First of is an EPW version really that necessary?
The B83 has a lot of omp for destroying a large area down to a certain depth. If enough damage around the entrance is affected it could make any attempt to dig out impossible.
With conventional nuclear weapons, the most you can hope for is damaging entrances. However you must have ironclad intelligence on the exact location of all entrances, and must not miss even a single entrance/exit (including emergency exits). Then even if you succeed in perfectly targeting and destroying all of them, the bunker will remain intact, and the people inside will still be able to survive and continue their duties (including prosecuting the war or authorizing follow-up nuclear strikes) for potentially weeks. Even worse, those destroyed tunnel entrances can be dug out given enough time, heavy machinery, and disposable workers.
From a functional military perspective, if you have a buried command bunker that you need to be destroyed, conventional nuclear weapons are painfully inadequate for this task unless the bunker is extremely shallowly buried and extremely poorly hardened.
Now what if you have an EPW? Not a piddly B61-11, but a proper RNEP, capable of deep penetration even in the most challenging soil conditions, precision targeting, and high blast yield? Then a single bomb can destroy the entire buried command complex in one hit, collapsing all of the buried tunnels and rooms, killing everyone inside, and destroying any infrastructure (or munitions) hidden inside the complex.
Yes, there are ways to armor buried command bunkers even against high-end EPWs, however the amount of time, money, and effort required makes these types of ultrasuperhardened command bunker complexes nearly impossible to construct even by the great power nations. We studied building one of these at one point, but ultimately decided against it because of the insane costs involved.
For an EPW version of the B83 with typical coupling factors, you can expect equivalent yields in the 18–30 megaton range. Let's call it 24 megatons.
I don't feel like rehashing the entire explanation for why EPWs are so much better than surface bursts for holding deeply buried targets at risk. It's long and complicated and I have far better uses for my time than hand-holding you through all of that. Instead, I'll refer you to the following chapter of the 2005 NAP report on EPWs. Please read it in full.
Read chapter 4 Effectiveness of Nuclear Weapons Against Hard and Deeply Buried Targets: Underground facilities are used extensively by many nations to con...
www.nationalacademies.org
We do have penetrator upgrade examples with a simple replacement of the shell steel material. Depleted Uranium would be best in terms of queezzing as much mass as possible into limited volume. What would change now is moving the nose crunch area to the larger casing body. Increrasing nose material volume for penetration performance, increase tail mass to serve as a pusher.
Yes, and that kind of work is effectively what the SEPW/RNEP programs were focused on. The SEPW program is what did the initial work on building and testing several variants of the B83 that had been modified for EPW use. The same design concepts would have been reused in the RNEP program, and are likely to be reused yet again for this modern nuclear EPW program if the B83 is once again selected as the baseline warhead to use for said program. Even if the B83 is not selected, the same work done on the B61 for said programs will be reused. Of course further additional work will still be required beyond that as well.
A pusher is not necessarily required. The need for one strongly depends on the L/D of the penetrator. For the B61 this ended up being needed in the end. However the B83 may or may not need one.
The B83 is a very heavy bomb compared to the B61 (over three times the weight), so it already has plenty of mass in it to begin with.