SYSTEM AND METHOD TO DETERMINE REACTIVITY

1 . A method of determining reactivity of a nuclear reactor, the method comprising:

receiving, by a reactivity computer comprising a processor and a memory, a neutron detector response for a discrete period of time;

performing, by the reactivity computer, a statistical check on the neutron detector response;

determining, by the reactivity computer, when the neutron detector response is acceptable based on the statistical check; and

calculating, by the reactivity computer, a reactivity using a prior delayed neutron concentration when the neutron detector response is not acceptable and using a newly calculated delayed neutron concentration when the neutron detector response is acceptable.

2 . The method of claim 1 , wherein performing the statistical check comprises determining, by the reactivity computer, when the neutron detector response changes by a predetermined number of standard deviations during the discrete time period, and

wherein determining, by the reactivity computer, when the neutron detector response is acceptable comprises determining, by the reactivity computer, that the neutron detector response is acceptable when the neutron detector response changes by less than the predetermined number of standard deviations during the discrete time period and determining that the neutron detector response is not acceptable when the neutron detector response changes by the predetermined number of standard deviations or more during the discrete time period.

3 . The method of claim 1 , wherein performing, by the reactivity computer, the statistical check comprises determining, by the reactivity computer, when the neutron detector response changes by a predetermined amount during the discrete time period, and

wherein determining, by the reactivity computer, when the neutron detector response is acceptable comprises determining that the neutron detector response is acceptable when the neutron detector response changes by less than the predetermined amount during the discrete time period and determining, by the reactivity computer, that the neutron detector response is not acceptable when the neutron detector response changes by the predetermined amount or more during the discrete time period.

4 . The method of claim 1 , wherein receiving, by a reactivity computer comprising a processor and a memory, a neutron detector response comprises receiving, by the reactivity computer, a response from the neutron detector operating in a first mode or operating in a second mode.

5 . The method of claim 4 , wherein receiving, by a reactivity computer, a response from the neutron detector operating in a first mode comprises receiving, by a reactivity computer, a response from the neutron detector operating in a pulse mode wherein a plurality of neutron pulses is detected and recorded, and

wherein receiving, by a reactivity computer, a response from the neutron detector operating in a second mode comprises receiving, by a reactivity computer, a response from the neutron detector operating in a mean-square voltage mode wherein a pre-amplifier is configured to amplify a plurality of pulse signals and provide a signal proportional to a square root of a reactor power.

6 . The method of claim 1 , wherein calculating reactivity, by the reactivity computer, comprises calculating, by the reactivity computer, an inverse point kinetics equation to calculate reactivity.

7 . A system for calculating reactivity of a reactor core, the system comprising:

a neutron detector configured to detect neutron flux produced in the reactor core; and

a reactivity computer configured to receive a neutron detector response based on an output of the neutron detector, the reactivity computer comprising a processor and a memory, the memory configured to store a reactivity calculation routine and the processor being configured to execute the reactivity calculation routine, the reactivity routine comprising:

receiving, by the reactivity computer, the neutron detector response for a discrete period of time;

performing, by the reactivity computer, a statistical check on the neutron detector response;

determining, by the reactivity computer, when the neutron detector response is acceptable based on the statistical check; and

calculating, by the reactivity computer, a reactivity using a prior delayed neutron concentration when the neutron detector response is not acceptable and using a newly calculated delayed neutron concentration when the neutron detector response is acceptable.