Deuterium, in larger quantities, yes... like a compressed cylinder, roughly twice the size of a camping propane canister, with a microwave-emitting detonation device and a rip-cord primer handle. This, we call the meltabomb.
Or, on a weaker scale, in massive magneto-resonance chambers housed inside bulky gun-casings, deuterium can be superheated by electricity, then sprayed forward by the magnetic field, producing the effect of a bolt of bluish white plasma gas, racing towards an ork.
Or an even bigger scale, Kawasaki Ninja sized body of ceramic unobtanium-lined inter-stellar torpedo able to survive entry through an atmosphere, containing roughly a one ton TNT equivalent hydrogen bomb without the radiation.. This, we call a melta torpedo.
Back on the subject of Deuterium as a core, in the 3rd ed BGB (the paperback thing they stopped selling maybe 8 years ago?) showed a model of the bolter round, I think, or perhaps it was that edition's space marine codex. Either way, in the old design, it was recorded as deuterium, but I'm sure GW changed the name to depleted uranium when they realized that it was widely known that deuterium was just hydrogen with an extra neutron.
As to the caseless issue. I have seen a lot of diagrams showing bolter shells and their casings. In some, the casing is very short, just enough tubing around the bolter shell to hold it there until the primer is triggered, but in other cases, the casing is much longer, housing about half the rocket fuel inside the casing. I would presume this has to do with ammo stability and making sure the backing (and used primer) are ejected properly without any jamming issues. With an actual casing, you have something big to fish out when it jams, if you have a small back plate with the spent primer, you have little to reach for, and probably won't be able to dislodge it.