PWR core safety analysis with 3-dimensional methods

The main focus of safety analysis is to demonstrate the required safety level of the reactor core. Because of the demanding requirements, the quality of the safety analysis strongly affects the confidence in the operational safety of a reactor. To ensure the highest quality, it is essential that the methodology consists of appropriate analysis tools, an extensive validation base, and last but not least highly educated engineers applying the methodology. The sophisticated 3-dimensional core models applied by AREVA ensure that all physical effects relevant for safety are treated and the results are reliable and conservative. Presently AREVA employs SCIENCE, CASMO/NEMO and CASCADE-3D for pressurized water reactors. These codes are currently being consolidated into the next generation 3D code system ARCADIA (R). AREVA continuously extends the validation base, including measurement campaigns in test facilities and comparisons of the predictions of steady state and transient measured data gathered from plants during many years of operation. Thus, the core models provide reliable and comprehensive results for a wide range of applications. For the application of these powerful tools, AREVA is taking benefit of its interdisciplinary know-how and international teamwork. Experienced engineers of different technical backgrounds are working together to ensure an appropriate interpretation of the calculation results, uncertainty analysis, along with continuously maintaining and enhancing the quality of the analysis methodologies. In this paper, an overview of AREVA's broad application experience as well as the broad validation base of its code systems is given. The importance and necessity of the comprehensive 3-dimensional methodology is illustrated by example analyses of a rod ejection accident and an 'inadvertent opening of the pressurizer safety valve' transient. The examples refer to the safety criteria pellet averaged fuel enthalpy, fast fuel enthalpy rise, number of fuel assemblies in film boiling and the maximum fuel temperature and illustrate, how 3D-methods provide evidence of bigger safety margins or archive more reliable results. (c) 2014 Elsevier Ltd. All rights reserved.