Validation of relap5/mod3.3 against a load step transient at Ringhals 4 u

Paper in proceeding, 2015

ABSTRACT The Unit 4 of the Ringhals Nuclear Power Plant has recently undergone a large component replacement project with installation of new steam generators and a pressurizer, targeting a power uprate. A series of startup and maneuverability tests has been performed, mainly focusing on evaluation of the system responses for various perturbations. The subject of the present numerical analysis is a test with a ± 10 % steps applied in the load. The data collected during test provided a good opportunity for validation of the full plant model, which was prepared recently for the RELAP5/Mod3.3 Patch04 computer code, with incorporation of the new component models. The paper introduces the test procedure and shows an overview on the key parameters that are utilized as initial and boundary conditions. Strategies applied for achievement of steady-state conditions are addressed in the document. Furthermore, the paper summarizes the results of the validation study using the transient data to simulate the startup test. It has been proven that the stand-alone RELAP5 thermal-hydraulic model is capable of reproduction of the key features and events of the test. Sufficiently good agreement has been achieved between the measured and simulated thermal hydraulic parameters, already in its current stage of model development. On the basis of successful verification at the original power, it is expectable that the new Ringhals 4 model will be able to predict the fluid conditions in other types of transients, even at uprated conditions.