A nuclear tunnelbot sounds like the end of the world is nigh.
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All deep space / long term probes requires a lump of nuclear material (plutonium) to provide an energy source. Voyager 1 and 2 used plutonium. As did Cassini, Curiosity, and New Horizons.
My Dad was the program manager at GE who led the development of the RTGs on the Voyager spacecraft!