ML20062C654

Forwards Summary Rept of Evaluation of Recirculation Nozzle to Safe End Weld Indication & Proposed Disposition to Permit Unit 1 Cycle 4 Operation. Rept Withheld (Ref 10CFR2.790)

ML20062C654
Person / Time
Site:	Limerick
Issue date:	10/23/1990
From:	Hunger G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML19310C797	List: ML20062C654 ML20062C656
References
NUDOCS 9011020035
Download: ML20062C654 (3)

Text

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( .. PldlLADELPHIA ELECTRIC COMPANY NUCLEAR GROUP HE.ADQUARTERS 955 65 CHESTERBROOK BLVD.

WAYNE, PA 19087 5691  :!

(n:) no. ooo October 23, 1990 Docket No. 50-352~

s License No. WPF-39 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555

SUBJECT:

Limerick Generating Station, Unit 1 Summary Report of the Evaluation of the Indication in the Recirculation Riser Nozzle to Safe End Weld and Proposed Disposition to Permit Cycle 4 Operation Gentlemen:

4 Our letter dated April 3, 1989 provided an evaluation of an indication discovered in one of the recirculation riser nozzle to safe.end welds (i.e. -the N2H nozzle) as a result of inspections performed during the Limerick Generating Station (LGS), Unit I second refueling outage which began on January 13, 1989..

As stated in our April 3, 1989 letter, the_ indication appeared to exhibit the characteristics of intergrannular stress corrosion cracking (IGSCC). The April- j g 3, 1989 letter also transmitted our proposal and justification to operate Unit 1 for cycle 3 with the N2il nozzle to safe end weld in the "as found" condition-based on the use of an on-line crack growth monitoring system and the- . ,

establishment of specific action steps if the monitoring specimen crack growth was greater than or equal to certain conservatively set values. NRC letter dated May 2, 1989, forwarded the Safety Evaluation (SE) approving cycle 3 operation of Unit I with the N2H nozzle to safe end weld-left in the "as found" condition. By letter dated August 10, 1990; we submitted our plans for the j disposition of the N2H nozzle to safe end weld indication,'and explained that one.of the four identified alternatives would be selected based on the results of the inspection of the N2H nozzle to safe end weld performed during the third Unit I refueling outage.

l The monitoring specimen crack growth did not reach any of the action step values during Unit 1 cycle 3 operation. The third Unit I refueling outage '

began on September 8,1990, and ultrasonic- (UT) inspections of the: N2H nozzle to - o safe end weld were completed by September 21,1990. : The results showed a small '

change to the existing indication and an extention of.the circumferential length of the existing indication by 1.6 inches,'with a maximus' depth of 0.47 inches.

9011020035 901023 PDR ADOCK 05000352 H 'I P PDC Ek fg-9, q

Document Control Desk October 23, 1990

. , . Page 2 Philadelphia Electric Company (PECo), along with our consultant, the General Electric (GE) Company, have evaluated the recent N2H nozzle to safe end weld UT inspection results and have assessed the effect of the maximum (i.e.,

most conservative) growth rate for this indication on the integrity of the N2H nozzle to safe end weld. We have concluded that operation of Unit 1 for the -

l next (i.e., fourth) cycle is acceptable without taking corrective actions at 0 this time. We will consult to continued monitoring and the establishment of action step specimen growth values as described below, o Continue monitoring the indication using the on-line crack growth monitoring system utilized during cycle 3 operation, o if the monitoring specimen crack growth is greater than or equal to 0.1 inches afLer nine months of plant operation, an examination of the N2H nozzle to safe end weld will be performed if the plant is shut down for a forced outage that is planned to last for greater than two weeks.

o if the monitoring specimen crack growth is greater than or equal to 0.15 inches after nine months of plant operation, the plant will be shut down and an examination of the N2H nozzle to safe end will be performed.

Note that the action step values for the monitoring specimen crack growth have been reduced by a factor of two from those established for cycle 3 operation to provide an additional margin with respect to structural integrity.

A corrective action plan for the N2H nozzle to safe end weld will be finalized prior to the end of the first nine months of Unit I cycle 4 operation and submitted to the NRC. This corrective action will be implemented during cycle 4 operation if warranted as a result of the monitoring specimen reaching action step crack growth values and weld inspection findings. Otherwise, a corrective action plan to be implemented during the Unit 1 fourth refueling outage outage. will be finalized and submitted to the NRC prior to the fourth refueling In either case, we will request NRC approval of the corrective action method if it is other than safe end replacement.

A summary report of our evaluation of the recent N2H nozzle to safe end weld indication, and the justification for proceeding with cycle 4 operation of Unit I with the indication in the "as found" condition, is attached for your review and approval. Our current outage schedule shows that Unit I will be ready for startup by November 12, 1990. We therefore request your timely attention to this matter.

The information in the attached report was presented to the NRC during a meeting held on October 5,1990 at the NRC White Flint office. Some of the information contained in the attached report is proprietary to GE. Accordingly, GE requests that the attachment be withheld from public disclosure in accordance with 10 CFR 2.790(a)(4). An affidavit supporting this request in accordance with 10 CFR 2.790(b)(1) is enclosed.

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Document Control Desk October 23.'1990= i Page.3 i If you have any questions, or require additional information, please contact us.

Very truly yours,

'fs G. A. Hunger, Jr.

-Manager Licensing Section .

1 Nuclear Engineering and-Services Enclosure Attachment cc: T. T. Martin, Administrator, Region I. USNRC w/ attachment.

T. J. Kenny, USNRC Senior Resident Inspector LGS w/ attachment 1

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