Trends in joining technology development for PHWR fuel assemblies in India

Various types of welding/brazing techniques and equipment are used in the production of different kinds of PHWR fuel assemblies. These assemblies are of 19-element, 22-element, 28-element and 37-element type and are unique in joint design. All joints in PHWR fuel assemblies are either welded or brazed without any mechanical joints. Resistance welding, GTAW, Electron Beam welding, brazing and ultrasonic welding are some of the feasible techniques. Resistance welding and brazing are extensively used in fabrication of fuel assemblies involving joining of Zirconium alloys components of different shape and geometry. This paper describes recent advances made and work caused out at Atomic Fuels Division of Bhabha Atomic Research Centre in India in fabrication of different types of PHWR fuel assemblies. Vast experience gained in development of technologies and large-scale production of different core components was utilised to evaluate, develop and assess joining techniques for production. Various joining processes were utilised to achieve improved reliability and economy of products. Several non-conventional processes of joining have been under consideration. Modern Developments in welding power sources, methods of achieving improved weld quality and consistency, advances in weld monitoring etc are described. Efforts made towards better joint quality, ease of production and improved fuel performance is discussed Paper includes work carried out successfully in indigenous fabrication of some equipment, automation of processes and monitoring system. (author)