lol
That would be a great story.
If you can make it short enough you should submit it:
I know...
Someone already did a similar one.. Way back in time (as in decares ago) when I had subscriptions of IASF and F&SF mags (and it seems there was one other), one of them published a story along those lines, but instead of powering a tunneling device, the unit was used as a garbage disposal providing the useful service of disposing of the trash while supplying useful energy. Until one day someone tried to adjust it..
The device emitted a sound similar to "poof" and the energy output ceased. They discovered a miniscule round hole in the flooring. And in the concrete basement floor directly below..