It is the 5oth anniversary of the sinking of the nuclear sub USS Thresher. As I recall, the sub started taking on water, and sank below crush depth-at hat point catastrophic failure of the hull occurred -and the tremendous compression of the air in the hull led to a diesel-like explosion. The sub was basically blown to bits.
Was any radiation from the reactor fuel detected at the surface? I never read of any clean up efforts-was the plutonium, U-235 in the reactor contained? Is the area around the reactor dangerous today?
Wiki says the site is monitored, the reactor is intact, and there has been no notable contamination. I’d guess that’s all true; a reactor might have been crushed in by the depth but would not necessarily have been torn apart. If anything, it’s possible that the containment shell was crushed around the core, all but sealing it.
It’s also 8400 feet down, which isolates it pretty well.
Sad story; killed by low-bid errors in construction.
An aside, but I sincerely wonder about the sub that recently had the interior fire. The fire reached extreme temps (1500 degrees) and lasted for many hours; you can’t tell me that didn’t affect the pressure hull. I don’t know if they have any good way to test the metal, welds etc. the way they were tested during construction. I would not want to crew on that boat…
Incorrect, the Thresher taking on water was not the direct cause of her loss and she did not explode. For exact reasons that will probably remain forever uncertain, she started diving and was unable to pull out of it. At 09:17 her final, garbled transmission including the words “exceeding test depth” was received by the submarine rescue ship Skylark which was accompanying her on testing and at 09:18 she imploded, her hull no longer able to resist the pressure from the surrounding water. A message from her, also partly garbled, at 09:13 indicated “”[We are] experiencing minor difficulty, have positive up-angle, attempting to blow." Norman Polmar, a well known naval analyst who wrote a book on the loss of the Thresher noted the oddness of this message, as it spoke of minor difficulties but also of attempting to blow - a statement analogous to a driver stating he is attempting to apply the brakes.
I remember learning in a High School oceanography class that the Thresher was caught in a pressure wave. It may have been conjecture, but I remember the teacher teaching it as fact (of course this was in 1985, so I could be remembering incorrectly).
Everyone has seen the toys that have two liquids of different densities, one clear and one blue. You can set up waves on the boundary layer, just like waves on the surface. The sub getts caught on the downslope of a wave, and even though it has positive up bubble, it continues to descend to below crush depth, and then “pop”. There were pictures of the wreckage sitting on the bottom of the ocean in the textbook, and it was really mangled.
The ‘diesel-air-compression-explosion’ idea is only a theoretical possibility, one which I think most experts don’t believe in. In fact, large subs that fall below crush depth may not really ‘implode’, at least not like you see in the movies. Only one part of the sub’s hull may fail, then water may enter & fill the rest of the sub so quickly (destroying bulkheads) that the pressure is essentially equalized as it floods.
I thought that the accepted theory on the Thresher’s sinking was that the reactor scramed (did an emergency shut-down for some reason) and since the sub was at less than neutral buoyancy it was only maintaining depth via forward thrust on the dive planes. As they began to sink they tried to do an emergency blow of the ballast tanks, but the filters that the air for the ballast tanks travel thru immediately iced-over and froze, blocking them.
Here is a website that mentions the “wave” theory as speculation:http://www.subsim.com/ssr/thresher.html
Yes, I recall that the Thresher was on its “shake down” cruise, and that all sorts of defects had been discovered-switches wired backwards, welds hastily done. As I recall, the BOI decided that a silver brazed pipe joint had ruptured, allowing a seawater leak to soak a reactor control panel-which caused the reactor to automatically shut down. At that point, the ship was doomed. As for “low bid”-I don’t understand-the ship had been built at the Portsmouth Naval Shipyard, a government owned entity. The disaster spurred reforms, so at least some good came of it.
Did the bodies recovered from the Soviet, Golf-Class SSB K-129 exhibit any signs of scorching? They were recovered from 16,000 feet, and I don’t believe the hatches were open during the descent. The bang from the implosion was what gave the USN a head start on K-129’s resting place, after all.
Physics is funny, though. You could hypothesize just about any weird physical effects and I’d have a hard time dismissing it, considering the sudden release of the force behind 500 bar of pressure
FWIW, the recovered Golf crewmen above had to be buried in lead-lined coffins. Though this was due to their being recovered in the torpedo room of the sub, and she was carrying nuclear torpedoes, which presumably leaked. Somewhat related to the OP, who knows what would have happened if the crewman from the Soviet, Yankee-class SSBN K-219 hadn’t manually SCRAMmed one of its reactors?
nothing to add just pointing out that the OP wanted to know about the safety levels of radiation , not how the sub sunk , but its all good interesting stuff anyway lol !!!
