For at least four decades GRS, a technical and scientific support organization working for the German government, has been and still is developing a simulation system for nuclear power plants. It consists of different codes to simulate the plant conditions during normal operation and accidents.
New and innovative reactor concepts as well as modelling phenomena of new interest require to further develop and to couple these codes. Thereby, each new version must be verified and validated again.
A continuous integration process has been setup to build and test them automatically. Challenges solved during its introduction will be shown which should be applicable to other legacy codes.