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This study is directed toward the determination of the effects of annealing cycles with rapid heating rates, short hold times at specific temperatures, and rapid cool-down rates on the hardness of Zircaloy fuel cladding. These rapid annealing cycles are designed to provide preliminary annealing behavior data on Loss-of-Fluid-Test Reactor cladding samples. Information has been obtained on (1) the time dependence of the hardness as a function of annealing temperature, and (2) a correlation of single- and multitransient annealing relationships. Both single- and triple-cycle transients were used; four hold times at each of five maximum temperatures comprised the data set (each portion of the triple-cycle experiments had isothermal hold times equal to one-third of their analogous single-cycle times). It was found that there was little difference in the hardness response between single- and triple-cycle transients for a given total hold time at a particular temperature. Test temperatures range from 1000 to 1400/sup 0/F (538 to 760/sup 0/C) and hold times from 5 to 135 sec. The 1100/sup 0/F (593/sup 0/C) level was found to be the transition level for hardness changes, with shorter times (5 and 15 sec) effecting little or no hardness decrease and the longer times (45 and 135more » sec) producing partially and fully annealed material, respectively. Temperatures equal to or greater than 1300/sup 0/F (704/sup 0/C) resulted in fully annealed material for all hold times. The 1000/sup 0/F (538/sup 0/C) tests produced no measurable softening.« less |
