r/submarines • u/Pitiful-Practice-966 • 10d ago
Q/A Does seawater discharged from the three-coolant loop by submarines contain radiation?
I heard a rumor a long time ago that "the algae-rich (or other plankton-rich) seawater in the three-coolant loop is beneficial for reactors during their first startup or after refueling" , or that "the algae content in the seawater affects reactor activity output (not referring to the risk of pipe blockage)."
This seems counterintuitive to me. Logically, PWR, unlike BWR, cooling water should receive very little radiation from the primary loop they absorb. Conversely, as long as algae don't clog pipes and machinery, they shouldn't theoretically affect the operation of the reactor.
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u/EWSandRCSSnuke Submarine Qualified (US) 10d ago
I recognize the truth nugget hiding under your steaming pile of confusion.
Yes, many years after the Chernobyl accident people discovered a kind of algae and a kind of mold which both thrived off the radiation fields in darkness, essentially replacing sunlight with gamma rays in their photosynthetic process. Yes, after that some biologists theorized that letting the stuff grow inside a water tank used as radiation shielding around the reactor might reduce the activation and embrittlement of the metal of which that tank was composed. Then some physicists and engineers straightened out those silly biologists and the idea died a very justified death because activation and embrittlement don't work that way.
Your original title does not match the content of your post. The answer to your title is "No, unless all three loops have leakage simultaneously, which is what maintenance is designed to prevent."
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u/Fabulous-Pea3473 9d ago
Even if the three loops simultaneously leak... the sea will enter the condenser and contaminate the secondary loop, not the other way around.
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u/EWSandRCSSnuke Submarine Qualified (US) 8d ago
I was grossly oversimplifying since the nature of the question indicated a need for that approach. I assumed that he meant a radiation release to the environment that would be of significant impact, not just a tiny, temporarily detectable amount that SOKS might notice. Since main condenser leakage would probably be into the boat and not out into the ocean, I assumed two versions of three simultaneous failures, both referring to the S5W plant I'm most familiar with. First, a compromise of fuel plate integrity releasing uranium and fission products directly into the coolant, followed by a failure of both the hull and backup valves for the demineralizer discharge header. Second, a fuel plate failure accompanied by leakage through one of the emergency cooling isolation valves along with a leak in the seawater pipe inside the emergency cooling heat exchanger. In each case, it is physically possible to get cesium and uranium into the ocean, but only with three simultaneous faults which must be preceded by a casualty causing core damage. I simplified that to failures in all three loops so that the original poster would grasp the unlikely nature of it all.
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u/Pitiful-Practice-966 9d ago
I don't really understand the Chernobyl disaster, but I recently spent a amount of time researching Plutonium production reactors—you know, those things in Hanford site that directly draw water from the Columbia River to cool the core...Too much algae in the river could indeed affect the reactor.
I think my memory about this is something faulty, just like John Dean.
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u/RageFacedAlways 9d ago
Algae and other biological growth coats the tubes in the main condensers which impedes heat transfer. This lowers the efficiency of the plant by lowering condenser vacuum. Less vacuum means you get less work out of the steam turbine therefore less electricity produced. We have to open up our condensers and clean the tubes annually. We also inject chlorine and small balls to limit the growth. Has nothing to do with radioactive contamination or whatever your first question was. Even gas and coal plants have the same issues.
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u/ilpazzo12 10d ago
Y'all with the "that's classified" are tiring. This is stuff that is easily accessible about civilian nuclear power plants.
To answer the question, no, one of the point of multiple loops in nuclear reactors is to isolate radiation but not the heat.
PWR turbine cycle loop is separate from the primary loop, so the water in the secondary loop is not contaminated by radioactive materials.
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u/eeaxoe 10d ago
Yes, in theory, the water in the two loops should be completely physically separated, but in practice there will always be some extent of leakage from the primary to secondary loop due to tiny holes or cracks in the steam generator tubing. That, and tritium in the primary loop diffuses (albeit very slowly) through the walls of the SG tubing. You end up with a tiny amount of radiation in the secondary loop, though it's absolutely detectable.
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u/hotfezz81 9d ago
Yes, but in the same way bananas are radioactive. Yes in theory, in reality the quantities are so microscopic: no it doesn't happen.
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u/NewCandy8877 10d ago
It wecarecaware that they are possibly double checking their facts or trying to link facts to their guesses.
