S. G. Margolis’s research while affiliated with Westinghouse Electric Company and other places

ABS>Lightly damped core power oscillations with a frequency characterized by the reciprocal of the core transport time have been observed in boiling reactors. The oscillations are attributed to regenerative feedback through the "inner" reactivity feedback loop in which the feedback path consists of heat generation in the fuel, heat transfer to the coolant, and reduction of coolant density by steam voids. The voids drive the power and thus close the inner loop. A simplified analytical model for investigating the stability of the reactivity feedback loop in a boiling reactor is proposed. (W.D.M.)

The delayed neutron effects in flux tilt transients were examined in a ; simple model of an initially uniform bare core with energy group and one group of ; delayed precursors. Transient behavior of the flux shape was examined by a first-; order perturbation theory and a modal expansion. (C.J.G.);

Xenon feedback can produce spatial oscillations in large power reactors. ; Depending on the reactor size, materials inventory, power, and temperature ; coefficient, these oscillations may be either transient or persistent. This ; phenomenon is treated by a modal analysis in which nonlinear terms are retained. ; The nonlinear effects are shown to limit the amplitude of the oscillation and to ; cause the position of the flux peak to precess azimuthally; a formula for ; calculating the limiting amplitude of the oscillation is derived and compared ; with analog computer results. (auth)