VALCO: Validation of transient analysis codes for VVER by using measurement data

VALCO is an EU FP5 project on transient analysis code validation for VVER type reactors that continues the work of the former EU Phare project SRR1/95. Twelve organisations from nine East and West European countries are participating. For the validation of coupled neutronic / thermal-hydraulic codes that are used in VVER safety analyses, five measured transients from different VVER-440 and VVER-1000 plants have been documented. Two of them have been chosen for validation calculations. First results of an ATHLET / DYN3D calculations for a MCP trip measured in the Kozloduy-6 VVER-1000 are presented. Uncertainty analysis applying the SUSA methodology developed at GRS to coupled-code calculations for VVER will be performed. To validate the stand-alone three-dimensional neutronic codes together with the applied two-group diffusion parameters independently from thermohydraulic feedback, the analysis of measurements in the V-1000 zero-power facility (KI Moscow), which is a full-scale VVER-1000 mock-up, is going to be performed. Preliminary results of DYN3D steady-state calculations using a HELIOS two-group data library and albedo coefficients calculated by the transport code MARIKO are compared to measurement data.