Effect of thermal cycling on the stress orientation and circumferential ductility in Zircaloy-2

Stress Reorientation of Hydrides in Recrystallized Zircaloy-2 Sheet

“…Mishima and Okubo have reported a similar effect that ten-cycles and 30-cycles experiments resulted in a more pronounced reorientation than a one-cycle experiment. 12) 5. Influence of Hydride Morphology before Hydride Reorientation Test Several W-type specimens were water-quenched after diffusion annealing at 723 K and subjected to the hydride reorientation test to examine the effect of hydride morphology before the hydride reorientation test.…”

“…4,5) The condition of RH formation is an important factor to assess the integrity of fuel rods, hence both the experimental and theoretical studies on the stress reorientation of hydrides have been conducted. [6][7][8][9][10][11][12][13] These studies have indicated that several factors such as texture, [6][7][8][9] temperature, 6,7) strength, 10,11) hydrogen concentration, 6,7,12) grain size, 9,10) thermal cycling 12) and cold-work 9,13) affected the stress reorientation of hydrides in zirconium alloys. This variety of factors requires systematic measurements to elucidate the effect of each factor and the correlation between the factors.…”

Hydride reorientation in Zircaloy-4 cladding

“…In addition to the effect of thermal cycling [27][28][29], Hong and Lee [4] and Chen et al [30] have concluded that the formation of radial hydrides was also a time-dependent process because an increase in annealing time also raised the amount of radial hydrides in an isothermal heat treatment. In order to compare the difference between isothermal annealing and thermal cycling heat treatments, a cladding tube of 320 ppm H were solution treated at 400°C for 24 h for one cycle.…”

Behavior of Zircaloy Fuel Cladding Tubes

“…From these data, the empirical equation expressing the external-pressure creep strain, applicable to stress-relieved tube supported internally at intervals of 20 mm by the pellet flanges, was derived in the form s= _ 5 _ 6 x 10 sto.soc -a 1 )1.•s. exp(-z;;oo) , (22) where s : External-pressure creep strain t: Time (days) a 1 : Nominal hoop stress (kg/mm2) R: Gas constant (cal/mol·"K) T: Temperature ("K) h 0 : Initial wall thickness (mm) a 0 : Initial outer radius (mm) Pt: Internal pressure (kg/cm 8 ) P 0 : External pressure (kgjcm 2 ) (23) The solid Jines in Fig. 14 An unexpected behavior, revealed by a comparison of the results at 350oC between the data of Figs.…”