Hello everyone,
I am trying to perform a full core depletion analysis for the mixed spectrum reactor concept.
The idea is there are two regions inside the core, one is moderated and the other is not. So, the reactor can utilize the benefits of both spectrum of neutrons. However, the official depletion chain xml files are given only for either thermal spectrum or fast spectrum. Is there any combined depletion chain xml available? Or can anyone guide me on how I can modify the files?
Thanks in advance. I am attaching my core design for further scrutiny should you need it.
I apologize for the messy code. A lot of trial and errors are present here.
To produce a depletion chain you run one of the generate scripts, such as this one
To add the branching ratios for a PWR or SFR you run this script which splits some of the n,gamma reactions into multiple n,gamma reactions into metastable and ground. This could be the stage where you use different branching ratios.
https://openmc.org/depletion-chains has details on the combination of nuclear data and branching ratios used when generating each downloadable chain file.
You could however compute your own branching ratios by tallying total capture reaction rates, capture to ground, and capture to metastable states for specific isotopes. This is how the SFR branching ratios were found. “The effective branching ratios were taken to be the ratio of reactions to ground to total number of capture reactions for each isotope.” The fantastic Serpent wiki also provides some info on calculating branching rarios Default isomeric branching ratios - Serpent Wiki
You could also remove nuclides with long half lives with this script.
Another customisation that you might be interested in is to include more reactions in the chain file generation. See this issue for more details.
I have a fork of the openmc-dev/data repo over here which might also be of interest as it has chain files that have be generated with all 83 of these reactions instead of the default 6.