High-Temperature Acoustic Sensors for Boiling Detection

A system utilizing immersed acoustic noise detectors to detect boiling is one possible solution to the problem of detecting loss of cooling in a fuel channel of a liquid metal cooled fast breeder reactor. Two models of a symmetric drive sensor incorporating lithium niobate as the piezoelectric element have been fabricated and tested for acoustic response in water at room temperature and in an air furnace up to 600??C. Sensitivities of both models were 500pC/bar, with acoustic response to 100kHz when immersed in water. The sensors were not adversely affected by exposure in the furnace. Decreasing internal resistance with increasing temperature limits the useful range of present models to about 540??C.