Operating performance and actions taken to achieve zero fuel defects at Cernavoda NPP

Defective fuel is defined as a breach in the containment of a fuel element, resulting in gaseous fission products release and/or uranium material loss into the primary heat transport system. During spreading throughout the primary circuit, some radioactive material deposits on circuit components, becoming a source of high gamma radiation field, with potential radiological impact on personnel exposure during operation or maintenance activities. Although rare, fuel defects have always been an important issue for CANDU plants operation. At Cernavoda Nuclear Power Plant, which currently operates two CANDU-6 units, policies and procedures in use clearly state the expectation that nuclear fuel should be designed, manufactured, stored, handled and operated in a manner appropriate to avoid failures. Consequently, a strategy for achieving high standards for fuel performance is currently implemented with the aim to achieve failure-free fuel operation. It addresses the main aspects of the surveillance process required to achieve a good fuel performance: preliminary inspections on fresh fuel bundles prior their loading into the core, core monitoring to detect and localize suspect defective bundles in the core, specific procedures for discharging the suspect defective bundles from the core, performing "root-cause" analyses to determine failure mechanisms, feedback to the fuel manufacturer to improve the nuclear fuel quality. The present paper reviews the main steps and actions taken at Cernavoda Nuclear Power Plant for improving fuel performance and achieving a zero failure target. (author)