Novel model illustrates the finer details of nuclear fission

Novel model illustrates the finer details of nuclear fission
Snapshots of the total density profile of the 240Pu fission process.

For nearly 80 years, nuclear fission has awaited a description within a microscopic framework. In the first study of its kind, scientists collaborating from the University of Washington, Warsaw University of Technology (Poland), Pacific Northwest National Laboratory, and Los Alamos National Laboratory, developed a novel model to take a more intricate look at what happens during the last stages of the fission process. Using the model, they determined that fission fragments remain connected far longer than expected before the daughter nuclei split apart. Moreover, they noted the predicted kinetic energy agreed with results from experimental observations. This discovery indicates that complex calculations of real-time fission dynamics without physical restrictions are feasible and opens a pathway to a theoretical microscopic framework with abundant predictive power.

In addition to its publication, "Induced Fission of 240Pu Within a Real-time Microscopic Framework" was highlighted as an Editors' Suggestion by Physical Review Letters—ranked first among physics and mathematics journals by the Google Scholar five-year h-index. Only about one letter in six is highlighted based on its particular importance, innovation, and broad appeal.

Apart from its fundamental significance in theoretical physics, providing a usable capability that can accurately model dynamics will impact research areas such as future reactor fuel compositions, nuclear forensics, and studies of nuclear reactions. Excitation energies of fission fragments are not directly accessible by experiments but are crucial inputs to key activities at National Nuclear Security Administration laboratories. The capability developed by this research stands to improve activities that depend upon empirical data and evaluation models by aligning these with predictive theory.

The researchers extended the density functional theory (DFT) modeling method designed for electronic structure systems to strongly interacting many-fermion systems and real-time dynamics, creating a time-dependent superfluid local density approximation (TDSLDA). For the study reported, evaluating the theory amounted to solving ≈56,000 complex coupled nonlinear, time-dependent, three-dimensional partial differential equations for a 240Pu nucleus using a highly efficient parallelized graphic processing unit (GPU) code. The calculations required ≈1760 GPUs and 550 minutes total wall time on Titan, a Cray XK7 supercomputer located at the Oak Ridge Leadership Computing Facility (OLCF).

Unlike other models that incorporate a nuclear energy density functional, the TDSLDA is the only theoretical framework that allows the nucleus to evolve non-adiabatically while including all known collective degrees of freedom. The potential and kinetic energies remain a continuous function of the nuclear shape with no restrictions.

"One notable discovery in using the framework was the time it takes a nucleus to descend to the scission configuration—timescales an order of magnitude greater than those predicted in existing literature," explained co-author Kenneth Roche, a scientist in PNNL's High Performance Computing Group and an Affiliate Associate Professor with the University of Washington, Department of Physics. "One might expect this slow evolution was due to viscosity, but the simulations suggest that many shape and pairing modes are excited, causing energy exchanges in the collective degrees of freedom."

In their article, the authors note that their method could be extended to two-body observables within the fission process, including mass and charge, and eventually, they may be able to introduce additional random aspects that will result in more detailed information.


Explore further

Dynamics of nuclear fission at low excitation energy

More information: Aurel Bulgac et al. Induced Fission of within a Real-Time Microscopic Framework , Physical Review Letters (2016). DOI: 10.1103/PhysRevLett.116.122504
Journal information: Physical Review Letters

Citation: Novel model illustrates the finer details of nuclear fission (2016, May 2) retrieved 17 September 2019 from https://phys.org/news/2016-05-finer-nuclear-fission.html
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May 02, 2016
Give it up.

We have toyed with this dangerous stuff for over 60 years, and have produced nasty waste we cannot even store safely.

Time to end it and to clean up the messes we have made. But where and how do you keep it?

May 02, 2016
Getting closer to the hole. Try looking at high speed protons as they disrupt the outer shell of an atom and the neutron instabilities in the nucleus. Suggest we throw out the standard model. Might speed up your simulation, i.e. fewer processes. juz say'n

May 02, 2016
What we call waste is unused material! That is, a reaction without controls! I standfast that Modern Physics is ??

May 02, 2016
gkam -

Nuclear waste is wasted fuel. And storage is a political problem, not a scientific or engineering problem.

If you really hate the waste, you should be advocating for Gen-4 reactors that can use it as fuel. Because there's only two things you can do with long-term TRUs - bury it for a zillion years, or fission it down into short-lived FPs, the residue of which becomes virtually benign in about 300 years.

And any civilization that can't figure out how to safely store the residue for 300 years should pack it in and go back to horses and buggies. Which could actually work - if we got rid of about 6 billion people.

In lieu of that, let's push forward and use the stuff to generate gigawatts of clean electricity.


May 02, 2016
gkam -

Nuclear waste is wasted fuel. And storage is a political problem, not a scientific or engineering problem.

If you really hate the waste, you should be advocating for Gen-4 reactors that can use it as fuel. Because there's only two things you can do with long-term TRU waste - bury it for a zillion years, or fission it down into short-lived FPs, the residue of which becomes virtually benign in about 300 years.

And any civilization that can't figure out how to safely store the residue for 300 years should pack it in and go back to horses and buggies. Which could actually work - if we got rid of about 6 billion people.

In lieu of that, let's push forward and use the stuff to generate gigawatts of clean electricity.


May 02, 2016
WTFlux, we have heard it before. I am 71, and have seen too many of these schemes which will save us. Nope. Time ran out already. If you can build one, good luck, but do not believe it will solve any problems.

May 02, 2016
Flux, I hope you are right, but do not want to see us go down another radioactive Road To Nowhere.

May 02, 2016
I am 71, and have seen too many of these schemes which will save us.
please, a tin foil hat for gskam
https://fsmedia.i...amp;q=75
http://static1.bu...ment.jpg
https://static.sp...-hat.jpg

May 02, 2016
You nuke-lovers are the ones who need the shielding!

3,000,000-degree Neutrons need lots of shielding, Willie, so lay on the lead for your hat.

May 03, 2016
flux: after fukushimas nuclear incident, Chernobyl and 3 mile island, you still believe nuclear power is safe? Evolution took place over millions of years buddy. We adapted to potassium and several radioactive elements over MILLIONS of years. These man-made radioactive isotopes are brand-spanking new, and only an individual in denial would believe they're safe. Clearly, your deep-seated trust in nuclear power believes evolution can adapt to it in a day. We're lollygaggin with our genes; for-truck-sake man. Clearly we adapted to plagues and such, but detaching our DNAS histones like dissolving salt in water? This aint no ion-dipole interaction.

May 03, 2016
OK, so maybe we are doing it wrong. Not sure we know that we can or we can't modulate the fields to define better results and better controls. Juz say'n I like my block diagram for using nuclear power. Go with what we know. Most is this is escaping neutrons, few proton collisions, electrons scatter. Maybe we can define the path of ...

May 04, 2016
If you guys think nuclear energy is dangerous, just think how the world would have looked if we had had all fossil fuel burning instead of nuclear energy; not only greenhouse gasses, but also acid rains and radioactive ashes. With some research, fast neutron reactors may become reality and those will burn nuclear wastes and also make their own fuel out of thorium.

May 04, 2016
Gigel, I have heard the promises of nuke supporters for most of my 71 years.

Instead, we got hundreds of thousands of tons of radioactive waste we cannot even store safely, costly electricity, Fukushima, Chernobyl, and the next several disasters.

Give it up. we do not need it.

May 04, 2016
Fukushima, Chernobyl, ...
Most of the anti-nuclear/pro-renewable activists already have their well-deserved public reputations as over-exaggerated liars/fibbers/pretenders/manipulator fear-mongers.

May 04, 2016
Why isn't Benni, supernuclearengineer guy on this thread? Seems like it would be a natural fit for him...

May 04, 2016
He's off differentiating.

May 04, 2016
WTFlux, we have heard it before. I am 71, and have seen too many of these schemes which will save us. Nope. Time ran out already. If you can build one, good luck, but do not believe it will solve any problems
Newcomers to this site need to be informed that gkam/George kamburoff has proven himself to be a serial liar and fact-fabricator.

Engaging in discussion with him is therefore pointless as he participates here not for mutual enlightenment but for attention, and for the thrill he gets from deceiving others.

George kamburoff exhibits all the aspects one would expect to observe in a psychopath.

If you want to learn more about psychopaths however, feel free to poke and prod George kamburoff at will because he has deluded himself into thinking that because of his superior nature, no one here is on to him.

Only a psychopath with decades of practice in self-deception could maintain that frame of mind.

May 04, 2016
for the thrill he gets from deceiving others
Well then I would guess he goes to bed feeling pretty disappointed after spending his days here thrill seeking. So far he has not deceived anybody but himself in thinking he is getting the best of the "goobers" here. (And a few peoples who feel sorry for him, but I think that has to do with intra-tribal sympathies like "the enemy of my enemy is my friend" so to speak, eh?)

May 04, 2016
I suggest we start a pool for which nation screws up and has the next Nuclear Emergency. Do we need a complete meltdown for that category? A minimum number of square miles made uninhabitable?

We have a lot to decide.

May 04, 2016
How do you gather these into your TWT? Looks like we might have a few loose in the water. Interesting. Wonder how to be an electric eel under digital control. Yeah stupid idea. Physics! Maybe we can even find a better way to shake the particles loose under our controls. Prove me wrong? I can't place the bet, I have no tools. But I can define a measure to ping anything either an EMF pulse to spec or particle at speed to event. Each event has a set of keys. Music. the universe speaks to us in musical tones and occasional tiny bells and on and on.

