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Need help with KW h

  1. Jan 17, 2012 #1
    Hello everyone!

    Could you please help me with choosing the correct term?
    The situation is as follows:

    A reactor generates energy throughtout the core life and it is measured in MW h.
    What would you call this characteristic that is measured in MW h?


    If translated from Russian (I'm from Russia) word by word it may sound as:

    Energy generation

    I guess it's not a proper term for that?

    Help me please.

    Thank you
     
  2. jcsd
  3. Jan 17, 2012 #2

    jedishrfu

    Staff: Mentor

    Last edited: Jan 17, 2012
  4. Jan 17, 2012 #3
    Thank you.

    I've already looked through the Wiki, it just explains what is kW h.

    I rather need the name of the characteristic measured in kW h that relates to the energy generated over the reactor core life (or a cycle). It describes the amount of energy generated over the period of time between the two fuel reshufflings (reloadings).
    I don't believe it is necessarily electric power.

    What I'm asking about is... Here is an example:
    The characteristic measured in seconds is time.
    The characterisitic measured in degrees celcius is temperature.
    The characteristic measured in km/h is speed.

    What is the characteristic measured in kW h (keeping in mind that it relates to the amount of energy generated over the core life)?
     
  5. Jan 17, 2012 #4

    jim hardy

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    not quite sure who's your audience..

    power production comes to mind, though it sounds not rigorously correct, does it..?

    the numbers get mighty big.

    reactor engineers use unit of megawatt-days, MWD, and call it 'burnup'
    or megaqatt-days per metric ton of uranium, MWD/MTU , still called burnup.
    they are more interested in the core's nuclide inventory than in resale of energy
    and burnup is convenient for tracking that.

    plant engineers are more interested in how much electrical energy was produced and sold,
    and that we called 'generation',
    'gross generation' is what the turbo-generator produced
    and 'net generation' is what went out to grid after subtracting our in-house consumption.
     
  6. Jan 17, 2012 #5
    Thank you very much!
    In fact I'm working for a nuclear engineering company. The term "burnup" is used very often here and it's usualy measured in MW day/t U as you mentioned.
    I do not know why, but our guys additionally use the term that, if directly translated from Russian, sounds like "power production" or "energy generation".
    One of the guys suggested "energy-producing" that he found in a certain dictionary, but I feel it sounds pretty awkward...
    I was also explained that the term in question is the amount of energy produced over a cycle (the time that one core is in operation until the next reloading). The units of measurement that are used for the above magnitude is MW h (which looks pretty simlar to MWD).

    The situation is that both burnup and "power production" could be used in a table with characteristcs and they need to be differentiated somehow.
    My view here is that it does not look approprate if "burnup" is used two times in the same table, or in a paper, even with different units of measurements.
    It may cause a lot of confusion.

    Thank you again for the response and wonderful clarification.
     
    Last edited: Jan 17, 2012
  7. Jan 17, 2012 #6

    jim hardy

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    you're speaking aboout total heat produced by the reactor over a cycle ?
    that's a lot of megawatt hours . our reactor was over 2 gw.

    if your audience is mechanical engineers why not call it Q[itex]_{total}[/itex] or [itex]\Sigma[/itex]Q or ∫power ?

    make units BTU's and really confuse things..
    :) :)
     
    Last edited: Jan 17, 2012
  8. Jan 17, 2012 #7

    jim hardy

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    aha - i think we would have called that "thermal generation" (or something similar) for purpose of drawing listener's mind toward energy and away from nucleonics.
     
  9. Jan 17, 2012 #8
    The characteristic measured in kw-hr is 'energy.' Other units for energy include joule, BTU, calorie, erg, horsepower-hour, electron volt, newton meter, and foot-pound.

    I don't think there is an english term for the thermal energy generated by the core over one cycle. We might just call it "the thermal energy generated over the cycle." Burnup is a term reserved for discussions of how much of the uranium has been used. It is related to your question but it is different since it is (always) the energy generated per unit mass of uranium (typically MW-days per ton of uranium). In other words, a 'specific energy generation.'
     
  10. Jan 17, 2012 #9
    This is wrong or at least it is apt to be confusing. A MW-hr is the energy it takes to generate one MW for one hour. Not in one hour. Watt is a unit of power, it already has the time term in the denominator.

    Also, MW-hr is not necessarily reserved for electrical energy. To help keep things straight, core power is typically noted as MWth (where the 'th' signifies 'thermal') and generator electrical output is noted as MWe (where 'e' signifies 'electric').
     
  11. Jan 17, 2012 #10
    Thanks to everyone!

    Out of what I have read above, I guess that it would be proper to use:

    Generated Energy

    The units of measurement are appropriate and it is in good correlation with the Russian term.

    So what do you say? Will it sound ok in the context?


    I'm not sure of what type of energy our guys are speaking here.
    I can only assume it is thermal energy, but I'm not sure.

    Thanks again
     
  12. Jan 17, 2012 #11
    That's what I said to the engineer that asked me about this term!
     
    Last edited: Jan 17, 2012
  13. Jan 17, 2012 #12

    jim hardy

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    that sounds okay.

    here's a little more background from a plant guy's perspective:

    we calculated thermal energy produced every minute
    and measured electrical energy going out
    kept hourly and daily running totals
    divided the two
    to get "Heat Rate"

    which is just efficiency
    we used units of BTU/KWH but you guys are doubtless SI over there.

    we did not track long term
    just an hourly and a daily heat rate.
    point being numerator is heat and denominator is KWH both accumulated over same interval


    10,800 was our approximate heat rate
    adjacent fossil units would do 9,000 on oil
    i'm told combined cycle units can beat 6,000

    heat-rate was the number of interest to our financial types.

    i'm not sure of what use total heat procuced in a cycle would be
    but you can't average rates,
    so if you want a number for the whole year's heat rate you have to accumulate heat and kwh separately and divide them.
    they'll be huge numbers so have your programmers check to make sure you wont overflow your spreadsheet's math algorithms - some i've heard only go to 10^35.
    probably that's enough though. just that ounce of prevention

    if that's what you are doing with the number , maybe a label or subscript like 'accumulated cycle (heat, Q, gigaloules - pick a mnemonic noun)' ?

    you know your audience and i dont. can you ask one of them via a backdoor?

    good for you for so much effort in choosing a name. Lavoisier wrote at length in his introduction to treatise on chemistry about importance of naming terms. google his name and 'lemoyne.edu'
     
    Last edited: Jan 17, 2012
  14. Jan 17, 2012 #13
    I just looked through the papers and it turns out to be that the guys use QT to denote the energy generated by the certain moment of the cycle (they measure it in GW h). It relates to cacluations of burnup distribution.
    My audience is the guys who develop computer codes.
     
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