Hotfix: incomplete calculation of nu-fission
Hotfix: incomplete calculation of nu-fission

energy grid length `n_grid` is different for different temperatures.
walshjon/openmc,liangjg/openmc,liangjg/openmc,shikhar413/openmc,wbinventor/openmc,smharper/openmc,paulromano/openmc,wbinventor/openmc,amandalund/openmc,smharper/openmc,liangjg/openmc,paulromano/openmc,amandalund/openmc,shikhar413/openmc,shikhar413/openmc,mit-crpg/openmc,shikhar413/openmc,amandalund/openmc,mit-crpg/openmc,wbinventor/openmc,wbinventor/openmc,walshjon/openmc,paulromano/openmc,mit-crpg/openmc,walshjon/openmc,walshjon/openmc,amandalund/openmc,mit-crpg/openmc,liangjg/openmc,smharper/openmc,smharper/openmc,paulromano/openmc