ML20235A347
| ML20235A347 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry, Sequoyah, 05000000 |
| Issue date: | 03/17/1983 |
| From: | Harwell E, Woods T TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML082420107 | List: |
| References | |
| NUDOCS 8709230282 | |
| Download: ML20235A347 (6) | |
Text
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M ETA LLU RGIC AL REPORT FAILURE EVALUATION SEQUOYAH NUCLEAR PLANT UNIT 1 MOISTURE SEPARATOR REHEATER DRAIN TANK 1 1/2-INCH LINE FAILURE-
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1.0 Introduction The subject piping was submitted to the NCO Meta 11urgy'and Codes Section for failure analysis. The failed pipe section is one of'six identical sections found on.the bypass configuration upstream of the No. 2 feedwater heaters on unit 1.
Similar piping configurations also exist upstream of the No. 1 heaters on units 1 and 2 and the No. 2 heater on unit 2.
Failure may result in forced outages to make necessary repairs and may also be a personnel hazard.
s 2.0 Discussion The failed pipe section was replaced with a pipe of similar material.
Examination of the 1 1/2-inch diameter schedule 40 carbon steel pipe identified the failure mode as steam erosion. Saturated steam conditions result from a 30 psis pressure drop across level control valve (LCV) 6-72A. The pressure drop causes the condensate from the'-
moisture separator drain tank to flash to a 2-phase mixture (saturated steam). This mixture is flowing at a high velocity causing erosion of the interior surface of the pipe.
Attached are photographs of the subject piping.
3 30 Conclusion i
The metallurgical examination identified the failure mode as steam erosion. It is recommended that the 1 1/2' inch piping in this location and other similar locations be replaced at the earliest available opportunity with type 304 stainless steel, We also recommend that ultrasonic test (UT) measurements be performed on the 4-inch diameter piping downstream of the level control valves, since wet steam conditions will exist in this a'rea also, to determine if similar wall degradation exists.
We will assist you, if necessary, with establishing a correct grid 1
size for this piping and also help evaluate the UT data generated.
TRW:FSB Attachments 3/8/83 B2067B.FB O
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FIGURE 1: Photograph showing position and orientation of failed pipe seccion.
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j FICURE 2: Photograph showing replaced section of piping.
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FIGURE 3: Photograph showing overview of moisture separacor reheater drain tank lines.
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Plfl W,_A_kk THINNING INSPECTION DATA PLANT:
IdM UNIT:
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~7M'4 MTL. CLASS./ REFERENCE THICKNESS:
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LOCATIONS INSPECTED:
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PURPOSE OF INSPECTION:
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FOR WALL THINNING 7 G Aepd' INSPECTION DETAILS:
METHOD:
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UT INSTRUMENTS:
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GRIDS:
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INSPECTION RESULTS:
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CORRECTIVE ACTIONS: AfEAv A 4 - C-ud ' -
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REPAIR / REPLACEMENT 7 MATERIALS CHANGES 7 FAILURE ANALYSIS?
DOCUMENTATION: Ale nn
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L29 841203 983 6
DEC 4 1984
.R.
r mer oya Nuclear Plant
Subject:
SEQUOYAH NUCLEAR PLANT UNIT 2 - INSPECTION OF CROSSAROUND PIPING, TARGET TEES, AND EXTRACTION STEAM PIPING FOR SALL DEGRADATION I
The subject report is attached. _ These inspections were performed by Terry R. Woods of the NCO Welding and Metallurgy Section at_the request of
. your Codes and Standards Section.
O J. H. Miller GJP:JHF:TRW:FSD Attachment oc (Attachment):
NUC PR ARMS, 1520 CST 2-C This was prepared principally by T. R. Woods.
B4331A.FD COORDINATION: OE/Boyd 9
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