EXAMINATION OF NOZZLE INNER RADIUS AND PIPING FROM THE OUTER SURFACE

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1 More Info at Open Access Database ABSTRACT NEW DEVELOPMENTS FOR AUTOMATED NOZZLE INNER RADIUS AND PIPING INSPECTIONS D. Eargle,WesDyne International, USA WesDyne has recently engaged in developing and deploying methods for automated Inner Radius Inspections for Boiling Water Reactor (BWR) vessel nozzles from the outside surface. The system is also capable of performing automated dissimilar metal weld and piping examinations using the same base platform as the automated inner radius scanner. This system was developed to replace the existing automated piping scanner which used a flexible spring steel track with magnetic drive wheels. The newly developed scanner utilizes a modular scanner mounting platform and a rigid round track and integral gear rack for an adaptable scanning platform and robust drive train. Many BWR plants require periodic inspections of the reactor vessel nozzle inner radius regions and dissimilar metal welds. The varying clearances and nozzle and piping geometries provide difficulties for automated inspections. WesDyne has developed a modular design that is adaptable to multiple configurations, geometries and a variety of nozzle sizes. This allows for one base design to be used for multiple applications and configurations. These inspections have been demonstrated in accordance with the requirements of the American Society of Mechanical Engineers (ASME) Code, Section XI, Appendix VIII and through the Performance Demonstration Initiative (PDI) program. The first automated inner radius inspection was completed on four feed-water nozzles at a BWR Type 4 reactor with a Mark I type containment. The simplified and modular design allows for improved performance, reduced site support, lower personnel dose and reduced inspection durations. Other projected uses for this system are steam generator dissimilar metal weld and nozzle inner radius examinations and feed water heater nozzle dissimilar metal weld examinations for Pressurized Water Reactors. EXAMINATION OF NOZZLE INNER RADIUS AND PIPING FROM THE OUTER SURFACE Inspection Background Many existing BWR plants require periodic UT inspections of the reactor vessel nozzle inner radius (IR) regions from the outside diameter (OD) of the vessel shell, the OD blend radius area and nozzle barrel surface searching for nozzle inner radius (IR) flaws oriented in the radial-axial plane. This UT process must be qualified to ASME Section XI, Appendix VIII [1] as modified by the EPRI/PDI performance demonstration program. The inspection areas are shown in Figure

2 Figure 1: ASME Section XI, Figure IWB , Nozzle Inner Radius and Nozzle to Shell Weld Examination Areas Previously, WesDyne performed manual conventional UT inspections of the nozzle IR regions from the OD. These inspections required personnel to remain at the nozzle in high dose areas for extended periods of time, and the data cannot be stored for later review. With the benefits of lower dose exposure and data storage, many customers in the BWR industry were interested in an automated OD inspection of the IR regions. WesDyne already provided automated OD inspections of the reactor vessel nozzle safe- end welds; however, the existing system was not capable of performing the additional inspection of the IR region. Approach Given the variety of nozzle sizes, plant dry well configurations and inspection environment obstructions, a modular and adaptable design approach was developed for automated inspection of the nozzle IR regions. Improvements over the existing safe-end weld inspection system were incorporated in the design and a common platform for IR and safeend examinations was pursued to improve inspection performance, reduce site support requirements, lower personnel dose, reduce inspection durations and maximize inspection coverage. The scanner is installed locally, but all equipment is designed for quick installation, reconfiguration and disassembly to require inspection personnel to remain in the inspection area as little as possible to reduce dose. The automated piping portion of the scanner was designed to carry conventional or phased array probes, as required for the given inspection. The automated inner radius scanner was designed to carry conventional probes with a quick disconnect end-effector for rapid changes between probe and wedge configurations. The 2- or 4-axis scanner design, piping and inner radius respectively, includes two elevated track sections that can be customized for each individual pipe and mounting location geometry. The track is assembled in two halves with an integral dovetail and key providing track alignment at assembly and positive interlocking of the track sections. The lower track section is pre-set prior to installation and the top track assembly holds the encoded circumferential motor assembly and scanner mount trolley. Once the track sections are locked together, the upper track section is adjusted to secure the track to the pipe. The scanner arm is then installed using the integral dovetail and fastened to the scanner trolley. Any scanner arm can be mounted in multiple configurations to the scanner trolley as required and configured for the given inspection(s) through the integral dovetail connection. 799

