fusion produces far more energy than fission – the reason being simply that the universe is full of galaxies which are full of stars, all of which are producing energy by means of the process of fusion.

Fission by contrast happens only rather rarely, when enough very heavy elements have gotten together in one place in combination with a moderator of some sort which can slow the neutrons adequately enough, so that one has a critical density of fissionable material in place. That can happen naturally of course, but it is rather rare, especially at the current epoch in the Earth’s history. When the Earth was young it would have been easier, but still, the energy release is small in comparison to that coming from the Sun.

In terms of the energy release per fusion reaction the same is true – more energy is released per nucleon by going from hydrogen to nickel-62, than is released per nucleon by going from uranium-235 to the fission products, which are a range of nuclides peaked near mass 90 and mass 140.

You can see this all by taking a close look at the curve of binding energy. It’s derivative is large positive for light nuclei, curving over near the iron group of elements, and then becoming small and negative as the atomic mass increases further.

Let’s talk bombs first. Fission bombs are relatively simple. And the fact of the matter is, with some good mechanics, and a quality machine shop you could build one yourself. All you need is some fissile material and you slam two pieces (smaller than a critical mass) together and make a piece bigger than a critical mass. It is big, bulky, and really inefficient. Which is why no one is building bombs like this. Generally they build much more sophisticated designs that compress a core evenly with explosives all around it. It turns out fission has a cap on how much energy it can produce in a single go. If you put too much together, it forms a critical mass and explodes. And there is a limit on how quickly you can compress it. So you can only put so much in proximity and compress, before it blows itself apart. In general in a 10kg warhead, only a tiny percentage of the material actually undergoes fission. Most of it is blown away from the reaction before it can react.

Fusion bombs are harder to get going. Hydrogen is inflammable. But it doesn’t fuse under normal earth like conditions. So you can put lot of it together. And it’s reaction tends to breed more fusion (for a fraction of a second longer, it also tends to blow itself apart). But if you heat and compress hydrogen enough it makes a more impressive and longer lasting reaction (by nanoseconds). A hydrogen bomb makes a bigger boom, hundreds of kilotons rather than tens of kilotons. Interestingly to get the kind of compression you need to start fission, you need the kind of heat and pressure found in an atomic blast. So what a hydrogen bomb does is it uses a series of fission bombs to compress the hydrogen and set of fusion in the hydrogen. They should really be considered joint fission & fusion bombs

Then some bright guys figured out you could build the things like jawbreakers (they called them layer cakes) with a layer of fission compressing layer of fusion that would compress another layer of fission and another layer of fusion. For each double layer you added, you could get a significant increase in yield. The Soviets even built a 100 megaton bomb (about 700 Hiroshimas) called the Tsar Bomba, but they only tested it at half strength.

Now on to reactors. Fission reactors are again easier. This is for two reasons. First again if you get enough fissile material together they just start reacting. And second, if you put an absorbent material in and around the fissile material it will pick up the decaying particles the fissile material is throwing off and stop the reaction. That means we can start, stop, and dial up and dial down the reaction as we please. Assuming all goes well, the design is solid.

Fusion is hard to get going, hard to get going, and hard to control while it is going. The sun does it naturally. Gravity holds all the particles in place. And the massive energy pushes against it. Reaction produces too much energy, the sun swells and the reaction falters. Reaction produces too little, the sun collapses. The reaction itself produces the pressure and heat to produce exactly the pressure and heat the reaction needs.