The final rule will amend the Commission's regulations by adding additional requirements for licensees who possess significant quantities of uranium hexafluoride (UF6). The proposed amendments would require such licensees to conduct integrated safety analyses (ISAs) similar to the ISAs performed by 10 CFR part 70 licensees, set possession limits for UF6 for determining licensing authority NRC or Agreement States, and require the NRC to perform a backfit analysis under specified circumstances. The proposed amendment would require applicants and licensees who possess or plan to possess significant amounts of UF6 to conduct an ISA and submit an ISA summary to the NRC. The ISA, which evaluates and categorizes the consequences of accidents at NRC licensed facilities, would address both the radiological and chemical hazards from licensed material and hazardous chemicals produced in the processing of licensed material. The NRC is also proposing new guidance on the implementation of the additional regulatory requirements for licensees that would be authorized under this rulemaking. In a Staff Requirements Memorandum dated May 3, 2013, the Commission disapproved the publication of the final rule. Instead, the Commission directed the NRC staff to conduct additional analyses, revise the final rule, and resubmit it to the Commission for reconsideration.