May 04, 2016
OK, build a cite that can harvest the matter as a plasma without the explosion; then contain the electrons and protons separately. now regulate the current flow, via volume speed and density flow. But I would not call it waste until I understood why Not. It sounds a lot like a TWT on steroids, Something Tesla would probably come up with. A self contained self regulating system, too big to fail! In fact build with all the material in mind. Build the system to deplete the matter on control. We can define nanobots to exist here and die away or refresh themselves, small challenge. WE have the knowledge bank of NASA.

May 04, 2016
OK, build a cite that can harvest the matter as a plasma without the explosion; then contain the electrons and protons separately. now regulate the current flow, via volume speed and density flow. But I would not call it waste until I understood why Not. It sounds a lot like a TWT on steroids, Something Tesla would probably come up with. A self contained self regulating system, too big to fail! In fact build with all the material in mind. Build the system to deplete the matter on control. We can define nanobots to exist here and die away or refresh themselves, small challenge. WE have the knowledge bank of NASA.

You're not related to the betterexists person on here, are ya...?

May 08, 2016
It still comes down to, as they so very close to all but said, is that they need to be able to study things going several orders faster than we are able to detect now because they are detecting finer structure yet in the finest structures they can clearly or semi-clearly define, there is highly detailed and intricate structures at that level that do things that we presently do not understand, it took until recently to figure just Exactly why the light from butterfly wings seemed brighter than the ambient light, partially because it was transforming some of the ultraviolet by stepping it down through a crystalline structure. We are getting there, but they see the need to be able to see not only smaller, but at the same timeframe as the size is, but we look at tiny things and apply macro tie scales to it, so obviously there are holes and warpsand aberrations in their observational windows.

May 08, 2016
WhatTheFlux is also right, GE originally set the whole system to be run on two types of reactor, slow 'burn' (term used for convenience), which was actually the more dangerously radioactive one as it was splitting primarily the larger Uranium cores. The 'used' rods were to be transported, usually just a matter of hundreds of yards was the plan, for them to do the Hot Burn phase, which while it burns a bit hotter physically, it was doing a hotter breakdown of the more dangerous secondary radioactives produced from the 'Slow Burn'. However, scared NIMBY folks convinced their Representatives to Not Have The Hot Phase built at ALL. So, we have these pools of rods meant for about a dozen cycles back and forth, instead stuck on a single use, 'disposable problem' system. Properly built and responsibly run nuclear programs are rather safe, the US Navy program has been VERY Safe, and the Europeans, after initial bumps. But the Hot Burn will remove much radioactive waste to safer forms.

May 08, 2016
This comment has been removed by a moderator.

May 08, 2016
Uncle Ira 4.4 /5 (7) May 04, 2016

(And a few peoples who feel sorry for him, but I think that has to do with intra-tribal sympathies like "the enemy of my enemy is my friend" so to speak, eh?)


Why do you think you score 4+ constantly? Hate to break it to ya coonie, but it's not the witty repartee.

May 08, 2016
We discover new nuclear physics that will be used in all sorts of ways to improve our understanding of quantum physics, and all Gracie can do is whine about how dangerous nuclear energy is?

Pitiful.

May 08, 2016
"Gracie"? Is that limit of your verbal skills?

No whining here. Just educated concern.

I think if you had done the testing I did, you might have another opinion.

May 08, 2016
Uncle Ira 4.4 /5 (7) May 04, 2016

(And a few peoples who feel sorry for him, but I think that has to do with intra-tribal sympathies like "the enemy of my enemy is my friend" so to speak, eh?)


Why do you think you score 4+ constantly? Hate to break it to ya coonie, but it's not the witty repartee.


I do not care about my karma points. Vote me down, or vote me up, don't matter to me non. Idiots are idiots no matter what their score is, eh? The ones with the highest opinion of them selfs are the only ones who care, and they are the most fun too.

I am just another couyon on the interweb, so I don't invest much time trying to make peoples see me any certain way, as all the ego-maniacs on here tell me all the time, I am irrelevant. (Only problem with them telling me that is, I seem to be the only one who actually believes it.)

May 09, 2016
OK, build a cite that can harvest the matter as a plasma without the explosion; then contain the electrons and protons separately. now regulate the current flow, via volume speed and density flow. But I would not call it waste until I understood why Not. It sounds a lot like a TWT on steroids, Something Tesla would probably come up with. A self contained self regulating system, too big to fail! In fact build with all the material in mind. Build the system to deplete the matter on control. We can define nanobots to exist here and die away or refresh themselves, small challenge. WE have the knowledge bank of NASA.

You're not related to the betterexists person on here, are ya...?

You referring to Higgs? No it can't exist do the math.

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