ML20085K464

Forwards Core Shroud Insp Plan for Pbaps,Unit 3,per Reporting Requirement 2 of GL 94-03, IGSCC of Core Shrouds in Bwrs

ML20085K464
Person / Time
Site:	Peach Bottom
Issue date:	06/16/1995
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 9506230386
Download: ML20085K464 (5)

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Nuclear Group Headquarters 965 Chesterbrook Boulevard Wayne PA 19087 5691 June 16, It195 Docket No. 50-278 Ucense No. DPR-56 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555

Subject:

Peach Bottom Atomic Power Station, Unit 3 Submittal of Inspection Plan in Response to Generic Letter 94-03, 'intergranular 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. Reporting Reouirement 2 of the GL requested that an inspection plan of the core shroud be submitted to the U. S. Nuclear Regulatory Commission (USNRC) no latsr 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 inspection plan for PBAPS, Unit 3.

It should be noted that the attached inspection plan represents the first comprehensive inspection of the PBAPS. Unit 3 core shroud conducted in accordance with the Boiling Water Reactor Vessel and Intemals Project (BWRVIP) guidance. As discussed in our August 24,1994 response, an augmented core shroud inspection was performed at PBAPS, Unit 3 during the Fall of 1993 Refueling Outage 9. A final report documenting this inspection, and an evaluation of its results, was forwarded to the USNRC in a letter from G. A. Hunger, Jr. (PECO Energy Company) to USNRC dated March 14,1994. Additionally, these results were reviewed with the USNRC b a meeting on November 3,1993. These limited augmented shroud inspections consisted of enhanced visual examinations only, which were implemented as a response to GE Nuclear Energy Service Information Letter (SIL) 572.

If you have any questions, please contact us.

Very truly yours, w.c. m y G. A. Hunger, Jr.,

Director - Licensing Attachments cc: T. T. Martin, Administrator, Region I, USNRC W. L Schmidt, USNRC Senior Resident inspector, PBAPS onnn'c M 9506230386 950616 1 PDR ADOCK 05000278 i P PDR \D

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• COMMONWEALTH OF PENNSYLVANIA  :-

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1 COUNTY OF CHESTER .:

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, 'W. H. Smith, III, being first-duly sworn, deposes and says: j f

That he is Vice President of PECO Energy Company; that he  !

has read the enclosed additional response to Generic Letter j 03, for Peach Bottom Facility Operating License DPR-56, and.knows  !

the contents thereof; and that the statements'and matters set [

forth therein are.true and correct to the best.of his knowledge, informatiott and belief.

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VicePrpident F

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Subscribed and sworn to before me this /6N day of 1995. '

I No(3 ry Public NotarialSeal tou Skrockl, Notary Public '

n Twp., Ches'er County My ssion Expires May 17,1999 Meneer,Pennsytvania Assocaban of Notne

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, PEACH BOTTOM ATOMIC POWER STATION, UNIT 3 I SECOND RESPONSE TO NRC GENERIC LETTER 94 03 CORE SHROUD INSPECTION PLAN BACKGROUND:

In accordance with Reporting Requirement Number 2 of NRC Generic Letter (GL) 94-03, dated 7/25/94, the following inspection plan, for Peach Bottom Atomic Power Station (PBAPS), Unit 3, is provided. This plan has been developed for implementation during the next refueling outage l of PBAPS, Unit 3 (3R10), which is scheduled to begin on September 16,1995.

l The inspection methods, scope, and flaw evaluation criteria of this inspecticn plan satisfy the j recommendations of the Boiling Water Reactor Vessel and intemals Project (VIP), 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 hr been developed in response to " Requested Licensee Actions,"

Number 3, of the GL. It has been developed using the ongoing guidance provided by the VIP, l recommendations of General Electric Nuclear Energy (GENE) Co., and site specific experience r gained through previous shroud inspections at PBAPS, Unit 2. The key factors considered in t the development of the plan include: hot operating years materials of fabrication, and water .l chemistry history as def.cribed in Reference 3.  !

i' The PBAPS, Unit 3 shroud is considered to be highly susceptible to Intergranular Stress Corrosion Cracking (IGSCC); due primarily to mater!al, age, and water chemistry history. l Additionally, some shroud weld indications were visually identified during the last refueling . I outage of PBAPS, Unit 3 (3R09), in October 1993. These inspection results and their j evaluations were submitted to the NRC via Refererre 1, and were reviewed with the NRC in a '

meeting on November 3,1993. However, the PBAPS, Unit 3 shroud was fabricated using -

seamless, roll-forged rings, which have consistently shown an immunity to severe stress corrosion cracking in the weld heat affected zone (HAZ) in these applications (e.g. no plant which has inspected has found extensive cracking in forged rings). This mitigating factor has been acknowledged by the VIP, as documented in Section 2.1 of Reference 3.

