I've read about some theoretical designs that would open the field to allow all negative charged particles out and use these electrons as power directly.

But first, designs would have to be able to keep the containment pressure/temperature much higher than it currently is.

https://en.wikipedia.org/wiki/Aneutronic_fusion#Energy_captu...

The Focus Fusion http://lppfusion.com/ reactor does direct conversion to electricity.

A Shame these guys are the least funded contender in this race and could do their research on a rounding error from ITAR.

Steam initially, but effect ways of converting all that heat to electricity are pretty limited at the moment.

One way to convert the heat from radioactive decay into electricity is through thermocouples (typically found in RTGs used on deep space probes and Mars exploration craft). They're incredibly inefficient though, less efficient than simply turning steam turbines.