Support for laboratory angle-energy data (ACE LAW=67) #1487
Description
OpenMC doesn't currently have an implementation of ACE LAW=67 (laboratory angle-energy data) that corresponds to ENDF MF=6, LAW=7. I had never bothered to implement this because it doesn't seem to appear in any modern libraries. However, there are a few cases of it in older libraries, e.g., FENDL 2.0 (see discussion on openmc-dev/data#21).