The facility will consolidate all HEU that is currently stored at several sites of the Y-12 complex. According to NNSA, transfer of most of the the material will be completed within 90 days.
UPDATE 01/26/10: Frank Munger quotes Y-12 site officials as saying that the HEUMF has a capacity to hold about 12,000 cans of enriched uranium, and a like number of drums. The actual inventory of uranium housed at Y-12 is classified.