Patent Number: 051125650
Section: claims

1. A control system for a nuclear reactor in which the power level is altered by adjustments in reactor reactivity, comprising: means for determining the reactivity of the nuclear reactor, said determining means having a cycle time which is less than the delayed neutron lifetimes in the nuclear reactor; and  stepping drive means for adjusting said reactivity by incrementally changing a parameter by a fixed amount of either plus or minus one unit. 2. The control system as defined in claim 1, wherein said stepping drive means for adjusting said reactivity comprises apparatus for changing a position of movable control rods within the nuclear reactor by a fixed unit amount. 3. The control system as defined in claim 1, further including response function means for determining a required change in reactivity of the nuclear reactor to achieve said altered power level. 4. The control system as defined in claim 3, wherein said response function means uses digital topology to produce a non-linear response. 5. The control system as defined in claim 1, wherein said means for determining the reactivity of the nuclear reactor includes means, linear or non-linear, for determining a required reactivity of the nuclear reactor to reach a desired power level and comparing it with an existing reactivity to determine a control signal. 6. The control system as defined in claim 5, further including means for detecting a period of the nuclear reactor, said determining means comparing said reactor period with a required reactor period and producing a response representative of a difference therebetween, said stepping drive means for adjusting said reactivity being responsive to said difference causing said reactor period to approach said required reactor period. 7. The control system as defined in claim 6, further including means for limiting said reactor period, said means for determining the reactivity of the nuclear reactor preventing said required reactor period from exceeding a period produced by said limiting reactor period means.