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Fast vs thermal reactor cost

  1. Jul 10, 2017 #1
    Is a "fast" reactor more economical in terms of capital investment than a thermal one? I am asking this because I assume a fast reactor only needs a smaller startup U235 source of on average 20% enrichment but can later run on its own produced fissile material and would normally for the rest of its life use natural uranium U238 or Thorium as it's fuel source, is there significant savings made due to the fact that the natural U and Th are not enriched and so don't go through the enrichment facilities through which normal thermal reactor Uranium fuel goes.?

    This thought struck my mind after reading up on centrifuge enrichment and also gas diffusion process I saw that on average such a plant needs its own nuclear reactor/s to power the energy it needs for the isotope separation process like the French Tricastin NPP which if I understand correctly powers a nearby enrichment facility which is located on site.
  2. jcsd
  3. Jul 10, 2017 #2
    Don't forget that the enrichment plant is producing fuel for many reactors. I understand the energy used to enrich the fuel is ~ 2% of the energy produced when that fuel is used.

    Someone else can answer the economic question on thermal vs fast reactors.
  4. Jul 10, 2017 #3
    To be able to understand more easily the question I want to ask is how much MWh of electrical energy are needed to supply a full fuel load of a 1000MW electrical output PWR or BWR plant since they are the most common reactors out there. I do know there is this measurement for enrichment as SWU and that a single fuel load is changed not altogether but in steps since core regions burn up faster than the outer ones yet still speaking in terms of electricity in to enrich and electricity out as the available power to load is simpler to my mind.

    surely fast reactors must be more demanding in terms of materials and engineering so that would probably drive their cost higher in terms of building the plant.
  5. Jul 10, 2017 #4
    There are some numbers here:

    The overall EROI is calculated as 59 for a 40-year plant life and 70 for a 60-year life. Note that the enrichment values assume centrifuge operation which I believe is a lot less energy intensive than the older gas diffusion tech.

    On the other hand, "During the 20-year Megatons to Megawatts program, as much as 10 percent of the electricity produced in the United States was generated by fuel fabricated using LEU from Russian HEU." https://en.wikipedia.org/wiki/Megatons_to_Megawatts_Program

    That means half the reactor fuel used in the US required no energy input for enrichment, it was downblended from the Soviet weapons uranium.
  6. Jul 11, 2017 #5
    Fuel costs are not the main part in the price of energy generated in NPPs. If you look it from this angle, fast reactors are far less economical since almost all of them are one-of-a-type one right now.

    If you consider the the price of the fuel generated too, then - well, right now even the reprocessing is barely viable. And fuel generated in fast reactors needs to be reprocessed first before it can be used in other reactors.
  7. Jul 13, 2017 #6
    well technically fast reactors could simply be used like ordinary reactors only instead of regular refueling these could fuel themselves as enough fissile material is extracted from the blanket it can be then put in the primary fission core or so.
    I assume there is some reason why fast reactors are one of a kind experimental devices instead of routine reactors being built according to plan and certain design.
    I assume it has to do with two factors, firstly that we now know we have enough uranium to fuel our current needs for some time and the second factor could be that fast reactors are technically more challenging both with respect to materials endurance and other factors??

    does someone here know what's going on with the molten salt concept? I realize while reading it has some good potential in terms of fast reactors with onsite fuel reprocessing due to the molten liquid nature of the fuel.?

    oh and I guess that the second biggest investment right after building a NPP and getting the licensing done is the decommissioning of the plant after it's planned life cycle ends, probably fuel enrichment is only a small fraction of the cost if compared to these.
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