Nuclear Submarine

Several movies have involved an out-of-control nuclear reactor aboard a nuclear submarine. We are told that the containment vessel is about to fail and that the best action is to move the sub several hundred meters underwater. When the explosion occurs down there, what might happen?

Answer

Submariners love to dive in their submarines. A dive to several hundred meters under the surface may be effective in limiting the initial spread of the debris from the thermal explosion. No nuclear explosion would occur, or else everything around would be vaporized by the energy released, in which case the depth in the water would help very little in preventing the spread of energy in many forms. The thermal explosion in a nuclear reactor in the sub releases the fuel and coolant, so radioactive particles and debris will be sent out in all directions. Some of this stuff would be slowed effectively by the water, and some probably would make the surface and escape into the air.

When the Chernobyl nuclear reactor broke its containment vessel in the 1980s, its nuclear particles were detected around the world within hours to days. At the University of California at Irvine, the air filtering system at the local nuclear reactor recorded the radioactive cesium and iodine particles in parts per billion from the Chernobyl incident 10 days after the chemical explosion.