Analysis of delayed creep rupture test conditions to qualify new calandria tubes for CANDU-6 reactors

CATHENA Mod 3.5c/Rev 0 model was used to conservatively calculate the quasi steady-state temperature and pressure conditions that are likely to exist if a pressure tube were to break spontaneously within a CANDU-6 reactor during normal operating conditions. The objective of the analysis was to recommend test conditions to assess calandria-tube resistance to delayed creep failure. These CT test conditions are required to design full-scale creep rupture tests that represent the conditions expected in a CANDU-6 reactor that would exist shortly after a spontaneous pressure-tube rupture. The calculated average through-wall CT temperatures for the quasi steady-state period following inlet, centre, and outlet pressure-tube breaks were 176oC, 186oC, and 194oC, respectively. Thus the analysis indicated that it would be conservative if future creep-rupture tests for new CANDU-6 calandria tubes were performed at a uniform temperature between 176oC and 194oC. The 176oC and 194oC average calandria-tube temperatures correspond to a pressure of 11.02 MPa and 10.55 MPa, respectively. (author)