Cortex Project

A new project was launched in July 2010 at the MAI: the CORTEX project, from the historic partnership between the MMC Department of EDF R&D and EPRI (USA). Led by François Vaillant (image at left), a senior researcher at EDF, CORTEX aims to conduct further investigations and a research program on corrosion of bottom mounted instrumentation (BMI) nozzles in nuclear power plants. « These are passages for the instrumentation of the reactor vessel, said François. The project follows prior investigations in the U.S. to address the cracking of two BMI were nozzles in the South Texas Project power plant. Because there has been no similar case yet in any plant owned by the MAI members, we wanted to further research this topic. » Thanks to feedback from EPRI on South Texas Project, the MAI could get samples from the cracked BMI nozzles of the American plant. The purpose of CORTEX is twofold: investigate the mechanical properties of the material in tension and define an index of sensitivity to stress corrosion cracking (SCC) of the material used. « When we introduce the characteristics of the material taken from the engineering model used by EDF to estimate the lifetime of the alloy 600* components we do not find precisely the time after which the cracks were detected. We therefore need to conduct experimental work to understand this phenomenon. » The first samples made available by EPRI will be transferred to the EDF laboratory of AMI Chinon (France) for stretching tests. This MAI Associate laboratory allows work on irradiated materials. It is through these laboratory tests that we will attempt to define the sensibility index of the material to SCC. « Stress corrosion tests of samples will be performed in another MAI Associate laboratory, says François. It can be either VTT in Finland or Studsvik in Sweden. With the results that come from this work, we will verify whether the EDF model correctly predicts material degradation. » CORTEX is a symbol of the excellence partnership that constitutes the MAI: Members of the MAI are working together on the BMI corrosion which is a major issue for nuclear operators, particularly in terms of safety. (* Alloy 600: 75% nickel, 15% chromium and 10% iron).