Patent Number: 044329300
Section: claims

1. A method of operating a nuclear reactor comprising: determining the current power density of each core zone;  predicting the anticipated reactivity change of each of said core zones after movement of the corresponding reactor coolant displacer elements, based on the equation EQU .DELTA.R=K.times.BU.times.APD  determining the reactivity change needed to achieve the desired reactor core power level;  selecting an appropriate displacer element for movement to attain the desired reactivity change; and  moving said selected displacer element relative to said core for attaining the desired reactor core power level.  determining the fraction of the total core power that is attributed to each of said core zones;  predicting the anticipated fraction of the total core power that would be attributed to each of said core zones after movement of the corresponding reactor coolant displacer element; and  selecting said appropriate displacer element for movement to attain the desired reactivity change without disturbing the total core power distribution.  NPD=core zone power density after displacer element movement;  OPD=core zone power density prior to displacer element movement;  BU=burnup in MWD/MTU;  a=a constant; and  b=a constant. 2. The method according to claim 1 wherein said method further comprises: 3. The method according to claim 2 wherein said step of predicting the anticipated fraction of the total core power that would be attributed to each of said core zones after movement of the corresponding displacer element comprises predicting said fraction where: EQU NPD=(a+b.times.BU).times.OPD 4. The method according to claim 3 wherein said method further comprises prior to moving said selected displacer element, selecting the next appropriate displacer element for movement and determining that said selected appropriate displacer element movement would not preclude moving said next appropriate displacer element. 5. The method according to claim 4 wherein K=0.0054. 6. The method according to claim 5 wherein a=1.17 and b=0.00033.