Patent Number: 046817280
Section: abstract

A nuclear reactor including, in the upper internals, a guide structure capable of effectively accommodating and guiding without binding the large number of neutron-absorber rods included in modern reactors of improved efficiency. The neutron-absorber rods include control rods, gray rods, and water-displacement rods. All rods are suspended in clusters from spiders or vanes. The upper internals of the reactor includes cruciform guides for the control-rod and gray-rod clusters. Each of these guides is composed of a plurality of vertical guide sections of transverse cruciform cross section. Plates extending throughout the cross-section of the reactor are supported between each pair of successive guide sections. The plates are perforated, the perforations in each plate being patterned to pass the water-displacement rod clusters. The plates are oriented so that the patterned perforations are aligned to serve as guides for the water-displacement rod clusters. The plates are of very large diameter and, as perforated, would not be self-supporting unless they were very thick. To overcome this drawback, each plate is formed of separate plate sections which are, when assembled nested together, like the parts of a "jig-saw puzzle".