Nuclear Rocket Program, Metallurgy Division progress report for quarter ending December 31, 1964

Abstract

A. Cladding Requirements 7B. Pressure Bonding 71. Autoclave Testing 72. Thermocouple Failures 77 3. Bonding Tests 79 VII. Properties of High-Temperature Materials. 8l A. Properties and Materials Considered 82 B. Young' s Modulus of Unalloyed Tungsten 82 C. Young*s Modulus of Tungsten-25w/o Rhenium 85

Literature review of thermal and radiation performance parameters for high-temperature, uranium dioxide fueled cermet materials

“…Burt et al [8] obtained a different result (greater fuel loss) as the effect of W coating on UO 2 particles for a W-25 vol.% UO 2 cermet. The researchers believed that the increased UO 2 loss with W coating on UO 2 was a result of fracture caused by thermal expansion mismatch between UO 2 and the W coating.…”

“…The authors stated, however, that the appearance of the coprecipitated powders indicated probable impurity contamination. Burt et al [8] also showed results in which cermets containing coarser particles gave better UO 2 loss performance; under thermal cycling at 2460°C in H 2 , W-50 vol.% UO 2 that contained 'micronized' (smaller) UO 2 particle sizes failed more quickly than a cermet containing 'ceramic grade' (larger) particle sizes. No explanation was given for the particle-size effect.…”

“…Some physical property testing was also completed. The reports from this laboratory, specifically, Burt et al [8] and Battles et al [9], and ANL [1] are drawn from the mid-to-late-1960s. Samples were fabricated by either sintering of pressed compacts, isostatic pressing of compacts, or by pneumatic impaction of vapor-deposited-coated UO particles.…”

“…The formation of UH 3 is accompanied by large increases in volume that can cause separation of W grains and create avenues for subsequent migration of UO 2 to the cermet surface. This migration results in loss of both UO 2 and mechanical integrity [16,8]. Fig.…”

“…Saunders et al [16] stated that free U not only forms UH 3 but also reoxidizes to form UO 2 ; both processes result in a large volume expansion, which can negatively impact mechanical integrity. Burt et al [8] stated that the reaction to remove oxygen from UO 2 reaches equilibrium and does not proceed as long as path- showing free U at grain boundaries. The specimen was heat treated for five 1-h intervals at 2500°C in H 2 with cooling to room temperatures between cycles [16].…”