I have a problem on my MCNP5 cross-section library

In summary, the speaker is having trouble running input files with materials containing elements with atomic numbers 34000 and 52000 in their MCNP5 cross-section library. They suggest building the materials using individual isotopes or finding a substitute material. It is also possible to search for the data online and use the isotope library utilities in MCNP to add it to the library.
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i have a problem on my MCNP5 cross-section library
I have a problem with my MCNP5 cross-section library. Se and Te elements with atomic numbers; 34000 and 52000, respectively, have no neutron cross-section stored, either neutron contentious or neutron other, in the library, and so I can't run any input file that has any material of them because of the neutron cross-section.!!
 
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  • #2
34000 and 52000 indicate the natural form of these elements. That is, it is asking MCNP to look for the natural isotope distribution library for Se and Te. Several of the natural substances are not there while the individual isotopes are there.

Depending what is in your library, you have some choices. If the individual isotopes are there, you could build your material out of them. So, Se for example: https://en.wikipedia.org/wiki/Selenium

You could look in your lib for 34074. 34076, 34077, 34078, 34080, and 34082. If they are all there you can build natural Se out of them. Pretty close, anyway.

If those isotopes are not in your library, you can try to find a material that you can substitute. That's a fairly complicated thing. And it's difficult to be confident if you don't have any data to guide you. Maybe if only some of those isotopes are present, you could build a partial model, maybe using the more common isotopes.

If you are keen, and need these isotopes, and you have the time, you could see if the data exists somewhere on line. Then you could learn the isotope library utils that come with MCNP. NJOY is one of them.
 
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