Patent Number: 
Section: claims

1. A risk-informed method for safety analyses of nuclear power generating systems, said method comprising:ordering events by an initiating event frequency;defining an initiating event frequency threshold value;defining acceptance criteria having an adjusted amount of conservatism, wherein the amount of conservatism is a function of the initiating event frequency;determining if an event has an event initiating frequency at or above the threshold value;determining if an event has an event initiating frequency below the threshold value; anddetermining if a nuclear power generating system meets licensing requirements by:analyzing an event by a deterministic safety analysis methodology when the event has an event initiating frequency at or above the threshold value to produce an event analysis result; oranalyzing an event by a probabilistic risk assessment methodology when the event has an event initiating frequency below the threshold value to produce an event analysis result;comparing the event analysis result to the defined acceptance criteria to determine if the nuclear power generating system meets licensing requirements; andoutputting a comparison result that indicates if the nuclear power generating system meets licensing requirements. 2. A method in accordance with claim 1 further comprising determining an amount of conservatism used in the deterministic safety analysis methodology, wherein the amount of conservatism is a function of the initiating event frequency. 3. A method in accordance with claim 2 further comprising:identifying additional system failures that are not a direct consequence of the initiating event;defining a total threshold frequency for the combination of the initiating event frequency and the additional failure frequency; andadding additional system failures to the safety analysis, one at a time, until a total frequency of an event plus additional failures is less than the total threshold frequency when the initiating event frequency is above the total threshold frequency. 4. A method in accordance with claim 2 wherein determining an amount of conservatism used in the deterministic safety analysis methodology comprises developing at least one deterministic safety analysis methodology containing a predetermined amount of conservatism based on the initiating event frequency, wherein the predetermined amount of conservatism used in a deterministic safety analysis methodology is a function of the difference between the initiating event frequency and the initiating event frequency threshold value. 5. A method in accordance with claim 1 wherein defining acceptance criteria having an adjusted amount of conservatism comprises developing at least one acceptance criteria containing a predetermined amount of conservatism based on the initiating event frequency, wherein the predetermined amount of conservatism for an acceptance criteria is a function of the difference between the initiating event frequency and the initiating event frequency threshold value. 6. A system for performing risk-informed safety analyses of nuclear power generating systems, said system comprising a computer configured to:order events by an initiating event frequency;define an initiating event frequency threshold value;define acceptance criteria having an adjusted amount of conservatism, wherein the amount of conservatism is a function of the initiating event frequency;determine if an event has an event initiating frequency at or above the threshold value;determine if an event has an event initiating frequency below the threshold value; anddetermine if a nuclear power generating system meets licensing requirements by:analyzing an event by a deterministic safety analysis methodology when the event has an event initiating frequency at or above the threshold value to produce an event analysis result; oranalyzing an event by a probabilistic risk assessment methodology when the event has an event initiating frequency below the threshold value to produce an event analysis result;comparing the event analysis result to the defined acceptance criteria to determine if the nuclear power generating system meets licensing requirements; andoutputting a comparison result that indicates if the nuclear power generating system meets licensing requirements. 7. A system in accordance with claim 6 wherein said computer is further configured to determine an amount of conservatism used in the deterministic safety analysis methodology, wherein the amount of conservatism is a function of the initiating event frequency. 8. A system in accordance with claim 7 wherein said computer is further configured to:identify additional system failures that are not a direct consequence of the initiating event;define a total threshold frequency for the combination of the initiating event frequency and the additional failure frequency; andadd additional system failures to the safety analysis, one at a time, until a total frequency of an event plus additional failures is less than the total threshold frequency when the initiating event frequency is above the total threshold frequency. 9. A system in accordance with claim 7 wherein said computer is further configured to develop at least one deterministic safety analysis methodology containing a predetermined amount of conservatism based on the initiating event frequency, wherein the predetermined amount of conservatism used in a deterministic safety analysis methodology is a function of the difference between the initiating event frequency and the initiating event frequency threshold value. 10. A system in accordance with claim 6 wherein said computer is further configured to develop at least one acceptance criteria containing a predetermined amount of conservatism based on the initiating event frequency, wherein the predetermined amount of conservatism for an acceptance criteria is a function of the difference between the initiating event frequency and the initiating event frequency threshold value. 11. A computer program embodied on a computer readable medium for performing risk-informed safety analyses of nuclear power generating systems, said program comprising a code segment that:orders events by an initiating event frequency;defines an initiating event frequency threshold value;defines acceptance criteria having an adjusted amount of conservatism, wherein the amount of conservatism is a function of the initiating event frequency;determines if an event has an event initiating frequency at or above the threshold value;determines if an event has an event initiating frequency below the threshold value; anddetermines if a nuclear power generating system meets licensing requirements by:analyzing an event by a deterministic safety analysis methodology when the event has an event initiating frequency at or above the threshold value to produce an event analysis result; oranalyzing an event by a probabilistic risk assessment methodology when the event has an event initiating frequency below the threshold value to produce an event analysis result;comparing the event analysis result to the defined acceptance criteria to determine if the nuclear power generating system meets licensing requirements; andoutputting a comparison result that indicates if the nuclear power generating system meets licensing requirements. 12. A computer program in accordance with claim 11 further comprising a code segment that determines an amount of conservatism used in the deterministic safety analysis methodology, wherein the amount of conservatism is a function of the initiating event frequency. 13. A computer program in accordance with claim 12 further comprising a code segment that:identifies additional system failures that are not a direct consequence of the initiating event;defines a total threshold frequency for the combination of the initiating event frequency and the additional failure frequency; andadds additional system failures to the safety analysis, one at a time, until a total frequency of an event plus additional failures is less than the total threshold frequency when the initiating event frequency is above the total threshold frequency. 14. A computer program in accordance with claim 11 further comprising a code segment that develops at least one deterministic safety analysis methodology containing a predetermined amount of conservatism based on the initiating event frequency, wherein the predetermined amount of conservatism used in a deterministic safety analysis methodology is a function of the difference between the initiating event frequency and the initiating event frequency threshold value. 15. A computer program in accordance with claim 11 further comprising a code segment that develops at least one acceptance criteria containing a predetermined amount of conservatism based on the initiating event frequency, wherein the predetermined amount of conservatism for an acceptance criteria is a function of the difference between the initiating event frequency and the initiating event frequency threshold value.