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Question on Nuclear waste

Discussion in 'Topical Discussions (In Depth)' started by Cigarlover, Jul 17, 2017.



  1. Cigarlover

    Cigarlover Gold Member Gold Chaser

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    Currently we have no place to send all of our nuclear waste. What happens if you melt those rods used in power plants? Like if you just dropped one in a volcano or something.
     
  2. Joe King

    Joe King Gold Member Gold Chaser

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    Next eruption you'd get radioactive lava and ash?
    ...but I like the idea. That should be the point of attempts to drill into the magma under the crust. The spent fuel rods could be injected in to it, melting into the magma under the crust. By the time it emerges at mid-Ocean rifts to form new crust it'll have lost most/all radioactivity.
     
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  3. Cigarlover

    Cigarlover Gold Member Gold Chaser

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    I was thinking also it could be buried at induction zones where the plates meet. It would eventually get ground up to nothing and turned back into magma. We could do that with all of our hazardous wastes as long as heat breaks it down to basic elements without spewing contaminants all over the globe.
     
  4. brosil

    brosil Gold Member Gold Chaser Site Supporter

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    Wouldn't it be so much simpler to reprocess the rods and just use them for fuel again?
     
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  5. Joe King

    Joe King Gold Member Gold Chaser

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    Why don't they do that now?

    Because it's cheaper and/or easier to make new ones?
    ...and reprocessing actually increases the volume of radioactive waste that must be dealt with.


    BTW, "spent" fuel rods still contain about 95% fissionable material. Yes, only 5% of the material is even used to generate power with. Imagine if every time you used 5% of a full tank of gas you had to throw the rest of it away and buy another tank full just to be able to make your car go at all.
    Ie: everyone would be able to see the stupidity of that.

    IMHO, nuclear energy is one of the dumbest things ever. We use 5% of its potential to generate power that is used up as we go, but are left with stuff that's super deadly for 250,000 years. It just doesn't make any sense.
    ....and most nuclear plants fail deadly, not safe. If we ever get the giant CME or anything else that ever causes a massive "grid down" scenario, we'll be lucky to not end up with dozens (maybe 100's?) of Fukashima-type disasters all around the World.
     
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  6. brosil

    brosil Gold Member Gold Chaser Site Supporter

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    Well Joe, it's simple. We signed a treaty saying we wouldn't reprocess the rods so the world would be safer. France didn't and their high level nuke waste takes up a space the size of 2 high school gyms. Does the world seem safer to you? Oh yeah, one of the countries we signed with isn't around anymore.
     
  7. SWRichmond

    SWRichmond Seeker Seeker

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    Like all industries nuclear power is a creature of lobbying, and thus of government and regulation. And the purpose of government is looting.

    Natural uranium is about 0.7% U235, and the rest is U238 (more neutrons). Owing to some peculiarities which we don't need t worry about here, U235 is the stuff which is fissile (fissile material is material capable of sustaining a nuclear fission chain reaction). Fuel is enriched to about 5% or so, modern fuel contains a variety but variations around 4-5%. Core designs are such that a typical fuel bundle (bundle of rods) spends about four and a half years in a power reactor, one third each in three different sectors of the core, based on neutron flux in different core regions. A refueling outage replaces about one third of the bundles each time, and moves around the remainder of the bundles as determined by the core design guys' calculations.

    U238 is not fissile; it can absorb a neutron but will not fission when it does so. When U238 absorbs a neutron that neutron is unavailable for absorption by U235, so U238 is a kind of poison in the core. In order to sustain the reaction, "enrichment" of the proportion of U235 is needed. This is why "enrichment" facilities are such a hot international topic. You need fuel enriched to about 20% or more U235 in order to make a bomb. This process is incredibly energy-intensive and time consuming.

    Un-irradiated enriched fuel is relatively simple to handle. Once it has been in a working reactor and exposed to neutrons, fission has occurred and the fuel contains fission products which are horrible stuff. Nuke plant refuelings occur underwater; part of containment is a refueling structure which allows the head to be removed and the entire area flooded so that the fuel is moved around while under several feet of water for cooling and shielding. Spent fuel is moved into the spent fuel pool where it is kept underwater for cooling purposes for several years. After heat release 9caused by decay of fission products) has dropped considerably, the fuel can be removed from the pool and placed in "dry casks".

    So the U238 in the fuel absorbs neutrons, and will decay in a few days to plutonium Pu239, which is fissile.
    [​IMG]

    So any commercial reactor is producing Pu239, from which bombs can be made. The process of getting the Pu239 out of the fuel is a simple chemical one, since plutonium has different chemical properties than uranium, as opposed to the very expensive enrichment process for U235. The difficulty is in the fact that the Pu239 is contained in highly radioactive fuel rods. So getting the very useful Pu239 out of the fuel rods is expensive. Treaties have been written to bar fuel reprocessing, which would enable the recovery of U235 as well as Pu239.

    But government has used this "breeding" process for decades, irradiating U238 with neutrons in order to chop up the irradiated fuel, dissolve it in acids, and then chemically extract the Pu239 in order to make bombs. And all of the byproduct of this process is in underground tanks at Hanford; highly acidic and highly radioactive liquid wastes, producing lots of heat from radioactive decay. Hanford is a disaster area. It doesn't have to be, but government...

    The French reprocess their fuel, coming much closer to closing the fuel cycle. But no doubt due to lobbying from various industry groups, we don't do that here. Too much money to be made.
     
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