Sinusoidal source perturbation experiments with a breached fuel subassembly in the experimental breeder reactor II

A bifrequency reactivity oscillation procedure (ROP) was devised at the Experimental Breeder Reactor II (EBR-II) to be used as a diagnostic tool for characterizing mechanisms responsible for the release and transport of short-lived fission products from the surface of exposed fuel. A series of ROP experiments was conducted during operation of 74% of full power with a breached fuel pin in the core. Detailed analyses of the results using bivariate spectral decomposition and cross-correlation techniques are presented. Comparison of the results of these experiments with those obtained from earlier tests with an unclad fuel source provides conclusive evidence that all nonrecoil fission product release phenomena originate from mechanisms acting inside the breached element itself. In this paper implications of the findings from this study in terms of the goals of high-sensitivity fission product surveillance are discussed.