9 research outputs found
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Effect of oxidizing environment on the strength and oxidation kinetics of HTGR graphites. Part I. Reactivity and strength loss of H451, PGX and IG-11 graphites
The effects of oxidizing atmosphere and temperature on the reactivities and strengths of PGX, H451, and IG-11 were examined. Preliminary measurements of the oxidation kinetics of these graphites in H/sub 2/O-, CO/sub 2/- and O/sub 2/-containing atmospheres indicated that the reactivities of H451 graphite toward O/sub 2/ and H/sub 2/O are quite similar to those of IG-11 graphite. The apparent activation energy for oxidation of these in O/sub 2/ were estimated to be approx. 175 kJ/mol while that in H/sub 2/O is probably approx. 200 kJ/mol. The apparent activation energy of IG-11 graphite oxidized in CO/sub 2/ is 255 +- 18 kJ/mol. PGX graphite was found to be quite variable in its reactivity toward H/sub 2/O. A linear dependence with (Fe) was determined, but other intrinsic properties were found to affect its absolute reactivity by as much as a factor of X50
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Effect of prestress and stress on the strength and oxidation rate of nuclear graphite
Effects of prestress or stress during oxidation on the reactivities and strengths of PGX and H451 graphites were examined at oxidation temperatures of 450 to 600/sup 0/C in air and 550 to 750/sup 0/C in 2% H/sub 2/O/He. Little or no effect of compressive prestress at stress levels of up to 75% of the mean fracture strengths, was found. A small effect on the reactivity of H451 graphite was observed in the case of 2% H/sub 2/O/He, i.e., the rate was enhanced by no more than 30% for compressive prestress levels of up to 90% of the fracture strength. Tensile and compressive stresses during oxidation did not affect the reactivities of these graphites at stress levels of up to 28% of the mean compressive strength and 35% of the mean tensile strength for H451 graphite, and 44% and 56% for PGX graphite, respectively. 13 refs., 18 figs