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  1. M

    Cumulative yield database

    I couldn’t find a table of cumulative fission yields on the web, so I made one in a database simulation. Who might be interested? The full table covers the evolution of 1322 isotopes over 34 years. The results are in the form of 31 “snapshots” of the isotopic composition as the reactor ages...
  2. M

    "half-life" under flux

    I'm surprised the old fuel is placed at the rim. The neutron flux should be less out there. I would think placing fresh fuel at the edge would minimize the difference in energy output from the center out to the edge. I've heard hot spots are a problem. Doesn't putting fresh fuel at the center...
  3. M

    "half-life" under flux

    I associate transmutation with a change of element, not just a new isotope of the same element. Is there a special verb for that? “The neutron plumps the 235-U nucleus if it doesn’t cause fission…” I didn’t specify stable, so your lambda+ term will help. This is in reference to my nuclear...
  4. M

    "half-life" under flux

    Given an initial mass of some isotope subjected to a constant neutron flux, how fast will the mass drop off? Would not the survival curve look exactly like the curve for radioactive decay? Both cases describe a starting mass subjected to a constant transformative force at a rate that depends...
  5. M

    Concurrent decay calculations in an operating reactor

    Indeed, extraction of the fission products is another facet of MSR operation that I need to handle. Like neutron absorption, I'm putting that off until I nail down a simple decay-only methodology. I have data for the rarer and short-lived isotopes. Removing them is slightly error-prone. The...
  6. M

    Concurrent decay calculations in an operating reactor

    I'm thinking that the problem is a lot simpler if the fuel isn't fixed in place. How much of ORIGEN's code is devoted to the composition of each fuel pellet, which stays in place for ~18 months? How much sim time is devoted to rearranging half-used fuel bundles in different configurations at...
  7. M

    Concurrent decay calculations in an operating reactor

    I 'm not ignoring decay chains. I just haven't gotten to them yet. And I'll handle absorption after that. I'm trying to separate the problem of tracking cumulative yields into manageable pieces. To put this in context, I am trying to simulate the isotopic composition of the salt in a molten...
  8. M

    Concurrent decay calculations in an operating reactor

    OK. Without transmutation, and with no contributions from decaying parents, what is the estimate for cumulative yield with respect to initial yield for an isotope that has reached equilibrium?
  9. M

    Concurrent decay calculations in an operating reactor

    I can’t find yield data for the concurrent creation and decay of fission products in an operating reactor. All the references I can find on the net are for the decay of a fixed lump. In an operating reactor the lump is (for a while) growing at the same time it is decaying. So, I started my...
  10. M

    Odd Isotope half-life help

    To mathman, re http://atom.kaeri.re.kr/ton/ (This forum doesn't indent enough!) Yes I visited the Korean site, twice. On my second visit I followed one reference URL back to a UK paper on PDF at Brookhaven. A bit roundabout, but very worldly. The PDF topic is not really half-lives, but they...
  11. M

    Odd Isotope half-life help

    Sorry. I do mean the first excited state. None of the isotopes on my list show up on the list you provided. These aren't exactly rare fission products. The max yield for 109-Ru-m1 is over 1%, albeit for 142-Am-m1 as the fuel. For 85-Se-m1 it's ~0.5% for 233-U and 235-U. I expect they aren't...
  12. M

    Odd Isotope half-life help

    Ooh, so close. Got the first one on the list, then went 0 for 6. Thanks.
  13. M

    Odd Isotope half-life help

    The Sigma database at Brookhaven lists seven isotopes as fission products for which I can't find half-life data. I've tried nea6287-JEFF-20-1, the NuDat_2 web site, Nuclear Wallet Cards and Wikipedia. Anybody have any other ideas? The isotopes are 74-As-m1 85-Se-m1 86-Br-m1 109-Ru-m1...
  14. M

    Get rid of transuranians in Liquid Fluoride Thorium Reactors?

    The collection point in the MSRE was the fuel input tank. It was partially filled with helium. They bubbled helium gas up through the fuel and this helped carry about 5/6ths of the xenon away. This paper from 1969 mentions that, and some of the research requirements for future MSR development...
  15. M

    Get rid of transuranians in Liquid Fluoride Thorium Reactors?

    For a fast, solid fuel reactor, probably. This thread is about LFTR, a thermal liquid fueled reactor. There are fast liquid fueled reactor designs. Gaseous fission products bubble out of the liquid for either. Not a pressure problem, but piping the gasses off elsewhere has a number of other...
  16. M

    Get rid of transuranians in Liquid Fluoride Thorium Reactors?

    Thanks. I didn't know the 14MeV data was for fusion. This simplifies things. I would use just two bins, fast and slow. The user would have some design in mind, and possibly some high-powered sims to estimate the energy distribution. That estimate would, with some more work, yield two...
  17. M

    Get rid of transuranians in Liquid Fluoride Thorium Reactors?

    From Wikipedia (Molten salt reactor or Liquid fluoride thorium reactor) LFTR uses enriched Lithium, 99+% 7-Li. The remaining 6-Li will capture neutrons to a small extent, producing pesky Tritium. Minuscule amounts of Fluorine and Beryllium (and 7-Li) will also be transmuted. I would suggest...
  18. M

    Get rid of transuranians in Liquid Fluoride Thorium Reactors?

    Interesting geometry there. And I didn't know the fissions from fast neutrons was so high. But that depends on your definition of "fast". I have seen fission yield data for three speed bins, labeled 0.0253, 500K, and. 14 million eV. Do you include the middle energy bin in you 8-10%? What is...
  19. M

    Get rid of transuranians in Liquid Fluoride Thorium Reactors?

    The first neutron is required to produce 233-U anyway. 233-Pa has a capture cross-section of 39.5, and a half-life of a month. It is a bit of a race, but I think far more will decay before it absorbs. I don't know the math needed to prove that. I just figure a fuel atom "lives" in the core...
  20. M

    Slow or fast neutrons in LFTRs (Liquid Fluoride Thorium Reactors)

    I think the breeding ratio for one of ORNL's designs was 1.07. They sacrificed just about every other design consideration to achieve that, however. These days, given the availability of uranium, 10 or 20% makeup fuel is not a big deal. This expands the design space nicely.
  21. M

    Get rid of transuranians in Liquid Fluoride Thorium Reactors?

    We need some definitions here. Processing is too broad a term. Some folks will think immediately of PUREX, and that is way off. There is one on-line process common to all MSR designs. That is called an off-gas system. The 135-Xenon, in particular, will bubble out of the liquid with a...
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