# talley question in OPENMC

**URL:** <https://openmc.discourse.group/t/talley-question-in-openmc/171>\
**Category:** User Support\
**Created:** [September 30, 2015, 3:39am UTC](https://openmc.discourse.group/t/talley-question-in-openmc/171 "2015-09-30T03:39:05Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![niuoba](https://avatars.discourse-cdn.com/v4/letter/n/f04885/32.png) [@niuoba](https://openmc.discourse.group/u/niuoba)\
**Post date:** [September 30, 2015, 3:39am UTC](https://openmc.discourse.group/t/talley-question-in-openmc/171/1 "2015-09-30T03:39:05Z")

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Hi, All:

In OPENMC, (n,2n) and (n,3n) tally is write like n2n and n3n in tallies.xml file  
Is there any feasibility to tally (n,gamma) and (n,p) reaction ration in tallies.xml file

Yours NiuOBA

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**Author:** ![paulromano](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/paulromano/32/486_2.png) [@paulromano](https://openmc.discourse.group/u/paulromano)\
**Post date:** [September 30, 2015, 3:56am UTC](https://openmc.discourse.group/t/talley-question-in-openmc/171/2 "2015-09-30T03:56:02Z")

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In the developmental branch, there is now a capability to explicitly name reactions, so for example you could give:

(n,2n) (n,3n) (n,gamma) (n,p)

In the currently released version, the same can be achieved, but MT numbers must be used for the (n,gamma) and (n,p), so it would be:

n2n n3n 102 103

Best,  
Paul

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**Author:** ![niuoba](https://avatars.discourse-cdn.com/v4/letter/n/f04885/32.png) [@niuoba](https://openmc.discourse.group/u/niuoba)\
**Post date:** [September 30, 2015, 4:54am UTC](https://openmc.discourse.group/t/talley-question-in-openmc/171/3 "2015-09-30T04:54:36Z")

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Dear Paul Romano

Thank you for your quickly reply  
It really helps me a lot

Another question is:  
How can I find the TM token number real physical meaning, do you have a table?

The tally result for n2n n3n 102 and 103 is Reaction Ratio, which means Macro-Cross section times flux.  
Is there and feasibility for me to get micro-cross section times flux, directly from OPENMC.  
I mean not manually change the result into micro-.

Thank you for your help in advance.

Yours  
NiuOBA

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**Author:** ![paulromano](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/paulromano/32/486_2.png) [@paulromano](https://openmc.discourse.group/u/paulromano)\
**Post date:** [September 30, 2015, 6:39am UTC](https://openmc.discourse.group/t/talley-question-in-openmc/171/4 "2015-09-30T06:39:26Z")

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The physical meaning of MT numbers can be found in Appendix B of ENDF-102:  
[https://www.oecd-nea.org/dbdata/data/manual-endf/endf102.pdf](https://www.oecd-nea.org/dbdata/data/manual-endf/endf102.pdf)

Currently no, there is no automatic way to obtain microscopic cross sections; you’d have to do it manually using the known number densities. I would suggest taking a look at the new Python API as that might aid your post-processing. An example can be found here:  
[http://mit-crpg.github.io/openmc/pythonapi/examples/pandas-dataframes.html](http://mit-crpg.github.io/openmc/pythonapi/examples/pandas-dataframes.html)

Best,  
Paul