I’ve read a lot about the loss of the USS Thresher, and the consensus is that she was indeed lost due to flooding in the engine room, compounded by the operating procedures at the time, and submarine design philosophy not keeping up with the increasing depths that subs were capable of.
It’s believed that the flooding was caused by a defective silver braze on a seawater pipe in the engine room. The flooding may have been spraying on some of the electrical equipment for the reactor, leading to either an automatic shutdown of the reactor, or the reactor may have been shut down manually by the crew. The philosophy of the naval nuclear power program at the time was to protect the integrity of the reactor core at all costs, which is why the reactor may have shut down (automatically or manually), and why there was no provision for a fast restart.
The other problem was the main ballast tank (MBT) blow system. It was what is now considered to be a “normal blow” system, which had relatively small-diameter, tortuous piping with a lot of bends, and the air was not dehumidified when it was compressed. The system was also not routinely tested for long blows. It’s thought that at some point during the blow, that water vapor in the compressed air created blockages of ice in the lines, and slowing or stopping the evacuation of the MBTs.
At that point, if the crew could not quickly get the flooding under control, they were doomed. This is because they needed propulsion power to drive back to the surface, decreasing the surrounding sea pressure, and decreasing the rate of flooding. Without the reactor on line, though, they had only the residual heat/steam in the steam generators, and incredibly, the procedure at the time in the event of a reactor shutdown was to shut the valves on the main steam headers (cutting off all steam to the turbines) to prevent an over-rapid cooling of the reactor. As the flooding continued, the ship would get less buoyant, and continue to sink, increasing the surrounding pressure, which increased the rate of flooding, setting up a vicious cycle until the sub exceeded crush depth.
Some of the changes as a result of the loss of the USS Thresher include:
[ul]
[li]The number of hull penetrations in subs has been greatly reduced. Submarines used to have hundreds of hull penetrations for various piping systems, which may been OK for relatively shallow-diving subs (such as the WWII-era fleet boats), but is a serious weakness for deeper-diving subs. These fewer (albeit larger) hull openings can also be quickly shut hydraulically in event of flooding. This design philosophy change is part of the SUBSAFE program.[/li][li]The other major part of the SUBSAFE program is setting up a quality assurance program for all work conducted and materials used on hull integrity and piping systems exposed to sea pressure.[/li][li]The reactor is kept online during flooding, and can be quickly restarted if it automatically shuts down. If the reactor is shut down, steam can still be drawn off of the steam generators, though the rate of cool-down is closely monitored.[/li][li]A backup “emergency blow” system was added with much larger diameter, shorter pipes. Also, the compressed air used is dehumidified, and the system is frequently tested.[/li][/ul]
As for the integrity of the reactor core of the USS Thresher today, it is believed to be intact. As designed, the surrounding seawater would have provided sufficient cooling for decay heat in the immediate aftermath of the disaster (which is what caused all the problems in the Fukushima accident). The fuel cladding and reactor pressure vessel were also designed to contain the fuel, even if the submarine sank.
Good post Robby. Let me simply endorse above comments that the Thresher imploded - not exploded which is the rather more dramatic but wrong impression of events. As for radiation, these machines are not bombs - even nuclear torpedos - and there is no engineering reason to expect significant release of radio-active material.
Yes it could happen. But the amount would be small over a period of time.
Just as a side note of general frustration - does nobody teach nuclear physics these day for pitys sake? The precision required to create an atomic explosion is mind numbingly precise meaning that accidental explosions are unknown. They do not happen.
Yes, but how the sub was ultimately destroyed is a key factor in estimating any radiological contamination, i.e how it ultimately broke apart/exploded/imploded etc.
Nothing much to add, but one of the guys who was sent to look for the wreckage was the professor of the elective Oceanography class I took in college. As a “one-off” lecture, he gave us a slide-show of the wreckage (that which wasn’t classified) and told us what he could about the disaster.
I found it fascinating!
I suppose I wasn’t entirely clear in what I meant, I was replying to ralph124c’s statement that the flooding caused her to sink and that she exploded. What I meant by it not being the direct cause of her loss is that in and of itself taking on water from a failed pipe should not have caused her to sink; she should have been able to surface either from the positive up angle of her sail combined with increasing her speed or by blowing her ballast tanks. For probable reasons you have noted, she was unable to do either. The flooding was certainly at least a contributory or indirect cause for her loss.
My question about the Thresher possibly exploding was prompted by Robert Ballard’s discovery that the wreck was in a million pieces-is it reasonable that the reactor survived intact? Or was it broken apart as well?
It is reasonable to assume that the reactor core and reactor pressure vessel survived intact, and periodic monitoring of the wreck site has confirmed this. A reactor pressure vessel is much more robust than the pressure hull of the submarine itself. (And before you ask, the reason why the pressure hull of the submarine cannot be designed to a similar level of strength as the reactor pressure vessel comes down to size and weight.)