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There's an estimated 2 billion years worth of dissolved uranium. Not truly renewable I suppose, but by that metric solar power isn't renewable either. Eventuall

There's an estimated 2 billion years worth of dissolved uranium. Not truly renewable I suppose, but by that metric solar power isn't renewable either. Eventually all the hydrogen in th sun will be fused.

pfdietz 7y ago
You have mangled your data there. That claim is incorrect.
- manfredo 7y ago
  This estimate says a billion years: https://www.forbes.com/sites/jamesconca/2016/07/01/uranium-seawater-extraction-makes-nuclear-power-completely-renewable/ https://www.forbes.com/sites/jamesconca/2016/07/01/uranium-s...
  - pfdietz 7y ago
    Um, no it doesn't. It claims that dissolved U would be replenished faster than we'd u se it (but that claim is wrong, I think); it doesn't say the U that us currently dissolved would last a billion years.
    - wahern 7y ago
      FWIW, this might be the primary source everybody is unintentionally quoting, or at least much closer to the primary source: > Although the concentration of uranium is quite low, about 3.3 ppb (parts per billion) in seawater of average oceanic salinity, the amount present in the total volume of the oceans is very great, some 4.5 billion tonnes. Of this, perhaps only that uranium contained in the upper 100 meters or so of the surface well-mixed layer should be considered accessible for recovery, some 160 million tonnes. Practically speaking, the amount contained in the ocean surface layers is unlimited with respect to large scale extraction in the forseeable future. This results from the replenishment by continental weathering and river runoff being much larger than forseeable extraction rates. ... > 1) The surface waters of the oceans comprise a virtually inexhaustible uranium resource of some 160 million tonnes, extractible indefinitely at a rate of a few thousand tonnes per year. Exxon Nuclear Company, "EXTRACTION OF URANIUM FROM SEAWATER: EVALUATION OF URANIUM RESOURCES AND PLANT SITING, VOLUME I", pp 6-7, 9, February 1979, https://www.osti.gov/servlets/purl/6191296 https://www.osti.gov/servlets/purl/6191296 The above quotes are from the executive summary. Page 35 has the money quote: > This represents an influx of about 9000 tonnes annually. Which supports your contention that sea water CANNOT provide an endless supply considering that current annual consumption is ~90,000 tonnes, 10x the replacement rate. EDIT: s/CANNOT NOT/CANNOT/
      - pfdietz 7y ago
        The problem with pointing to the influx from rivers is that you also have to look at the outflow of uranium (and there must be such an outflow, probably reduction of uranium to insoluble U(IV) in sediments, since it's in steady state.) Any human extraction is on top of this existing outflow, it doesn't replace it.
        manfredo 7y ago
        The outflow is from the earth's crust at the bottom of the ocean. Sure, it doesn't get replaced. But there's enough uranium to last on the order of billions of years. By this logic, solar power isn't renewable either because the hydrogen in the sun doesn't get replaced.
        pfdietz 7y ago
        No, I believe it's mostly from rivers. Oceanic crust is depleted in uranium relative to continental crust. Moreover, uranium becomes soluble in oxidizing conditions (as U(VI)), not in reducing conditions (as U(IV)).
        pfdietz 7y ago
        I misread what you wrote there. Anyway, in steady state the consumption from the oceans can be only equal to the inflow from rivers. If that's (as I've seen estimated) 25,000 tons/year, that's enough to power the world if breeders are used, but not enough if today's thermal burner reactors are used.
        wahern 7y ago
        The paper does look at the outflow. In fact, in the same paragraph as the "money quote" I copied it says, "uranium has a residence time of approximately 500,000 years". It's not clear to me that the 9000 tonnes is net or gross, but either way your original point still stands: ocean uranium is nowhere near a limitless resource, and could likely be made economically unviable[1] in a rather short timespan, perhaps even in a single human lifespan if we switched overnight to 100% energy generation from dissolved uranium. What's more surprising, actually, is how much uranium we consume currently. And AFAIU, we do so very inefficiently. Seems to me we'd get a much better RoI by using uranium more efficiently than by turning to seawater for more uranium to waste. [1] Assuming it becomes viable in the first place. It certainly doesn't seem economically viable, today.
    - manfredo 7y ago
      > However, seawater concentrations of uranium are controlled by steady-state, or pseudo-equilibrium, chemical reactions between waters and rocks on the Earth, both in the ocean and on land. And those rocks contain 100 trillion tons of uranium. So whenever uranium is extracted from seawater, more is leached from rocks to replace it, to the same concentration. It is impossible for humans to extract enough uranium over the next billion years to lower the overall seawater concentrations of uranium, even if nuclear provided 100% of our energy and our species lasted a billion years.

