ML20215E369
| ML20215E369 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 12/05/1986 |
| From: | Haynes J ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| To: | Kirsch D NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| ANPP-39248-JGH, DER-86-29, NUDOCS 8612220238 | |
| Download: ML20215E369 (4) | |
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fj?ED Arizona Nuclear Power Proj q k lQ P O. BOX 52034 e PHOENIX, ARIZONA 85072-20 A 9y9 December 5, D// \\/
ANPP-39248-JGH/DJW/DRL-92.11 U. S. Nuclear Regulatory Commission Region V 1450 Maria Lane - Suite 210 Walnut Creek, CA 94596-5368 Attention:
Mr. D. F. Kirsch, Director Division of Reactor Safety and Projects Palo Verde Nuclear Generating Station (PVNGS)
Unit 3 Docket No. 50/530
Subject:
Interim Report - DER 86-29 A 50.55(e) Potentially Reportabl-Deficiency Relating to Letdown Heat Exchanger Nozzle Crack File: 86-006-216; D.4.33.2
Reference:
Telephone Conversation between R. C. Sorenson and D. R. Larkin on November 14,1986 (Initial Notification - DER 86-29)
Dear Sir:
The NRC was notified of a potentially reportable deficiency in the referenced telephone conversation. At that time, it was estimated that a determination of reportability would be made within thirty (30) days. (December 14, 1986)
Due to the extensive investigation and evaluation required, an Interim Report is attcched. It is now expected that this information will be finalized by January 15, 1987 at which time a complete report will be submitted.
Very trul yours, sn.b w J. G. Haynes Vice President Nuclear Production JGH/DRL:kp Attachment ec: See Page Two t
861222O238 861205 PDR ADOCK 05000530 S
PDR Q'-Q I
'n DER 86 Interim Report Mr. D. F. Kirsch Director Page Two j.
December 5, 1936 ANPP-39248-JGH/DJW/DRL-92.11 cc:
J. M. Taylor Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission Washfogton, D. C.
20555 i
A. C. Gehr (4141)
R. P. Zimmerman (6295)
Records Center Institute of Nuclear Power Operations 1100 circle 75 Parkway - Suite 1500 Atlanta, Georgia 30339 P
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INTERIM REPORT - DER 86-29 POTENTIAL REPORTABLE DEFICIENCY ARIZONA NUCLEAR POWER ;ROJECT PVNGS UNIT 3 I.
Potential Problem During the heat-up phase of Hot Functional Testing in Unit 3, a crack was discovered in the letdown inlet nozzle (Nozzle "A" on vendor print N001-7.03-28-7) of the letdown heat exchanger (tag No. 3MCHNE02). The nozzle cracked at the weld joint connection with the shell of the vessel. The crack was 120' circumferential and through-wall, located on the top side of the nozzle. The crack was detectable by both visual and dye penetrant examination.
II.
Apprt_wh To and Status of Proposed Resolution During normal plant operation, a letdown pipe break or crack outside containment, such as the one under investigation, would result in the discharge of reaction coolant outside of containment into the auxiliary building.
However, per PVNGS FSAR/CESSAR Section 15.6.2, a double ended break of a letdown line outside containment "results in a two-hour thyroid inhalation dose which is a small fraction of 10CFR100 guidelines." It is expected that a break or crack of a letdown line at the Letdown Heat Exchanger nozzle would result in offsite doses bounded by those reported in FSAR/CESSAR Section 15.6.2.
The nozzle crack was repaired under Nonconformance Report NA-1942 and Hot Functional Testing was continued. The nozzle / weld /shell material was analyzed in situ by Bechtel M&QS.
An assessment of the potential consequences of this event is being performed. The following conditions are being reviewed to determine the cause of the crack.
Pipe Strain Minor Hydraulic Transients
" saible Shipping Damage Listed below is the current status of the ongoing review.
The inlet piping was cut loose from the nozzle and the free movement.
was measured at 1/8", 1/8", 1/4" in the horizontal, vertical, and axial directions, respectively. The nozzle could easily be moved by hand back into position.
Therefore, pipe strain is not considered to be a cause of failure.
Minor hydraulic transients associated with stroking the letdown control valves and back pressure valves were recorded during the course of HFT following the nozzle failure and repair. The impact of these transients 's being analyzed.
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There were no indications that the heat exchanger had been damaged after it was manufactured. Therefore, improper handling during construction or start-up is not considered to be a cause of failure.
The conclusions of the forthcoming M&QS report will help determine (1) the acceptability of the repaired nozzle, and (2), the root cause of the failure. At this time, fatigue is suspected as being the failure mode.
Operation of Units 1 and 2:
Based on the results of the investigation to date, visual examinations of letdown heat exchangers in Units 1 and 2, and the FSAR/CESSAR analysis of the consequences of postulated breaks in the letdown lines outside containment, continued use of the components addressed herein does not pose a hazard to the safe operation of Units 1 and 2.
III. Projected-Completion of Corrective Action and Submittal of the Final Report The complete evaluation and final report are forecast to be completed by January 15, 1987.
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