CONTROL ROD DROP SURVEILLANCE USING TWO FRICTION COEFFICIENTS

摘要

In the case of large burnup, a control rod (CR) guide tube in the pressurized water reactor of a commercial nuclear power plant might bend. As a consequence, a CR drop experiment may indicate an event of a CR partially inserted and whether the CR should be deemed inoperable. Early prevention of such an event can be achieved by measuring two friction coefficients: the hydraulic coeffi- cient and the sliding coefficient. The hydraulic coefficient hardly changes, so that the curvature of the guide tube can only be detected thanks to a variation of the sliding coefficient. A simple model for the CR drop is established and validated with CR drop experiments. If t_(mx) denotes the instant of CR maximum velocity, a linear relationship between (t_(mx))~(-2) and the sliding coefficient is found.