OVERVIEW AND DISCUSSION OF PHASE I OF THE OECD LWR UAM BENCHMARK ACTIVITY

The ongoing OECD Light Water Reactor (LWR) Uncertainty Analysis in Modeling (UAM) benchmark activity contributes to establishing unified framework to determine the uncertainty in LWR system calculations at all stages of a coupled reactor physics/thermal hydraulics calculation. This benchmark sequence started in 2007, and integrates the expertise in reactor physics, thermalhydraulics and reactor system modeling as well as uncertainty and sensitivity analysis. Such an effort has been undertaken within the framework of a program of international co-operation that benefits from the coordination of the NEA Nuclear Science Committee (NSC), and from interfacing with the Committee of Safety of Nuclear Installations (CSNI). Reference LWR systems and scenarios for coupled code analysis are defined. Three main LWR types are selected, based on previous benchmark experiences and available data – BWR, PWR and VVER-1000. The full chain of uncertainty propagation from basic data, engineering uncertainties, across different scales (multi-scale), and physics phenomena (multi-physics) is tested on a number of benchmark exercises for which experimental data is available and for which the power plant details have been released. The above-described approach is based on the introduction of nine steps (exercises). These exercises are carried out in three phases, and follow the established routine calculation scheme for LWR design and safety analysis in industry and regulation. This paper provides overview and discussion in detail of the Phase I (Neutronics Phase). In its conclusion part the paper summarizes the priorities of Phase II (Core Phase) and Phase III (System Phase).