Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Send radioactive waste to bottom of the ocean?

  1. Jun 18, 2013 #1
    Why don't they just place spent fuel rods in canisters and put them on the bottom of the ocean (at a traceable location, of course)? Water is one of the best radiation shields. You wouldn't have to worry about digging out mountain caverns and such.
     
  2. jcsd
  3. Jun 18, 2013 #2

    etudiant

    User Avatar
    Gold Member

    Afaik, the concern is that there is no known technology that would ensure the waste would not leak unexpectedly.
    Sea water is quite corrosive and there are strong currents and large land slides (some from Hawaii have run out as much as 80 miles.
    There have been serious proposals to bury the wastes in the ooze at the bottom of some subduction zones, with the thought that any wastes buried there would not reemerge for millions of years, but the reality that most wastes are hot enough to ensure their environment remains chemically and physically active has scotched that.
    Imho, we are not going to find a safe place to dump this stuff permanently. We will have to find a way, perhaps through advanced accelerators or similar, to neutralize the waste. Meanwhile, it needs to be stored in reasonably safe containers, casks good for a century or so, but always accessible. That way everything can be kept above board and no slop creeps in, the way it does when people are deluded enough to believe the 'permanent repository' BS.
     
  4. Jun 19, 2013 #3

    SteamKing

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    I guess you don't mind if your fish sticks cook themselves and then glow in the dark.

    Yummm!
     
  5. Jun 19, 2013 #4
    https://en.wikipedia.org/wiki/Radiation_protection#Shielding_design

    If placed at the bottom of the ocean, the gamma rays would be practically undetectable (heck, even at the bottom of a lake.). Water's halving thickness is 18cm. Perhaps they could net the area off to keep marine life away, but I don't think it would even be a problem unless wildife got closer than a few feet...
     
  6. Jun 19, 2013 #5

    QuantumPion

    User Avatar
    Science Advisor
    Gold Member

    This is actually a perfectly valid proposal, the opposition to such a solution is political.
     
  7. Jun 19, 2013 #6

    SteamKing

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    But if the radioisotopes escape containment and enter the food chain, you've got magic food and magic aquatic life which can travel globally. Containment is not so much about radiation shielding as it is about keeping the hot stuff from migrating outside of the storage device and into the air or water.

    The Russians have had all sorts of problems trying to keep the containment dome intact over the Chernobyl reactor and it's on dry land. We aren't even 30 years from the accident there and a new containment dome is already being constructed to replace the original.
     
  8. Jun 19, 2013 #7

    QuantumPion

    User Avatar
    Science Advisor
    Gold Member

    At the bottom of the ocean that is not really an issue. It's much easier to contain waste under the ocean than in the air. The water is very cold, dense, high pressure, and still. Even if there was a leak, it wouldn't really go anywhere or be hazardous to anything that wasn't in direct contact.

    Note that there are at least a couple nuclear reactors sitting at the bottom of the ocean to this day, due to the loss of a few nuclear powered submarines. Theses weren't sealed or designed to be stored in such a condition yet they have still remained contained just fine over decades.
     
  9. Jun 19, 2013 #8

    Astronuc

    User Avatar

    Staff: Mentor

    It would be an environment that humans could not control.

    At the bottom of the ocean under high pressure, in the dark, where it is very cold, corrosion occur very slowly. For example, a lot of the Titanic is preserved.

    Nevertheless, it is the lack of engineered barriers (beyond the cannister), lack of control and too much uncertainty that preclude dropping spent fuel cannisters in the ocean depths.
     
    Last edited: Jun 19, 2013
  10. Jun 19, 2013 #9

    SteamKing

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Although the remains of the Titanic are currently recognizable, the very metal of the ship's hull is under constant attack by the microorganisms which live at those depths. In several hundred years, all that may remain of the Titanic is a couple of giant piles of rust at the bottom of the Atlantic. Most, if not all, organic material from the ship disappeared long ago. Oceans are very hungry places to be.
     
  11. Jun 19, 2013 #10
    Like other people have said, corrosion, and radiation to the environment are big factors in this. Imagine if even one of the canisters broke how much of an impact it would have on the ocean environment which is already very touchy. The reason they dig out caverns is because there is less environmental impact if there was leakage. But also, they can treat the radioactive waste and instead of having it last thousands of years it only needs several hundred years. Therefore, if it is in a cavern for several hundred years it will lose it's radioactivity, without ever impacting the environment.
     
  12. Jun 19, 2013 #11
    Why could it not be controlled? We have sonar that has mapped the entire ocean depths of the earth. If we can track sharks and fish with tags, there is no reason why we couldn't track a canister. Water would stop virtually all gamma rays after only about 1.8m (10*halving thickness). So radiation wouldn't be a problem in the ocean. I can maybe see that if the stuff leaked out it could chemically react and be toxic, radiation would not cause trouble underwater. That's why we can take pictures like this images?q=tbn:ANd9GcRpLWYX2f9zO_Q-6E2AwmO11jwUr4k7mx0WPcMgIWjusm3EkWk_.jpg
    Only water, no other barriers required.
     