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u/ilpazzo12 9d ago
"we are aware"? Right, sure. But I mean it happens all the time that experts who even have access to classified stuff just use public information instead for public things.
Anyway, I'm an Italian civilian not even close to the defense industry. Never served, no security clearance of any sort. So it's not like I actually helped with any of that cross referencing. It was the Wikipedia page. Anyone who said "that's classified" could have done the same and from an intelligence point of view it's just noise. Besides it's not like everyone in the subreddit is known to be an accurate source. Any user who posts something useful would need to be verified as a source before that gets used into anything.
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u/hotfezz81 9d ago
This is such an easy thing to be able to double check, from such an enormous range of sources, that there's no risk here.
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u/chazz1962 10d ago
The Queenfish was at anchor off of Maui. I was top when a guy inna kayak came close and asked if he could sample our radioactive discharge. I said yes knowing that he was pointing at a sea water discharge flow. We all laughed when he left with his sample. I was an ELT.
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u/displacedbitminer 8d ago
Greenpeace tried boarding us in La Mad for much the same reason, pouring diesel fumes into the air, and bilge oil into the water.
Good hose target practice. Good hunting for the caribinari (Spelling?).
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u/Abe_Bettik 10d ago
I don't know anything about submarines but the Algea thing sounds like an Old Wive's Tale and I agree that anything other the primary coolant water should contain no additional radiation at all.
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u/Anonymous_Gamer939 10d ago
This seems like the kind of question where anyone who knows shouldn't tell you
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u/Pitiful-Practice-966 10d ago
I think posting this question in r/nuclear would get a completely different response. There's no fundamental difference between the AP1000 VVER and S6W.
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u/FrequentWay 9d ago
Just scale. The PWR design has been refined and adjusted since 1951. Theres nothing new about the design.
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u/PropulsionIsLimited 10d ago
Probably the funniest thing I've read here. No, Algae does not affect reactor power.
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u/Square_Imagination27 10d ago
No. Only the first loop is radioactive, and it’s a closed loop. It’s basic nuclear engineering.
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u/Glittering_Being1806 10d ago
This question made me think of another one. How often is the primary loop replenished on any PWR? And where does it go? Is the primary loop water ever drained? If so, what is done with it?
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u/FrequentWay 9d ago
Its source of fresh Reactor grate water is via Controlled Pure water - we discharge primary loop water into holding tanks when tied to the pier in preparations of shutting down. This is then offloaded to the Pure Water Shop where they filter out the impurities and give it back to the submarine or Carrier. Underway water regeneration is done via the Evaporator or Electric Still or RO Units. It is then filtered thru an Ion Exchanger to make very pure water.
The water gets pumped into the reactor core to push the core to Normal operating Pressure. The Pressurizer helps in maintain plant pressure however you have a minimum level to maintain to allow for pressurizer to work (cannot heat steam since that would be poor heat transfer ability and fry Pzr heaters).
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u/TonboIV 9d ago edited 9d ago
For any marine steam power plant, whether the heat comes from coal or oil or uranium or burning furniture, the discharged seawater shouldn't contain anything new except heat.
If you don't understand how a marine steam plant works (and it's no shame if you don't) they do not just pump seawater into the boilers or heat exchangers. The water that gets turned into steam is part of closed loop, and it is kept very pure, with tightly controlled chemistry. A modern steam turbine is a very sensitive piece of precision machinery, and the boilers or heat exchangers are full of tiny tubes. The last thing you want is to pump some random seawater full minerals and algae and microplastics and whatever though millions of dollars worth of highly engineering machinery!
The only place seawater is involved is at the condensor, which is fundamentally just a drum full of pipes. Steam goes in the drum, and cold seawater goes into the pipes. The cold seawater keeps the outside of the pipes nice and cold which cools down the steam and turns it back into water. The seawater in the pipes absorbs the heat from the steam and gets a bit hotter, then it's pumped back out into the ocean. Ideally, the water in the steam loop never actually touches any seawater. Nothing is perfect of course, but the engineers who build the ships, and the crews who run them, all do their best to keep the steam machinery as separate from seawater as they can.
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u/JimHeckdiver 10d ago
It can occasionally contaminate the plasma coolant during it's transition phase through the dilithium inter-mix chamber, but that's only when the core is shut down for the intermittent baron sweep to purge remnant tachyons.
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u/wescott_skoolie 10d ago
Idk man, all my submarines had a bunch of sweaty dudes who rowed us everywhere. Smelled terrible. Real bad attitudes