Patent ID: 6259756
Filing Date: 2001-07-10
Classification: G21C,Y02E

Abstract:
In a nuclear reactor having a core, said core including plural control blades and fuel assemblies with each control blade operationally associated with four fuel bundles of each fuel assembly, sets of said control blades forming discrete control blade groups forming a core pattern including first and second main groups thereof, respectively, symmetrically and asymmetrically arranged about the core, each main group having first and second sub-groups, said first sub-groups of said main group including first and second operational sub-groups, respectively, of control blades;each first sub-group of said first main group being flanked by first sub-groups of said second main group in a first direction and by the second sub-group of said second main group in a second direction normal to said first direction;each second sub-group of said first main group being flanked by second sub-groups of said second main group in said first direction and by first sub-groups of said second main group in the second direction;each first sub-group of said second main group being flanked by a first sub-group of said first main group in the first direction and by said second sub-group of said first main group in the second direction;each second sub-group of said second main group being flanked by a second sub-group of said first main group in the first direction and by the first sub-group of said first main group in the second direction;each blade of each first main group being movable between withdrawn, deep and shallow positions relative to said core and said fuel bundles associated with said first main group, each blade of each second main group being movable between withdrawn and shallow positions relative to said core and to fuel bundles associated with said second main group;a method of operating the nuclear reactor comprising the steps of:inserting into the core from a withdrawn position into a deep position a different sub-group of the blades of the first and second sub-groups and operational sub-groups of said first main group at the beginning of at least each of three successive time periods, respectively, with predetermined sub-groups of blades of said first and second main groups withdrawn from the core at the beginning of each said successive time period;inserting into the core from a withdrawn position into a shallow position a different sub-group of the blades of the first and second sub-groups of said first and second main groups at the beginning of each of said successive time periods with said predetermined sub-groups of blades of said first and second main groups withdrawn from the core at the beginning if each said successive time period; andmaintaining selected sub-groups of said withdrawn blades at the beginning of each successive time period in a withdrawn position for at least two consecutive time periods.