Six Benefits of Pass 2 Analysis
Undetected corrosion is a safety issue. Precision Wear Rate Analysis (WRA) helps keep operators informed and systems safe. GSE uses CHECWORKS™ Steam/Feedwater Application (SFA) with Pass 2 analysis data to correct the predicted wear rates. Let’s look at the six benefits of this approach.
Before we dive in, it’s helpful to understand how CHECWORKS SFA uses inspection data to correct the predicted wear rates. For all components and inspections not flagged as “Do Not Use Measured Wear” within a WRA run, a correction factor is calculated by dividing the predicted wear by the measured wear. Then, for each WRA run, a Line Correction Factor (LCF) is calculated using the median of all of the individual correction factors (if a run has an even number of included inspections, it uses the average of the two median values). The LCF is then applied to the wear rate of all components in that run to obtain the Pass 2 predicted wear rate.
A Pass 2 analysis determines the calibration status for each WRA run in the CHECWORKS SFA model. It involves using inspection data to modify the Pass 1 predictions to better correlate with actual plant wear conditions. It helps the user determine a degree of confidence in the model predictions. An approach using Pass 2 analysis offers six valuable benefits:
Boost your trust in your CHECWORKS SFA model predictions: Without an up-to-date Pass 2 Analysis, all WRA runs in the CHECWORKS SFA are considered non-calibrated. The Pass 2 analysis results do not reflect actual plant conditions. Relative FAC wear rates can be used, but the predicted remaining service life does not indicate the actual life. More inspections are required to understand wear trends in uncalibrated WRA runs.
Use it as a self-checking mechanism: Poor correlation between measured and predicted wear can result from a modeling error or a poor inspection analysis. Evaluating outliers and bounding inspections for each run can give you an idea of where problems exist in your program. These errors can sometimes be non-conservative, resulting in a potential for component failure.
Save money on inspections: Calibrated runs require fewer inspections. With the right tools, experience, and proper upkeep, the effort for a well-documented Pass 2 analysis can be as low as 3-5 days of program owner labor per cycle. This will pay for itself when an inspection is deemed unnecessary.
Also, understanding the factors contributing to a run’s calibration status can help the user understand when a run cannot be calibrated. If a large percentage of components have been inspected and carefully analyzed, but the run still does not show a good correlation between measured and predicted wear, that run may be experiencing conditions that are not accurately modeled or are outside CHECWORKS SFA’s modeling capabilities. In these cases, more inspections may not help obtain the run’s calibration status. It saves money to recognize these cases and avoid extraneous inspections.
Ease program turnover: New program owners tend to increase the size of the inspection scope until they become comfortable with the program. A well-documented Pass 2 analysis can show a new owner the wear trends in certain plant areas, relate levels of confidence in each area, and increase confidence in the program without needing extra inspections. It also sets higher expectations for program upkeep and long-term inspection scope reduction.
Meet procedure requirements: At most utilities, updating and reviewing the calibration status with new inspections after every refueling outage is required. At the least, the status of the predictive model should be considered in a Program Health Report.
Helpful for audits: Auditors will often ask about how many calibrated runs are contained in a model and why non-calibrated runs aren’t calibrated. If you have performed inspections on a run since the last Pass 2 effort, you are failing to meet NSAC-202L requirements for calibration. Having some non-calibrated runs is not inherently bad, but the inability to calibrate any runs can indicate apathy or neglect.
To learn more about using Pass 2 Analysis to correct the predicted wear rates, talk with the experts at GSE or visit https://gses.com/balance-of-plant-bop/
