The Russian Atomic Powered Cruise missile

I'm not sure how many of you read about this but I found it pretty interesting because one blew up recently and killed several Russian Scientists. Putin wanted an unlimited range Cruise missile that could fly at about 10 to 20 feet off the ground to evade radar detection over water or land and because no human is on board it could make course corrections that would literally kill anything living that was on board because of the severity of the movements up, down or sideways. But, the problem with a cruise missile like this is it would radiate all lands and ocean that it travels over with radioactive fallout and would carry a nuclear warhead but it would have unlimited range simply because it is atomic powered as well. So, once you launched something like this it could travel anywhere mostly undetected except from space because it would run under the radar which I think need things to be at least 100 feet or more above the ground to detect them.