Are US Navy Nuclear reactors "Fail Safe"?

I just saw the Harrison Ford/Liam Neeson film “K-19”-about the tragic accident aboard a Russian nuclear submarine. In the film, a cooling pump inside the reactor fails, and the crew is faced with death (core overheating) , unless they can jerry-rig an emergency means to cool the reator. This they do, by entering the reactor compartement and welding a pipe to the reactor (and cooling it with water pumped in). Of course, all of the men who volunteer for this duty get cooked by radiation…but they do save the ship.
My question is: are the reactors in US navy subs designed such that they can survive the loss of the cooling pumps? Are there sufficient backup systems such that what the poor Russian sailors had to do, would never be done on a US sub?
I believe that most of the crew ofthe K-19 died later from radiation posoning…was there any other way tosave thisship?
I also recall reading that later Russian subs had two reactors 9presumably as a safety measure). Did the improve the design of these?

I have no idea of its accuracy, but in the movie they made the point that the backup system simply hadn’t been installed because they rushed the sub out of port too quickly.

I’ve read that the actual sailors from K-19 liked the movie, though they did say it was exaggerated in typical hollywood style.

Sorry that I don’t have a cite, but I recall a program on Discovery or History that explained the redundant systems built into US nuke subs to preclude the same sort of thing as happened on the Soviet boat.

If they are, the current season of 24 is shot. :eek:

All US Navy reactors follow one of a few well-tested designs, and of these, all of them are of the Pressurized Water Reactor variety.
They are designed with an interesting feature: they are inherently stable, for reasons I describe here and here.

All Naval reactors have systems to protect the core in a loss-of-flow accident. In a submarine, they can open certain valves and allow seawater to simply flow over the core, entering and leaving the sub by natural convection. Of course, the plant is trashed, but the core doesn’t melt down.
In a surface ship, they have a Reactor Fill system that is designed to pump thousands of gallons of water into the reactor vessel in the event of something awful such as a ruptured coolant pipe. Mind you, this system is designed to handle things far worse than a coolant pump failing. One would want to get off the ship pronto.

Of course, pumping cold water into a pressurized water reactor has its own dangers, ranging from brittle fracture to uncontrolled power spikes due to the very same auto-stabilizing mechanism I described in those linked posts.

I do recall that the emergency procedures for such events also involved everybody hiding behind turbines, generators, and any other large chunk of metal that could be interposed between onesself and the reactor compartment :eek:.

In addition to the various means of controlling and cooling the core in a loss of coolant accident, many US sub plants today operate without cooling pumps, at all, depending entirely on thermally driven natural circulation.

Also the pumps used in the US Navy’s nuclear plants are as close to never-fail as we currently have. I was an engineering sailor on the USS Virginia, and no one had done any maintenance on our main coolant pumps during the entire lifetime of the ship. Granted, such reliability isn’t achieved cheaply. But, by making the entire pump sealed, and over-engineering the pump for the stresses it is expected to face, it is hard to imagine any scenario where cooling the core would be a problem similar to what you’re describing from the K-19 scenario.

However, there are costs for the way that the Navy runs/operates its plants: compared to a civilian power plant where something like 90%, or more, of the heat generated by fission is used to generate electricity, Naval plants have an efficiency closer to 30%. Part of that is that naval plants have to operate at many different load conditions, instead of just at one optimal, and maximum, rating. But much of it is the redundancies, and controls built into the Navy’s plants.*

  • This is not a swipe at the safety of civilian plants. Just a recognition that naval plants have to worry about scenarios that civilian plants just don’t have to consider. Battle damage, for one.

And comparisons between US nuclear subs and Soviet subs can be hard to make. For the longest time the US intelligence community believed, for example, that the Soviet Alfa class submarine had to have a liquid sodium cooled reactor plant to be able to produce the speed noted in the field by actual observations.

The reality proved to be both chilling, and much different: The Soviets instead simply skimped on the shielding on the reactor between that and the crew. :eek:

I don’t have the numbers available at the moment, but my understanding is that soviet sub crews (the whole crews, not just the engineering sailors) were expected to be getting exposed to about 1 REM for every cruise they went on. For contrast - in the Navy, most submarine sailors actually recieve less dose during a cruise than they would being on shore, and exposed to sunlight and cosmic rays.

I know that during my time in Admiral Rickover’s Navy the people who got the highest dose from the reactors were either standing watch right next to the secondary shield - or spending a LOT of time on the weather decks. :slight_smile:

When the crippled Russian sub surfaces, the captain (played by harrision Ford) debates asking for help from the Americans. They refer to some kind of military base on Jan mayen Island (a Norwegian island in the Arctic Ocean).Is there actually a US Naval base on Jan Mayen Island? Or is it some kind of listening post?