Since the PBAPS, Unit 3 core shroud has experienced more than 6 hot operating years, and is ~

fabricated primarily with higher carbon content stainless steel. it has been identified bv Reference 3 as an inspection Category C facility. For inspection Category C, Refererm.:: 3 ,

recommends a comprehensive inspection of shroud weids. This comprehensive inspection {

includes inspection of all circumferential shroud welds (i.e. H-1 through H-7).  ;

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PEACH BOTTOM ATOMIC POWER STATION, UNIT 3 )

SECOND RESPONSE TO NRC GENERIC LETTER 94-03 1 CORE SHROUD INSPECTION PLAN SCOPE OF INSPECTION: ,

The PBAPS, Unit 3 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 inillal 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 PBAPS, Unit 3 include shroud circumferential welds H 1 thra'igh H-7.

EXTENT OF INSPECTION:

The e:ctent of inspection of each of these seven welds is based on accessibility for state-of-the-ar+ inspection equipment.

The inspection ic hree planned for these initial inspections is Ultrasonic Testing. This technique is latendeo b interrogate the volume of thf subject welds and associated heat affected zones for cracking initiating on the inside surface and the outside surface (OD). The equipment planned for use during these inspections includes the GE OD Tracker. This equipment will maximize the ability to access the shroud welds. This NDE technology has already been successfully demonstrated at several BWR core shrouds inspections in the last 18 months, including PBAPS, Unit 2. The evaluation of inspection results will be suitable for the inspection technique and delivery system used. j i

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

The initial extent of inspections planned, using the inspection system described above, is as follows: l Weld Number Extent Of Inspection Planned l

H-1 through H-7 Accessible length in a 360* segment ,

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PEACH BOTTOM ATOMIC POWER STATION, UNIT 3 SECOND RESPONSE TO NRC GENERIC LETTER 94-03 CORE SHROUD INSPECTION PLAN EVALUATION:

The evaluation of the results of the inspections willinclude a combination of fracture mechanics methodologies. As recommended in Reference 3, for welds which have a projected neutron exposure (fluence) level greater than 3X10'* N/CM2 through the next two operating cycles, the 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: i WELD NUMBER METHODOLOGIES H-1 Limit Load only H-2 Limit Load only H-3 Limit Load and LEFM H-4 Limit Load and LEFM H-5 Limit Load only ,

H-6 Limit Load only H-7 Limit Load only The initial evaluations will consider all identified Indications to be through-wall cracks. A minimum of two cycles of crack growth and an NDE uncertainty factor will be included in the evaluation. Detailed evaluations, including flaw depth sizing, in accordance with Reference 3, <

may be conducted, based on inspection results. +

REPAIR:

l If the results of the shroud inspections do not satisfactorily demonstrate structuralintegrity of the shroud, a contingency repair option has be7n planned. This option includes a complete shroud repair (Modification P-00435), consisting of tie rods and horizontal stabilizers. The complete repair is being designed by GENE to fully replace the function of the H-1 through H-7 welds, using the VIP Core Shroud Repair Design Criteria (Reference 4). All details relative to the design, fabrication, materials, installation, examination, and testing of the contingency repair are being submitted to the NRC under a separate submittal.

REFERENCES:

1. Letter from G. A. Hunger Jr. (PECO Energy Company) to USNRC, dated March 14, 1994.

2. PECO Energy Response to Generic Letter 94-03, dated August 24,1994.

3. BWR Core Shroud Inspection and Flaw Evaluation Guidelines, GENE-523-113-0894, Rev.1, dated March 1995.

4. BWR Core Shroud Repair Design Criteria, Revision 1, dated September 12,1994.

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