Doel 3 - Tihange 2 / German RSK Evaluation & Reply

methods used. However, the RSK cannot rule out smaller cracks hidden behind larger flakes and therefore proposes to analyse the potential influence of such hidden cracks.

2. For the RSK, doubts remain as to whether the simplified 1D analysis of the LOCAs actually provides results which conservatively cover crack driving forces for the specific situation in Doel-3 and Tihange-2 with the multitude of flakes or whether cold plumes or strip-like cooling would have to be considered with a 3D analysis. 3. From the point of view of the RSK, moderate residual tensile stresses over a range approximately equivalent to the depth of the heat-affected zone should be considered in a conservative safety analysis for the assessment of sub-clad cracks. 4. From the point of view of the RSK, the fracture-mechanical behaviour of a flawed RPV has not been considered adequately in the analysis of the load-bearing capacity according to ASME III, NB-3228.3 described by FANC. The tensile tests carried out with inclined flakes show a reduced ductility and load-bearing capacity. Thus, it cannot be assumed without doubt that the required safety factor of 1.5 is maintained regarding the plastic collapse load.

RSK/ESK Secretariat at the Federal Office for the Safety of Nuclear Waste Management

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