The weapon, a high-speed nuclear-powered torpedo, isn't like other nuclear weapons. While there's a risk of radioactivity any time an atom is split, nuclear weapons have typically used nuclear detonations to create heat and pressure, with lingering radioactivity emerging only as a dangerous side effect.

But the new Russian torpedo uses radioactive waste to deter, scare and potentially punish enemies for decades.

"Nuclear weapons only generate significant amounts of radioactive fallout when they are detonated at, near, or beneath ground level," Stephen Schwartz, the author of “Atomic Audit: The Costs and Consequences of US Nuclear Weapons Since 1940,” told Business Insider.

These types of nuclear explosions "suck up dirt, or water, contaminates it with debris from the bomb, and then lofts it into the atmosphere," leaving deadly radioactive fallout potentially strewn across thousands of miles, Schwartz said. What's more, the bomb is rumored to have its nuclear core coated in a metal that would make the fallout last for half a century.

Russia hasn't specified how big the nuclear warhead is, but Kristensen said reports indicated it's "anything from a normal yield to up to 100 megatons," making it potentially one of the biggest bombs ever built.

Russia has advertised a simple mission for the torpedo: "Going in and blowing up a harbor with the purpose of blanketing a coastal area with radiation to make it uninhabitable" in a "blatant violation on the international laws of war, which require them to avoid collateral damage," Kristensen said.

Russia, which first leaked images of the weapon in 2015, released the video of the torpedo, called "Poseidon," along with several other updates on new weapons programs. Putin announced all of the weapons in a March 1 speech in which he said they'd been designed to defeat all existing US defenses.

The video of the Poseidon shows its stern suspended in a factory with engineers standing by. Lines across its hull indicate where its various components and chambers separate and indicate a large space for a warhead.