Patent Number: 039714446
Section: claims

1. In a nuclear reactor, a rection vessel, a charge of spherical reaction elements positioned in said vessel, means for providing a continuous circulation of said reaction elements through said vessel during operation thereof, a plurality of control rods and means for advancing said control rods into said charge during operation in direct contact with said elements and for retracting said control rods from said charge, wherein the improvement comprises that said charge consists of two groups of said spherical elements, all of the elements in each of said groups being of the same diameter and the elements in each one of said groups being a different diameter from the elements in the other one of said groups, all of said elements being uniformly mixed together in said vessel and the different diameters of said groups being selected so that the diameter of one said group differs from the diameter of the other said group within a range of from 5 to 35% of the diameter of the other said group and the arrangement of the spherical elements is such that during the circulation of said spherical elements through said vessel during vessel operation the substantial segregation of said elements into said groups does not take place and the selected range in diameters prevents the charge of spherical elements from packing tightly together so that the advancement of said control rods into the charge in direct contact with the spherical elements is facilitated without causing damaging stresses to said spherical elements or to said control rods. 2. In a nuclear reactor, as set forth in claim 1, wherein the difference in diameter of the one said group from the diameter of the other said group is within the range of 5 to 20% of the diameter of the other said group. 3. In a nuclear reactor, as set forth in claim 2, wherein in the charge consisting of two groups of said elements, the diameter of one of said groups is 60mm and the diameter of the other said group is in the range of 48 to 57mm. 4. In a nuclear reactor, as set forth in claim 2, wherein in the charge consisting of two groups of said elements, the diameter of one of said groups is 60mm and the diameter of the other group is in the range of 63 to 72mm.