Report of the IAEA-IWGFR specialists meeting on 'Sodium boiling noise detection' 9-11 June 1981

The background of the meeting was the general concern to detect a fault in a LMFBR sub-assembly early to prevent any damage spreading to neighbouring sub-assemblies. Its purpose was to review methods available for detecting the initial stages of accidents in fast reactor sub-assemblies, with special attention to acoustic methods, and to make recommendations. National and specialist papers were presented from France, FRG, India, Italy, Japan and the UK, and also Australia and GDR. Acoustic detection techniques are being improved, to increase the signal-to-noise ratio. Analysis of signals is being explored using several techniques, including pattern recognition, correlations between multiple sensors, and cross-correlation (eg. with neutronic signals). Several countries have made reactor experiments in addition to rig and/or computer simulations. Future work directed to producing reliable surveillance systems is required in the fields of out-of-pile investigations to define the characteristics of signals from boiling in certain fault situations, acoustic propagation in internal structures, analysis of background noise in operating reactors and its variation with varying operating parameters, and reactor trials to demonstrate the capability of acoustic methods of detecting faults. (author)