TXX-4069, Forwards Nonproprietary & Proprietary Versions of Technical Bases for Eliminating Large Primary Loop Pipe Ruptures as Structural Design Basis for Comanche Peak Units 1 & 2. Proprietary Version Withheld (Ref 10CFR2.790)

Forwards Nonproprietary & Proprietary Versions of Technical Bases for Eliminating Large Primary Loop Pipe Ruptures as Structural Design Basis for Comanche Peak Units 1 & 2. Proprietary Version Withheld (Ref 10CFR2.790)

ML20081E787
Person / Time
Site:	Comanche Peak
Issue date:	10/31/1983
From:	Schmidt H TEXAS UTILITIES SERVICES, INC.
To:	Youngblood B Office of Nuclear Reactor Regulation
Shared Package
ML19268E343	List: ML20081E806 ML20081E815 TXX-4069, Forwards Nonproprietary & Proprietary Versions of Technical Bases for Eliminating Large Primary Loop Pipe Ruptures as Structural Design Basis for Comanche Peak Units 1 & 2. Proprietary Version Withheld (Ref 10CFR2.790)
References
TXX-4069, NUDOCS 8311020237
Download: ML20081E787 (5)

Text

e TEXAS UTILITIES SERVICES INC. Log # TXX-4069

.mu nnym tuwen mu.araxw mm amo File # 903.9 October 31, 1983 Mr. B. J. Youngblood, Chief Division of Licensing Licensing Branch No. 1 Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Comanche Peak Steam Electric Station Docket Nos. 50-445 and 50-446 Transmittal of Leak-Before-Break Analysis

References:

(a) Letter from Harold Denton (NRC) to Morray Edelman (AIF) dated May 2, 1983 (b) Letter from E.P. Rahe (Westinghouse) te Richard Vollmer (NRC) dated May 11, 1983 (c) Letter from J.J. Ray (ACRS) to William Dircks (NRC) dated June 14, 1983 (d) Letter from William Dircks (NRC) to J.J. Ray (ACRS) dated July 29, 1983

Dear Mr. Youngblood:

Texas Utilities Generating Company has evaluated the technical feasibility and potential benefits of eliminating postulated pipe breaks in the reactor coolant system (RCS) primary loop from the structural design basis of the Comanche Peak Plant. In our review of this concept we find that considerable industry development work and NRC-sponsored research has been completed. Mr. Harold Denton's letter of May 2, 1983 (Reference (a)) indicates that the Staff is technically satisfied with generic information previously submitted by Westinghouse. As a result of their development efforts, Westinghouse has requested from the Staff (Reference (b)) generic approval to eliminate RCS primary loop pipe breaks from the structural design basis of all Westinghouse plants.

The results of NRC-sponsored research also support the elimina-tion of RCS primary loop pipe breaks in all Westinghouse plants east of the Rocky Mountains. The ACRS has reviewed both industry

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I and NRC efforts in this area and concluded (Reference (c))

that such an approach is feasible. Additionally (Reference (d)), Mr. Dircks has indicated that the Staf f is continuing toward the implementation of this concept on a case-by-case basis.

Westinghouse has informed Texas Utilities that generic information previously submitted to the NRC to justify the elimination of RCS primary loop pipe breaks, as part of the resolution to Generic Issue A-2, is applicable to CPSES.

ENCLOSURES The elimination of RCS primary loop pipe breaks was discussed with your Staff, Westinghouse, and Texas Utilities in a meeting on October 12, 1983. At this meeting the St: 'f outlined the type of information required by the NRC to Iw ~.ew the elimination of RCS primary loop pipe breaks. The tech. cal information requested by the Staff is enclosed as follows:

(1) Twenty copies of Westinghouse Report MT-SME-3135, "Tochnical Bases for Eliminating Large Primary Loop Pipe Ruptures as the Structural Design Basis for Comanche Peak Units 1 and 2," October 1983, proprietary.

, (2) Twenty copies of Westinghouse Report MT-SME-3136,

" Technical Bases for Eliminating Larje Primary Loop Pipe Ruptures as the Structural Design Basis for Comanche Peak Units 1 and 2," October 1983, non-proprietary.

(3) One copy of Application for Withholding, CAW-83-95.

REQUEST FOR ACTION Based on the information contained in the enclosed reports, Westinghouse has demonstrated the applicability of the " leak-before-break" concept for the RCS primary loop in Comanche Peak Units 1 and 2. As such, Texas Utilities plans to incorporate this concept in the structural design basis of Comanche Peak Units 1 and 2 and requests NRC approval of the following:

(1) Eliminate the need to postulate circumferential and longitudinal pipe breaks in the RCS primary loop (hot leg, cold leg, and cross-over leg piping) through the application of the leak-before-break concept.

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(2) Eliminate the need to install pipe whip restraints and jet shields associated with previously postulated breaks in the RCS primary Aoop.

(3) Eliminate the need to consider dynamic effects and loading conditions associated with previously postulated pipe breaks in the RCS primary loop.

These effects include jet impingement loads, cavity pressure loads, blowdown loads in the RCS and attached piping, and subcompartment pressure loads.

