Specifying temperatures in MCNP

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Temperature in MCNP
How do I express the temperature in the cell cards of the MCNP?, Say the temperature of the fuel is 500K, how do I write it as the following PWR example?
 

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  • #2
rpp
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In the cell cards, you specify the temperature in units of MeV by multiplying the temperature in Kelvin by the Boltzmann constant 8.617e-11 MeV/K. For example, 600K would be "tmp=5.17020E-08"

However, this is not the only place you need to worry about temperatures. In the material cards, you need to attach the library generated at the correct temperatures. A list of the library identifiers and temperatures used to be included in the "Appendix G" of the users manual, but it has now moved to a separate document. There may be a newer version, but I have report LA-UR-17-20709.
If you are using the ENDF/B-VII.1 cross sections, ".80c" is at 293.6 K, ".81c" is at 600 K, ".82c" is at 900 K, etc.

Finally, you also need to make sure you are using the correct temperature S(alpha,beta) cards. These can be found in Appendix G also.

If you need temperatures that do not line up with the library temperatures, there is a utility program "makxsf" that you can use to interpolate existing libraries and create libraries at user specified temperatures.

There is also development work to allow "on-the-fly" temperatures, but I am not sure what the status of this is. It will probably be released in a future version of MCNP.
 
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  • #3
rpp
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I also suggest that you change the name of the post to something that has to do with specifying temperatures in MCNP. Your question has nothing to do with supercritical water reactors.
 
  • #4
berkeman
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I also suggest that you change the name of the post to something that has to do with specifying temperatures in MCNP. Your question has nothing to do with supercritical water reactors.
@rpp -- Can you propose a new title? I think the edit window for the OP has expired, but the Mentors can change the title still...
 
  • #5
rpp
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@rpp -- Can you propose a new title? I think the edit window for the OP has expired, but the Mentors can change the title still...
How about "Specifying temperatures in MCNP"?
 
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  • #6
berkeman
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Done. Thanks!
 
  • #7
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How about "Specifying temperatures in MCNP"?
I also suggest that you change the name of the post to something that has to do with specifying temperatures in MCNP. Your question has nothing to do with supercritical water reactors.
I'm very thankful to you, and I apologize for the fatal mistake of the title but I couldn't edit it when I saw your reply two days ago.
 

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