The proposed ORNL Research Reactor is designed to serve as a general purpose research tool delivering a maximum thermal flux of 8x10^13 n/cm2-sec at the initial power level of five megawatts. Operation at power levels up to ten megawatts is proposed for such items as sufficient cooling capacity is available to handle the increased heat load. The reactor will use MTR-type fuel elements and beryllium reflector pieces in a 7 x 9 grid with moderation and cooling provided by forced circulation of demineralized water. The reactor tanks are submerged in a barytes concrete pool, filled with water, which serves as a biological shield. Experimental facilities include two 18" diameter "Engineering Test Facilities" and six 6" diameter beam holes. In addition, access to the core is available through the water of the pool. The result on the surrounding population of release to the atmosphere of a large fraction of the radioactive material in the core has been computed by two methods. It is shown that under certain conditions off-area personnel could be subjected to greater than the maximum permissible exposure. An analysis of the maximum hazard caused by the release of the entire contents of the core to the local watershed …

This memorandum sets forth a recommended uniform basis for designing the ORN shield.This includes design values for power level and emergent radiation, standards values for various material properties, and basic radiation intensities.

The fabrication of heat exchangers and radiators to be used in conjunction with high-temperature nuclear reactors may present exceedingly complex problems. Rigid heat transfer requirements may necessitate the use of compact assemblies of thin-walled small-diameter tubes as integral parts of the heat transfer units. Intricate designs may also be required in which cooling fins must be securely joined to the tubes at closely spaced intervals. In addition to the difficulties in fabrication imposed by the designs themselves, the high operating temperatures involved require the careful selection of materials and joining techniques. The choice of fabrication procedure for a given component must not only be based upon the stresses and temperatures to be encountered, but also upon special factors peculiar to nuclear service. Since many reactor applications employ highly corrosive environments, compatibility of the structural ma terials with the corrosive media is of paramount importance. The low nuclear cross-section require ment for brazing alloys to be used inside the re actor also places stringent limitations on the possible choices of in-pile applications. The use of boron in alloys for certain service may not be considered feasible, for example, because of its high nuclear absorption cross section. Although welding is used extensively …

Several plates of 98.7% Th - 1.2% U 235 (clad in aluminum) were irradiated in the MTR for an integrated flux of 2.6 x 10 21 neutrons/cm2. Although these samples represent an early development in bonding of aluminum to thorium and there are better methods at present, the bond proved to be quite strong and both clad and core were dimensionally stable under irradiation. The production of uranium 233 was as much as theory would indicate and the total amount of fissionable material material after irradiation and after decay of the protactinium 233 was greater than before irradiation. A fuel element of this nature appears to offer excellent potentialities from the standpoint of radiation stability.

This report presents data obtained from processing 33 Clementine Reactor fuel elements in the ORNL Metal Recovery Plant to recover approximately 15 kg of plutonium and 0.16 g of americium.