Are you getting a BSOD? When the NUC shuts off do you see any light from it?
No BSOD. It just powers down without doing or saying anything. I thought it was the monitor at first but no light is showing on the NUC. It is definitely turning off. It was odd that it happened while installing the drivers. Hard to say but I think I had just finished installing the Rapid Storage drive. I may try wiping the HD clean and re-installing windows again.
This seems to be a power failure as you say so I think that if the NUC is a new system and issue persists, contact the place of purchase or our support center to get warranty on the product: