Modelling of a radial pump fast startup with the CATHARE-3 code and analyse of the loop response

A predictive transient two-phase flow rotodynamic pump model has been developed in the Code for Analysis of THermalhydraulics during an Accident of Reactor and safety Evaluation (CATHARE-3). Flow inside parts of the pump (suction, impeller, diffuser, volute) is computed according to a one-dimensional discretization following a mean flow path. Transient governing equations of the model are solved using a implicit resolution method and integrated along the curvilinear abscissa of the element. This model has been first qualified at the component scale during years 2017-18 by comparison to an existing experimental database. The present study aims at extending the validation at the system scale: a whole experimental test loop is modelled. The ability of the transient pump model to predict flow rate, head and torque as a function of time during a 1-second pump fast start-up is presented. Evolution of the pressure upstream and downstream from the centrifugal pump obtained in the simulation is similar to the measurements during the transient.