Nuclear Sub Accidents

This is an excellent post from Remy C’s Green Nuclear Butterfly site, click above.

Written by Hugh Haskell

As someone who served on the same nuclear aircraft carrier as McCain once did (although at different times) I may have some light to throw on this subject, although my nuclear carrier experience was little more enlightening on these questions than McCain's was.

First, naval nuclear power has some advantages over civilian nuclear power. First is size. the naval reactors are much smaller than civilian reactors, and are of a different design, so they are more self-contained than civilian reactors, and they are in a much more restricted environment, which tends to make them a bit safer--clearly the Navy doesn't want it reactors to be blowing up all the time, so they take great pains to build in heavy safety safeguards, and profit is not an issue, so if they need an extra safety valve, radiation monitor or better fire protection, they put it in. reactor personnel are very thoroughly trained, since they cannot call on the manufacturers for help when they are at sea, and, of all the departments that make up the ship's company, only the reactor department is always fully staffed and never subject to being moved to other duties, either temporarily or permanently.

That said, one must always remember that the function of naval ships is, when necessary, to sail in harm's way. We have never had one of our nuclear ships engaged in a battle at sea where shots, bombs or missiles were exchanged, so we have never had to face the prospect of the contamination that might result from a breached reactor in battle. I suspect that it would not be insignificant. However, we have had two nuclear submarines lost at sea, and the Russians more than two.

Neither of our lost subs were carrying nuclear missiles. Both the Thresher and the Scorpion were lost in deep sea accidents. They were both "attack" subs, rather than ballistic missile subs. Scorpion was returning tot he US from an operational deployment when it's accident occurred (circumstances not known for sure and all suggested causes have been rather controversial) so it was carrying nuclear weapons, but not missiles, probably just torpedoes). Thresher was on a test voyage after a major overhaul and so was carrying no weapons at all. Whether either reactor was destroyed in the accidents, I do not know, but it is known that neither reactor was involved in the cause of what happened.

Since naval reactors must have the capability of rapidly varying their power output, and we do not want to have to refuel them any more often than absolutely necessary, they are fuel with weapons-grade uranium, that is, 90% or higher U-235 enriched. The USS Enterprise, the nuclear carrier that both McCain and I served on carries 8 reactors, it has been refueled at least three times, maybe four. The way they do that is to cut holes in the flight deck and all the decks down to the reactor compartment, and pull the whole reactor out with a crane, and replace it with a new reactor, presumably improved and with a longer lifetime (presumably another reason why naval reactors tend to be safer--they do not have old components that have been around longer than the fuel they are using). The newer nuclear carriers have much improved designs and use only two larger reactors.

Submarines are never refueled. They are designed so that the reactor fuel will last for the design lifetime of the boat, and when they would need to be refueled, they are retired from service and broken up. That turns out to be cheaper than refueling them.

The reactors are, I believe, shipped to the Naval Nuclear Reactor Facility in Idaho, where they are dismantled and the spent fuel recovered. What happens to the waste from there, I do not know, but there is clearly plenty of it. I'm pretty sure that the spent fuel in not reprocessed, since, being mostly U-235 to start with, there won't be much plutonium to recover. But the reactor parts are all pretty radioactive by this time so they have to be handled as radioactive waste, and I'm not sure what that process is.

I'm not sure what is done with the Russian Naval reactors. What is pretty certain is that they were not built to anywhere near the standards that our boats were, nor has their waste material been as well handled (such as it is) as ours. They have lost at least three nuclear subs (and several other non-nuclear, but nuclear armed subs) and I think that the reactors in those subs may be leaking radioactive materials into the sea. At least one of them was lost in shallow water, and I don't recall if that boat was recovered. If not, it is almost certainly leaking into the Arctic Ocean at depths that can result in threats to humans.

All reactors, land-based or sea-based, discharge more or less small amounts of radioactive water, mostly containing tritium. Ships are supposed to catch the water to be released and bring it back to port with them, but it doesn't always happen, as recent admissions about radioactivity releases in Japanese waters reveals. It is worthy of note that at one point, the Navy had in its inventory, a submarine detector that worked by looking for the gamma radiation emitted by all reactors, which ended up in discharged water into the boat's wake.

The airborne detector looked for a slight increase in gamma radiation in the water, and then attempted to follow the track of that radiation to the sub. I don't know if it ever worked as advertised, but I recall that they Navy claimed that it had detected at least one Russian submarine with the device. I doubt that it was ever sensitive enough to be a reliable detector, and, of course, it only worked on nuclear-powered subs, which were never a majority of the Soviet submarine fleet.

A long response to a short question, but I hope it clarifies things a bit.

So how long does one submarine last for?

Not being a submariner, I don't know the answer to that question, but it's at least 15 years, maybe more. I think you can figure out the answer by looking at the commissioning and decommissioning dates for nuclear submarines in "Jane's Fighting Ships," which includes that kind of data. It might also be found in Wikipedia.

I left Enterprise in 1969, as it was entering the shipyard for its second refueling, which was scheduled to put reactors in that had a 15-year lifetime. So it has been refueled at least once since then, probably around 1985 (I retired from the Navy in 1976, so didn't follow those details much after that). Whether the reactors installed in 1985 had a 20-year lifetime or a longer one will determine if it has been refueled a fourth time. In any event, that one is likely to be its last, since it has now been in service for over 50 years, a very long time for a warship. It will be refueled a fourth time (if it hasn't already), and it is scheduled for decommissioning sometime around 2030, by which time it will have been in service for 75 years.

But submarines have a much shorter lifetime, especially modern ones with maximum depths well in excess of 1500 feet. Cycling to and from those extreme pressures accelerates the metal fatigue of the hull, and that is mainly what limits their useful lifetime. Nuclear reactor lifetime can be adjusted to pretty much whatever limits are imposed by hull life.

Hugh Haskell

United States
USS Thresher (SSN-593) (sank, 129 killed)
USS Scorpion (SSN-589) (sank, 99 killed)
Both sank for reasons unrelated to their reactor plants and still lie on the Atlantic sea floor.