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Nuclear power for desalinization not power?

  1. Feb 5, 2014 #1
    In 2005 the American Nuclear Society endorsed the use of nuclear energy for desalinisation -- see http://www.ans.org/pi/ps/docs/ps62.pdf

    Would there be any advantages in terms of safety and / or cost to using nuclear fission to desalinate seawater (or perform some other non-electricity-generation process) rather than as a source of power for the electricity grid ? I ask this in light of California's current drought and fresh water vulnerabilities world-wide.

    Here are some topics for comment or exploration relating to the use of nuclear energy for desalinisation excluding power generation for the grid.

    1) Seawater will likely have to be pumped some distance to the plant, given concerns about nuclear plants being located in flooding zones. Such concerns are not as great for desalinization plants using fossil or renewable energy sources.

    2) Plant will _not_ have to operate in a way that supports the needs of the electrical grid -- this might be an advantage in method, safety, and cost of operation.

    2) The most obvious desalinisation method would be using heat of fission to distill fresh water from seawater. Other methods might include the generation of steam to produce mechanical energy that is the motive force for vacuum distillation equipment; the generation of electricity to support an electrochemical method of removing salt from seawater; the use of radioactivity to drive or facilitate a chemical process with fresh water as the end product (I don't know whether these last two are physically possible or not).

    Many thanks.
    Cheers,
    Arthur R.
     
    Last edited: Feb 5, 2014
  2. jcsd
  3. Feb 6, 2014 #2
    The idea is to use heat directly, without converting it to mechanical or electrical energy first, since such conversions are below 40% efficiency.
     
  4. Feb 6, 2014 #3

    Astronuc

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    1) Many nuclear plants are located along coast lines, and they use the ocean as a heat sink. Obviously there are concerns about tsunami or hurricances depending on the location.

    2) Such a plant might produce electricity as well as process heat for desalination.

    3) One would not design a plant to use radioactivity to facilitate a chemical process. The radiation in the core consists of neutrons as well as gamma and beta particles. The neutrons are absorbed by nuclei and 'activate' them, i.e., increase the number of neutrons in the nuclide, which then decays by beta decay (or isomeric transition).
     
  5. Feb 7, 2014 #4
    Thank you, Nikkom and Astronuc, for your comments and insights.

    Perhaps my question is more in the realm of economics than engineering, but I think that engineering is a component in answering the economic question. Some further pros and cons in addition to neccesity of pumping seawater farther than would be necessary for a a fossil / renewable desalinisation plant, and possible operational advantages to not having to use plant to meet the needs of the electric grid:

    1) Pro: Plant does not require turbines, generators, staff, and equipment necessary to generate electricity and feed it into the grid.

    2) Pro: Security measures - staff, equipment, and operations - might be less expensive because of the lesser security consequences of halting operations or damaging plant. Interrupting the production of freshwater seems to have far lower risks for the economy and safety of society than interruption / damage to grid electricity supply.

    3) Con: Plant takes in seawater, rather than freshwater, so the corrosive properties of seawater are a concern in the design.

    Since safety and cost are obstacles to the use of nuclear power, if a nuclear desalinisation plant could be demontrably safer and/or cheaper than a nuclear electricity-generating plant, this might overcome an obstacle to the deployment of nuclear energy in our economy. Note, I'm not against using nuclear energy for generating electricity, I'm just interested in increasing the possibilities for use of nuclear technology if they make engineering and economic sense.
     
    Last edited: Feb 7, 2014
  6. Feb 7, 2014 #5

    Astronuc

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    A nuclear reactor/core requires cooling, and the cooling would be high purity water (low electrical conductivity), or perhaps gas or liquid metal (probably Pb-Bi, rather than Na or NaK which have rather nasty reactions with water). Cooling requires pumps and an electrical supply (from the grid). The need for cooling increases with power density and burnup.

    Since the plant contains special nuclear material, there would be a need for security.

    We already have seawater desalination plants, so the corrosion issues are understood. There are special alloys that have good corrosion resistance in seawater, as well as carbon, plastic and ceramics.
     
  7. Feb 8, 2014 #6
    There is the obvious question: What about the risk of producing radioactive water?
     
  8. Feb 8, 2014 #7

    Astronuc

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    There would be different circuits for cooling and desalination, which would imply one or more heat exchangers. Leaking tubes would be a concern.
     
  9. Mar 10, 2014 #8

    SteamKing

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    You're always going to need some staff to monitor the operation of the reactor, perform maintenance, etc. It's dangerous to have nukes operating on auto-pilot.

    You can only live without fresh water for a matter of days, without electricity a lot longer, although not comfortably. Just ask the folks in California how they're doing with a greatly reduced supply of fresh water. Even more worrisome, fresh water can be contaminated with biological or radiological impurities which are not apparent to consumers without testing.

    A very large percentage of the cost of a nuclear plant is the nuclear bits. Turbines and generators can be constructed without the regulatory oversight which obtaining a nuclear operating license entails. The reactor components and the plant buildings are quite costly themselves to construct. You still have to consider the additional nuclear waste creation of non-generating nukes, as well.
     
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