Bowing behavior of a cold-worked 316 stainless steel duct

Abstract

Duct bowing, swelling, and irradiation creep strain gradients were measured on a cold-worked 316 SS internal duct in a blanket rod test that was irradiated in the EBR-II facility. This duct is unique because for the first time axial profiles of swelling and irradiation creep data were obtained in addition to the bow deflection. The irradiation creep data were obtained from scribe marks placed on the duct prior to irradiation. Large differences of swelling and irradiation creep strain were measured on opposite sides of the fluted duct. The qualitative behavior of the measured bowing, swelling, and irradiation creep strain gradients was self-consistent. The NUBOW-3D Inelastic computer program was used to predict the bow deflection and axial irradiation creep strain profiles were calculated using the NUBOW-3D Inelastic computer code (a time history stress analysis program) using a swelling equation developed from the duct immersion density data. The predicted bow deflection and irradiation creep strain profiles were in good agreement with the data. Bow deflection predictions were found to be most sensitive to irradiation creep. A 60% reduction in the Mark 6 irradiation creep equation was necessary to obtain consistency between the calculation and measurements. This reduction is qualitatively consisten with irradiation creep strain modifications derived from a slit tube test.