Eddy’s talent for inspection23 December 1999
Westinghouse has developed new eddy current tube inspection processes to meet modern demands for speed and accuracy. The ST98 Steam Generator Inspection and Repair Management System is now the state of the art.
In the drive towards shorter outages, accurate and rapid steam generator tube inspection and repair has become increaingly important. And data management is now a critical issue. This has happened as advances in eddy current inspection tooling, robotics and processes, have reduced the time required to carry out an inspection from weeks to days. The time limiting factor now is not data accumulation but analysis and interpretation. As inspection techniques have become more sophisticated, regulators have introduced new repair criteria which demand higher standards at plants and plant owners are demanding more from inspection and data management systems. Real time access to data and progress reports every 12 hours are now demanded by utilities.
In a typical plant it is necessary to examine thousands of tubes using eddy current inspection within five to ten days. Based on this initial inspection, plant operators may have to expand the scope of the inspection programme, compare data with previous inspection results, perform supplementary eddy current or ultrasonic inspections and carry out in-situ pressure tests. It may also be necessary to remove tubes for metallurgical analysis or to take repair measures such as tube plugging or sleeving.
These decisions have to be made in near real time. It is essential that outage management personnel responsible for implementation of the additional inspection or repair activities and engineering staff responsible for generating the plant condition monitoring and operational assessments have access to timely and accurate reports concerning the inspection progress and results.
To meet these demands Westinghouse Nuclear Services Business Unit (NSBU), Steam Generators, Non-destructive Evaluation (SG NDE) Applications group has developed the ST98 Steam Generator Inspection and Repair Management System.
“We’ve spent two years developing the system and we are happy that it is state of the art,” said system designer and project engineer Ron Shaffer. “We have planned a continual improvement process to keep it that way.”
ST98 functions include:
• Preparing steam generator tube eddy current inspection programmes.
• Tracking progress of inspection programmes.
• Ensuring that all appropriate historical indications are addressed.
• Preparing daily status reports.
• Preparing retest lists.
• Performing quality checks on each analysis report.
• Preparing expansion programmes.
• Preparing alternate repair criteria inspection programmes based on bobbin inspection results.
• Preparing tube repair lists.
• Generating analysis feedback reports and files.
• Determining sleeving candidates and managing the sleeve installation process.
• Managing the alternate repair criteria (ARC) growth rate analysis process to assure accurate results.
• Transmitting data daily to Westinghouse NSBU.
• Transferring data daily to customers’ databases.
• Preparing final reports.
• Preparing Electric Power Research Institute (EPRI) database compatible transfer files.
A team game
Three teams are required to carry out a steam generator tube inspection. The collection team operates the robots and other equipment that drive the probes through the tubes. The analysis group interprets raw data, determines the condition of the tubing and produces condition reports. The third group is the data management team.
Once an analysis report is finished, the ST98 system accesses it through a computer network and performs quality checks. If the report passes these checks it is loaded into the ST98 system. ST98 determines whether the tests have been completed to a satisfactory standard and orders any retests it considers necessary. The retest list is sent back to the collection team. It is the data management team’s responsibility to ensure that an inspection is completed to plant and regulatory standards. The data management team also has to produce a report for the customer on a once or twice daily basis and run analysis performance software which provides feedback for the analysts as to how closely their production results match the official results. At the end of the job accurate repair lists are produced as well as final reports and data transfers to the customer.
ST98 is Westinghouse’s third generation microcomputer steam generator data management system. A computerised system was first used in 1982. In developing ST98 the NSD steam generator non destructive evaluation applications group, headed by Ron Shaffer and programmer Darren Siegel, established a number of goals, including:
• Creating a new system with specific features and functions for Westinghouse NSBU to use in implementing its steam generator inspection and repair contracts. The system is not designed to be sold but may be used by Westinghouse customers.
• Create a state of the art, high performance system based on hardware and software components that will not become obsolete.
• Create a multi-user system to allow multiple personnel to work on the same steam generator database simultaneously.
• Automate the maximum number of functions possible without sacrificing quality, thus reducing the work that operators must perform.
• Create a multi-tasking system so that separate agent programs can operate simultaneously, performing tasks that humans used to do.
• Create a system that will interface with ANSER, Eddynet and Eddyvision analysis software systems, as well as the ROSA robot.
• Attain 100% reliability for TCP/IP network protocol transactions.
• Provide a guest operator mode for safe customer access to the databases during the job.
“Compared with the old system it is far more efficient,” said Shaffer. “Certain programs fire themselves off automatically – previously each one had to be done manually. Using multi-tasking software we made the system do as much as it can automatically. It also has better networking facilities and a better interface with very good ergonomics. The main screen shows everything you need to see at a glance.
“All this means operators can spend less time on mundane tasks and can therefore work in a less stressful manner. Our contribution to an outage is most apparent at the end when final checks are taking place. This system can save as much as 12 hours compared to its predecessor.”