DISCUSSION As discussed with the Staff on October 12, 1983, the construction of Comanche Peak Unit 1 is nearing completion.

Evaluation of jets from postulated RCS primary loop pipe breaks has indicated that jet impingement barriers may be required for certain postulated breaks. Currently, such barriers for Unit 1 have been neither designed nor installed.

Because of the current urgency of this situation on Unit 1, Texas Utilities requests that, at this time, the Staff review the enclosed reports as a basis for eliminating the need to consider jets from postulated RCS primary loop pipe breaks.

This could also result in considerable economic benefits for Comanche Peak.

Relating to this specific request for Unit 1, Texas Utilities has met all the design criteria in the FSAR for the design of the RCS primary loop. In particular, RCS primary loop pipe whip restraints have been installed and RCS components and supports have been designed for the combination of LOCA and SSE loads.

The CPSES Reactor Coolant Pressure Boundary Leak Detection System meets the requirements of Regulatory Guide 1.45 as discussed in Section 5.2.5 of the CPSES Final Safety Analysis Report (FSAR). Specific detection requirements are described in the CPSES Technical Specifications, Section 3/4.4.6.

As noted in Reference (d), the NRC is in the process of developing plans to implement the leak-before-break concept.

As part of their efforts, the Staff is considering the need to change GDC 4. In reviewing this proposed regulation change, Texas Utilities does not consider such a change necessary in order to eliminate RCS primary loop pipe breaks. The basis for our position on this issue is provided in Attachment A.

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However, if the Staff considers it necessary for Texas Utilities to request relief from any regulations, please notify us as soon as possible so that the appropriate action can be initiated.

In summary. Texas Utilities has provided the Staff with the technical basis for eliminating RCS primary loep pipe breaks on Comanche Peak Units 1 and 2. Based on current construction schedules and physical limitations, NRC apprcval for the elimination of the need to consider jets from postulated RCS primary loop pipe breaks for Unit 1 is requested by November 30, 1983. Approval for application of the leak-before-break concept for the structural design basis of the RCS primary loop for Units 1 and 2 is requested by December 15, 1983.

PROPRIETARY INFORMATION Enclosure 1 contains information proprietary to Westing-house Electric Corporation, the owner of the information. The enclosed affidavit signed by Westinghouse management sets forth the basis on which the information contained in the proprietary version may be withheld from public disclosure by the NRC in accordance with the requirements of 10 C.F.R. 2.790 (b) (1) .

The affidavit addresses the specific considerations of 10 C.F.R 2.790 (b) (4) . Correspondence with respect to the proprietary ,

aspects of the affidavit and Application for Withholding should reference CAW-83-95 and should be addressed to R. A. Wiesemann, Manager, Regulatory and Legislative Affairs, Westinghouse

Electric Corporation, P.O. Box 355, Pittsburgh, Pennsylvania, Zip 15230.

If you have any questions regarding this submittal, please contact us.

Sincerel ,

H. C. Schmidt Manager, Nuclear Services I

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Attachment A i

ARGUishia AGAINST RULE CHANGE Provided herein is the basis for the position that current regulations do not require a change in order to eliminate pipe breaks from the RCS primary loop.

. Specifically, the NRC ir considering changing GDC 4. However, the NRC inter-i pretation'of GDC 4 since its initial adoption leads to the conclusion that no rule change is necessary to eliminate. pipe. breaks. in the reactor coolant systes.

The folloiwni; are exampler of how the Cassission has interpreted GDC 4:

i. Analysis of pipe breaks in tihe . reactor coolant system was not undertaken or required for many plants licensed under GDC 4 requirements. The plants in this category include many plants addressing Generic Issue A-Z (asyumatric loads). ,

i Z. Under current letc Ticensing practice the 75tc has perinitted the usa of limited break areas (as. low as 75 square inches) at specific locations in the reactor coolant systems for structural evaluations.

3. The NRC does ncit require pipe breaks to be postulated at all locations in the reactor coolant system and always has provided the criteria to be. used. for postulating or excluding pipe breaks from the reactor coolant system in guidance documents . -

4. The letC has issued cMteria.tn SEP plants which permit these plants to exclude pipa breaks in high _ energy piping systems in containment. l In addition to these various, interpretiationr. the following points are also ,

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l'. GDC 4 consistently has been interpreted to require that contain-l ment design ECC3 design, and environmental effects be based on a loss of reactor coolant from a flow. area. equivalent to twice the flow area of the-l largest pipe in the, reactor coolant pressure boundary.

2 TG CPR Part 50.. Appendix A does not define LOCA as a pipe break but, rather, as a flow area equal to'twice the flow area of the largest pipe in the reactor coolant pressure boundary.

3. The footnote to the definttion of LOCA. in Appendix A indicates that the type size and. orientation of pipe breakr are under develop 1ent Historically the IEtC has implemented. this footnote through guidance documents such as Regulatory Gufda T.46., Branch T'achnical Position EB 3-1. MESand 3-T guide-recently lines for resolving pipe break issues provided to SEP plants.

was revised in July 198T as part of IEJREE-08DD (Standard Review Pian).

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