Nuclear Batteries

[The Thing]

What are some ways that researchers are currently harnessing nuclear power for batteries? I know the RTGs and those using decay heat to heat water to generate electricity. I've heard of the Beta Voltaic way, what's that?

Are there any other ways to create efficient nuclear batteries? And how do they get rid of the materials after the battery's exhausted after decades? Like the water from a decay heat battery?

Thanks.

[DV8 2XL]

Try this link;

 

http://en.wikipedia.org/wiki/Atomic_battery

 

Which I modestly admit to having worked on.