ML20073F519

Forwards Listing of Documents Describing Proposed Alternative Repair Plan,Per 10CFR50.55a(a)(3).Attached Info Being Submitted at Time to Avail NRC Max Time Possible to Review 10CFR50.55a(a)(3) Request

ML20073F519
Person / Time
Site:	Peach Bottom
Issue date:	09/16/1994
From:	Hunger G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20073F527	List: ML20073F519 ML20073F533 ML20073F544 ML20073F554 ML20073F567 ML20073F661 ML20073F681
References
NUDOCS 9410030141
Download: ML20073F519 (6)

Text

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8 Et tion Supptri Dep rtmcat 10 CFR 50.55a(a)(3)

PECO ENERGY reco <"erov ce-ne v Nuclear Group Headquarters 965 Chesterbrook Boulevard Wayne, PA 19087-5691 September 16,1994 Docket No. 50-277 License No. DPR-44 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555

Subject:

Peach Bottom Atomic Power Station, Unit 2 Submittal of Proposed Alternative Repair Plan in Accordance with 10 CFR 50.55a(a)(3)

Dear Sir:

in a letter dated August 31,1994 from A. C. Thadani (U. S. Nuclear Regulatory Commission (USNRC)) to R. A. Pinelli (Boiling Water Reactors Owner's Group (BWROG)), the USNRC provided guidance that the shroud repair options presented to the USNRC by the Boiling Water Reactor Vessel Internals Project (BWRVIP) do not fall under the ASME Code,Section XI definition for repair or replacement. Additionally, the letter states that shroud repair options considered to date are alternatives to Section XI, and require review and approval by the USNRC.

Accordingly, PECO Energy Company requests review and approval of the proposed repair plan for the Peach Bottom Atomic Power Station, Unit 2 core shroud in accordance with 10 CFR 50.55a(a)(3), in the event that such a repair is determined to be necessary. Attachment 1 is a listing of documents which describe the proposed repair. Please note that some of the attached documents are preliminary. Additionally, we acknowledge that the attached documents constitute only a portion of the information to support our 50.55a(a)(3) request. The attached information is being submitted at this time to avail the USNRC the maximum time possible to review our 50.55a(a)(3) request. The additional information which completes our request will be provided by September 26,1994.

941003o141 94o916 PDR ADOCK 05ooo277 g

September 16,1994 Page 2 inspections of the core shroud have been rescheduled to begin September 21, 1994. If a shroud repair is determined to be necessary following completion of the inspections, the currently scheduled date to begin the repair is October 5, 1994. In order to support this repair contingency, we request that you review and approve our 50.55a(a)(3) request by October 3,1994.

In the event that the repair is deemed unnecessary during the inspections, the USNRC will be promptly notified.

As discussed in 10 CFR 50.55a(a)(3)(i), proposed attematives may be used when the applicant demonstrates that the proposed alternatives would provide an acceptable level of quality and safety. The proposed repair of the PBAPS, Unit 2 shroud is being designed by General Electric Company, and utilizes the shroud repair design criteria of the BWRVIP. This repair will provide a permanent mechanical repair that ensures that the shroud will meet its design basis safety function in the event of failure of circumferential welds. The proposed repair is being designed to ensure the structural integrity of the core shroud during normal operation and under postulated transient and design basis accident conditions for the remaining plant life. Appropriate codes and standards will be utilized to ensure that the proposed alternative repair will provide an acceptable level of quality and safety. Therefore, the proposed alternative repair would meet the acceptability criteria of 10 CFR 50.55a(a)(3)(i).

If you have any questions, please contact us.

Very truly yours,

. 0.

G. A. Hunger, Director - Licensing Attachments cc:

T. T. Martin, Administrator, Region I, USNRC W. L Schmidt, USNRC Senior Resident inspector, PBAPS

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ATTACHMENT 1 Document Status 1

1. Modification Description Final

2. Project Instruction, GENE-771-54-0894, Rev. O, dated Final August 1994

3. Design Specification - Shroud Stabilizer Hardware, Preliminary 25A5579

4. Code Design Specification - Shroud Stabilizers, Preliminary 25A5580

5. Fabrication Specification - Fabrication of Shroud Preliminary Stabilizer, 25A5601

6. Installation Specification - Cleaning and Cleanliness Preliminary Control for Field Modifications of Vessel Components, 21A2040

7. Installation Specification - Stabilizer Installation, Preliminary 25A5581 i

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MODIFICATION DESCRIPTION CORE STRUCTURE CHARACTERISTICS AND FUNCTIONS The basic function of contingency modification P00435 is to provide a non-welded, mechanical solution to the problem of unacceptable Reactor Pressure Vessel (RPV) Core Shroud welds which may be found in Peach Bottom Unit 2 as a result of examinations planned during the refueling outage beginning September 16, 1994.

