Pile Transfer Function Analysis

Pile Transfer Function Analysis - S. G. Dean, H. Greenspan, 

The general treatment of the time-dependent response of a reactor to a local change in reactivity is quite complicated and involves explicitly the geometry of the reactor. 12 if the reactivity change is distributed uniformly over the reactor volume, only the fxmdamental space mode of the reactor is involved (i.e., the initial space distribution of neutron flux is preserved, and the only reactor characteristics needed to describe the response are the neutron lifetime and the delayed neutron characteristics. The same is true for a localized reactivity variation if the time rate of change is low enough and if the response is measured at some distance from the location of the reactivity change. 

The purpose of the calculations reported herein was to examine theoretically whether such fundamental mode pile transfer experiments could be used to obtain significant data on the kinetic properties of fast reactors. Specifically, calculations of amplitude response and phase shift response were made as a function of driving function frequency fox a series of short lifetimes, and also for three different delayed neutron fractions, since both of these quantitites are presently in considerable doubt. A wide range of frequencies was explored in the calculations, no consideration being given at this time as to the practicability of an experiment which makes fundamental mode measurements possible. 

In addition, some calculations were made to investigate the relative effect of the various delay groups on amplitude response. 

Harrer, R. E. Boyar, D. Krucoff, Measurement of CP-2 Reactor Transfer Function, ANL-4373 January, 1952. 

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Pile noise analysis is a convenient method for obtaining the shape of reactor transfer functions, and for determining reactor prompt neutron lifetimes. The method is especially useful at frequencies which are inconveniently high for other methods, and requires much simpler equipment than many existing techniques. Other possible applications of this technique include the observation of the shape of the transfer function of power reactors in the study of instabilities, and the determination of prompt neutron lifetime in fast reactors. The latter application would require a detector with high sensitivity to fast neutrons, and the former a chamber that would operate well at the high fluxes involved. 

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