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  1. Declassified 26 Nov 1973.<>29:020142Declassified 28 Nov 1973. onstrate the performance on a full-scale reference SNAP 2 fuel element when subjected to an environment which simulated the most severe conditions (i.e., peak temperature, burnup, and burnup rate) encountered in a SNAP 2 reactor core upgraded to produce 125 kW(t). This experiment was irradiated for twentythree reactor cycles in the Materials Testing Reactor and was discharged on August 18, 1965. The fuel element achieved its de sign peak burnup of 0.08 metal at.% in an equivalent of one year at full power. The design peak cladding temperature of 1300 deg F (whichmore » is nominally equivalent to a peak fuel temperature of 1507 deg F) was maintained within plus or minus 50 deg F during 93.4% of the time that the reactor was at full power. The post-irradiation condition of the fuel element and the irradiation assembly was excellent. Both the uranium--zirconium hydride fuel rod and the Hastelloy-N cladding were intact and in excellent condition. The performance of the fuel element, in terms of suitability for use under 125 kW(t) SNAP 2 reactor conditions, was completely satisfactory. The design, analysis, fabrication, in-pile operation, and post-irradiation examination and evaluation of the NAA 82-1 experiment are described. (27 references) (auth)« less
  2. Data on graphite neutron absorption cross sections which may be related to chemical impurity levels are presented. (J.R.D.)
  3. Several liquid metal sealants were investigated for sodium-pump shafts. (W.L.H.)
  4. Nuclear grade beryllium oxide powders from commercial suppliers may be pressed at temperatures of 1500 deg to 1900 deg C and under pressures from 2000 to 6000 psi in graphite dies into a variety of shapes having densities in the range 98 to 100% of the theoretical value. Addition of 1% MgO facilitates the process and improves the rate and uniformity of densification. The compaction of BeO as a function of pressure, temperature and time may be deacribed by a flow relation involving a viscosity and a critical shear stress for grain boundary movement. Thermal expansion is isotropic to aboutmore » 1700 deg C and is well described to 2000 deg C by a quadratic function of the temperature. The specific heat of BeO at 1500 deg C is 0.52 cal/g- deg C, slightly above the Dulong and Petit value. From 500 deg to about 1800 deg C the thermal conductivity decreases as 1/T, from a high value at room temperature of about 0.50 cal/cm- deg C for dense material. A decrease in density of 5% diminished the thermal conductivity by approximately 13%. Information given earlier on the creep, elastic and anelastic properties of dense material was extended, and relations were employed showing that significant fractions of thermal stresses encountered in practice may be relaxed if given time. An elasticity due to grain boundaries also appears to confirm the view on flow during densification in hot pressing. A preliminary estimate of rupture strength for completely dense material with grain size of approximately 35 mu is 36,000 psi at room temperature. Lowering the density 1% reduces the strength about 4100 psi. The status of knowledge of other properties is reviewed briefly. (auth)« less

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"Carniglia, S.C."

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