Information Notice No. 81-04: Cracking in Main Steam Lines
SSINS No.: 6835
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
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
February 27, 1981
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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.
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