The total scope of welds involved in this repair are welds H1 through H7 asshown below.

REACTOR PRESSURE VESSEL - SHROUD PEACH BOTTOM ATOMIC POWER STATION UNIT 2 & 3 DRYER / SEPARATOR SUPPORT RINO i:j ITEM 7 AtB2-F 304 0.035 % C VI l

)#2 Hj ITEM 5 A240 TP.304 0.002 %, C (MAX) gp p T,0P GUIDE SUPPORT RINO, omi ITE M 6 A182-F 304 0.020 % C IUNIT 21 j 0.030 % C (UNIT 3)

H3 ITEM 4 A240 TP.304 0.000 X C (MAX) v3 lv4 H4 y$

yg ITEM 14 A240 TP. 304 0.0E0 % C (MAX) gCDRE PLATE SUPPORT RING H5

'A 11EM 13 A182-F 304 0.030 % C (UN1 2) 0.e25 % C (L iT 3, ITEM 12 A240 TP.304 0.059 % C (MAX)

H7 V7 V8 SHROUD POR YLINDER REF. DWG. M-1-B-26 1 OF 3

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The specific core structure components that are directly

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n affected by this modification are the core shroud, shroud i

support plate, shroud head and steam separator assembly, core support, and the top guid_.

i Core Shroud 5

The functions of the core shroud are to provide a partition j

to separate the upward flow of coolant through the core from the downward recirculation flow in the annulus and to i

provide a floodable core region following a recirculation line break.

The core shroud also helps to limit the postulated deflection of other vessel internals and assure that the control rods and the Core Standby Cooling Systems can perform their safety functions during abnormal

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operational transients.

t Shroud Succort Plate t

The shroud support plate is connected between the shroud and the RPV.

It provides support for the shroud and forms the lower boundary for the downcomer annulus between the core r

shroud and the reactor vessel wall.

The shroud support plate also provides the openings for the welded discharge connections for the 20 jet pump assemblies.

Shroud Head and Steam Seoarator Assembly This component is bolted to the top of the upper shroud to form the top of the core discharge plenum.

This plenum l

provides a mixing chamber for the steam-water. mixture before it enters the steam separators.

Individual stainless steel axial flow steam separators are attached to standpipes which are welded to the shroud head.

h Core Suenort (Core Plate)

The core support consists of a circular stainless steel plate stiffened with a rim and beam structure.

Perforations in the plate provide lateral support and guidance for the control rod guide tubes, peripheral fuel support pieces, in-core flux monitor guide tubes, and start-up neutron sources.

4 The entire assembly is bolted to a support ledge, between l

the central and lower portions of the core shroud.

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i Too Guide I

The cop fuel guide is formed by a series of stainless steel beams joined at right angles to form square openings.

Each opening provides lateral support and guidance for four fuel assemblies.

Holes are provided in the bottom of the beams j

to anchor the in-core flux monitor guide tubes and start-up L

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t' neutron sources.

The top fuel guide is located near the top of'the shroud.

CORE SHROUD STABILIZER-TIE ROD ASSEMBLIES This modification involves the installation of 4 core shroud stabilizer-tie rod assemblies between the shroud support plate and shroud head and separator interface, similar to the Edwin I. Hatch Nuclear Plant Unit 1 design.

Each assembly includes spring restraints to minimize any lateral shroud movement to assure acceptable deflections for control rod insertion, and vertical tie rods to restrain the uplift forces due to pressure drops across the reactor internals.

The upper spring is attached to a bracket that is hooked over the top of the shroud and through a notch machined in the shroud head and separator assembly.

This bracket and spring limit the movement of the sections above weld H3 by providing a load path from the shroud, at the top guide elevation, to the RPV.

The lower spring and dowel provides the same function between the core plate elevation and the RPV for the shroud sections below weld H4.

Additionally, an intermediate limit stop is installed on each tie rod between the RPV and the tie rod to increase the natural frequency of the tie rods and thereby preventing unacceptable response due to flow induced vibrations.

The tie rods are installed between the upper brackets and the lower springs to provide a vertical load path between the top of the shroud and the shroud support plate as well as providing support for the springs.

Each stabilizer assembly is attached to the shroud support plate by means of a pinned connection and a base l

plate with two self locking "L"

bolts.

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