Check for elastic scattering with isotropic mu.
Check for elastic scattering with isotropic mu.

This apparently happens for Sm150 in JEFF 3.2.

smharper/openmc,paulromano/openmc,liangjg/openmc,liangjg/openmc,walshjon/openmc,paulromano/openmc,smharper/openmc,mit-crpg/openmc,shikhar413/openmc,wbinventor/openmc,paulromano/openmc,wbinventor/openmc,johnnyliu27/openmc,johnnyliu27/openmc,shikhar413/openmc,shikhar413/openmc,johnnyliu27/openmc,mit-crpg/openmc,shikhar413/openmc,smharper/openmc,paulromano/openmc,smharper/openmc,johnnyliu27/openmc,amandalund/openmc,mit-crpg/openmc,amandalund/openmc,amandalund/openmc,wbinventor/openmc,mit-crpg/openmc,walshjon/openmc,wbinventor/openmc,liangjg/openmc,walshjon/openmc,amandalund/openmc,walshjon/openmc,liangjg/openmc