Results from the field
The ST98 system was first used at outages at six plants last spring and was used at eight plants with outages this autumn. According to Shaffer, the system has performed successfully at every site.
Probably the most challenging outage so far was at Sequoyah in Tennessee last spring.
“The schedule was so aggressive we inspected all four generators in five days, a plant record,” said Shaffer. “We were all working hard to keep up. Without the new system we wouldn’t have been able to do it in that time.”
The ability of operators to input more than one analysis report into the same steam generator database simultaneously is a good example of how the system helped to reduce the time required to complete the job. The previous data management system would not have kept up.
The ST98 system boasts a range of high level software and design features. The main database contains many fields, including rotating probe crack (RPC) fields. RPCs can take readings throughout a 360? rotation and offer more comprehensive detection and characterisation of certain types of tube degradation than non-rotating probes. The dedicated crack fields mean that two or more analysis report records are combined into one ST98 record, which enhances query and sorting capability.
The database also contains unlimited historical records. It loads reports for analysis types such as primary, secondary, resolution and auto dent. A timer based agent process monitors the status of the analysis ‘cal’ board and updates the DataCenter display with the current status of all analysis parties. The cal board is a multi-user application for the analysts and collection operators to indicate which data calibration sets are in progress and which are final. The DataCenter is the main production program for network interface to the analysis workstations.
A timer based agent process periodically runs queries and distributes the output files to Westinghouse engineering. It also distributes copies of the current inspection results to all the ANSER analysis workstations as a reference for the analysis. Another timer based agent process monitors the raw data servers to track each eddy current test performed by the collection team within minutes of the actual collection. This information is then loaded into a database and the DataCenter is updated. Also, on screen graphical displays of the steam generator are redisplayed with each run. These displays show exactly where the collection team is working in each leg of each steam generator.
Analysis performance feedback software provides feedback files to the ANSER workstations so that the production analysts can check their production results in the database. This is because the resolution process which generates the final report versions, often changes the original production results.
The steam generator Tubesheet Graphic program is written with a multiple document interface (MDI) that allows many tubesheet map files to be open simultaneously for cross-map work. It has numerous powerful manipulation features which enable the easy creation of complex maps.
The Query / Reporting program runs a subset of standard SQL database computer language. The report parameters can be stored in a query file. These files can be used by other programs within the system, integrating the operator skills with the main query program and minimising user interfaces on many other programs. The programme also has flexible ties to the steam generator tubesheet graphic programme.
The QueryQueue feature allows a user to build a file of queries and then run all the queries by running the QueryQueue name. This makes daily status reporting much quicker and more consistent.
The Inspection Planning program accepts maps or queries for plan generation. The query base plans can automatically be checked later in the inspection to see if more tests can be added to the plan. The QA Queries in the DataCenter allow operators to build queries using quality checking logic based on site specific guidelines and repair criteria. These queries are automatically run on every analysis report prior to entry into the main database.
The History Matching program allows the operator to set up a history subset of prior indications that must be addressed during this inspection. The history check is run on every analysis report prior to entry into the main database. It is also run on the entire database as a final check prior to loading the final reports into the database.
The Resolution Check tool allows the operator to check the final report for errors introduced in the resolution process. This program provides a colour keyed display to assist the operator in identifying mistakes in the resolution report. This check is made prior to loading the final reports into the database.
The Smartest program makes possible automation of the tube based selection processes such as sleeving. This program is loaded with various qualification and disqualification queries. Output from the Smartlist run provides a report of the tubes with no disqualifications and the tubes with disqualifications. The program is much more efficient and error free than manual methods of developing complex tube repair candidate lists.
The List Manager program allows the operator to load unlimited information about tubes. This can include tubesheet expansion processes, sleeves, repair tooling zones and tube pull candidates. Any output report from the main Query program can then be instantly checked for matches to the List Manager database, reminding the operator of conditions that may be important to the particular query results.
The ARC Toolkit efficiently controls the growth rate analysis and current and historical data to support ARC programmes.
The Nuclear Regulatory Commission is approving ARC programmes which allow certain tube degradation to be left in-service in the steam generators. In the past these tubes would have had to be removed from service. Certain plants in Europe have had similar policies for some time. This is partly a reflection of the improvements in inspection techniques which means far smaller cracks can be pinpointed than in the past. ARC programmes are the implementation designed to account for this changing policy.
ST98 is designed to manage large amounts of steam generator tube inspection and repair information quickly and accurately. It meets the twin needs of increasing the quantity and quality of information available while cutting the time needed to carry out the job. The system supports inspection and repair activities which take place during plant outages, it monitors the conditions of the tubes and develops plant specific condition monitoring and operational assessments. These functions are critical to the quality and efficiency of steam generator inspection and repair.