Wear Characteristics of the Nuclear Control Rod Drive Mechanism (CRDM) Movable Latch Serviced in High Temperature Water

Abstract

The current research of nuclear control rod drive mechanism (CRDM) movable latch only makes a simple measurement of wear mass. The wear volume and difference in various claw surfaces are ignored and the degradation mechanism of each claw surface is not clear. In this paper, a detailed degradation analysis was carried out on each claw surface of movable latch combined with wear result and worn morphology. Results indicate that the boundary of carbide is preferred for corrosion because carbide presents a nobler Volta potential compared to the metal matrix or boundary region. Due to the oscillation of drive shaft between the claw surfaces of movable latch, the dominant wear mechanism on the upper surface of claw (USC) and lower surface of claw (LSC) is plastic deformation caused by impact wear. Mechanical impact wear will cause the fragmentation of carbides because of the high hardness and low ductility of carbides. Corrosion promotes the broken carbides to fall off from the metal matrix. The generated fine carbides (abrasive particles) cause extra abrasive wear on USC when the movable brings the drive shaft upward or downward. As a result, USC has a higher wear volume than LSC. This research proposes a method to evaluate the wear on the whole movable latches using a 3D full-size scanner.

Noise Reduction Method for the Vibration Signal of Reactor CRDM Based on CEEMDAACN-SK

“…Refs. [11][12][13][14] introduce the research contents related to fault analysis and detection of control rod drive mechanism in nuclear reactors in recent years. Aiming at the weld crack fault of the drive mechanism, scholars designed a decimeter size cable-driven elastic spine worm robot [11], which has high adaptability in the weld crack detection between the reactor pressure vessel (RPV) and the CRDM.…”

“…The experimental results show that this method can effectively eliminate the noise interference and realize the roll state diagnosis. The current research on the movable latch of the nuclear control rod drive mechanism (CRDM) only made a simple measurement of the wear quality, ignored the wear amount and difference of each claw surface, and did not know the degradation mechanism of each claw surface [13]. Combined with the wear results and wear patterns, a detailed degradation analysis was carried out on each claw surface of the movable latch.…”