updated equation for PromptNuFissionXS
updated equation for PromptNuFissionXS

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