Validation of the PAR code REKO-DIREKT against large scale experiments performed in the frame of the OECD/NEA-THAI project

Summary In the frame of the OECD/NEA THAI and THAI2 projects, a comprehensive database on the operational behaviour of passive auto-catalytic recombiners (PARs) has been established. Measurements of the overall pressure, gas composition and temperature at the PAR inlet and outlet, and the catalyst temperature provide useful data for the validation of numerical PAR models. For the validation of the PAR code REKO-DIREKT, a total of 32 experiments performed with two different PAR types (AREVA and AECL) have been simulated. Taking into account the broad variety of boundary conditions (pressure between 1 – 3 bar, steam concentration up to 60 vol.%, partially low-oxygen conditions) as well as the significant geometrical differences of both PAR types, the results confirm convincingly the capability of the code to simulate the operational behaviour of full scale PARs independent of their corresponding geometry. The results also point out the need for more detailed experimental investigations of the PAR start-up behaviour. The paper summarises the basic features of the REKO-DIREKT code and discusses the validation results. A. INTRODUCTION