Ever wonder what happens to old nuclear bombs when no one needs them anymore?

It's way more complicated than parting out a '67 Chevy.

In the case of the B83, one of America's most potent thermonuclear weapons, some of those parts are coming to Savannah River Site.

We're just not sure how many. Or when. That's a tightly guarded secret.

For the past three years, the National Nuclear Security Administration, which keeps track of nuclear weapons and related materials, has been preparing the Y-12 Security Complex near Oak Ridge, Tenn., for a new dismantling program for retired B83 warheads.

Last week, in a short press release, the NNSA acknowledged the new Y12 facilities and personnel had completed the first such "dismantlement"  and that others will follow.

Barely 12 feet long, and weighing about 2,400 pounds, the B83 was first deployed in 1984. Published reports say at least 650 of the bombs were built, each with a 1.2 megaton explosive capability, which is about 80 times more powerful than the 1945 Hiroshima bomb.

As part of an effort to reduce the nation's nuclear arsenal - and also protect leftover parts from exploitation by terrorists - many of those warheads are being retired.

As far as the specifics of the B83 program, and the role of Savannah River Site, here is what NNSA had to say:

"When a weapon is retired, it is returned to the Pantex Plant in Texas, where the high explosives are removed from special nuclear material, and the plutonium core is removed from the weapon. The plutonium is placed in highly secure storage at Pantex. Non-nuclear components are sent to the Savannah River Site and the Kansas City Plant for final disposition."

Officials at SRS say the most common leftovers bound for South Carolina would be reservoirs of tritium, a radioactive gas used to boost the weapon's explosive power.

"Nuclear weapon disassembly is principally conducted at Pantex and sub-assemblies from dismantlements (like the reservoirs and many other parts) are sent to other NNSA facilities, such the Savannah River Site," a site spokesman told me.