In der Helmholt2-Gemainschaft T.JJiU" Hauptabtei:ung Bibliotnek lind Medien Gesellschaft für Kernforschung m.b.H •• Karlsruhe +Vork performed within the essociation in the field of fast reactors between the uropean~tomic Energy Community and Gesellsc~aft für Kernforschunf-mbH, Y2rlsruhe ++ NATO Postdoctoral Fellow -1 -+ ABSTRACT A method is presented for calculating the space. energy and detector dependent correlation function. which is the goal of noise analysis experiments in nuclear

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... The diffusion and short time approximations to the dyna~lic Boltzmann equation are made for the sake of simplicity and clarity. Abrief description is given of the salient features of the multigroup diffusion code used in these calculations. with the emphasls placed on those features required to calculate the correlation function. A simple reactor consisting of a U-235 spherical core surrounded by a graphite reflector was chosen to illustrate how higher modes of the correlation function may be observed in noise analysis experiments. In particular. it i6 seen that a Rossi-alpha experiment may measure two decay modes. corresponding to the fundamental mode and the most significant higher mode. or only the single fundamental mode. depending on the spectral sensitivity and the location of the two detectors used in the experiment.