Inelastic Scattering and data reading bugs/issues

User Support
1

I’ve been doing some cross code validation of several MC codes and included OpenMC, I have found a number of issues I think you need to be aware of and/or should be addressed. What is the best form to provide the group with these results?

2

Hi Andrew,

Thanks for getting in touch! Emailing this list is fine. Other users might be interested in your findings as well.

Look forward to hearing more.

Best regards,
Paul

3

Hi I’ve just realised that I didn’t post anything!

Please find attached the PDF https://www.dropbox.com/s/guuplo39nf240qq/validation_report.pdf, the first one to be aware of is N-15, very few codes can get this one right and there are a few others. Ar-38 is an issue, Ca-40 is also a problem.

One thing that is very good with regards to OpenMC is that a lot of data checking is done, which is not done by MCNP for example. If you have any comments or questions please feel free to contact me.

Thanks

Andy

4

Hi Andy,
Thanks for posting this. Let me get the context straight here: it looks like you set up an infinite media, single nuclide fixed source problem with a monoenergetic source at 20MeV and tallied the flux spectra in ultrafine groups? Is that right? It looks like you did 1E7 particles total? Finally, this was the ENDF/B VII.1 release which is shipped with MCNP6, or is it a custom NJOY run?

Next, that’s actually pretty good to see we get most of the reactions right. Since most nuclides are just fine, we probably do have the energy/angle sampling right, but just need to better handle some NJOY & ACE ‘eccentricities.’ In fact, just this week I was struggling with a Ca-40 issue; looking back at my notes it seems that (in ENDF VII.0 at least) there are two incoming energies for angular distributions (i.e., file 4 data) which are the same value.

5

Thanks for the excellent study Andy. It appears we do have some issues to look into.

Adam – is that you volunteering to figure out the discrepancies? :slight_smile:

Best regards,
Paul

6

I’m definitely interested, I think progress will be slow for the next months (limited time to graduate and a new baby coming in 6 weeks), but I can definitely volunteer for it.