Results of vera application to the AP1000^® PWR startup

This paper describes the application of the Virtual Environment for Reactor Applications, VERA, under development by the Consortium for Advanced Simulation of LWRs (CASL) to the core physics analysis of the AP1000 PWR. The AP1000 PWR features an advanced first core with radial and axial heterogeneities which provides significant enhancements compared to traditional first cores, allowing best fuel usage and short transition to the equilibrium cycle with subsequent fuel reloads. These core advanced features can pose some challenges to the core physics tools making application of VERA to the AP1000 PWR first core especially relevant to qualify VERA performance. This paper focuses on the qualification efforts at hot zero power conditions, where Monte-Carlo reference solutions have also been established. In particular, the paper focuses on the comparison of the predictions obtained with VERA for the four AP1000 units that recently started up with the measured values. It is shown that there is excellent agreement between VERA and the key reactor physics parameters measured during the AP1000 startup.