Development, qualification and application of the coupled RELAP5/PANTHER/COBRA code package for integrated PWR accident analysis

At Tractebel Engineering (TE), a dynamic coupling has been developed between the best estimate thermal-hydraulics system code RELAP5 and the 3-dimensional neutronics code PANTHER via the transient analysis code linkage program TALINK. An interface between PANTHER and the subchannel core thermal-hydraulic analysis code COBRA 3C has been established for on-line calculation of the Departure from Nucleate Boiling Ratio. Since each client code has been qualified separately, the TE coupled code package has been qualified only by validation of the data exchange interface using OECD TMI-1 MSLB benchmark exercises. It has been then applied to develop a MSLB accident analysis methodology based on the TE deterministic bounding approach. The results of coupled thermal-hydraulic and neutronic analysis of SLB show that there exists an important margin in the traditional FSAR MSLB accident analysis. The methodology has been applied for MSLB accident analysis in support of licensing of the power uprate and steam generator replacement of the Doel 2 plant. The TE coupled code package will be applied for integrated safety analysis of other PWR accidents. (author)