Feasibility study of relaxation of quasi-static approach for reactor transient analyses

Abstract

This dissertation is concerned with an implementation of the Quasi-Static (QS) approaches for analyzing reactor systems along with the contemplation made for the enhancement of its performance. The time-dependent multi-group diffusion equations and their modification to formulate Improved Quasi-Static method (IQM) and Predictor Corrector Quasi-Static method (PCQM) are elucidated in detail. To incorporate the feedback originating from the thermohydraulics (TH) effects, proper balance equations must be solved while taking the non-linear coupling with the neutronics calculation into account. Hence a comprehensive description for encompassing QS treatments in feedback-present systems is depicted. To enhance the performance of QS approach, the static treatment of the shape function is relaxed through a polynomial interpolation, whereas the conventional QS method regards shape to be steady within a time interval for computation. A one-dimensional two-group slab reactor system has been devised for validating the effectiveness of the proposed treatment. Although the model benchmark problem hardly embodies the meticulous features of the actual reactor systems, the numerical results exhibit that drastic improvement in the performance can be achieved by the relaxation of Quasi-Static treatment of the shape.