Zircaloy-2 fuel tubing with different compositions has been manufactured by a variety of thermomechanical processes to evaluate manufacturing variables that could influence nodular corrosion. The primary variables studied include: (1) alloy composition. (2) thermal annealing history, (3) tube texture, and (4) recrystallized versus stress relieved tubing. A total of 48 tubing variants were fabricated and tested.

Results from 793 K steam autoclave tests revealed that all variables examined influence the corrosion behavior with complex interactions between the variables. Alloy composition and thermal history exhibited the strongest influence. Improved corrosion resistance was observed for the material containing a lower Sn concentration and annealed at lower temperatures. The effect of thermal history was not consistent with the accumulated annealing parameter formulation. A single 1005 K anneal late in the manufacturing process produced extremely high weight gains compared to lower values when the same anneal occurred early in the process or when annealing for longer times at lower temperatures to obtain the same accumulated annealing parameter. Small improvements in corrosion resistance for the more sensitive materials were obtained from tubing produced with a more radial texture. Stress relieved tubing was generally less sensitive to nodular corrosion than comparable recrystallized tubing.

Microstructural examinations did not identify the cause for the observed variations in corrosion behavior. Particle size distributions were independent of the material or processing histories. This lack of any correlation indicates that the particles themselves do not control the corrosion behavior, but a specific microstructural feature was not found that would explain the corrosion behavior.