NUREG-1137, Safety Evaluation Supporting Util 870601 Proposal Re Pipe Break Criteria Used for Flooding Analyses & Addition of Moderate Energy non-seismic Category I Piping to Exceptions List.Nrc Does Not Entirely Agree W/Util Justification

Safety Evaluation Supporting Util 870601 Proposal Re Pipe Break Criteria Used for Flooding Analyses & Addition of Moderate Energy non-seismic Category I Piping to Exceptions List.Nrc Does Not Entirely Agree W/Util Justification

ML20237K833
Person / Time
Site:	Vogtle
Issue date:	08/14/1987
From:	NRC
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ML20237K777	List: NUREG-1137, Safety Evaluation Supporting Util 870601 Proposal Re Pipe Break Criteria Used for Flooding Analyses & Addition of Moderate Energy non-seismic Category I Piping to Exceptions List.Nrc Does Not Entirely Agree W/Util Justification
References
RTR-NUREG-1137 NUDOCS 8708190421
Download: ML20237K833 (3)

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l y Enclosure SAFETY EVALUATION ON PIPE BREAK CRITERIA FOR FLOODING ANALYSES i V0GTLE ELECTRIC GENERATING PLANT, UNIT 2

DOCKET N0. 50-425 In Section 3.6.1 of the Vogtle Safety Evaluation Report (SER), NUREG-1137, '

dated June 1985, the staff stipulated that based on the applicant's (Georgia Power Company) statement that all non-seismic Category I piping systems in j safety-related areas were seismically supported, only cracks rather than full- .

ruptures needed to be assumed in those moderate energy systems for flooding '

analyses assumptions.- By letter dated June 1, 1987, the licensee submitted a revision to the Final Safety Analysis Report (FSAR) that revised their response to FSAR Ouestion 410.15. In Ouestion 410.15, the staff stated its ,

4 position that for flooding analysis purposes, the complete failure of non-seismic 3 Category I moderate energy piping systems should be considered in lieu of cracks in determining the worst case flooding ~. Georgia Power Company's original response in Amendment 9 to the FSAR indicated that all non-seismic Category I piping in safety-related structures has been supported to withstand safe shutdown earthquake (SSE) loads. It was also indicated.in Amendment 9 that.for SSE loading, piping stresses are calculated to consider that they are maintained i within faulted allowables with certain specified exceptions. Faulted allowables are the calcu. lated piping stress limits including the SSE contribution, identified by Sect . III of the ASME Code, that if the stresses are not exceeded, the pipin' , expected to maintain its integrity. The June 1, 1987 submittal  :

rev' the specified exceptions (for Unit 2 only) to include nioderate energy l non-seismic Category I piping, 2 inches and smaller. However, these lites will be supported to seismic Category I criteria.

The flooding analysis will continue to postulate through wall leakage cracks l in the Unit 2 non-seismic Category I 2-inch and smaller pipes. The licensee  ;

contends that justification for postulating cracks in these small pipes in lieu of pipe ruptures is such that crack postulation satisfios the requirements of Standard Review Plan Section 3.6.1 and Branch Technical l Position MEB 3-1 which states that through wall leakage cracks should be

postulated in fluid system piping designed to non-seismic standards and

! through wall leakage cracks should be postulated in moderate energy fluid system piping.

l While the staff agrees with the licensee regarding postulating only through wall leakage cracks in these small lines, it does not agree with the justification as referenced. The referenced portion of MEB 3-1 which discusses cracks in moderate energy non-seismic Category I piping systems of any size is meant to ensure all types of postulated pipe failures have been considered in these pipes. In some instances, a pipe crack may result in more damage due to flooding than would a complete pipe rupture of the same pipe.

This may occur in the case when the full pipe rupture is immediately detectable while the leakage from the pipe crack could continue for some time before detection, f L

8708190421 870814 5 {

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As stated in the staff's SER for Vogtle, a complete failure (rupture) of non-seismic Category 1 piping systems need not be postulated because they are seismically supported. Because these lines continue to be seismically supported, the staff's conclusion as set forth in Section 3.6.1 of the SER remains valid and only through wall leakage cracks need be postulated in acderate energy piping that is not designed to seismic Category I requirements. The staff, therefore, concludes that the additionci exception y of not calculating pipe _ stresses to ensure they are maintained within faulted {

! allowables is acceptable for 2-inches and smaller non-seismic Category I  !

moderate energy piping, and the requirements of General Design Criterion 4 l

" Environmental and fiissile Design Bases," are still satisfied for Vogtle Unit 2. 1 l

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L j, .t- a, Mr. J. P. O'Reilly-5- Georgia Power Company Vogtle Electric Generating' Plant cc:

~Mr. L. T..Gucwa Resident Inspector Chief Nuclear Engineer Nuclear Regulatory Commission Georgia Power Company P. O. Box 572 '

P.O. Box 4545 Waynesboro, Georgia .30830 Atlanta,-Georgia 30302 Mr. Ruble A. Thomas Depoish Xirkland, III, Counsel.

Vice President - Licensing Office of the Consumers' Utility Vogtle Project Council Georgia Power Company / Suite 225 Southern Company Services, Inc. 32 Peachtree Street, N.W.

P.O. Box 2625. Atlanta, Georgia 30303 Birmingham, Alabama 35202 James E. Joiner Mr. Paul 0. Rice .

Troutman, Sanders, Lockerman, Vice President & Project General Manager -& Ashmore- 3 Georgia Power Company Candler Building j Post Office Box 299A, Route 2 127 Peachtree ' Street, N.E.

Waynesboro, Georgia 30830 Atlanta, Georgia 30303 Danny Feig .

Mr. J. A. Sailey 1130 Alta Avenue Project Licensing Manager Atlanta, Georgia 30307 Southern Company Services, Inc.

P.O. Box 2625 Carol Stangler Birmingham, Alabama 35202 Georgians Against Nuclear Energy 425 Euclid Terrace Ernest L. Blake, Jr. Atlanta, Georgia 30307 Bruce W. Churchill, Esq.

Shaw, Pittman, Potts and Trowbridge 2300 N Street , N. - W.

, Washington, D. C. 20037 Mr. G. Bockhold, Jr.

i Vogtle Plant Manager '

Georgia Power Company Route 2, Box 299-A Waynesboro, Georgia 30830 I

Regional Administrator, Region II l U.S. Nuclear Regulatory Comission l 101 Marietta Street, N.W., Suite 2900

[ Atlanta, Georgia 30323  !

Mr. R. E. Conway Senior Vice President and Project Director Georgia Power Company '

Rt. 2, P. 0. Box 299A l Waynesboro, Georgia 30830 i

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