Analysis of fuel element to pressure tube contact using the mini-smartt computer code.

Abstract

This paper quantifies the thermal-mechanical effects of potential contact between the fuel element and the pressure tube (FE/PT contact) during a postulated large break LOCA transient in a CANDU reactor. At issue is the possibility of local strain failure of the pressure tube early in the LOCA transient. Calculations have been performed using the code MINI-SMARTT which was developed specifically for this analysis. It is shown that pressure tube local strain is most sensitive to the contact conductance, contact width, and transient time of FE/PT contact. The strain response of the pressure tube is derived over a broad range for the above parameters. A critical FE/PT contact conductance value is derived as a function of contact width. Assuming Hertzian mechanics, the critical contact conductance is sufficiently high that pressure tube failure would be precluded.