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Coherent Nuclear Excitations

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42 points_Microft12 comments

As a nuclear engineering manager, I sometimes ask in interviews what far-out physics development would be most impactful for nuclear power. My personal answer would be to be able to select which fission products emerge from all fissions. If you could control this (with some kind of crazy laser in a cryogenic environment, or something), you could choose one several minute half-life delayed neutron precursor that makes the reactor easily controllable and something else that decays within minutes to another stable nuclide. That could alleviate radiological hazards nicely, especially if you could avoid creating minor actinides as well to avoid the long-lived nuclear waste source term.

This development here makes me wish even harder.

Still, physicists have told me to dream on.

This is a fantastic idea and I don't think it's impossible. Though I'm only an amateur physicist, it seems plausible that decay could be a little less random than we think.

I remember reading about seasonal half-life variability that could have been due to changes in solar neutrino flux.

I also remember something about changes in half-life when atoms were placed inside c60 spheres.

I haven't read anything for or against it, but I'd be interested in if a Bose-Einstein condensate of a fissile material may exhibit a tendency to particular products.

I'm with you on this one, and I think there is much room for improvement and further experiment.

> Though I'm only an amateur physicist, it seems plausible that decay could be a little less random than we think.

How is that plausible? Wouldn't that falsify all the quantum mechanics?

If the presence of a neutrino (or dark mater particle) is required for fission to occur, would this really be testable currently? Maybe there are other effects that influence decay that we haven't fully been able to investigate.

I'm just saying that we don't know everything yet, and it may be possible to influence these things in some way in the future.

People have looked into this using fission. There are many possible ways to emit a given fission fragment (different nuclei, reactions, etc). You can look at whether the history of a particular nucleus produced from fission influences its decay. I haven't seen one of these studies that has observed deviation from the expected markovian behavior outside of measurement uncertainty.

Long long ago, I worked in nuclear sciences/engineering consulting, somewhere with backed-in vehicle habits and computers named after Simpsons' characters.

Yes, the problems are many, including entropy.

Achievable today are spreading-out and confining fuels and wastes in tiny quantities using lithographic techniques similar to IC production. Molten salt SMRs solve some problems, but they still don't adequately contain radioactivity in fixed areas as well as heatpipe SSRs (i.e., eVinci) do. Heatpipe SSRs furthermore aren't as good at inherent containment and safety as SSR lithographic cell reactors, which contain minuscule amounts of fissile material/waste per unit volume embedded in chunky, rugged substrates comprising a very small module, reprocessed as a whole. Many, many modules linked together then represent a genset, from large to small. If modules can be standardized, they could be distributed as highly-controlled items as "batteries" for numerous applications.

In the long-term, fusion is The Way™.

The field of nuclear quantum theory was like a snake swallowing a hippo of funding. People studying electronic structure end up bringing advances back to nuclear theory, because many of the practitioners of advanced nuclear shell structure simply aged away before computers got so powerful. I'm optimistic that there will be more developments... There's several laser accessible transitions known. https://arxiv.org/abs/2001.08320

IIUC, this says there are nuclear excitation states that can be selectively and controllably pumped with X-rays. Any chance of creating a population inversion for lasing action? (Or whatever it would be called at nuclear energies/wavelengths?)

edit:typo

Might be hard to figure out what nuclei are usable for that, but I’m sure high frequency lasers would be useful

A fun Wikipedia page about another time results were published on coherent nuclear excitations is "Hafnium Controversy"[0]. In that case, it was thought that hafnium nuclei could put into a stable state that, through stimulated emission, could be rapidly transitioned to a lower energy state and made to produce an xray photon. This behavior would let you build a really high-power xray laser or bomb.

It seems like the hafnium finding was made in error, but the experiment in this post seems much less showy and more real. Could be really cool for clocks - right now optical atomic clocks are much better than the old RF atomic clocks, with the trend being toward ultraviolet atomic clocks. Xray clocks would be orders of magnitude better than even UV clocks!

[0] - https://en.wikipedia.org/wiki/Hafnium_controversy

> A single quantum jump made by a nuclear component can thus pump up to a million times more energy into it – or get it out again

Is this different than nuclear isomers? Are they saying they made progress controlling them?

That's what I thought too. They are not saying this directly, but what else could they mean?

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