Overview of non-destructive tests on mixed oxide fuel pins

The (U,Pu)O₂, Mixed Oxide (MOX) fuel pellets are fabricated by conventional powder metallurgical route involving steps like mixing, milling, pre-compaction, granulation and final compaction followed by sintering. The stack of fuel pellets is loaded in bottom end plug welded clad tubes. The tubes are sealed by end plugs using GTAW welding procedure. Various non-destructive tests are carried out on finished MOX fuel pins like X-ray radiography, Helium leak testing and X-ray Gamma Autoradiography (X-GAR). X-ray radiography is carried out to check the physical integrity of end plug welds. Helium leak testing is carried out to eliminate the possibilities of existence of leak in the fuel pins. X-GAR technique is used to check internal hardware components and cross mixing of DDUO₂, pellets in stack of MOX and vice-versa