Experimental study and simulation of wear phenomena under Impact-Fretting-Wear conditions in pressurized water environments: Optimization of the design of future nuclear reactors. – Fretting Wear Design

The industrial chair project "Fretting Wear Design," developed in partnership between the CMAT laboratory (UMR 7633), MINES Paris - Université PSL (École des Mines de Paris), and the company Framatome, aims to establish a center of excellence in research at CMAT focused on wear issues induced by Impact-Fretting (low amplitude alternating sliding) in pressurized water environments (155 bar and 315°C). If confirmed, this research project will be involved in the R&D "Wear Challenge" program launched by Framatome, which aims to develop future nuclear reactors that are more reliable and cost-effective in terms of maintenance.

Indeed, under the action of the coolant fluid (pure water at 315°C, 155 bar), the fuel cladding, as well as the control rod guide tubes in the primary circuit, undergo significant wear due to impact-fretting. The perforation of these tube bundles could be critical for the operation of nuclear power plants. It is therefore essential to model these phenomena and optimize the mitigative measures (surface treatments). This research will focus on two specific issues: impact-fretting phenomena (variable normal force) observed in fuel assemblies and impact-fretting phenomena observed in guide rod contacts.

The goal of the "Fretting Wear Design" industrial chair is to address these scientific and industrial challenges:

Inspired from an existing "atmospheric" impact-fretting testing bench (IF1) at CMAT, a new experimental impact-fretting test in pressurized water (pure water at 315°C, 155 bar) will be developed and set up at CMAT (IF2) to better represent the real conditions of a PWR environment. With this unique experimental setup, CMAT will conduct experimental research to better understand these wear phenomena, establish damage scenarios, and compile experimental data to develop wear models that combine mechanical stresses and tribo-corrosion.

With the experimental data, numerical models will be developed and transferred to the design offices of Framatome to better predict the lifespan of future "tube bundle" assemblies in nuclear reactors. In parallel with the development of a sizing strategy, optimization work will be carried out experimentally to optimize the choice of mitigative measures (surface treatments) and thus increase the lifespan of these future assemblies.

Thus, the continuation of this industrial chair will focus on research aimed at optimizing new surface treatments specific to the PWR environment, as well as studying new challenges such as fast-neutron reactors, the development of Small Nuclear Reactors (SNR), and even studying impact-fretting phenomena observed in fusion reactors (ITER, DEMO).

This chair will involve three 36-month CIFRE PhDs from Framatome (2 experimental + 1 wear simulation), two CDD engineers for the management of experimental developments (2 x 18 months), and an 18-month postdoctoral researcher responsible for developing artificial intelligence approaches to exploit the project's experimental data, as well as developing fast methods to predict local perforation of cladding and tubes. The project will involve four academic researchers (1 CNRS (lead) and 3 faculty members from EMP), as well as a technical supervisor from CMAT.