THEORETICAL FEEDBACK ANALYSIS IN BOILING WATER REACTORS

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Abstract

The dynamic behavior of boiling-water reactors for small perturbations was investigated in a systematic way. General expressions for the transfer functions associated with the individual feedback mechanisms were obtained for an arbitrary flux distribution, weighting function, and steam velocity distribution. Specific forms were derived in the case of a first power flux weighting, a uniform steam velocity distribution, and a sinusoidal flux distribution with an adjustable wave length. These forms were simplified and single time-constant transfer functions were obtained. The error involved in the lumped time-constant approximation was shown to be as large as 4 db in amplitude in certain feedback mechanisms. Theoretical results were applied to the experimental power-void transfer function obtained at Ramo-Wooldridge Research Laboratory, and to the EBWR transfer function. In the former case, the agreement was found to be reasonably good, but yet more systematic experimental data were needed to reach a definite conclusion as to the validity of the proposed model, which assumes a time lag associated with steam formation and a steam perturbation speed greater than the steady-state steam velocity. In the second application, the agreement between the experimental and calculated reactor responses was proved to be better than 5 db in amplitude andmore » 10 deg in phase, in the entire frequency range from 0.01 to 100 rad/sec. (auth)« less

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