ML20128D546
| ML20128D546 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 04/30/1985 |
| From: | Tucker H DUKE POWER CO. |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| 414-85-02, 414-85-2, NUDOCS 8505290111 | |
| Download: ML20128D546 (3) | |
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DUKE POWER GOMPANY P.O. HOX 33180 CHARLOTrE, N.C. 28242 HALB. TUCKER TELEPHONE (704) 37& 4338 viceenemmmwr
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April 30, 1985
-Dr. J. Nelson Grace, Regional Administrator U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 RE: Catawba Nuclear Station, Unit 2 Docket Nos. 50-414 Significant Deficiency No. 414/85-02
Dear Dr. Grace:
Please find attached the final report on this item concerning welds on the Unit 2 SIS Accumulator Tanks. This report updates the status of corrective action described in our initial report of February 22, 1985.
Very truly yours, Hal B. Tucker-LTP/mjf Attachment cc: Director Mr. Robert Guild, Esq.
Office of Inspection and Enforcement Attorney-at-Law U. S. Nuclear Regulatory Commission P. O. Box 12097 Washington, D. C. 20555 Charleston, South Carolina 29412 NRC Resident Inspector Mr. Jesse L. Riley Catawba Nuclear Station Carolina Environmental Study Group Palmetto Alliance 854 Henley Place 2135 Devine Street Charlotte, North Carolina 28207 Columbia, South Carolina 29205 INP0 Records Center Suite 1500 1100 circle 75 Parkway Atlanta, Georgia 30339 8505290211 850430 P f
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CATAWBA NUCLEAR STATION REPORT NUMBER:
SD 414/85-02 REPORT DATE:
4/30/85 FACILITY:
Catawba Nuclear Station Unit 2 IDENTIFICATION OF DEFICIENCY:
While performing a preservice inspection on the shell to upper-head weld on Safety injection Accumulator Tank 2D, Babcock & Wilcox discovered multiple rejectable indications. Due to this discovery and rejection by Babcock & Wilcox, Duke radiographed the tank weld in question which was made by Southwest Fabricating and Welding Company, a Westinghouse sub-vendor. The subsequent radiograph, divided into 34,12" intervals, yielded 31 intervals rejectable due to possible slag in the fill of this vendor weld. Examination of radiographs determined that slag may possibly be present in 4-5% of weld thickness in 33-34% of weld length. This was reported as Duke Nonconforming Item (NCI) 19227.
INITIAL REPORT:
. On January 25,1985, C. Burger, NRC Region II, Atlanta, GA was notified of this deficiency by L. M. Coggins, D. M. Collings and T. L. Utterback of Duke Power Company, P. O. Box 33189, Charlotte, N. C. 28242.
COMPONENT AND/OR SUPPLIER:
Safety Injection System Accumulator tank Supplier:
Westinghouse Electric Corporation Haymaker Road / Northern Pike Pittsburgh, PA 15230 Manufacturer:
Southwest Fabricating and Welding 7525 Sherman Street Houston, Texas 77261 DESCRIPTION OF DEFICIENCY:
The accumulators are part of the Safety Injection System (SIS), which provides emergency core and containment cooling in the event of a pipe break in either the primary Reactor Coolant or secondary Main Steam system. In the worst of these cases, rapid depressurization of the Reactor Coolant system occurs and the SIS provides rapid injection of the tank contents (borated water) when the reactor coolant pressure drops below the tank cover gas pressure.
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~'The weld containing the indications joins the shell to the hemispherical
- upper-head. Both the shell and head are made from SA-264 composite material consisting of SA-537 class 1 base steel with 5/32" SA-240 Type 304 cladding.
The minimum composite thickness of the head is 0.95 inches and the minimum composite thickness of the shell is 1.88 inches.
ANALYSIS OF SAFETY IMPLICATIONS:
A fracture evaluation was performed by the Westinghouse Materials Technology Group to determine the safety significance of these indications. This evaluation concluded that even in the worst case, where the indications are assumed to extend to the inside surface and to be continuous around the vessel, sufficient safety margin exists to preclude tank failure. In any case, there would be a leak before break condition.
CORRECTIVE ACTION AND STATUS:
-Additional ultrasonic inspection has confirmed that linear indications are present in portions of the upper head to shell weld on tank 2D. Southwest Fabricating
'is developing a procedure for removing these indications and repairing the weld.
This procedure will be reviewed by Duke and Westinghouse, and if found accept-able, repairs will begin around May 6,1985.
Furthermore, weld examinations on the other SIS Accumulator tanks at Catawba have been completed. Af ter evaluation by Duke, Southwest, and Westinghouse personnel, it was determined that no other weld repairs are required. The SIS Accumulator Tanks at Catawba are the only tanks in the Duke system built by Southwest Fabricating and welding.
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