ML20008F155
| ML20008F155 | |
| Person / Time | |
|---|---|
| Site: | 05000516, Washington Public Power Supply System |
| Issue date: | 01/30/1981 |
| From: | Mazur D WASHINGTON PUBLIC POWER SUPPLY SYSTEM |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, GO1-81-25, NUDOCS 8103120406 | |
| Download: ML20008F155 (3) | |
Text
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W shington Public Power Supply System A JOINT OPERATING AGENCY 55 P o. som 9ee sooo Geo. WasMimsrom Way RICMLaseo. WasMeNerom 9 93 52 PHONE (509) 3 75-5000 Nuclear Regulatory Commission January 30, 1981 Region V G01-81-25 Suite 202, Walnut Creek Plaza 1990 N. California Boulevard
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Walnut Creek, California 94596 x
$ sA M Attention:
Mr. R. H. Engelken, Director U
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6 Gentlemen:
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Subject:
WPPSS Tiuclear Projects Nos. ?
4 Docket Nos. 50-460 and 50-513
'l3 Potentially Reportable Deficiency 10CFR50.55(e)
DECAY HEAT REMOVAL HEAT EXCHANGERS
Reference:
- 1) Telecon TJ Houchins, WPPSS to DF Kirsch, Region V, Nuclear Regulatory Commission dated January 17, 1981 In reference 1) the Supply System informed your office of a potentially reportable deficiency under 10CFR50.55(e).
Attachment A to the letter provides the WPPSS interim report on the subject condition.
If you have any questions or desire further information please advise.
Very truly yours,
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d D. W. Ma r
Program Director, WNP- (
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cc: JR Lewis - Bonneville Power Administration 2 /gg7 A T CR Bryant - Bonneville Power Administration V. Mani - United Engineers & Constructors, Inc.
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o ATTACHMENT A WNP-1/4 DOCKET NOS:
50-460 & 50-513 REPORTABLE CONDITION 10 CFR 50.55(e) (P0TENTIAL)
DECAY HEAT REMOVAL HEAT EXCHANGER TUBING BACKGR0utlD The Supply System has had recent experiences which identified a problem that may be generic to certain types of seam welded heat exchanger tubing.
Examinations of the WNP-3 shutdown cooling water heat exchangers having SA-249 Grade TP 394 tubes has revealed inside diameter lack of fusion and other weld defects in the seam weld area. The Supply System is in the process of investigating the integrity of seam welded tubing used in the decay heat removal heat exchangers supplied for WNP-1 and 4 by Babcock & Wilcox Company. These heat exchangers were manufactured for Babcock & Wilcox by Ametek, Schutte and Koerting Division, Whitlock and Bethayres Plants.
Preliminary examination of selected tubes also show indications of linear imperfections along the seam weld area.
DESCRIPTION OF POTENTIAL DEFICIENCY Because of the findings associated with the WNP-3 heat exchangers, the Supply System has undertaken a program to categorize and evaluate the type of tubes used in the WNP-1/4 heat exchangers.
Particular import-ance is being placed on those heat exchangers that have been supplied with seam welded tubing. The decay heat removal heat exchangers were first chosen for visual inspection because of their safety classifica-tion and in-plant location. A visual examination was performed on the inside surface of a number of tubes in each of the four decay heat removal heat exchangers at WNP-1/4.
This examination was performed using an eight foot long boroscope and a video tape system for recording purposes. Linear type indications along the seam weld were identified during this visual examination.
The Supply System's experience with similar seam welded tubing indica-tions has shown that these indications include inside diameter lack of fusion in the seam weld amounting to 20%-40% of the wall and other defects ranging from 4%-12% in depth. The potential for tubes exhibiting a generic deficient condition is being investigated.
SAFETY IMPLICATIONS The HNP-1/4 design utilizes the decay heat removal heat exchangers to perform both normal and cmergency functions through separate and redun-dant flow paths and equipment. The heat exchangers remove sensible heat and decay heat generated during a normal shutdown to reduce the tempera-ture of the reactor coolant to permit refueling.
Each decay heat removal heat exchanger cools the injection water during the recirculation
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mode following a Loss-of-Coolant Accident to provide core cooling.
If failures to a heat exchanger force it out of service, the redundant string would be ava,ilable to continue cooldown, but at a slower rate.
However, the p6tential for a generic deficient tube condition is seen as requiring evaluation and possible repair to ensure the adequacy of the components to perform their intended safety function.
CORRECTIVE ACTION PLANNED An eddy current testing program will be completed on the decay heat removal heat exchanger tubing to supplement the visual data. WPPSS plans to have the supplier, Babcock & Wilcox, collaborate and investi-gate the potential deficiencies associated with the tubing and to pursue an acceptable resolution.
It is anticipated that final resolution and disposition can be completed in the second quarter of 1981 and results provided to the NRC at that time.