3 The piping scanner consists of a single axis scanner arm with encoder feedback for axial probe positioning. The inner radius scanner consists of three independent encoded axes allowing for single and coordinated axis motion to accommodated scanning of both simple and complex geometries. Each scanner incorporates constant force springs for probe delivery and constant and reliable probe contact over the entire scanning surface. The inner radius scanner end-effector incorporates a self locking, manually operated skew axis that is preset prior to mounting the end-effector. Figure 2 shows the inner radius scanner installed on a full size BWR N4 feed-water nozzle mock- up. Figure 2: Inner Radius Scanner Installed on Feed-water Nozzle Mock-up Remote operation and multiple on-board and overview cameras are used to allow the operators to calibrate the scanner position, set-up and execute scans and verify probe contact from a remote location; this process eliminates the need for a track handler in the high dose areas around the pipe at all times. In addition, dose reduction is achieved by the operator manipulating the scanner arm out of the nozzle window to allow inspection personnel to change end-effectors out of the high dose areas. The UT process consists of a conventional shear wave transducer mounted to a flat wedge for vessel and barrel scans and a contoured wedge for blend radius scans. Using the EPRI 3D Modeling Toolkit V1.0R1, the probe skew, beam angles, scan surfaces, required radial position and metal paths are determined. Data acquisition and analysis is performed using the WesDyne IntraSpect TM system. Figure 3 shows a WesDyne IntraSpect UT image of notch located along the nozzle bore ID surface; the scans were conducted from the OD surface of the nozzle barrel. Figure 3: Inner Radius Data Collected Using WesDyne IntraSpect TM System 800

4 System Qualification Internal scanner qualifications and UT process development were conducted on a full size feed-water nozzle mock-up representing a BWR N4 nozzle. Scanner positional and environmental calibration processes were developed, along with completion of scanner kinematic and positional accuracy testing. From the testing, the system global positional accuracy and repeatability was determined to be less than 4.6mm. UT scan parameters were also tested and optimized for data quality and achievement of maximum scan speeds. Additional procedure and personnel qualifications were completed at EPRI on various size test samples in accordance with the EPRI/PDI performance demonstration process and using nozzle modeling [2]. The samples consisted of BWR N1, N2, N3, N8 and N9 nozzles ranging in pipe mounting location sizes from 5.12 (130mm) to 30 (760mm). The data was collected on all samples at a maximum scan speed of 3 /sec (75mm/sec). The WesDyne procedure WDI-STD-1117 [3] was qualified for detection of flaws along with several WesDyne inspection personnel. Field Application The inspection system was applied in the field in September It was specifically applied in four BWR N4 feed-water nozzle inner radius region inspections. Figure 4 shows the scanner installed on one of the feed-water nozzles. Figure 4: Inner Radius Scanner Installed on Feed-water Nozzle at Site Bioshield wall obstructions prevented >90% automated coverage on three of the four feed-water nozzles. The additional >90% coverage was obtained using a qualified manual UT process. However, after identification of the scanning limitations, additional endeffectors were developed to improve the scanner performance. These additional endeffectors are shown in Figures 5 and 6. These new end-effectors allow for an inverted scanner arm orientation around the bioshield wall obstructions and provide improved transducer contact over the inspection surfaces. Figure 5: 90 Oriented EE for Improved Nozzle Barrel Scanning 801

5 Figure 6: 45 Oriented EE for Improved Nozzle Blend Radius Scanning In addition to BWR reactor vessel nozzles, other proposed inspections for the WesDyne Track mounted ROSA based EXamination (T-REX) system include PWR reactor vessel nozzles, new plant steam generator to reactor coolant pump welds, new plant reactor coolant pump to main coolant pump welds, cast SS piping, UT in lieu of RT applications, and feedwater heater nozzle and piping inspections. REFERENCES [1] American Society of Mechanical Engineers, Section XI: Rules for Inservice Inspection of Nuclear Power Plant Components, Appendix VIII: Performance Demonstration for Ultrasonic Examination Systems, 2004 Edition. [2] WesDyne Nozzle Examination Qualification, EPRI, Palo Alto, CA, IR [3] Automated Ultrasonic Procedure for Examination of Nozzle Inner Radius Corner Radius Areas in Accordance with ASME Section XI, Including Appendix VIII, WesDyne International, WDI-STD