Don't allow source energies above 20 MeV for the time being.
Don't allow source energies above 20 MeV for the time being.

kellyrowland/openmc,shikhar413/openmc,wbinventor/openmc,walshjon/openmc,lilulu/openmc,mit-crpg/openmc,samuelshaner/openmc,amandalund/openmc,walshjon/openmc,mit-crpg/openmc,lilulu/openmc,shikhar413/openmc,wbinventor/openmc,sxds/opemmc,amandalund/openmc,johnnyliu27/openmc,mjlong/openmc,sxds/opemmc,shikhar413/openmc,liangjg/openmc,samuelshaner/openmc,wbinventor/openmc,amandalund/openmc,bhermanmit/openmc,smharper/openmc,lilulu/openmc,paulromano/openmc,liangjg/openmc,johnnyliu27/openmc,kellyrowland/openmc,shikhar413/openmc,mit-crpg/openmc,paulromano/openmc,walshjon/openmc,mjlong/openmc,johnnyliu27/openmc,smharper/openmc,mit-crpg/openmc,samuelshaner/openmc,bhermanmit/openmc,walshjon/openmc,wbinventor/openmc,paulromano/openmc,smharper/openmc,liangjg/openmc,johnnyliu27/openmc,samuelshaner/openmc,smharper/openmc,amandalund/openmc,paulromano/openmc,liangjg/openmc