Spacer grid with hybrid flow-mixing device for nuclear fuel assembly

Abstract

A spacer grid with hybrid flow-mixing devices for nuclear fuel bundle is made up of an intersection of a plurality of thin straps at right angles to form a plurality of cells for receiving and supporting fuel rods. Each strap is composed of two types of strap units, called a primary strap unit and a secondary strap unit, which are alternately arranged along the strap. The primary strap unit is a strap section having a primary vane set, and a secondary strap unit is a strap section having a secondary vane set. The straps intersect such that, by primary and secondary strap units, each intersection forms a hybrid flow-mixing device around the top of each junction. The primary vane set, consisting of a trapezoidal primary vane stand and two bent primary mixing vanes on both sides, protrudes upwardly from the strap and is primarily for generating cross flow between channels. Meanwhile, the secondary vane set, consisting of a trapezoidal secondary vane stand and two bent primary mixing vanes on both sides, also protrudes upwardly from the strap, but is primarily for swirl flow generation within the channels. The hybrid flow-mixing device induces a complex but effective flow pattern in flow channels for fuel rod cooling.