ML20071K937

Forwards Pressurizer Safety Line Piping & Support Evaluation Under Safety Valve Discharge Loading, in Response to NUREG-0737,Item II.D.1

ML20071K937
Person / Time
Site:	Farley
Issue date:	07/26/1994
From:	Dennis Morey SOUTHERN NUCLEAR OPERATING CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20071K940	List: ML20071K937 ML20071K941
References
RTR-NUREG-0737, RTR-NUREG-737, TASK-2.D.1, TASK-TM NUDOCS 9408020099
Download: ML20071K937 (2)

Text

i Southern Nuclear Operating Company Post O*ce Box 1295 i Birmmgham. Alabama 35201 l TNephore (205) 868-5131 L k om um, Southern Nudear Operating Company Vice Preudamt rac ey Pwet the souven elecmc spm July 26, 1994 Docket No.: 50-348 50-364 U. S. Nuclear Regulatory Commission ATFN: Document Control Desk Washington, DC 20555 Joseph M. Farley Nuclear Plant Response to NUR_EG-0737 Item II D_J Ladies and Gentlemen:

NUREG-0737 Item II.D.1, " Performance Testing of BWR and PWR Relief and Safety Valves," was issued by the Nuclear Regulatory Commission (NRC) to address the concern that if the pressurizer safety valves opened due to high reactor coolant system pressure, the pooled water in the loop scals upstream of the safety valves might cause a waterhammer effect that could over-stress downstream piping and supports.

Southern Nuclear Operating Company (SNC) letter dated August 7,1992, provides a summary of FNP actions taken to address the concern. The SNC letter also included a repon titled " Pressurizer Safety Line Piping and Support Evaluation Under Safety Valve Discharge Loading." This report was intended to address NUREG-0737 Item II.D.! based on inciastic piping stress analysis techniques. This report was supplemented with information provided in an SNC letter to the NRC dated October 12,1993.

After review of the analysis, the NRC issued a letter dated March 23,1994, that expressed several concerns associated with the methodology and conclusions. SNC and the NRC met to discuss the concerns on April 26,1994. By letter dated May 9,1994, the NRC issued a summary of the April 26,1994 meeting Consistent with discussions at the meeting, two options for final resolution ofItem II.D.1 were identified in the meeting summary. The first option was to re-analyze to determine iflocalized stresses in the piping downstream of the safety valves can be reduced to meet faulted allowables and to verify that anchor bolts have a minimum safety factor of three. The second option was to modify the existing piping as required to uithstan<i the postulated loading.

SNC has performed a re-analysis documented in the attached report, " Pressurizer Safety Line Piping and Support Evaluation Under Safety Valve Discharge Loading." The re-analysis was performed using traditional clastic analysis techniques and documents that predicted stresses in pressurizer safety valve W

0*n<Cs l PJS P

188N Mh8 g ,

l

U. S. Nuclear Regulatory Commission Page 2 discharge piping are significantly lower than prior analyses. These stress reductions are primarily attributable to more accurate modeling of the loop scal discharge characteristics based on data from EPRI testing of safety valves. The re-analysis demonstrates that all ash 1E Class I piping and supports satisfy applicable code allowables, including a safety factor of at least 4.0 for concrete expansion bolts. The analysis also demonstrates that stresses for non-nuclear safety (NNS) piping remain below faulted code allowables under all postulated conditions and that the safety factor for all concrete expansion bolts is greater than 3.0. The marginal benefit to plant safety associated with raising NNS anchor bolt safety factors from 3.0 to 4.0 is not commensurate with the cost in terms of person rem exposure and dollars. In

addition, existing FNP procedures require inspection of NNS piping subsequent to a transient resulting in safety valve lift and accompanying loop seal discharge.  !

Therefore, SNC requests that the NRC approve the analysis and conclusions of the enclosure, " Pressurizer Safety Line Piping and Support Evaluation Under Safety Valve Discharge Loading" as resolution of the remaining II.D.] issues. Upon receipt of NRC approval, the analysis and conclusions of the enclosure will become the licensing basis for the NNS portion of the pressurizer discharge piping.

l If there ace any questions, or if additional infonnation is needed, please adsisc.

Respectfully submitted, SOUTilERN NUCLEAR OPERATING COhiPANT llf }/ipf Dave hiorey /

DPil/ cit:iidleval. doc Enclosure 1

cc: hir. S. D. Ebneter hir. D. L. Siegel hir. T. hi. Ross 1

i I

i

-_- - - - - - _ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -