Alternative repository criticality-control strategies for fissile uranium wastes

Methods to prevent long term, disposal site nuclear criticality from fissile uranium isotopes in wastes were investigated. Long term refers to the time period after waste package (WP) failure and the subsequent loss of geometry and chemistry control within the WP. The preferred method of control was found to be the addition of sufficient depleted uranium to each WP so that the uranium enrichment is reduced to < 1 wt % {sup 235}U and < 0.66 wt % {sup 233}U in {sup 238}U.