Diametral Creep Assessment of Pressure Tubes at GENTILLY-2 Up Until 2003 (5900 EFPD)

Abstract

Pressure tube (PT) diametral creep in a CANDU-6 reactor is a permanent strain due to the phenomenon of irradiation. Creep affects the coolant flow in the fuel channels and reduces, at constant channel flow, the margin to critical heat flux (CHF). As a result, creep affects the safety margins and must be compensated by reducing the station power. AECL developed the RC-1980 correlation to predict creep strain as a function of the operating conditions (flux, temperature, and pressure), based on CANDU-6 inspection data through 1997. Between 1987 and 2003, creep measurements were performed on 62 PTs at Gentilly-2 during outages. The results have revealed that the average creep represents only about 84% of its prediction.