Patent Number: 
Section: claims

1. A method of employing at least one robotically controlled eddy current sensor and at least one digital computing device to non-destructively assess a current condition of a number of tubes of a steam generator of a nuclear power plant, the method comprising:collecting at a first time with a digital computing device and using an eddy current sensor received in and robotically advanced through each of at least some of the number of tubes a historic data set at a tube sheet transition for each of at least some of the number of tubes;collecting at a second time with a digital computing device and using an eddy current sensor received in each of at least some of the number of tubes and robotically advanced therethrough a current data set at the tube sheet transition for each of at least some of the number of tubes; andemploying a digital computing device and at least a portion of the historic data set together with a corresponding at least portion of the current data set to suppress from the current data set aspects of the tube sheet transition that were present in the historic data set and to generate another data set representative of a change in condition of a tube of the number of tubes between the first time and the second time. 2. The method of claim 1 wherein the employing further comprises subtracting one of the at least portion of the historic data set and the corresponding at least portion of the current data set from the other of the at least portion of the historic data set and the corresponding at least portion of the current data set to form the another data set. 3. The method of claim 2, further comprising amplifying at least a portion of the another data set. 4. The method of claim 1, further comprising:determining a difference in operating parameters between a first eddy current sensor that was employed in collecting the historic data set and a second eddy current sensor that was employed in collecting the current data set;applying at least a portion of the difference in operating parameters to one of the historic data set and the current data set to scale the one of the historic data set and the current data set; andcomparing the scaled one of the historic data set and the current data set with the other of the historic data set and the current data set to generate the another data set. 5. The method of claim 1 wherein the collecting at the first time the historic data set comprises collecting the historic data set prior to the time the steam generator is placed in service. 6. The method of claim 1 wherein the collecting at the first time the historic data set comprises collecting the historic data set during an in-service inspection of the steam generator. 7. The method of claim 1, further comprising:collecting at an additional time an additional historic data set for each of at least some of the number of tubes, the additional time being between the first time and the second time; andcomparing the current data set with both the historic data set and the additional historic data set to generate the another data set. 8. The method of claim 1, further comprising:collecting as the historic data set a set of amplitude and phase values for each of a plurality of data points in a tube sheet transition region for each of at least some of the number of tubes; andcollecting as the current data set a set of amplitude and phase values for each of a plurality of data points in a tube sheet transition region for each of at least some of the number of tubes. 9. The method of claim 1, further comprising:determining a difference in operating parameters between a first set of instrumentation that was employed in collecting the historic data set and a second set of instrumentation that was employed in collecting the current data set; andapplying at least a portion of the difference in operating parameters to one of the historic data set and the current data set to scale the one of the historic data set and the current data set. 10. The method of claim 1, further comprising reversing at least a portion of one of the historic data set and the current data set to enable comparison of the historic and current data sets due to collection of the historic and current data sets in opposite longitudinal directions along the tube. 11. A non-transitory machine readable storage medium having stored thereon instructions which, when executed on a processor of a digital computing device, cause the digital computing device to perform the operations of claim 1. 12. A method of characterizing an initial condition of a number of tubes of a steam generator of a nuclear power plant, the method comprising:collecting at a first time with an eddy current sensor received in and robotically advanced through each of at least some of the number of tubes a historic data set at a tube sheet transition for each of at least some of the number of tubes; andstoring with a digital computing device connected with the eddy current sensor the historic data set for future comparison with a current data set at the tube sheet transition for each of at least some of the number of tubes collected at a second time to suppress from the current data set aspects of the tube sheet transition that were present in the historic data set and to generate another data set representative of a change in condition of a tube of the number of tubes between the first time and the second time. 13. The method of claim 12 wherein the collecting at the first time the historic data set comprises collecting the historic data set prior to the time the steam generator is placed in service. 14. The method of claim 12, further comprising storing as part of the historic data set one or more operating parameters of the eddy current sensor that was employed in collecting the historic data set to enable scaling of one of the historic data set and the current data set.