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The primary purpose of this synthesis report is to deliver a coherent and comprehensive review of research into thermal fatigue performed during Euratom Framework Programmes 4, 5, 6 and 7, linking the research to the related projects, reports, materials and components.

To ensure a consistent treatment of a given ageing mechanism as well as across different ageing mechanisms, consideration is given to the research outputs from Euratom projects that fulfill certain criteria, as follows:

  • Sufficiently detailed information exists regarding materials and conditions of experiments or simulations;
  • The materials in the experiments or simulations correspond to those used in operating European nuclear power plants (NPPs);
  • The conditions investigated correspond to the operating conditions of European NPPs.

Thermal fatigue was within the focus of FP5, FP6 and FP7 as well as JRC Direct Actions due to the occurrence of incidents in piping systems in NPPs, such as at the French Civaux 1 NPP.

In the context of the aforementioned criteria, the majority of potentially relevant Euratom FP5 projects (such as ASTAR, ECORA, FLOMIX-R and THERFAT) directly dealt with thermal fatigue and modelling of thermo-hydraulic or mixing problems.

The focus of FP6 and FP7 projects (such as ARCHER, GETMAT, HELIMNET and MATTER) has been on characterising the behaviour of materials intended for Gen IV reactor systems, such as ferritic/martensitic steels (T91/P91) or oxide dispersion-strengthened (ODS) steels.

Projects which have been evaluated in the mechanical fatigue synthesis report and being also relevant for thermal fatigue are also included in this synthesis report. Consequently, the present synthesis report also takes into consideration the Framework Programmes of the European Coal and Steel Community (now RFCS) as well as materials technology and standardization projects of EC RTD FP5. Where appropriate, reference is also made to external reports coming from international research programmes.