Internal gelation as applied to the production of uranium nitride space nuclear fuel

The production of uranium nitride fuel depends upon a qualified and controlled method for obtaining a final fuel form. The final fuel form must have the desired properties, fuel density, fuel chemistry (X/U ratio), and impurity levels. These properties must be maintained throughout the entire fuel fabrication process and throughout the fuel operational lifetime. A variety of methods have been used during the past 40 years to obtain uranium nitride with applicable work performed on the (U, Pu)N-x system. These methods each have strengths and weaknesses with respect to the above criteria. Of the methods reviewed, the internal gelation process appears to be a viable method for well-controlled production of uranium nitride fuel for space nuclear reactors. It can be used to produce a uniform size microsphere that can in turn be used to produce high quality, low impurity UN fuel. This paper provides a summary review of many of the processes available for obtaining uranium nitride. The internal gelation process is described and limitations and advantages are discussed with respect to the fabrication of uranium nitride. Finally, recent results of uranium nitride fuel fabrication efforts using an internal gelation process are presented and discussed.