Stresses in an Oxidized Zircaloy Cladding Under Quench Conditions: Recalculation of Single-Rod Quench Tests

About 70 single-rod quench tests with fresh and preoxidized Zircaloy specimens are carried out at Forschungszentrum Karlsruhe with water and steam as quench media. A number of mechanical effects are observed on the cladding of the test rods by posttest examination; the most important ones are the occurrence of through-wall cracks mainly for thick oxide scales and a severe degradation of the -phase for water-quenched and steam-cooled tests.

Calculations of some tests are done with the WSPAN one-dimensional rod mechanics code. This code calculates a very high stress pulse in the oxide scale occurring at the phase transition in the oxide phase. With the assumption of purely elastic behavior of the -phase at the high strain rates occurring at the phase transition, the cracking in the -phase and the formation of through-wall cracks can be understood.