Analysis of the performance of the KERENA^NT emergency condenser

With the aim of gaining experimental data on the behaviour and performances of the passive systems of the KERENA^NT reactor design, AREVA NP has built the INKA large-scale test facility situated in Karlstein, Germany. In order to support the experimental campaign by establishing a test matrix and a suitable experimental procedure for the evaluation of the performances of the emergency condenser (EC), pre-test simulations have been carried out by means of the best-estimate thermal-hydraulic code RELAP5/mod3.3. The results have shown that, in stationary conditions, a single train of the EC can remove a power up to about 70 MW at the nominal reactor pressure of 70 bar. Only a limited region of the operational range of the EC can be investigated at the INKA test facility in stationary conditions, due to the limited power of the steam supply to the RPV (up to 24 MW). Therefore, a transient experimental procedure has been designed aimed at the "quasi-stationary" characterization of the EC over a wide range of power levels and pressures, which range far beyond the steady-state power supply available at the INKA facility. The transient procedure has been tested and verified by means of RELAP5/mod3.3, and a data evaluation methodology based on windows-averaging has been proposed and applied, aimed at deriving the field of quasi-stationary characteristics of the EC. The experimental procedure has been successfully employed by AREVA at the INKA test facility and the experimental results have been used to validate RELAP5 for the passive emergency condenser. The validated RELAP5 model will be used to perform an uncertainty analysis of the experimental results with regard to the dynamic measuring errors originating from the quasi-stationary approach. The physical insights on the EC behavior gained by the RELAP5 simulations are also presented in the paper. (author)