The influence of water flow on the impact/sliding wear and oxidation of PWR control rods specimens

Some mechanical components of PWR nuclear power plants can be sensitive to wear damage resulting from contacts with their supports or guides due to fl ow-induced vibrations. It is particularly the case of the control rods (rod cluster control assemblies (RCCAs)) and RCC guide tubes inside the reactor pressure vessel. In order to improve our knowledge about the wear behavior of such component s, an extensive research program has been conducted during these past years by CEA and EDF including numerous wear tests performed on specific wear si mulators. Within the framework of this program, the influence of the water flow on the wear process and damage has been studied on such components. Se veral wear tests have been conducted on specimens by EDF and CEA using the wear simulators ERABLE 1&2 (EDF) and SYRACUSE 1&2 (CEA) developed by Atomic Energy of Canada Limited (AECL). These simulators are operating in experim ental conditions close to the PWR primary system (temperature, pressure, ox ygen content, etc.). Both types of simulators are very similar except the w ater flow which is present only in the EDF machines. Several water flow rat es have been taken into account in this program. Complementary to the tests , some extensive non destructive and destructive examinations of the specim ens have been performed including the determination of the wear volumes usi ng weights, three-dimensional (3D) profilometry and metallurgical examinati ons of the surfaces. The results obtained by CEA and EDF are compared and analyzed. The influenc e of the water flow on the behavior of the specimens is clearly shown, part icularly on the dynamic behavior of the system and on the oxidation of the specimens. The effect on the wear pattern seems to be less significant even though the wear volumes are different. (C) 2001 Elsevier Science B.V. All rights reserved.