Volume 5, Issue 2 (February 2008)
Behavior and Mechanisms of Irradiation—Thermal Creep of Cladding Tubes Made of Zirconium Alloys
The objective of this work was to study the irradiation-thermal creep behavior of cladding tubes made of two Russian zirconium alloys: the widely used E110 (Zr-1Nb) alloy and the advanced E635 (Zr-1Nb-1.2Sn-0.35Fe); and to demonstrate the advantages of E365 claddings for VVER fuel rod application with respect to fuel pellet-cladding gap at high burnups. For this purpose, a creep test concept and an analysis methodology were developed. Creep tests using cladding tubes made from both alloys were carried out. The test results along with published data allowed development of predictive models of irradiation-thermal creep for the cladding tubes of both alloys. The models describe strain processes in non-irradiated claddings and in claddings under and after irradiation. The models benchmark well to dimensional changes in VVER fuel rods. The models show the fuel pellet-cladding gap to disappear at higher burnup values if E635 is used for VVER cladding as opposed to the E110 alloy.