In this work, non-modal stability theory is used to study the non-linear dynamics of the Pressurised Water Reactor (PWR), using a zero-dimensional model. Usually, stability analysis for nuclear reactors is performed using modal methods. Instead, the non-modal approach used in the present work offers a different perspective. This approach considers the so-called short-term behaviour following a disturbance instead of the asymptotic (long-term) one. In the model, point-reactor kinetics with six groups delayed neutrons is used for neutronics, whereas thermal-hydraulics is treated using a two-region model (fuel and coolant). The non-orthogonality of the dynamic matrix of the obtained system shows the possibility of transient energy growth following a disturbance, and the proposed stability analysis offers proof of this. A sensitivity analysis of some parameters is then carried out to study how their variation influences the short-term response of the system. The results of this analysis allow for a ranking of the parameters, allowing the identification of the most significant ones regarding system stability.

Stability analysis of a zero-dimensional model of PWR core using non-modal stability theory

Introini C.;Cammi A.;Giacobbo F.
2020

Abstract

In this work, non-modal stability theory is used to study the non-linear dynamics of the Pressurised Water Reactor (PWR), using a zero-dimensional model. Usually, stability analysis for nuclear reactors is performed using modal methods. Instead, the non-modal approach used in the present work offers a different perspective. This approach considers the so-called short-term behaviour following a disturbance instead of the asymptotic (long-term) one. In the model, point-reactor kinetics with six groups delayed neutrons is used for neutronics, whereas thermal-hydraulics is treated using a two-region model (fuel and coolant). The non-orthogonality of the dynamic matrix of the obtained system shows the possibility of transient energy growth following a disturbance, and the proposed stability analysis offers proof of this. A sensitivity analysis of some parameters is then carried out to study how their variation influences the short-term response of the system. The results of this analysis allow for a ranking of the parameters, allowing the identification of the most significant ones regarding system stability.
Non-modal stability theory
PWR
Sensitivity analysis
Stability analysis
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/1209167
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