ML20094D249

Forwards Core Shroud Insp Plan for LGS Unit 1,in Response to GL-94-03, IGSCC of Core Shrouds in Bwrs

ML20094D249
Person / Time
Site:	Limerick
Issue date:	10/27/1995
From:	Hunger G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-94-03, GL-94-3, NUDOCS 9511030233
Download: ML20094D249 (5)

Text

Ctatisn Suppstt Drpartmsnt GL 94 03 s

l IECO ENERGY Zi, ==:"Le,,

965 Chesterbrook Boulevard l

j Wayne PA 19087-5691 October 27,1995 Docket No. 50-352 License No. NPF 39 i

l 1

U. S. Nuclear Regulatory Commission  !

I Attn: Document Control Desk Washington, DC 20555

Subject:

Limerick Generating Station, Unit 1 Submittal of Inspection Plan in Response to Generic Letter 94-03, "Intergranula.' Stress Corrosion Cracking of Core Shrouds in Boiling Water Reactors"

Dear Sir:

On August 24,1994, PECO Energy Company responded to Generic Letter (GL) 94-03, dated July 25,1994. Your letter dated March 7,1995 providec' a Safety Evaluation Report for Limerick Generating Station (LGS), Unit 1 concerning GL 94-03. Reporting Requirement 2 of the GL requested that an inspection plan of the core shroud be submitted to the U. S. Nuclear Regulatory Commission (USNRC) no later than 3 months prior to performing the inspections except for those plants whose inspections would occur less than three months from the receipt of the GL. Accordingly, attached is the core shroud inspection plan for Limerick Generating Station, Unit 1.  ;

if you have any questions, please contact us.

Very truly yours, fi .

G. A. Hunger, Jr.,

Director - Licensing Attachment cc: T. T. Martin, Administrator, Region I, USNRC N. S. Perry, USNRC Senior Resident Inspector, LGS G200:j 0 0 9511030233 951027 \

PDR ADOCK 05000352 P PDR

.- . . . ~ . . - . . - - , - . - . . - . . - . _ . . . - . - . . . - . - . _ . - - . -

a 4

COMMONWEALTH OF PENNSYLVANIA 4

. ss.

COUNTY OF CHESTER  :

' O. B. Fetters, being first duly sworn, deposes and says:

1 That he is Vice President of PECO Energy Company; that he has read the enclosed additional response to Generic Letter 94-03, dated July 25,1994, for Limerick Generating Staticn,

' \

Unit 1 Facility Operating License NPF-39, and knows the contents thereof; and that the I

statements and matters set forth therein are true and correct to the best of his knowledge, l information and belief.

A..u~>\o Vice President Subscribed and sworn to before me thisc2[ day of0M 1995.

Notary F ic Notan.x Seal Mary Lou Skrocki. Notar/ Pubr.c Tredyttrin Two , Chester Cour.ty My Comm:sson Enires May 17.1999 c , c

LIMERICK GENERATING STATION, UNIT 1 SECOND RESPONSE TO NRC GENERIC LETTER 94-03 CORE SHROUD INSPECTION PLAN i I

l i

BACKGROUND: j In accordance with Reporting Requirement Number 2 of NRC Generic Letter (GL) 94-03, dated July 25,1994, and in response to the NRC Safety Evaluation (Reference 2), the following inspection plan for Limerick Generating Station (LGS), Unit 1, is provided. This plan was 4

developed for implementation during the next refueling outage of LGS, Unit 1 (1R06), which is scheduled to begin on January 27,1996.

The inspection methods, scope, and flaw evaluation criteria of this inspection plan satisfy the recommendations of the Boiling Water Reactor Vessel and internals Project (BWRVIP), as specified in the "BWR Core Shroud Inspection And Flaw Evaluation Guidelines" - GENE-523-113-0894, Rev.1, dated March 1995 (Reference 3).

This inspection plan was developed in response to " Requested Licensee Actions," Number 3, of the GL, based on the ongoing guidance provided by the BWRVIP, recommendations of General Electric Nuclear Energy (GENE), and site specific experience gained through previous shroud inspections at PBAPS, Units 2 & 3. The key factors considered in the development of the plan i include: hot operating years, materials of fabrication, water chemistry history, and current j industry experience (i.e., f all outages). l The LGS, Unit 1 shroud is considered to be moderately susceptible to Intergranular Stress  ;

Corrosion Cracking (IGSCC) due primarily to age, materials of fabrication, and water chemistry l history.

Since the LGS, Unit 1 core shroud has experienced more than 8 hot operating years, and is fabricated with low carbon content stainless steel, it has been identified by Reference 3 as an inspection Category B facility. For Inspection Category 9, Reference 3 recommends a limited inspection of specific shroud welds. This limited inspection includes a sufficient length of the subject circumferential shroud welds to enable determination of the structuralintegrity of the weld, considering crack growth and NDE uncertainties. The inspection scope includes circumferential shroud welds H-3, H-4, H-5, and H-7.

SCOPE OF INSPECTION:

The LGS, Unit 1 shroud welds can be divided into four groups:

1. Shroud attachment welds (e.g., shroud head bolt lugs)

2. Shroud vertical welds

3. Shroud support structure welds

4. Shroud circumferential welds The attachment welds, vertical welds, and support structure welds have been excluded from this initial inspection plan. The basis for exclusion of these welds from the initial inspection plan is addressed in Section 3.1 and Appendix A of Reference 3.

Therefore, the scope of welds included in this initial shroud baseline inspection plan for LGS, Unit 1 include shroud circumferential welds H-3, H-4, H-5, and H-7.

1

LIMERICK GENERATING STATION, UNIT 1 SECOND RESPONSE TO NRC GENERIC LETTER 94 03 CORE SHROUD INSPECTION PLAN J

EXTENT OF INSPECTION:

l I The extent of inspection of each of these four welds is based on accessibility for state-of-the-art l 3

inspection equipment.

i The inspection technique planned for these initialinspections is Ultrasonic Testing (UT). This

, technique is intended to interrogate the volume of the subject welds and associated heat affected zones for cracking initiating on the inside surface (ID) and the outside surface (OD) of the shroud. The equipment planned for use during these inspections is the General Electric Nuclear Energy (GENE) OD Tracker. This equipment will maximize the ability to access the

, shroud welds. This NDE technology has already been successfully demonstrated for the j BWRVIP, and has been effectively utilized for several BWR core shrouds inspections in the last 18 months, including PBAPS, Units 2 & 3. The evaluation of inspection results will be suitable for the inspection technique and delivery system used.

The extent of inspection of each circumferential weld may vary, depending on the specific weld characteristics (i.e., accessibility relative to invessel components and unexpected interferences).

The initial extent of inspections planned, using the inspection system described above, is as follows:

Weld Number Extent Of Inspection Planned H-3, H-4, H-5, and H-7 100% examination of the accessible length in a 360* segment If the cumulative indication length found in any weld is greater than or equal to 10% of the inspected weld length, the scope of the inspections will be extended to include welds H-1, H-2, and H-6.

l EVALUATION:

The evaluation of the results of the inspections will include a combination of fracture mechanics methodologies. As recommended in Reference 3, for welds which have a projected neutron exposure (fluence) level greater than 3X102 N/CM 2through the next two operating cycles, the l analysis will include both the Limit Load and Linear Elastic Fracture Mechanics (LEFM) methodologies. For welds with an exposure level below this threshold, the Limit Load technique will be used exclusively. The planned application of fracture mechanics analysis is as follows:

WELD NUMBER METHODOLOGIES H-3 Limit Load and LEFM H-4 Limit Load and LEFM H5 Limit Load only H-7 Limit Load only 2