Twice squaring method: non-linear acoustic signal processing technique for real-time detection of sodium boiling

A new signal processing method. named the Twice-Squaring method. for acoustic detection of sodium boiling in liquid metal fast breeder reactor has been developed. It uses a relatively simple nonlinear signal processing technique in time domain, consisting of band-pass filtering and squaring of signal in two folds. Its advantage is that real-time detection can be realized using only simple analog circuits without any digital calculation. In the present paper. we describe details of this method and the results of evaluation tests perfonned for sodium boiling acoustic data from KNS-l test rig and from BOR-60.