Patent Number: 050769987
Section: claims

1. A method for monitoring the power output of a nuclear reactor int he low power range, comprising: detecting neutrons produced by the reactor and producing, at the end of each of a succession of equal measuring intervals, a representation of the number of neutrons detected during a time period preceding the end of the respective measuring interval; and  producing a power output level indication having a value associated with each measuring interval by a digital operation in which the indication value associated with a preceding measuring interval is altered according to a function of the representation produced during said detecting step for the present measuring interval,  wherein said step of producing a power output level indication comprises: determining the difference between the value of the representation produced for the present measuring interval and the value of the power output level indication associated with a preceding measuring interval; providing a selected multiplying factor having a value less than unity; forming a representation of the value of the product of the difference determined in said determining step and the selected multiplying factor; and adding the product value representation to the power output level indication associated with the preceding measuring interval in order to produce the power output level indication associated with the present invention.  detecting means for detecting neutrons produced by the reactor and producing, at the end of each of a succession of equal measuring intervals, a representation of the number of neutrons detected during a time period preceding the end of the respective measuring interval; and  digital means connected for producing a power output level indication having a value associated with each measuring interval by a digital operation in which the indication value associated with a preceding time interval is altered according to a function of the representation produced by said detecting means for the present measuring interval,  wherein said digital means comprises: means for determining the difference between the value of the representation produced for the present measuring interval and the value of the power output level indication associated with a preceding measuring interval; means connected for providing a selected multiplying factor having a value less than unity; means connected for forming a representation of the value of the product of the difference determined by said means for determining and the selected multiplying factor; and means connected for adding the product value representation to the power output level indication associated with the preceding measuring interval in order to produce the power output level indication associated with the present interval. 2. A method as defined in claim 1 wherein said step of providing a selected multiplying factor comprises giving the multiplying factor a value inversely proportional to at least the value of the power output level indication associated with a preceding measuring interval. 3. A method as defined in claim 2 wherein the value of the multiplying factor is inversely proportional to the sum of value of the power output level indication associated with the proceeding measuring interval and the value of the representation produced for the present measuring interval. 4. A method as defined in claim 3 further comprising generating a reactor power output level rate of change indication having a value associated with each measuring interval by: deriving, during each measuring interval, a power level change representation having a value which is a function of the difference between the values of the power output level indications associated with the present measuring interval and with a preceding measuring interval; and producing a reactor power output level rate of change indication having a value associated with each measuring interval by modifying the rate of change indication value associated with a preceding measuring interval according to a function of the power level change representation value associated with the present measuring interval. 5. A method as defined in claim 5 wherein the function of the difference in said deriving step is the difference between the logs of the values of the power output level indications, divided by the duration of one measuring interval. 6. A method as defined in claim 1 further comprising generating a reactor power output level rate of change indication having a value associated with each measuring interval by: deriving, during each measuring interval, a power level change representation having a value which is a function of the difference between the values of the power output level indications associated with the present measuring interval and with a preceding measuring interval; and producing a reactor power output level rate of change indication having a value associated with each measuring interval by modifying the rate of change indication value associated with a preceding measuring interval according to a function of the power level change representation value associated with the present measuring interval. 7. A method as defined in claim 6 wherein the function of the difference in said deriving step is the difference between the logs of the values of the power output level indications, divided by the duration of one measuring interval. 8. A device for monitoring the power output of a nuclear reactor in the low power range, comprising: 9. A device as defined in claim 8 wherein said means for providing a selected multiplying factor comprises means for giving the multiplying factor a value inversely proportional to at least the value of the power output level indication associated with a preceding measuring interval. 10. A device as defined in claim 9 wherein the value of the multiplying factor is inversely proportional to the sum of value of the power output level indication associated with the proceeding measuring interval and the value of the representation produced for the present measuring interval. 11. A device as defined in claim 10 further comprising means for generating a reactor power output level rate of change indication having value associated with each measuring interval, said means for generating comprising: first calculating means for deriving, during each measuring interval, a power level change representation having a value which is a function of the difference between the values of the power output level indications associated with the present measuring interval and with a preceding measuring interval; and second calculating means connected to said first calculating means for producing a reactor power output level rate of change indication having a value associated with each measuring interval by modifying the rate of change indication value associated with a preceding measuring interval according to a function of the power level change representation value associated wit the present measuring interval. 12. A device as defined in claim 11 wherein the function of the difference between the values is the difference between the logs of the values of the power output level indications, divided by the duration of one measuring interval. 13. A device as defined in claim 8 further comprising means for generating a reactor power output level rate of change indication having value associated with each measuring interval, said means for generating comprising: first calculating means for deriving, during each measuring interval, a power level change representation having a value which is a function of the difference between the values of the power output level indications associated with the present measuring interval and with a preceding measuring interval; and second calculating means connected to said first calculating means for producing a reactor power output level rate of change indication having a value associated with each measuring interval by modifying the rate of change indication value associated with a preceding measuring interval according to a function of the power level change representation value associated wit the present measuring 14. A device as defined in claim 13 wherein the function of the difference between the values is the difference between the logs of the values of the power output level indications, divided by the duration of one measuring interval.