Study of the containment history of the VeRCoRS mock-up and prediction of the leakage rate under pressurization tests

As part of EDF’s study program for the safety and life extension of its Nuclear Power Plants fleet, an experimental mock-up of a reactor containment building at 1/3 scale has been built at “EDF Lab Les Renardières”. The construction has been completed at the end of 2015. Because of the scaling effects, the drying effects on the mock-up are about 9 times faster than in a full scale containment vessel. The mock up’s behaviour is monitored from the beginning of the construction: since the concrete pouring and for the duration of the research program, extensive data are collected. EDF proposes three successive benchmarks to challenge the international research community. Each benchmark deals with updated experimental measures. This paper focuses on themes 2 and 3 of the second benchmark (EDF, 2018): mechanical behaviour and air leakage. The behaviour of the containment building is modelled throughout its concreting followed by the prestressing cables tensioning and the 5 pressurization tests (PreOp, VC1, VD1, VD1bis and VD2). Some notable improvements are taken into account compared to previous works by M. Mozayan- Kharazi [1] and Thénint et al. [2]: - drying shrinkage, basic creep and drying creep are modelled by sate of the art numerical models, following results of Benboudjema [6]; - concrete cracking is modelled in the constitutive law: cracks open and close; - cracks can be introduced in the initial state, to deal with cracks observed in situ and not reproduced in our numerical simulations (no early age behaviour); - leakage rate is now deduced from an orthotropic non-linear gas flow, computed from all the information given by the non-linear constitutive law, including crack opening width. These improvements have been integrated, checked and validated in our in-house version of Code_Aster® and give very promising results. After updating the material parameters based on tests on specimens, the global model leads to an accurate prediction of the mechanical state. More, leakage rate is in very good agreement with the available at that time experimental measures. Finally, ad hoc post-processing gives insightful information on the local and global behaviour of the mock-up, leading to a better understanding of the involved physical phenomena and their interactions. 1 T. Thénint, V. le Corvec and S.