Reduce memory usage of Materials.export_to_xml
Reduce memory usage of Materials.export_to_xml

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