Photonuclear data

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colvinem
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Re: Photonuclear data

Post by colvinem » Fri Aug 07, 2020 5:30 am

Me again! I've been able to do everything I need to with the cross sections, I think - NJOY created the full library I need and I was able to create a script to correctly format the .xsdir file so that it could be used to generate an .xsdata file. All of that seems fine, my cross sections are listed with a .00p extension.

But Serpent just ignores it. This is what my library call looks like, the way I just attempted it:
set acelib "endfb7u" "/path1/endf70sab" "/path2/TENDL2019.xsdata" "/path2/general.xsdata"
set declib "sss_endfb7.dec"
set nfylib "sss_endfb7.nfy"
set pdatadir "/path2"

The general.xsdata file is the one generated from the two MCNP lib files, which just has elemental info, not broken down by isotope. When I look at the .out file from my model, I can see where it read the cross sections given in the general.xsdata file, but it's not doing anything with the TENDL data.

My materials are all listed like this:
mat Np237a ## burn 10
93237.03c ##
8016.03c ##
13027.03c ##
Do I need to do something that will tell it to look at the .00p cross sections as well as the .03c set? I'm not entirely clear on how it handles the cross sections and decides what to look at.

Thanks again, this has been immensely helpful for me, my research group, and the folks I'm working with this summer.

Ana Jambrina
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Re: Photonuclear data

Post by Ana Jambrina » Fri Aug 07, 2020 11:34 pm

Serpent reaches cross section data (neutron or photon) whenever is needed. Aside to make available the libraries, there is no say to Serpent what to read. If you are providing the neutron/photon cross section data and materials, with isotopic compositions related to those libraries, as it looks like you do, in principle everything should go as it supposed to, but I guess it does not.
I might need some help here, to know what is going on. Off the top of my head:
- Is there any warning/error outputted by Serpent? Or does it the calculation finish without any problem?
- I am guessing you want to run a coupled neutron-photon transport calculation. If that is the case, and the calculation finished just OK, and there is no trace of photon data in the output file, did you include the ‘ngamma’ option in the input file? (check: http://serpent.vtt.fi/mediawiki/index.p ... set_ngamma).

[It should be possible to just ‘set ngamma 1 or 2’ (using the default values); however there is a bug in Serpent 2.1.31 (which will be fix in the next release), related with the WMIN and NMAX for implicit mode (ngamma = 2).
For 'ngamma = 2' you have the following options: (1) modify initdata.c as suggested in a previous post (viewtopic.php?f=26&t=3318&p=10353&hilit=ngamma#p10353); (2) initialise it yourself to the default values, if not others, WMIN = 0.1 and NMAX = 10.0].
- Ana

colvinem
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Re: Photonuclear data

Post by colvinem » Sun Aug 09, 2020 3:12 am

-No errors. I'm getting a distribution of isotopes in my target approximately (within ~1%) of the results I get with just a neutron problem. In the file that saves what would show up in the terminal if I was running Serpent directly (I'm on a cluster with a submission system), the photon system gives me this:
Adding photon interaction data...
Element 1000.84p -- hydrogen (photon library)
Element 2000.84p -- helium (photon library)
Element 3000.84p -- lithium (photon library)
Element 4000.84p -- beryllium (photon library)
Element 5000.84p -- boron (photon library)
So it's not adding any of the other photon libraries. I have elemental data, but it won't do anything with isotopic data.

-ngamma is set to 1. As mentioned above, the results are slightly different than a pure neutron version, but it's not a huge difference, and it's showing that it's only seeing that .84p library, not the .19u.

-I've tried a few different things - I originally used the .00p extension (it automatically picked .00u, and I swapped that for p to get it through the xsdirconvert file), then went through and changed them all out for .19u to see if that worked. I also edited the .xsdata file to indicate that the associated temperature to see if that would fix it (before I went and reprocessed all of the cross section data)

Ana Jambrina
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Re: Photonuclear data

Post by Ana Jambrina » Sun Aug 09, 2020 3:21 pm

It might be the case that Serpent for photon transport calculation is looking for elemental data when looking at the material compositions - Serpent handles photon physics Z = 1-99 elements. (Check the '.out' file, you will see the list of nuclides and their corresponding flags; also, check '.xsdata' coming from mcplib63/mcplib84 to verify the format).
For more information about the photon physics model in Serpent 2.1.31, see the post: viewtopic.php?f=10&t=3429).

mcplib63/mcplib84 libraries contains element Z < 100 (including Z = 93, Neptunium). You can use your own processed cross section library from NJOY if you do not want to use those coming from MCNP; however, it might need to be element-based photon cross-sections (You can switch libraries, due to, the first library where a nuclide is included, is the one considered (for photons, since Serpent is not looking of library ID)).

