Pellet slide and inspection assembly in a nuclear fuel pellet surface

Abstract

A fuel pellet surface defect inspection apparatus has an infeed conveyor, a discharge conveyor, and a slide and inspection assembly between the conveyors. The assembly includes a slide defining an inclined track having exit and entry ends adjacent the respective discharge and infeed conveyors. The entry end is at a higher elevation than the exit end. The assembly also includes an inspection station located along the track between its entry and exit ends. The station has lower and upper sound reflectors configured to define an annular inspection chamber through which a pellet moves as the pellet slides down the inclined track. The chamber completely encloses the cylindrical surface of the pellet as the pellet moves through the chamber. An ultrasonic inspection head is mounted at the station and transmits and receives sound energy to and from a pellet as it moves through the chamber such that the sound energy completely surrounds the moving pellet being inspected within the chamber. The inclined track has an upper portion extending to the inspection chamber and a lower portion extending from the inspection chamber and having a shallower slope than the upper portion to cause deceleration of a pellet as it moves from the upper portion to the lower portion. Deceleration reduces the velocity of the inspected pellet as it approaches the exit end of the track and thereby reduces the chance of impacts with the discharge conveyor that might otherwise produce chips and cracks in the pellets.