Tribocorrosion in Pressurized Water Reactors

摘要

Most of the metallic alloys employed in pressurized water reactors (PWRs) have passivating properties that allow them to withstand relatively aggressive environmental conditions such as high temperatures, high pressure, and water-based coolants containing boric acid and lithium hydroxide. The working environment and the relative motions between components favor tribo-corrosion. For example, wear of the latch tips in the control rod drive mechanism was observed as a function of the operating time. Not only does this kind of wear threaten component efficiency and service life, but it also could raise safety issues. Therefore, the tribocorrosive wear mechanisms of latch tips were investigated by AREVA. Previously, AREVA had developed several simulative tests for component materials. These did not allow studies of the effects of irradiation and were not instrumented for studies of phenomena that occur at the scale of contact. Nor did the test times and costs permit effective study of the effects of mechanical and environmental variables. These issues prompted the design of a new apparatus to allow electrochemical measurements to be made during rubbing in simulative PWR environments. Under an AREVA-university collaborative effort that also considered a third-body approach to material flow, a series of ambient temperature and pressure experiments were performed to explore the joint influence of mechanical and environmental factors.