pfdietz 7y ago

You have mangled your data there. That claim is incorrect.

manfredo 7y ago
This estimate says a billion years: https://www.forbes.com/sites/jamesconca/2016/07/01/uranium-seawater-extraction-makes-nuclear-power-completely-renewable/ https://www.forbes.com/sites/jamesconca/2016/07/01/uranium-s...
- pfdietz 7y ago
  Um, no it doesn't. It claims that dissolved U would be replenished faster than we'd u se it (but that claim is wrong, I think); it doesn't say the U that us currently dissolved would last a billion years.
  - wahern 7y ago
    FWIW, this might be the primary source everybody is unintentionally quoting, or at least much closer to the primary source: > Although the concentration of uranium is quite low, about 3.3 ppb (parts per billion) in seawater of average oceanic salinity, the amount present in the total volume of the oceans is very great, some 4.5 billion tonnes. Of this, perhaps only that uranium contained in the upper 100 meters or so of the surface well-mixed layer should be considered accessible for recovery, some 160 million tonnes. Practically speaking, the amount contained in the ocean surface layers is unlimited with respect to large scale extraction in the forseeable future. This results from the replenishment by continental weathering and river runoff being much larger than forseeable extraction rates. ... > 1) The surface waters of the oceans comprise a virtually inexhaustible uranium resource of some 160 million tonnes, extractible indefinitely at a rate of a few thousand tonnes per year. Exxon Nuclear Company, "EXTRACTION OF URANIUM FROM SEAWATER: EVALUATION OF URANIUM RESOURCES AND PLANT SITING, VOLUME I", pp 6-7, 9, February 1979, https://www.osti.gov/servlets/purl/6191296 https://www.osti.gov/servlets/purl/6191296 The above quotes are from the executive summary. Page 35 has the money quote: > This represents an influx of about 9000 tonnes annually. Which supports your contention that sea water CANNOT provide an endless supply considering that current annual consumption is ~90,000 tonnes, 10x the replacement rate. EDIT: s/CANNOT NOT/CANNOT/
    - pfdietz 7y ago
      The problem with pointing to the influx from rivers is that you also have to look at the outflow of uranium (and there must be such an outflow, probably reduction of uranium to insoluble U(IV) in sediments, since it's in steady state.) Any human extraction is on top of this existing outflow, it doesn't replace it.
      - manfredo 7y ago
        The outflow is from the earth's crust at the bottom of the ocean. Sure, it doesn't get replaced. But there's enough uranium to last on the order of billions of years. By this logic, solar power isn't renewable either because the hydrogen in the sun doesn't get replaced.
        pfdietz 7y ago
        No, I believe it's mostly from rivers. Oceanic crust is depleted in uranium relative to continental crust. Moreover, uranium becomes soluble in oxidizing conditions (as U(VI)), not in reducing conditions (as U(IV)).
        pfdietz 7y ago
        I misread what you wrote there. Anyway, in steady state the consumption from the oceans can be only equal to the inflow from rivers. If that's (as I've seen estimated) 25,000 tons/year, that's enough to power the world if breeders are used, but not enough if today's thermal burner reactors are used.
      - wahern 7y ago
        The paper does look at the outflow. In fact, in the same paragraph as the "money quote" I copied it says, "uranium has a residence time of approximately 500,000 years". It's not clear to me that the 9000 tonnes is net or gross, but either way your original point still stands: ocean uranium is nowhere near a limitless resource, and could likely be made economically unviable[1] in a rather short timespan, perhaps even in a single human lifespan if we switched overnight to 100% energy generation from dissolved uranium. What's more surprising, actually, is how much uranium we consume currently. And AFAIU, we do so very inefficiently. Seems to me we'd get a much better RoI by using uranium more efficiently than by turning to seawater for more uranium to waste. [1] Assuming it becomes viable in the first place. It certainly doesn't seem economically viable, today.
  - manfredo 7y ago
    > However, seawater concentrations of uranium are controlled by steady-state, or pseudo-equilibrium, chemical reactions between waters and rocks on the Earth, both in the ocean and on land. And those rocks contain 100 trillion tons of uranium. So whenever uranium is extracted from seawater, more is leached from rocks to replace it, to the same concentration. It is impossible for humans to extract enough uranium over the next billion years to lower the overall seawater concentrations of uranium, even if nuclear provided 100% of our energy and our species lasted a billion years.