Add energy group structure: SCALE-999

[yrrepy]

Description

Adds SCALE-999 energy group.
This is frequently used in Origen for general purpose activation with the JEFF-3.0/A library.

Adds FOMG-16k and VESTA-43k. These are useful for multi-group binning (MGB) activation calculations where a fine energy structure is important, but a fine reaction-rate calculation in the neutron transport would be too slow. SigFigs: I have followed the exact VESTA precision, and favoured high precision for the FOMG numbers. But I could see why others might have different opinions on the formatting or number of values per row, etc. (Being that there are so many bins)

SCALE-999
https://www.ornl.gov/sites/default/files/2020-05/Pub%20ID%2058284%20-%20PHYSOR2016_SCALE62_Origen_extended_summary_v5_final.pdf
https://www.nrc.gov/docs/ML1218/ML12184A002.pdf
https://info.ornl.gov/sites/publications/Files/Pub67728.pdf

FOMG-16k

https://fispact.ukaea.uk/wp-content/uploads/2016/07/snamc2013_05203.pdf
https://etheses.whiterose.ac.uk/id/eprint/4427/1/PhD_Thesis_Corrected_FINAL_FINAL_3_9_13.pdf

VESTA-43k https://www.osti.gov/etdeweb/servlets/purl/20902503 https://roma.sckcen.be/ws/portalfiles/portal/4558859/An_Optimum_Approach_to_Monte_Carlo_Burn_Up.pdf https://rsicc.ornl.gov/codes/ccc/ccc7/ccc-769.html https://www.tandfonline.com/doi/abs/10.13182/NSE07-A2695

Checklist

• I have performed a self-review of my own code
• I have followed the style guidelines for Python source files (if applicable)
• I have made corresponding changes to the documentation (if applicable)

[paulromano]

For those large structures, perhaps it makes more sense to put them into a separate binary file and then load them in on-demand?

[yrrepy]

Not super sure how to do that, but that seems reasonable.
The fine energy structures are rather unsightly.

[shimwell]

If it helps I guess this PR could be broken down into two parts if it helps. A PR with the smaller SCALE-999 group structure. I think we could review and merge this quickly. A follow up PR with the two larger group structures in binary file like a h5 file

[yrrepy]

Done.

[shimwell]

This PR looks good to me. Will merge in on Monday if there are no objections

[paulromano]

Thanks guys for iterating on this. Good decision to punt on those large group structures but at least get the 999 group merged in 👍

[yrrepy]

These larger energy groups I believe follow equations, equal lethargy in this region, 1000 eV here, etc.
What about implementing it mathematically?

The optimal binning structure, named FOMG ( Fusion Opti-
mised Multi Group) is split into three distinct sections. The ther-
mal energy region is defined in the range 10−5eV ≤ E L < 1 eV
with 1,000 bins and an energy width of 1.0 meV. The mid en-
ergy group is defined in the range 1 eV ≤ E L < 2 MeV with
14,000 bins and a lethargy width of 1.036 × 10−3 . The high
energy group is defined in the range 2 MeV ≤ E H < 19.6 MeV
with 1,000 bins and an energy width of 17.6 keV.