Building a Derivative Library#

Sometimes you may want to investigate the effect of a single nuclide evaluation on a reactor model. For instance if you work on chloride molten salt, you may be aware that Cl35 \((n,\alpha)\) cross-sections are not very well known above 1MeV, and this may have large consequence on the reactor’s eigenvalue. Tahara shows some comparison library comparisons for an MCSFR model.

To target Cl35 specifically you may want to run a calculation your usual library (say, endfb8), and using this same library all nuclide except Cl35 where you might use JENDL-5.0 or whatever you’d prefer. The first step is to install JENDL-5.0:

$ ndf install jendl5

To build library derivative of ENDF-B/VIII.0, you could create an NDOmcer input file to rebuild the entire thing, but this would mean that hundreds of cross-section files would be duplicated with no benefit. Instead, the smarter way of building the library would be to build only the new Cl35.h5 file, and write the cross_sections.xml file such that all other nuclide point to the endfb8 library.

To do this, you can replace the base element in NDOmcer’s input file with a reuse element. This element should be associated with a library name already available to NDOmcer, such as the endfb8 library we created in the first tutorial.

# endfb8-jendl5-cl35.yml
name: endfb8-jendl5-cl35
summary: A library based on the ENDF-B/VIII.0 evaluations, with Cl35 from JENDL-5.0.
description: |
  A library based on the ENDF-B/VIII.0 evaluations, with Cl35 from JENDL-5.0.
neutron:
  reuse: endfb8
  add:
    jendl5: Cl35
  temperatures: 250 294 600 900 1200 2500
photon:
  base: endfb8
tsl:
  base: endfb8

You can now run NDOmcer:

ndo build endfb8-jendl5-cl35.yml

Looking at the library in your database should look something like this:

$NDMANAGER_HDF5/endfb8-jendl5-cl35
├── cross_sections.xml
├── input.yml
├── neutron
│   ├── Cl35.h5
│   └── logs
│       └── Cl35.log
├── photon
│   └── logs
└── tsl
    └── logs

With the cross_section.xml file referencing the endfb8 library for most nuclides.

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