This particular submarine , is a los angeles class 688 attack submarine, after it hit a seamount in the middle of the pacific doing 30 knots horizontally ,and then 4 knots vertically

city of san juan

Some egghead did the math on how much kinetic energy was released when the boat hit the mount and essentially compared it to a small nuke.

But for the original post , the reactors imediately scrammed and shut down, and the boat was able to limp into port on its own power, with assistance standing by if needed.

Some of the soviet submarine power plants were underpowered ,from what I heard , using two reactors was just a way of getting the equivalent amount of speed that a single western reactor would produce.

As well, if you remember watching the movie , the hunt for red october , you might have heard a phrase being mentioned , called a crazy ivan. This was due to the fact that between a quieter american power plant ,and soviet sonar tech , American boats were able to stay on the tails of soviet boomers and the russians would not even realize that they were there , until one john walker told em, hence that particular maneuver to clear the baffles.



It wasnt the San Juan that bounced, and by the way, it isnt the city of san juan, it is the USS San Juan. The only city of is Corpus Christi…

It *might be City of Cporpus Christi, notice it has sail planes NOT bow planes. It is a standard 688, whereas the SJ is an improved 688.

Damagewise, kiss off the sonar dome to begin with, sphere is covered, so cant tell bit it doesnt look good…, hydrophones probably well over 100 dead, foreward oxygen bank - if not damaged then compromised and very expensive, torpedo door fairings are toast, doors possible and linkages are in serious question, air banks 1 and 3 need examination [along with all the associated piping] the external portions of the main ballast tank blow system. Unless the navy wants to put in serious amounts of money and teh DoD will pony it up, it might be more cost efficient to just scrap the boat than repair it…and the money would be better used in overhauling a vessel that isnt as damaged - and as this is an older 688, it probably isnt worth the effort of repair anyway.

Did I mention Mr Aru was on the San Juan at one time=)

And the boat is the San Francisco. My husband served with the sailor that died. They were both stationed at NSSF Groton together. Small community=(

U.S. Navy reactors are just about the most fail-safe design possible for a nuclear reactor. They are all but idiot-proof. As minor7flat5 detailed so well in the thread he linked to, they are also inherently stable. They are truly an incredible feat of engineering.

For reliability, virtually the entire engine room is duplicated down the middle. Every major system, including steam generators, electrical turbogenerators, main engines, condensers, steam generators, etc. comes in independently operating pairs.

The reactor design itself also includes numerous backup systems. On the type of plant that I’m most familiar with, the S6G used in the 688-class of submarine, we had six reactor coolant pumps. Only four were needed for full-power operation. In an emergency, with a shut-down plant, only one would be needed to deal with residual decay heat. If all the reactor coolant pumps failed, there were other procedures available to deal with decay heat, including using natural circulation or a coolant feed/bleed.

In a loss-of-coolant casualty, we had three coolant injection pumps to inject make-up cooling water. For cooling water, we would first use the highly purified water designated for that use, and if that ran out, we would use potable water, and if that ran out, we would use seawater.

We had procedures for every imaginable casualty, and we trained constantly. Not to put too fine a point on it, but we also had the most intelligent personnel in the U.S. armed forces, and that is no exaggeration. Each nuclear-powered ship also has an annual ORSE (Operation Reactor Safeguards Examination) administered by Naval Reactors out of Washington, D.C. that makes or breaks careers.

We had regular materiel inspections, and if something broke, no expense was spared in getting it fixed. On my sub, we once had a $75K spare part flown to us in Norway via a C-141 flight that was set up with less than 12 hours notice. On another occasion, I had an auxiliary seawater pump ground out on me one Saturday morning, shut down in port. Within two hours, welders from the support activity on shore were cutting decks out of the way with welding torches to remove the pump. We were supposed to be getting underway the following Monday, and we made it with a newly replaced pump.

On preview, Aru, the boat I’ve been describing in the post was my sub, USS San Juan (SSN 751). :slight_smile: The boat in the photo is, of course, the USS San Francisco (SSN 711).

Of course, the scenario is very real, but is this a true story? I don’t know much about accidents in the Russian fleet of subs… If so, do you know when was this and what class of sub it was?

The posts by both “Danceswithcats” and “Engineer_comp_geek” imply it is at least based on a true story, correct?