You said that there are not differences between single physics neutron transport and coupled neutron/gamma transport. Is there photon production trace in the '_res.m' file? Have you set some detectors to verify that?

I do not know your end goal here, running a coupled neutron/gamma burnup simulation, but you might want to take a loop the energy deposition model in Serpent, (see: https://doi.org/10.1016/j.anucene.2019.02.003); which, for coupled neutron/gamma calculation, would correspond to ‘edepmode’ option - mode 3, (see: http://serpent.vtt.fi/mediawiki/index.p ... t_edepmode).

If you are looking for a radiation transport calculations involving activated materials, maybe modelling a radioactive decay source is an option: burnup/activation calculation to setup the decay source, followed by a photon transport calculation in decay source mode. (See: http://serpent.vtt.fi/mediawiki/index.p ... al_example). In photon transport mode it is possible to define isotopic material compositions; then, Serpent calculates the elemental compositions automatically.
- Ana

colvinem
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Re: Photonuclear data

Post by colvinem » Wed Aug 12, 2020 8:29 am

I'll have to go back and rethink things a bit, then. Essentially, what I'm trying to do is predict the irradiation of Np-237. The reaction we want is a neutron capture followed by beta decay into Pu-238. The thing I don't think we're accurately capturing right now is a (gamma,n) that will, down several decay stages, lead to Tl-208 which is a problem for actually handling material. We can't use ORIGEN on account of the gamma, but we'd hoped that running Serpent with ngamma 1 and running it as a burn problem would take us through the irradiation process. When I mentioned not seeing much change, it was in the ending composition of my targets.

I don't think a decay stage will work, because it's only going to see those high energy gammas at power, coming from fuel. I'll have to contemplate my options. I think I might be able to build a script to do some of what I need (eg, making the "neptunium" cross section based on the actual composition at each time step I care about). Do you know if there's been anything published on the photonuclear reactions? The article you linked just says that part is in another article, but I couldn't find one anywhere.

Again, I can't thank you enough for all your help!

Ana Jambrina
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Re: Photonuclear data

Post by Ana Jambrina » Wed Aug 12, 2020 10:33 am

- Ana

Warner
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Re: Photonuclear data

Post by Warner » Sun Feb 14, 2021 5:06 pm

Hi,

I have been trying to follow the instructions above to use photonuclear data. My end goal is to run neutron and gamma dose calculations based on the activation of reactor materials.

Here are the steps I'm following:
- I downloaded mcplib63, mcplib84, and xsdir-mcnp5-1.51-new from LANL (https://mcnp.lanl.gov/BUGS/BUGS.shtml)
- I put all three files above and xsdirconvert.pl into the same directory.
- I changed the first line of xsdir-mcnp5-1.51-new to be "datapath=/home/username/file_directory/"
- I ran the Perl script with "perl xsdirconvert.pl xsdir-mcnp5-1.51-new >> photon.xsdata"

The Perl script ran to completion, but threw errors for all the ace files missing (that doesn't seem to be an issue from previous posts). The photon.xsdata file was created in the directory, but it is an empty file.

Am I missing any steps or files to be able to do this conversion? Thanks!

Ana Jambrina
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Re: Photonuclear data

Post by Ana Jambrina » Sun Feb 14, 2021 5:34 pm

Couple of checks:
- The 1st line of ‘xsdir’ file should correspond with the absolute path of the directory where the data files are.
- The downloaded photon cross-section files might be named including a ‘.txt’ extension: ‘mcplib63.txt’ and ‘mcplib84.txt’. If that is the case, rename the files to: ‘mcplib63’ and ‘mcplib84’ to match the relative path included the ‘xsdir’ file.

After that you should be able to obtain a ’xsdata’ file including only the nuclides listed in both libraries. Keep in mind that when running the ‘xsdirconvert.pl’ script some print-outs will show up corresponding to missing libraries (‘does not exist’).

Note: in order to avoid any potential problem, perform the checking (and renaming) directly from the terminal.
- Ana

Warner
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Re: Photonuclear data

Post by Warner » Sun Feb 14, 2021 7:31 pm

Thanks Ana! I think I had somehow messed up the xsdirconvert.pl file. I redownloaded it and ran it again and got a properly populated .xdata file.

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