So what are the implications for reactor design, physicists?
Probably not much. There's so much empirical data about the behavior of fission in reactor-like conditions that, even without a deep understanding of why things happen that way, we pretty much know what happens. That's almost certainly why they simulated the reaction they did -- we have tons of data about it already, so you can tell if the model's good.
Some slight refinements might show up eventually, but the impact of a model like this on reactors will be small.
Most nuclear physicists aren't researching fission reactors, though. The ones pushing the boundaries of the field, coaxing colliders into producing heavier nuclei, investigating weird excited states, and such, are the ones who will really notice this.
It's been 25 years. I can do this for another 25.
Arlo Guthrie would be proud.