Quality surveillance of MOX fuels

Quality surveillance of nuclear fuels include all the technical and management aspects of fuel quality and safety during the entire manufacturing process - design, specification, research and development, manufacturing, quality control and use stages. Well structured quality assurance program is adopted and incorporated in the Quality Control plan made based on approved specification for a specific MOX fuel type used in a specific reactor (BWR, PHWR, PFBR). The presence of radiotoxic Plutonium in MOX fuels (U-Pu) makes its mandatory that the entire process of fabrication till encapsulation of fuel element is carried out inside leak tight glove boxes and dedicated ventilation system to control level of plutonium in air. The presence of plutonium requires smaller batch processing to avoid criticality and hence stringent process control at different stages of fabrication with additional inspection steps. Due to these factors the MOX fuel fabrication cost is many folds more than that of natural UO2 fuel and can be made competitive only by going to high burnups. Quality surveillance of feed material (UO2 and PuO2 powder), sintered fuel compacts, hardwares (clad, end plug, other internal components), final fuel element and fuel bundles ensures that the fuel performs reliably through the designed higher burn up. Automated inspection system with data logging in computer helps in generating reliable quality characteristic of the fuel. Special and complementary inspection techniques adopted considering various aspects viz. accuracy, reliability, type of testing (NDT or not), time taken for results and ease of documentation helps in monitoring the entire fabrication and inspection process. An overview of the quality assurance of MOX fuels for different reactors along with how the automated inspection techniques, real time inspection and special techniques adopted helps in quality surveillance of MOX fuels has been discussed here. (author)