Patent Number: 
Section: claims

1. A method for determining power limit criteria for a nuclear reactor based on operational thermal-mechanical limits of fuel rods in the nuclear reactor core, comprising the steps, executed by a computer, of: a) constructing individual fuel rod power histories for each nuclear fuel rod in the reactor core based on information acquired during previous fuel cycles and a projected operation of the reactor in an upcoming fuel cycle;  b) computing internal pressure data for each fuel rod in the core for an upcoming fuel cycle based on the power histories constructed in step (a);  c) identifying a fuel rod as having a greatest computed internal pressure as computed in step (b); and  d) establishing an operational thermal-mechanical limit based on the power history of the identified fuel rod. 2. The method of  claim 1  wherein step (b) includes computing thermal and mechanical overpower limits for fuel rods in the core. claim 1 3. The method of  claim 1  wherein steps (b) through (d) are repeated for each fuel cycle. claim 1 4. A method for establishing power limit criteria of a nuclear reactor based on operational thermal-mechanical limits of fuel rods in the nuclear reactor core, comprising the steps of: a) computing power history data for each fuel rod in the reactor based on historical operating data of the reactor;  b) computing fuel rod internal pressure data for each fuel rod in the reactor core based on a computed power history data of a fuel rod and a projected operation of the reactor in an upcoming fuel cycle;  c) identifying a maximum fuel rod internal pressure for the upcoming fuel cycle based on the fuel rod internal pressure data computed in step (b); and  d) confirming that the identified maximum is less than fundamental criteria established by the applicable licensing authority. 5. The method of  claim 4 , further including: claim 4 repeating steps (b) and (c) for each fuel cycle of the reactor. 6. A system for establishing power limit criteria for a nuclear reactor based on operational thermal-mechanical limits of fuel rods in the nuclear reactor core, said system comprising a computer including a data storage memory and one or more I/O or display devices, said computer programmed to: (i) construct individual fuel rod power histories for each nuclear fuel rod in the reactor core based on empirical information acquired during previous fuel cycles and the projected operation of the reactor in an upcoming fuel cycle;  (ii) compute internal pressure data for each fuel rod in the core for an upcoming fuel cycle based on the individual power histories; and  (iii) identify a fuel rod having a maximum internal pressure; wherein an operational power limit criteria is established based on thermal-mechanical limit data associated with the identified fuel rod. 7. The system of  claim 6  wherein the computer is further programmed to compute thermal overpower and mechanical overpower limit data for each fuel rod in the reactor core. claim 6 8. The system of  claim 6  wherein the computer provides, via an I/O or display device, output data identifying at least peak internal pressure and exposure information for one or more fuel rods in the reactor core. claim 6 9. A computer program product embodied on a computer-readable medium for distribution and/or storage on a computer system for execution to establish power limit criteria for a nuclear reactor based on operational thermal-mechanical limits of fuel rods in the nuclear reactor core, comprising: means for constructing individual fuel rod power histories for each nuclear fuel rod in the reactor core based on empirical information acquired during previous fuel cycles and the projected operation of the reactor in an upcoming fuel cycle; and  means for computing internal pressure data for each fuel rod in the core for an upcoming fuel cycle based on individual fuel rod power histories and for identifying a fuel rod having a maximum internal pressure. 10. The computer program product of  claim 9  further including means for computing thermal-mechanical limit data for each fuel rod in the core and for establishing an operational thermal-mechanical limit based on thermal-mechanical limit data associated with the identified fuel rod. claim 9 11. A method for demonstrating compliance of a nuclear reactor with fundamental licensing criteria for nuclear fuel rod internal pressure during nuclear reactor operation, comprising the steps of: a) constructing individual fuel rod power histories for each nuclear fuel rod in the reactor core based on empirical information acquired during previous fuel cycles and the projected operation of the reactor in an upcoming fuel cycle;  b) computing internal pressure data for each fuel rod in the core for an upcoming fuel cycle based on the power histories constructed in step (a);  c) identifying a fuel rod having a maximum internal pressure; and  d) confirming that the identified maximum is less than an established licensing limit criteria,  wherein the established power limit criteria is based on thermal-mechanical limit data associated with the identified fuel rod.