  • Jinx

As I understand it, a naval nuclear reactor tranfers heat from the core via a primary circuit, in which pressurized, very hot water circulates inside the core, and out to a heat exchanger. This heat exchanger then heats the water in the secondary circuit, which flasghes into high-pressure steam, driving the turbine (which drives the propeller shaft and the generators, etc.). The primary coolant becomes radioactive due to bits and pieces of the piping coming off…but the secondary coolant shuld be radiation free. In the Russian K-19 sub accident, the primary coolant leaked into the main compartment-presumably the sailors tracked the contamination into the other parts of the sub.
My question: if the soviet subs were so dangerous (i REM/voyage is a pretty severe dose), how did the Soviet Navy get volunteers for the sub fleet? I would think that this kind of duty would be shunned!

ralph124c, there would have to be a series of failures to cause what you have described:

In normal operation, the primary coolant is somewhat radioactive, due mostly to the fact that the water itself is passing through intense radiation, so any atoms present in the coolant (water itself, hydrogen, nitrogen, whatever) have the possibility of becoming radioactive. The stuff from the pipes usually collects in low-flow points in the system and causes hot spots, dominated by cobalt-60.

Having said that, the primary coolant normally is not terribly radioactive. Indeed, the Engineering Laboratory Technician (me :cool: ) draws a sample of the primary coolant every day at midnight and perform all kinds of interesting tests on it. We extracted the sample into a poly bottle and carried it to the lab in a rubber bucket, following a designated path so that any spill would be minimal.

The real problem with primary coolant radioactivity comes when the cladding of the fuel elements is breached – a fuel element failure. This allows huge amounts of fission products into the coolant, and this is the scenario where we were all supposed to hide behind large metal machinary. Part of our nightly primary coolant tests was looking for the presence of two particular ions that would indicate that fission products were leaking into the coolant.

Now, even at this point, we aren’t talking about people coming in contact with radioactive coolant: all of the coolant is still behind the secondary shield, in the reactor compartment.

If there is a further failure, a leak in the tubes of one of the steam generators, then the primary coolant could mix with the boiler water, causing radioactive coolant to circulate throughout the entire plant.

Even in this case, the steam plant is a closed system; virtually all of the boiler water is recirculated. For things to have progressed this far, the reactor would have to be in fairly sad shape, and would have likely been shut down at the very first sign of failure.

If there’s highly-radioactive coolant mixing with the boiler water, the sailors would have far more problems to worry about.

You have to know mrAru…

He has some great stories about repairs also - like doing the weapons shipping hatch in La Mad, and I have seen his rack full of parts when leaving on a run [he slept in a hammock in machinery 1 more than one run until his rack emptied out enough=)]

He had fun as a QA inspector his last shore duty. I still can’t believe what some of the yard workers think they can get away with!

The only real spanner in the works as regards the boats future disposition , is that it was just recently refueled, had the boat been approaching its refueling ,yeah it would have probably been scrapped.


Umm… 1 REM per voyage is a lot, compared to, say, a US naval plant. On the Virginia we averaged (including the high dose watchstanders with the low dose ones) about 8 mREM/month, or say 35 mREM/quarter while underway. (You really can’t compare cruises on subs and surface ships - and I was a surface fleet sailor so I can’t give you dose numbers for US subs, but I’d be surprised if they weren’t less than the ones we had.

1 REM is not biologically dangerous. Per Federal regulations, radiation workers are allowed to get up to 5 REM a year, and that’s considered to be a dose well below the point at which any immediate radiation effects will be noticable. The diference is that the Soviet Navy was accepting about 30-50 times the dose rate for its sailors than the US Navy would allow. (Which is limited to about a tenth of the dose allowed by Federal standards.) I just think, personally, it’s an excellent example of the way that the old Soviet system felt about where to cut corners - people were cheap and plentiful. :eek: :frowning:

The other thing to recall is that the Soviet military was running on universal conscription, IIRC. I don’t recall whether the Soviet sub fleet was volonteer, but the military had three levels of personnel, compared to the US’s officer/enlisted split: They had conscripts, who were serving usually a two year term, and didn’t often recieve any specialized training; they had mid-range NCO’s who were volonteers staying in for more time - I’m not certain if they were career enlisted, or not - and who got some training; and they had a career officer corps who were the only people who got the level of training that the lowest ranked enlisted engineer got in the US Navy.

You literally cannot imagine the difference between crew quality in the Soviet and US fleets. Given what I’d read of the Kursk accident - the modern Russian Navy is still far under-trained compared to the US. I am not trying to disparage the morale of the Soviet fleet - or their ability to fight. Just that there was, and is, a measurable difference in crew composition.

Oh, and like Minor7Flat5 says - the primary coolant in the reactor isn’t all that hot. There are stories of Rickover drinking some in front of Congress to make this point. And I can neither confirm, nor deny, that other ELT’s (And, yes, I was another Easy Living Tech, too.) aboard my ship may have claimed to be able to taste when the primary plant needed a chemical add. :eek: :smiley:

Another question regarding the movie, what´s up with red wine as a tretment for radiation exposure???

No clue, here. Never heard of it, before. The question that immediately comes to mind is whether this is a treatment similar to whiskey for snake bit - a means to anesthesize the dying?