The photograph shows the probe from a system designed to be robotically deployed on the underside of a nuclear reactor head, during shutdown.
The reactor head is carbon steel with a ¼” lining of inconel. The control rod drive mechanism (CRDM) attaches above, penetrates through a series of nozzles and attaches to the control rods within the core. Each nozzle is constructed of inconel-600 and has a thermal interference fit in the head bore hole. A ‘J’ groove weld of inconel (alloy 182) provided a barrier for the coolant.
Previous means of inspection with manually deployed penetrant testing was considered undesirable due to the high doses of radiation in the area around the reactor nozzles.