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Processing of Refractory Metal Alloys for JOYO Irradiations

Description: This is a summary of the refractory metal processing experienced by candidate Prometheus materiats as they were fabricated into specimens destined for testing within the JOYO test reactor, ex-reactor testing at Oak Ridge National Laboratory (ORNL), or testing within the NRPCT. The processing is described for each alloy from the point of inception to the point where processing was terminated due to the cancellation of Naval Reactor's involvement in the Prometheus Project. The alloys included three tantalum-base alloys (T-111, Ta-10W, and ASTAR-811C), a niobium-base alloy, (FS-85), and two molybdenum-rhenium alloys, one containing 44.5 w/o rhenium, and the other 47.5 w/o rhenium. Each of these alloys was either a primary candidate or back-up candidate for cladding and structural applications within the space reactor. Their production was intended to serve as a forerunner for large scale production ingots that were to be procured from commercial refractory metal vendors such as Wah Chang.
Date: February 21, 2006
Creator: Luther, RF & Petrichek, ME
Partner: UNT Libraries Government Documents Department

A Review of Tribological Coatings for Control Drive Mechanisms in Space Reactors

Description: Tribological coatings must provide lubrication for moving components of the control drive mechanism for a space reactor and prevent seizing due to friction or diffusion welding to provide highly reliable and precise control of reflector position over the mission lifetime. Several coatings were evaluated based on tribological performance at elevated temperatures and in ultrahigh vacuum environments. Candidates with proven performance in the anticipated environment are limited primarily to disulfide materials. Irradiation data for these coatings is nonexistent. Compatibility issues between coating materials and structural components may require the use of barrier layers between the solid lubricant and structural components to prevent deleterious interactions. It would be advisable to consider possible lubricant interactions prior to down-selection of structural materials. A battery of tests was proposed to provide the necessary data for eventual solid lubricant/coating selection.
Date: February 21, 2006
Creator: Larkin, CJ; Edington, JD & Close, BJ
Partner: UNT Libraries Government Documents Department

Mound Laboratory isotopic power fuels programs: July--September 1973

Description: Progress in the isotopes fuel program during July to Oct 1973 is reported. Preparation and fuel characterization studies of /sup 238/Pu fuels continued. The effect of lower pressing temperatures on pressed plutonium oxide (PPO) spheres was evaluated. Plutonium-238 dioxide feed material that was sintered to a maximum of only 900 deg C was pressed under otherwise normal conditions into a Multihundred Watt (MHW) type fuel sphere. This pressing resulted in a sphere with near-perfect surface texture. The surface was bright and totally free of any visible cracks. However, upon subjection to the normal 1500 deg C vacuum heat treatment, the sphere cracked severely. Metallographic examination of selected areas of MHLV- PPO spheres showed that the spheres were not uniform in microstructure. They possessed nonuniform grain size and porosity distribution. Spheres exposed to high-temperature heat treatments also were nonuniform in microstructure. Calculations were performed to determine the stresses that appear in MRW PPO spheres due to temperature gradients. Thermal shock analyses were also performed. The data obtained as a result of these analyses were used in establishing a controlled heating and cooling cycle for the 1500 deg C, 1-h outgassirg process for development and production spheres. In order to evaluate the performance of a quadrupole mass spectrometer capable of evolved gas analysis of PuO/sub 2/ up to 1850 deg C, a residual gas analysis system utilizing a quadrupole mass spectrometer was installed in an alpha glovebox. The installation and cold check-out of the system are essentially completed. Several nonradioactive samples and standands were analyzed to establish the sensitivity and to calibrate the instrument. Samples of iridium hemishells were examined using the quadrupole mass spectrometer and both transmission and scanning electron microscopy. These examinations were performed in an attempt to better identify the nature of the iridium being used in the Multihundred ...
Date: November 21, 1973
Partner: UNT Libraries Government Documents Department