Most of the times, you better sell cleaned tantalum. Either nitric-leach the casings (and recover silver from it - that will usually pay for the acid cost), leaving only tantalum behind, or you can take more "adventurous" route.
I cannot personally recommend this route, because it can be very very dangerous, but it is done fairly often to cut the nitric acid waste.
If you heat the caps in the steel drum past like 350-400°C - electrolyte inside will boil and cause them to explode. Loose, but heavy cover is required, as the explosions can be quite vigorous - like firecrackers. Then, after you are assured there are no more any "live" ones, you feed them into the crucible and melt. Tantalum dissolve poorly in CuZnAg melt, and porous pressed tantalum electrodes will float onto the top of the molten puddle. You can either fish them out or strain them - but do not use stainless to do this, as it will quickly erode. You will be left with brass containing few% of Ag and caked tantalum electrodes covered with brass. This, you can leach in nitric acid as the whole caps, but this time, you will use significantly less acid and make significantly less waste. And cast CuZnAg alloy can be electrorefined (after zinc removal) to recover the silver.
If you does not proceed diligently with first "popping" stage, and some "live" caps will remain to the melting stage, you can imagine what an exploding cap in molten metal will do. Ugly, bad things.
*Edit: electrolyte is most often some sort of sulfuric acid based one, so be prepared for H2SO4 vapor coming out of the drum. I posted this just as information, that some "adventurous" refiners do it this way. I personally doesn´t.