  13. Jun 20, 2013 #12

    SteamKing

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Your picture was not taken at the bottom of the ocean, though. It was probably taken in a pool located at a nuclear reactor on dry land.

    You claim water would stop 'virtually all' gamma rays after 1.8 m. What does 'virtually all' mean? Would you be willing to stand 2 m away from a gamma source with only water between you and the source? What about all that lead shielding that is used? Is that some conspiracy by the lead industry to fool us into thinking that water by itself can't do the job?

    So a picture was taken. How do you know that the camera wasn't remotely operated? Do you see anyone swimming in this pool?

    You don't seem to understand very much about radiation and its biological effects. Radioactive material is intrinsically toxic; no chemical reaction is required to make it toxic. If a spill does occur underwater, how is it going to be cleaned up? You saw the kind of massive cleanup required for the spill in the Gulf of Mexico, and most of the oil cleaned up floated to the surface. Can you imagine how much more complex a cleanup effort would be made if radioactive material was involved?

    Look, doctors now get uneasy if they have a patient who flies a lot or who undergoes too many X-rays or CAT scans in a year's time. Radiation is a serious business, not only due to the effects of immediate exposure, but also due to the lingering effects from radioactive material continuing to persist in the environment after the accident. You may think it is OK to store spent fuel rods in your swimming pool, but not every one is willing to put up with that kind of risk.
     
  14. Jun 20, 2013 #13
    I vote for disposal in deep boreholes in subduction zones on land. Under 3+ kilometers of rock and sinking? Sounds safe enough for me!

    Spent fuel should be reprocessed.

    This recovers unused U and Pu,
    reduces waste volume,
    allows waste to be converted into insoluble form (glass/synthetic rock),
    and most importantly, reduces long-term waste _activity_ (if transuranics are removed too)!

    The activity of reprocessing waste is dominated by Cs-137 and Sr-90 and is reduced by 1000 in only 300 years, thus, by a billion times in 900 years. Unprocessed spent fuel is much worse.

    I think the confidence level of "this container won't leak for 1000 years" statement is much better than of "this container won't leak for 100000 years" one.
     
  15. Jun 20, 2013 #14
    Totally unrelated, and I agree with your point, but if I remember Ballard's assessment correctly, the biggest issue causing the Titanic's corrosion is that the water it sits in is very stagnant. If it were in an area with a current, chances are the microorganisms wouldn't have attacked quite as badly.
     
  16. Jun 20, 2013 #15

    QuantumPion

    User Avatar
    Science Advisor
    Gold Member

    Radiation shielding is an exponential function. Every 18 cm of water reduces the radiation by half. So 180cm of water would reduce the radiation by 1-0.5^10=99.9%. That would be sufficient for the level of radiation emitted by spent nuclear fuel.

    Radioactive waste processed for long-term disposal would be vitrified into a solid, chemical inert material such as glass. Even if small amounts of radioactive waste were dispersed, they would be confined to the extreme depths of the ocean and eventually diluted. You wouldn't have to clean it up.

    The neat thing about nuclear power is that the waste is so concentrated and compact. The gulf oil spill was a hundred billion gallons of oil. The total world spent fuel inventory is something like 250,000 tons, of which 90% is uranium which could be reprocessed first. So you're looking at 25,000 tons of high level waste. That's a pretty small volume in the grand scheme of things.

    Yet doctors have no qualms about their patients driving to the clinic, which is about a hundred trillion times more dangerous than getting an x-ray or flying on a transatlantic flight.
     
  17. Jun 21, 2013 #16
    Not really.
    For example, freshly poured stainless steel containers with vitrified waste at La Hague emit in excess of one million rems per hour.
     
  18. Jun 21, 2013 #17

    QuantumPion

    User Avatar
    Science Advisor
    Gold Member

    That would be a dose rate of 16 R/minute. I wouldn't want to stay too long at that distance but it wouldn't be immediately harmful. But at 2.5 m the dose rate would be 10x lower and would be safe for an extended period of time.
     
  19. Jun 21, 2013 #18
    ???

    It's 277 rem per *second*.
     
  20. Jun 21, 2013 #19

    QuantumPion

    User Avatar
    Science Advisor
    Gold Member

    Not through 180 cm of water, which reduces the intensity by roughly 99.9%.
     
  21. Jun 23, 2013 #20
    Screw poor fish which doesn't know not to swim closer than 3 meters to those glowing blue cylinders, who cares about it?

    By this logic, dropping nuclear waste in shallow holes in the most inaccessible part of the Sahara should be relatively safe.
    No humans would approach it nearer than a few tens of kilometers, and desert foxes, well, they had it coming.
     
    Last edited: Jun 23, 2013
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Send radioactive waste to bottom of the ocean?
Loading...