I RTFA and did not find how the battery actually produces power - is it with a typical steam turbine, or some novel new system? The compact size of the battery also raises some interesting engineering problems. The one I am most interested is shielding - if there is not enough shielding between the reactor and the cooling parts, the radiation will corrode the parts to the point of failure, which is bad especially underground. It does make a lot of sense to use this for remote outposts like mining though.