From my understanding nuclear fission takes place in two different scenarios and correlates with the speed of a neutron. In terms of material, we have fissionable material which undergo nuclear fission after attaining a fast neutron or a relatively slow/low energy neutron. We also have fissile material which will only undergo fission when capturing a slow/low energy neutron. Nuclear fission in general happens when we start chucking neutrons at a heavy nucleus to cause it to become unstable and split into two. Massive amounts of energy and free neutrons are a byproduct of this reaction.

Suppose I was to create a field that messed around with the required ranges to induce nuclear fission in both fissile and fissionable material such that the speeds never line up appropriately for the heavy nucleus we are throwing free neutrons at (i.e. neutrons are either too fast, or way to slow in a range based on the nucleus material type). Maybe I start violating the Pauli Exclusion Principle to mess with the critical energy required to start a fission reaction, or maybe I just use pure handwavium to get the field up and running. Either way, I am messing with neutrons such that when in the field they cannot induce a nuclear fission reaction based on their speed.

What would the unforeseen consequences of this be? Would reality cease to be, or would we have a region with no nuclear fission possible with everything else fine and dandy. For example by messing with the speed and energy of free neutrons, would ionizing radiation from neutrons be possible, would radioactive decay even be possible, would it be possible to create isotopes etc.

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    $\begingroup$ Is that a Half-Life reference? :) $\endgroup$
    – Joachim
    Feb 6 at 12:37
  • $\begingroup$ Fissionable means "can fission." Fissile means "can fission from a low energy neutron." Either can fission from a high energy neutron. Fissile is important because the chance to fission (indicated by the cross section) is much larger at low energy. $\endgroup$
    – Dan
    Feb 6 at 14:36
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    $\begingroup$ Since there is no known method to do what you describe, you will have to use large quantities of handwavium. Since the properties of that are created by you, nobody can answer your question. $\endgroup$
    – Dan
    Feb 6 at 14:38
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    $\begingroup$ The Pauli exclusion principle will not do you any good. The PEP tells us that two fermions (such as electrons) cannot be in the same quantum state. So many energy states of atoms that would otherwise be possible are not. Neutrons and protons in the nucleus also have some energy states excluded. But that has already happened before you come along wanting to stop fission. $\endgroup$
    – Dan
    Feb 6 at 14:42

2 Answers 2


Nuclear fission is mediated by the elctromagnetic force, which is trying to split a nucleus due to the repulsion between protons, and the strong force which holds the nucleons together.

You probably shouldn't mess with the strength of the electromagnetic force, because you will probably break everything, from chemistry to the speed of light. If you were somehow able to increase the strength of the strong force, though, then you might be able to leave non-nuclear processes unaffected. A formerly fissionable nucleus like 235U would then always absorb a neutron turn into a heavier isotope like 236U and never undergo fission. Spontaneous fission will become much harder as will alpha decay and as such a lot of isotopes which are currently radioactive and unstable could become less unstable or even completely stable over any long timescales (so long as your stronger-force generator remains operational).

Other kinds of radioactive decay such as beta emission could still occur, and gamma radiation emission following neutron activation or beta decay will also be entirely possible because those processes aren't mediated by the strong force.

Assuming your powers of strong-force-strengthening are limited, it will still be possible to induce fission in a sufficiently neutron-rich nucleus, so you've made the problem much harder (and maybe made it impractical to do make fission powerplants or weapons) but not eliminated it entirely. If you look at the nuclear drip lines (where unstable nuclei can decay by proton or neutron emission) you'll probably find beta decay happening instead.

It may also make it easier to induce fusion in light elements, though I'm not sure by how much.

What would the unforeseen consequences of this be?

Assuming the size of the effect is small, you probably don't have to worry very much. If the effect were planetary scale, you risk things like cooling down the planet due to removing some or more of the radioactive heating that keeps the core toasty. That risks stopping the geodynamo in a few tens of millenia, with all the problems that a lack of a planetary magnetic field can entail.

Even larger scale effects that encompass stars will have more dramatic results. Increasing the strength of the strong force means that the diproton could become stable. I'm not entirely sure what this would do, but it will almost certainly be Very Bad... relatively rapid conversion of hydrogen to helium would dramatically shorten the life of affected stars (to maybe millions of years) and their power output would substantially increase, toasting any planetary systems they might have.

  • $\begingroup$ The strengthening field seems very useful for making more powerful, more compact bombs out of isotopes that wouldn't otherwise be stable. Just be careful where you store them, in case there are power issues with the field generator... $\endgroup$ Feb 6 at 18:10
  • $\begingroup$ @MikeSerfas could be a bomb in itself, if the prompt decay of the fielded materials yields enough oomph in a short enough time. $\endgroup$ Feb 6 at 18:43
  • $\begingroup$ Ah so reality breaking esque. Unfortunate. In that case would causing neutrons to miss a heavy nucleus yield then the same results? Thereby forcing the free neutrons inside the field to eventually decay leaving us w/ no possibility of reaction? $\endgroup$
    Feb 6 at 20:04
  • $\begingroup$ Nuclear fission is signficantly affected by the weak force. Beta decay is a weak force interaction, thus the neutrino. en.wikipedia.org/wiki/Beta_decay The rates of reactions and the energy released by them is very sensitive to the strength of all three of electromangetic, weak, and strong forces. $\endgroup$
    – Dan
    Feb 7 at 3:27
  • $\begingroup$ @Dan the weak force has some effect on the kind of things that fly out, but the actual business of fissioning is entirely down to the strong and electromagnetic forces. $\endgroup$ Feb 7 at 8:42

Semi-Science, Inc. (A division of ACME, supplier of high tech equipment used by coyotes to deal with high speed avians throughout the Galaxy) has just what you need. Our Neutron Dampening Device slows down the speed of the neutrons enough to suppress nuclear chain reactions.

A reactor subjected to a neutron dampening field (easily detectable by the strong breeze associated with high powered handwavium) might still operate, but the heat (and thus electric power generated) would be greatly reduced.

A nuclear weapon (or nuclear primed fusion weapon) would either be cause an explosion reduced by 4 to 5 orders of magnitude or else the weapon will just end up as quick flash leaving behind a pile of half melted radiactive fragments.

This shouldn't cause any major hiccups in reality. Just to be safe, we recommend not applying neutron damping technology to the core of a planet or to an entire star until further experiments have been conducted in uninhabited systems. Current models have a maximum radius of 200 km, which is more than enough to provide a high degree of protection against nuclear attack to ships, orbital facilities, and most cities.

Remember, your own nuclear reactors will be producing little or no power. Consult our brochure regarding the possible effects on different models of fusion reactors.


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