Safety in the Light-Water Reactor Fuel Cycle

Commercial fabrication of uranium oxide fuels for light-water reactors is the fastest maturing segment of the nuclear fuel cycle. Some ten commercial fuel faibii-cators now routinely manufacture uranium fuels bn a more or less mass production basis. With this maturing comes an increased incentive to increase production rates and thereby reduce fuel fabrication costs. One astutely observes that the mly restraints that prevent unlimited -fuel throu iput are the limits imposed to ensure criticality safety. K, therefore, behooves us to periodically reexamine plant equipment in light of advances in criticality safety technology and to adjust limits wherever possible to enhance the economics of the fuel cycle. 

This paper will discuss some of the criticality safety aspects of uranium oxide fuel fabrication, and present new information bn plutonium oxide/uranlum oxide fuel fabrication, which is now in the developmental production-line stage. 

The most challen g part of the process from the criticality safety viewpoint is the conversion of UF to UOi. Most widely used in commercial facilities is the ammonium dlurdnate (ADU) process. The chemistry bf this process involves two steps  

hydrolysis of UFa with ammonium hydroxide UFa + 4NHaOH- UOaFi + 4NHaF + 2HaO. 

Another production method used for the conversion of the UF-a to UO2 is the ammonium uranyl carbonate (AUC) process. The form of the AUC precipitate is probably (NHa) [UOz(COa)3]s. This compound is calcined to UOior UjOa, which is then reduced to UOa. 

---