A technical assessment of the current inventory [~70,150 metric tons of heavy metal (MTHM) as of
2011] of U.S.-discharged used nuclear fuel (UNF) has been performed to support decisions regarding fuel
cycle strategies and research, development and demonstration (RD&D) needs. The assessment considered
discharged UNF from commercial nuclear electricity generation and defense and research programs and
determined that the current UNF inventory can be divided into the following three categories: