Validation of a VVER 1000 Trace Model

Abstract

The presented article discusses developing and validation of a VVER 1000 TRACE V5.0p5 model. Developing such model for a TRACE computer code is important as it increases the capability of the analyses in simulating nuclear power plant behaviour for different accidents including capabilities for simulating 3D thermal hydraulic phenomena in the reactor core simultaneously with 3D reactor physics calculations. In this way, it is possible to conduct transients involving spatial thermal-hydraulic processes in the reactor core. In developing a VVER 1000 model for TRACE code an existing RELAP5 1D model has been used developed in the INRNE-BAS and widely validated and used for safety assessment of a VVER 1000 reactor system. The validation process includes comparisons of steady-state and transient calculations. The behaviour of selected important parameters calculated from the existing RELAP5 Mod3.3 VVER 1000 model has been compared with results received by using a TRACE V5.0p5 VVER 1000 new computer model. The integral response of the reactor system during a total station blackout (SBO) event has been investigated. The transient includes shutdown of the reactor system, isolating of the turbine, a transition from forced to natural circulation of the coolant in the primary circuit, switching off the feed water system from all steam generators (SGs), activation of safety valves in the secondary and primary circuits, dryout of SGs, loss of natural circulation, reactor core heat up, etc. The performed comparison shows a very good agreement between results received by TRACE model compared to the results received by RELAP5 model.