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Information Notice No. 81-04: Cracking in Main Steam Lines
SSINS No.: 6835 Accession No.: 8011040265 IN 81-04 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 February 27,1981 Information Notice No. 81-04: CRACKING IN MAIN STEAM LINES Description of Circumstances: The Virginia Electric Power Company promptly notified the NRC on February 23, 1981 that a radiography examination, during the ongoing steam generator replacement outage at Surry Unit 1, had revealed a lengthy crack indication in the I.D. counterbore area of a weldment on the in-line "T" fitting which connects the vertical run of 30-inch piping to the safety relief valve header and 30-inch main steam line of Steam Generator "A". This piping connection is located outside the containment penetration immediately upstream of the main steam isolation valve as shown in the attached sketch. A visual and dye penetrant examination on the pipe I.D. surface of the weldment nearest the containment penetration established that the cracking extended about 120F around the fitting counterbore between the 4 o'clock to 8 o'clock position. Cracking was also observed in the weld counterbore at the opposite end of the T-fitting during visual examination of the piping interior. Radiographic examination of "B" and "C" main steam line T-fitting welds disclosed crack indications at similar locations. Metallurgical specimens of the cracking were trepanned from the T-fitting of the "A" main steam line for analysis. Controlled excavation and depth measurements of the crack at its mid-length indicated a crack depth of about 0.090" in this location. The cause of cracking has not yet been established. VEPCO has planned an ultrasonic examination of similar weldments in Surry Unit 2 main steam lines utilizing "Hot Piping" ultrasonic techniques. Preparations are also being made to ultrasonic examine similar weldments at North Anna Unit 1, currently in cold shutdown for refueling. Recommendation to Licensees: This information is provided as an early notification of a significant safety matter that is still under review by the NRC staff. It is expected that recipients will review the information for possible applicability to their plants. For those plants having similar main steam line configurations which are currently in a refueling or extended repair outage, it is recommended that a ultrasonic and/or radiographic examination of the three welds and counterbore areas of the T-fittings be performed before resumption of operations, unless some current basis for assurance of piping integrity is available. . IN 81-04 February 27, 1981 Page 2 of 2 No response to this notice is requested at this time. If you have any questions regarding this matter, please contact the Director of the appropriate NRC Regional Office. Attachments: 1. Sketch 2. Recently issued IE Information Notices
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