Water displacer rod with hollow annular support pellets having sealed internal voids

This patent describes in a fuel assembly for use in a nuclear reactor having moderator-coolant liquid flowing therein, the fuel assembly including an organized array of nuclear fuel rods and at least one improved water displacer rod disposed among the fuel rods for displacing a portion of the moderator-coolant liquid flowing along the fuel rods. The displacer rod consists of (a) an elongated hollow hermetically-sealed tubular member; and (b) pellets composed of a material substantially transparent to neutrons and disposed in a stacked relationship within the tubular member throughout the length of the member, each of at least a substantial number of the pellets having (i) a body with opposite ends and a hollow annular cross-sectional shape defining a central void through the pellet, the central void of the body being substantially transparent to neutrons, and (ii) a solid web extending across and connected with at least one of the opposite ends of the body so as to close the void at the one body end such that the body end such that the respective voids of the bodies of the pellets disposed in the stacked relationship are enclosed individually one from the next