Simulation of the heat and coolant flow for a PMR200 reactor using a network approach in Flownex

Abstract

The VHTR (Very High-Temperature Reactor) Prismatic block reactor is one of the reactor designs considered in the range of 4th Generation Reactors which are under development today. The heat generated by the gas-cooled reactor can be used to produce electricity or as process heat to produce amongst others hydrogen. For the reactor's operation under normal and upset conditions, the conduction heat transfer through the prismatic block, convection heat transfer to the coolant, and radiative heat transfer to other critical components are of critical importance. Most of the research that has been done on different aspects of the PMR200 prismatic block reactor and the associated RCCS (Reactor Cavity Cooling System) was performed using 1D (One-dimensional) and 3D (Three-dimensional) numerical simulation packages. There was also some physical experimental testing done on certain parts of the RCCS and selected aspects of the PMR200 (Prismatic Modular Reactor). 3D simulation packages are employed to model specific components of a nuclear reactor which can range from a partial core simulation to a small single channel fuel module (SCFM) model simulation. The 3D simulation models are computationally intensive and require large computational resources and the simulation takes a long time to complete. Although the 3D simulation packages can provide detailed results, the long completion times and the large computational resources make it impractical for the analysis of full systems. 1D simulation packages have also been used to simulate specific components that can range from a full core to an SCFM model. But with 1D simulation packages, the network models are constructed to be representative models of these specific components. The representative models that are constructed using 1D simulation packages are much less computationally intensive compared to 3D models. Although the 1D packages do not give the same detailed results as the 3D packages, they can provide results of sufficient detail and accuracy that can be used for the evaluation and design of full systems. In the current study, the purpose is, to create a one-dimensional integrated full PMR200 reactor and RCCS thermal-hydraulic model that will give the required results of sufficient accuracy for the evaluation of the integrated system employing a 1D network approach. The 1D simulation package Flownex will be used to construct and test the network models for the PMR200 reactor, RCCS only and the combined PMR200 and RCCS. The integrated model will be used to evaluate the performance related to the heat transfer and coolant flow of the PMR200 reactor and the RCCS system for normal and selected off-normal conditions. III Selected thermal-hydraulic results obtained from steady-state simulations performed with the PMR200, RCCS and the integrated PMR200-RCCS models were compared with corresponding results obtained from literature and found to be in good agreement. It was therefore concluded that PMR200, RCCS only and integrated PMR200-RCCS model are valid representative models that can be used to evaluate the thermal-hydraulic performance of the reactor and associated RCCS. The capability of the models is shown to be helpful to evaluate the thermal-hydraulic performance of the reactor systems as demonstrated by the selected simulated scenarios.