As a contribution to the required quinquennial review of the American National Standard for Nuclear Criticality Safety in Operations with Fissionable Materials Outside Reactors (ANSI N16.1-1975/ANS-8.1), limits for homogeneous 233U systems have been recalculated to confirm their subcriticality or, where there were doubts, to propose more restrictive values. In addition, other limits were calculated to be proposed for inclusion, namely, limits for aqueous solutions of UO2(NO3)2 and limits for uranium oxides. The same three methods of calculation were used as in similar work done recently for plutonium and 235U systems. The validity of each was established by correlation with the results of pertinent critical experiments.