Closed loop configuration in the axial flux tilt control of a PWR

Abstract

Two closed loop configurations for the axial flux tilt control practice are compared in terms of certain controllability measures. To this end, the core of a PWR is taken into account. The Morari resiliency index and the Condition Number are adopted as reliable controllability measures examined for the open loop plant to evaluate the selected input/output pairs. In one scenario, boron injection is accompanied by the control rod as common means for the concurrent regulation of the core power and the pertaining axial offset. In the other case however, the boron mechanism is replaced for another regulating rod which implies the mechanical shim strategy proposed in more recent designs (e.g. IRIS or APR). A two-region modeling of the reactor core is resorted in both cases and the resultant TITO model is controlled by a Davison tuned PI regulator. Simulations indicate that the chemical shim configuration better meets the attempted controllability indices and thereby predicates a more resilient closed loop control practice. A step input perturbation is effected on the core inlet temperature to further verify this result.