Also, if you don't mind, I heard something about antimatter (if ever being used) on the discovery channel once describing that "...a matchbox-sized amount of antimatter would provide more energy than a railroadcar-sized amount of uranium..."
Airways1 - good answer
A normal nuclear reactor running on uranium will harness a uranium decay process to convert a very small % of the uranium's mass into energy, according to E=mc². The final waste products (a few steps down the decay chain) will weigh very slightly less than the original fuel.
With antimatter, you effectively get 200% (IE
the energy equivalent of the antimatter's mass, plus that of the matter it annihilates with). There should be no waste product in the ordinary sense; it's all been converted into gamma rays (&c), which can then be used to heat liquids that drive turbines, like in most other power stations.
So, yes, you could get as much power from a matchbox of antimatter as you could from (say) a railroad car of uranium. That's very true.
The problem is that we have uranium lying around, but not antimatter. If you wanted to create the antimatter first, then (allowing for inefficiencies) you'd need several
railroad cars full of uranium to power an antimatter-producing process for long enough to get the matchbox full.