The safety and reliability of all systems has to be maintained throughout the lifetime of a nuclear power plant (NPP). This requires a systematic ageing management procedure for justifying their safe long term operation. One fundamental part in this process is to demonstrate the integrity of the nuclear power plant components. The European project ATLAS+ aims to develop and validate advanced methods of structural integrity assessment applicable in the ageing and lifetime management of primary circuit components.

To support development and validation of those methods a large scale test programme was developed with the aim to investigate fracture behavior of relevant piping material at the component level.

Three of the planned large scale experiments focus on the fracture behavior of flawed ferritic pipe segments made of material WB 36 (15 NiCuMoNb 5); this material is representative of secondary feedwater lines installed in German NPPs.

In order to improve understanding of test results post-test simulations and fractographic examination of all large scale tests are planned, some of them have been already performed.

In this paper the post-test simulation of the mock-up FP2 (ferritic pipe with outer semi-elliptical circumferential crack) is presented and discussed. This mock-up was selected because it experienced an unexpected brittle fracture during the test, which occurred after limited ductile crack propagation.

To investigate both the ductile and the brittle crack propagation phases of the test detailed ductile tearing analysis and brittle fracture assessment have been performed. In addition, relevant results of fractographic examination of the mock-up FP2 are presented and discussed.

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