US 4,285,769 AGranted

Control cell nuclear reactor core

AssigneeGeneral Electric Company

InventorsSteven R. Specker, Craig D. Sawyer, Russell L. Crowther, Bennett J. Gitnick, Kenneth V. Walters, Robert E. Brown, Larry E. Fennern

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Abstract

A method and arrangement for operating a boiling water nuclear reactor and fuel assembly designs for such reactor wherein the reactor is operated with uniquely located control rods that serve the primary functions of power shaping and reactivity control. A second and separate distinct group of control rods is withdrawn when the reactor is at power and the control rods of this group serve the primary function of reactor shutdown. The design of the fuel assemblies and the selected patterns of fuel assemblies and control rods make the separation of control functions feasible. The power shaping and reactivity control control rods are located in low power regions of the core designated control cells. The design of the fuel is such that the control rods of the control cells may remain in fixed positions in these cells during the operating cycle until withdrawal for burnup reactivity compensation.

Claims33

Dependent claims

A method of fueling and operating a nuclear reactor core having a plurality of cells wherein each cell includes a plurality of individually replaceable fuel assemblies surrounding a selectively insertable control rod and wherein said reactor is shut down after each successive cycle of periodic operation for replacement of a fraction of the fuel assemblies of said core, comprising the steps of:

(1) designating a pattern of two kinds of cells in said core, namely, a set of control cells and a set of non-control cells wherein said control cells are separated from one another by at least one non-control cell;
(2) placing fuel assemblies of relatively high reactivity fuel in said non-control cells, the design thereof being particularly adapted for subsequent use in said control cells, said higher reactivity being sufficient for a residence time of said fuel assemblies in said core of n cycles of operation (n being greater than 1);
(3) placing fuel assemblies in said control cells of fuel of lower reactivity than that of said non-control cells, the design thereof being particularly adapted for use in said control cells;
(4) operating said reactor core throughout a cycle of operation with the control rods of said non-control cells substantially withdrawn from said core and with the control rods of at least some of said control cells selectively inserted in said core to control the power level thereof;
(5) shutting down said reactor for refueling of said core at the end of said cycle;
(6) removing all of the fuel assemblies from each of said control cells;
(7) replacing all of the fuel assemblies removed from said control cells with irradiated fuel assemblies moved from said non-control cells which fuel assemblies have resided in said core n-1 cycles;
(8) inserting in said non-control cells unirradiated fuel assemblies at least equal in number to the irradiated fuel assemblies moved into said control cells, the enrichment of said unirradiated fuel assemblies providing a reactivity sufficient for a residence time in said core of n cycles of operation;
and
(9) operating said reactor core through successive cycles of operation in accordance with steps (4)-(8).

7 more elements

A method of fueling and operating a nuclear reactor core having a plurality of individually replaceable fuel assemblies surrounding a selectively insertable control rod and wherein said reactor is shut down after each successive cycle of periodic operation for replacement of a fraction of the fuel assemblies of the core, comprising the steps of:

(1) designating a pattern of cells in said core including a first set of control cells sufficient in number so that the control rods thereof are capable of controlling said core at power, the cells thereof being separated from one another by at least one cell of other sets of cells,
a second set of control cells sufficient in number so that the control rods thereof are capable of controlling said core at power, the cells thereof being separated from one another by at least one cell of other sets of cells, the cells of said second set of control cells being located in different cell positions in said core than the cells of said first set of control cells, and
a set of non-control cells, the cells thereof being located among the cells of said first and second sets of control cells;
(2) positioning fuel assemblies of relatively high reactivity fuel in the cells of said non-control cells including at least some assemblies of unirradiated fuel having a reactivity sufficient for a residence time in said core of n cycles of operation (n being greater than 1);
(3) positioning fuel assemblies in the cells of said first set of control cells of fuel of lower reactivity than that of said non-control cells;
(4) positioning fuel assemblies in the cells of said second set of control cells which provide an average cell reactivity therein intermediate the average cell reactivity of the cells of said first set of control cells and the cells of said non-control cells, at least some of the fuel assemblies positioned in said second set of control cells having been irradiated for n-2 cycles of operation;
(5) operating said reactor core througout a cycle of operation with the control rods of said second set of control cells and of said non-control cells substantially withdrawn at power and with the control rods of at least some of the cells of said first set of control cells selectively inserted to control the reactor core;
(6) shutting down said reactor for refueling of said core at the end of said cycle;
(7) removing at least some of the fuel assemblies of each of the cells of said first set of control cells and replacing them with fuel assemblies of higher reactivity;
(8) removing at least some of the fuel assemblies from the cells of said non-control cells and replacing them with unirradiated fuel assemblies;
(9) positioning in the cells of said second set of control cells fuel assemblies of relatively low reactivity fuel including the retention therein of at least some of the fuel assemblies which have been irradiated for n-1 cycles of operation whereby movement of fuel assemblies during said refueling is minimized;
and
(10) operating said reactor core throughout another cycle of operation with the control rods of the cells of said first set of control cells and of said non-control cells substantially withdrawn at power and with the control rods of at least some of the cells of said second set of control cells selectively inserted to control the reactor core.

10 more elements

(1) designating a pattern of two kinds of cells in said core, namely, control cells and non-control cells wherein said control cells are separated from one another by at least one non-control cell;
(2) placing fuel assemblies of relatively low reactivity fuel in said control cells;
(3) placing fuel assemblies in said non control cells of fuel of higher reactivity than that of said control cells;
(4) placing fuel assemblies in the peripheral fuel assembly positions of said core of fuel of lower reactivity than that of said non-control cells;
(5) placing fuel assemblies in intermediate fuel assembly positions adjacent said peripheral fuel assembly positions of fuel of higher reactivity than that of the fuel assemblies of said peripheral fuel assembly positions;
(6) operating said reactor core throughout a cycle of operation with the control rods of said non-control cells withdrawn from said core and with the control rods of at least some of said control cells selectively inserted in said core to control the power level and neutron flux shape thereof;
(7) shutting down said core for refueling at the end of said cycle;
(8) removing all of the fuel assemblies from each of said control cells;
(9) replacing all of the fuel assemblies removed from said control cells with irradiated fuel assemblies from said non-control cells;
(10) removing and replacing the fuel assemblies of said peripheral fuel assembly positions;
(11) inserting unirradiated fuel assemblies in at least some of said non-control cells;
and
(12) operating said reactor core through successive cycles of operation in accordance with steps (4)-(11).

10 more elements

Dependencies are inferred from the claim text.