ML20207T663
| ML20207T663 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 03/06/1987 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| 87-108, NUDOCS 8703240224 | |
| Download: ML20207T663 (3) | |
Text
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O VINGINIA ELEC rHIC AND l'OWEH COMPANY Ricuxoxo,Vinorsu 23261 b*. \\ $
March 6, 1987
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Vaca Passinawr Noca.saa orumAttone Dr. J. Nelson Grace Serial No.87-108 Regional Administrator NO:vlh U. S. Nuclear Regulatory Commission Docket No.
50-281 101 Marietta Street, N. W.
License No. DPR-37 Suite 2900 Atlanta, Georgia 30323
Dear Dr. Grace:
VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNIT 2 FEEDWATER PIPING REPAIR In our January 14, 1987 letter (Serial No.87-009) which transmitted the Surry Unit 2 Reactor Trip and Feedwater Pipe Failure Report, Virginia Electric and Power Company indicated that the feedwater and condensate piping that did not meet our acceptance criterion would be replaced prior to restarting Unit 2.
The acceptance criterion assures that the pipe wall thickness will remain above code wall thickness over the next eighteen months.
Recent inspections of the steam generator feedwater lines (WFPD-109, 113, and 117) inside containment have indicated areas of wall thinning. Using the above acceptance criterion, line WFPD-109 (C steam generator) is acceptable. However, areas in line WFPD-117 and 113 (A and B steam generators respectively) do not meet the acceptance criterion and require corrective action. Rather than replacing the affected portions of the A and B steam generator feedwater lines repairs will be made in accordance with ASME,Section XI, Article IWA 4000 and performed in accordance with the Design Specification and Construction Code.
Background
information, repair technique, expected erosion / corrosion rates and inspect. ion plans are provided below.
The wall thinning was observed in the feedwater line at the spool piece between the loop seal and reducer just upstream of the steam generator. The measurements and affected areas are included in the Attachments. These spool pieces were installed during the Unit 2 Steam Generator Replacement Program in the fall of 1979. The "B" feedwater line spool piece was rat concentric as originally received.
During installation, the spool piece required weld buildup to return the piece to acceptable wall thickness. After veld buildup of the B feedwater line spool piece, the weld and spool piece were machined to accommodate radiography.
For each affected area the repair will consist of weld buildup to a wall thickness of approximately.740 to 1.10 inches.
In no case will the actual weld buildup exceed 0.75 inch. Base line NDE data will be established for the weld repaired wall. This repair technique will preserve this data point for further erosion / corrosion evaluation and provide actual data for design and pipe replacement.
The weld buildup areas will be blended with the existing material to remove discontinuties. Both lines WFPD-117 and WFPD-113 will have the entire spool piece built up.
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3703240224 870306ADOCK 05000201
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4 Erosion / corrosion rates for the 3 spool pieces were calculated based on 5 years of operation. The erosion / corrosion rate for the B feedwater line spool piece was.069 inch / year whereas A and C feedwater lines were.054 and.047 inch / year respectively. The erosion / corrosion rate for the B feedwater line I
spool piece was calculated using an assumed wall thickness of.835 inch based on originally installed pipe measurements. Based on this erosion / corrosion rate, the decision was made to build up the entire spool piece.
Approximately 6 months af ter startup, the Unit will be shutdown for feedwater piping inspection and re-evaluation of erosion / corrosion rates.
If you have any questions, please contact me.
Very truly yours.
OL SM W. L. Stewart Attachments cc:
U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C.
20555 Mr. W. E. Holland NRC Senior Resident Inspector Surry Power Station Mr. Chandu P. Patel NRC Surry Project Manager PWR Project Directorate No. 2 Division of PWR Licensing No. 2
~ ' ' '
Proj ected Minimum Erosion /
Measured Corrosion Area of Code Feedline Wall Rate Min. Reading Min. Wall "A" S/G
.550"
.054"/yr 6" x 7"
.499" WFPD 117 "B" S/G
.490"
.069"/yr (1) 1" x 1" (2)
.499" WFPD 113 "C" S/G
.590"
.047"/yr 13" x 4"
.499" WFPD 109 (1) This rate was determined using an assumed wall thickness of 0.835 inch based on an originally installed pipe eccentricity.
(2) Four additional measurements indicate very localized erosion / corrosion and are below code minimum wall thickness requirements.
Other measurements on the spool piece indicate wall thinning but are above the minimum code wall thickness requirement.
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