Nonlinear Analysis of Coupled Neutronic-Thermohydraulic Stability Characteristics of Supercritical Water-Cooled Reactor

• Published in: Annals of nuclear energy 2024-01, Vol.195, p.110197, Article 110197
• Main Authors: Shankar, Daya, Pandey, Manmohan, Basu, Dipankar N.
• Format: Article
• Language: English
• Subjects: Bifurcation analysis; Limit cycle; SCWR; Stability analysis; Stability map; Supercritical fluid
• ISSN: 0306-4549; 1873-2100
• DOI: 10.1016/j.anucene.2023.110197

•Linear and nonlinear stability analysis of SCWR using a lumped parameter model.•Identification of Generalized Hopf points, sub- and supercritical bifurcations.•Exact location of unstable limit cycles using the shooting technique.•Effects of neutronic, thermohydraulic, and geometric parameters on stability.•Parametric trends similar to those reported for BWR and CANDU SCWR. The Supercritical Water-Cooled Reactor (SCWR) exhibits significant changes in thermophysical properties of the coolant, but its dynamic characteristics are different from existing reactors, due to the supercritical conditions of the coolant. This necessitates the study of the stability behaviour of SCWR, which requires a dynamic model of the reactor. In this work, a simple unsteady lumped parameter model (LPM) for SCWR has been developed. The LPM includes point reactor kinetics for neutron balance and a two-region model for fuel and coolant thermal hydraulics. The two regions are separated from each other by a boundary that depends on the pseudocritical temperature of the coolant. Regions of stable and unstable operation are identified in the parameter space by linear stability analysis. Bifurcation analysis is carried out to capture the non-linear dynamics of the system. Generalised Hopf (GH) points are located, and parameter ranges for supercritical (soft and safe) and subcritical (hard and dangerous) Hopf bifurcation are identified. The type of transient behaviour of the system for finite (though small) perturbations is predicted based on this analysis. The existence of predicted limit cycles is confirmed by numerical simulation of the nonlinear ODEs, using the shooting technique in case of unstable limit cycles. Furthermore, the effects of geometric, control and neutronics parameters on the stability of the system are studied.