Rescuing a Treasure—Uranium-233

Uranium-233 ( 233 U) is a synthetic isotope of uranium formed under reactor conditions during neutron capture by natural thorium ( 232 Th). At high purities, this synthetic isotope serves as a crucial reference for accurately quantifying and characterizing natural uranium isotopes for domestic and international safeguards. Separated 233 U is stored in vaults at Oak Ridge National Laboratory (ORNL). These materials represent a broad spectrum of 233 U from the standpoint of isotopic purity—the purest being crucial for precise analyses in safeguarding uranium. All 233 U at ORNL currently is scheduled to be down blended with depleted uranium beginning in 2015. Such down blending will permanently destroy the potential value of pure 233 U materials as certified reference materials for use in uranium analyses. Furthermore, no replacement 233 U stocks are expected to be produced in the future due to a lack of operating production capability and the high cost of restarting operation of this currently shut down capability. This paper will outline a recent effort to assess the annual consumption of 233 U in the U.S., describes the gap between current supplies and future needs, and develops a program to rescue the purest of 233 U materials—arguably a national treasure—from destruction by down blending so it may be preserved for use as a crucial reference for safeguarding nuclear materia