A study on irradiated welding joints in ITER materials and its effects on FMECA analysis of components

ITER (International Thermonuclear Experimental Reactor) is a huge engineering challenge. ITER Project is in construction phase, the machine is very complex and is an assembly of hundreds of different components. Due to its large assembly and huge welding of different materials, it needs to have certain kind of reliability for safe operation. The reliability of machine is achieved in various lifecycle stages from design to manufacturing through ITER RAMI programme. Reliability and failure rate of weld influence availability of machine [1]. In this paper a study is done for the effects of irradiation on weldments and its mechanical properties and understanding various parameters which can affect the reliability of weld due to irradiation. Various papers were studied to understand changes in mechanical properties in weldment due to irradiation. Thus, by understanding various irradiation scenarios of ITER along with FMECA(Failure mode effect and criticality analysis) as tool, this work tries to systematically recognize, evaluate and prioritize the risk and potential failures. FMECA is a part of ITER RAMI programme. Failure rate data is an important input for FMECA analysis. In this study two weld seams, seam 1 and seam 2 were selected respectively in cryostat and neutral beam duct to understand irradiation condition under ITER working scenario. Flux and DPA at their Cartesian coordinates were found out with the help of various softwares for ITER project. FMECA chart is drawn to understand the severity and criticality under different irradiation scenario for these welds. Thus correlating mechanical properties of irradiated material to reliability, with FMECA as a tool will help in assessing availability of machine and lifecycle management of components. This will help in better understanding on failure rate data of non-irradiated conditions to be used for irradiated condition and changing neutron load in fusion reactors.