Ultrasonic Phased Array Evaluation of Control Rod Drive Mechanism (CRDM) Nozzle Interference Fit and Weld Region

Conference · Sun Jul 31 04:00:00 EDT 2011

OSTI ID:1038393

Cinson, Anthony D; Crawford, Susan L; MacFarlan, Paul J; Mathews, Royce; Hanson, Brady D; Diaz, Aaron A

Ultrasonic phased array data were collected on a removed-from-service CRDM nozzle specimen to assess a previously reported leak path. First a mock-up CRDM specimen was evaluated that contained two 0.076-mm (3.0-mil) interference fit regions formed from an actual Inconel CRDM tube and two 152.4-mm (6.0-in.) thick carbon steel blocks. One interference fit region has a series of precision crafted electric discharge machining (EDM) notches at various lengths, widths, depths, and spatial separations for establishing probe sensitivity, resolution and calibration. The other interference fit has zones of boric acid (crystal form) spaced periodically between the tube and block to represent an actively leaking CRDM nozzle assembly in the field. Ultrasonic phased-array evaluations were conducted using an immersion 8-element annular 5.0-MHz probe from the tube inner diameter (ID). A variety of focal laws were employed to evaluate the interference fit regions and J grove weld, where applicable. Responses from the mock-up specimen were evaluated to determine detection limits and characterization ability as well as contrast the ultrasonic response differences with the presence of boric acid in the fit region. Nozzle 63, from the North Anna Unit-2 nuclear power plant, was evaluated to assess leakage path(s) and was destructively dismantled to allow a visual verification of the leak path(s).

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1038393
• Report Number(s): PNNL-SA-78593; 401001060
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
36 MATERIALS SCIENCE
ACCURACY
BORIC ACID
CALIBRATION
CARBON STEELS
CONTROL ROD DRIVES
ELECTRIC DISCHARGES
EVALUATION
MACHINING
NOZZLES
NUCLEAR POWER PLANTS
PRESSURE VESSELS
PROBES
RESOLUTION
SENSITIVITY
ULTRASONIC WAVES
VERIFICATION
control drive rod mechanism
leak path assessment
phased array
ultrasonic