[en] In order to provide adequate bases for technical specifications it has been found desirable to expand the heat transfer analysis originally presented in the ORR Safety Analysis (ORNL 4169, Vol. II). Moreover, the treatment in that document tacitly assumed that the reactor fuel used in the ORR would be of the well-known U-Al alloy plate-type. A large amount of experience with this fuel in conditions similar to and more rigorous than those encountered in the ORR was available, and so there was no reason to include an extensive analysis of its limitations in ORNL 4169. It is now proposed to fabricate ORR fuel using the U₃O₈-Al dispersion technique which has been successfully used in the HFIR since 1965. The experience with HFIR has demonstrated conclusively that the U₃O₈-Al elements are superior to the U-Al fuel elements in virtually every respect. However, since it is also proposed to increase the ²³⁵U content above 265 grams per element, which is the maximum weight previously used in ORR, it appears prudent to examine the implications of the change to oxide fuel