An analysis of iodine stress corrosion cracking of zircaloy-4 tubing

Mechanistic Considerations Used in the Development of the PROFIT PCI Failure Model

“…As previously noted, all of the fixed load SCC laboratory tests on Zircaloy [13][14][15]18] were at load and temperature conditions that were conducive to (1) * Drop-in-load yielding, as used here, is defined as that characteristic of certain metals and alloys to continue to deform plastically under externallyapplied loads that are smaller than that necessary to cause the initial yielding. Figure 2.8, SEAF is not constant over wide ranges (2) of strain rate, but rather appears to vary with st rain rate, temperature, and environment in a systematic and predictable manner.…”

“…In those sec experiments where measurements were obtained, the reported deformations at failure ranged to about 3% [13,14]. There is a general consensus that sec, in fixed load tests, must be preceded by some plastic deformation.…”

“…An examination of fixed load SCC test data [13][14][15]18] reveals that the stress and temperature conditions were conducive to deformation by creep. In those sec experiments where measurements were obtained, the reported deformations at failure ranged to about 3% [13,14].…”

“…The primary source of these fuel failures is generally attributed to Qellet-~ladding interactions (PC!) of thermo-mechanical and thermo-chemical origins [7][8][9][10][11][12][13][14][15][16][17][18]. Current operating restrictions are an acknowledgment that fuel power increases and/or abnormal operating transients pose a potential for a significant incidence of fuel failures by PC!.…”

“…The range of strain *This is a manifestation of dislocation channeling. 13 rates over which the ~a/a anomaly was examined was relatively small, ranging from 0.0064 min-1 to 0.24 min-1 • Based on PIE un i axial (plane stress) tensile tests, Veevers et al [45] concluded that the ~a /a anomaly was reduced to insignificance after irradiation to a fluence ranging from 5.0 E 19 NVT to 1.0 E 19 NVT. As noted previously, radiation appears to lower the temperature at which the yield point, yield drop, and localized deformation occur.…”