ML20203F363
| ML20203F363 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 12/11/1997 |
| From: | Mccoy C SOUTHERN NUCLEAR OPERATING CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 50-424-97-04, 50-424-97-4, 50-425-97-04, 50-425-97-4, GL-89-10, LCV-0136-N, LCV-136-N, NUDOCS 9712170358 | |
| Download: ML20203F363 (7) | |
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. C. M. McCoy
- Southern Nuclear Vce President Operating Company. lac.
. Vogtle Project -
40invernen Co-wr Parkway _
P0 Box 129S Binningham. Alabama 35201.
Tel2059921122
'c fax 205M0403 -
SOUTHERN COMPANY Energyto Serve %ur%rld*
December 1ie 1997 LCV-0136-N Docket Nos.: 50-424 50-425 U. S. Nuclear Regulatory Commission A'ITN: Document Control Desk Washington, D. C. 20555 Gentlemen:
VOGTLE ELECTRIC GENERATING PLANT GENERIC LETTER 89-10 CLOSE-OUT INSPECTION The NRC performed an inspection of the Vogtle Electric Generating Plant (VEOP)
Generie Letter 39-10 (GL 89-10) program March 24-27,1997. As a result of this inspection, the NRC indicated that VEGP had implemt.nted a program in accordance with the recommendations contained in GL 89-10. However, certain issues were identined which the NRC felt needed additional attention n conjunction with the i
close-out of this program. Southern Nuclear Operating Company (SNC) issued letter LCV-0136-M, dated May 3,1997, which documents tl:ase issues and their proposed resolution. The NRC subsequently closed the VEGP GL 89-10 program in Inspection Report 50-424/97-04,50-425/97-04 dated May 21,1997.
SNC agreed to provide the NRC with the status af each of the issues discussed in the I
above refereneed letter by t' e end of 1997. The enclosure to this I->er summarizes h[
f the current status of each of the issues addressed in letter LCV-0136-M.
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<1 U. S. Nuclear Regulatory Commission Page 2 Should you require any additional information regarding this response, please contr.et my office.
Sincerely, c
hf C.K.McCo-CKM/IIET/het Enclosure xc:
Southern Nuskar Ooerating Comnanv. Inc.
hir. J.13. Beasley, Jr.
hir. hi. Sheibani NORhtS U. S. Nuclear Regulatory Commission hir. L. A. Reyes, Regional Administrator hir. D.11. Jaffe, Senior Project hianager, NRR NRC Senior Resident inspector, Vogtle LCV-0136-N
Enclosure Generic Letter 89-10 Close-Out Inspection Issues Issue No.1 Differential pressure testing was performed to support the use of a hybrid Fisher /EPRI methodology to predict Fisher butterfly valve torque requirements. The differential pressure testing indicated that the methodology provided a reasonable prediction of torque requirements, however, the calculations did not bound the test data in all cases.
There is a concern, due to the fact that this methodology does not include a substantial degree of margin, that the methodology may be utilized in a non-conservative mmmer in the future.
Status The VEGP Thrust /rorque Calculation, X4C1000UO2, has been revised to include a discussion regarding the differential pressure test results, and the basis forjustifying the use of the Fisher /EPRI methodology. This will ensure that the methodology will not be utilized in a non-conservative manner in the future, and that any limitations associated with the use of this methodology are clearly identified and documented.
Issue No. 2 The VEGP Generic Letter 89-10 program includes a total of 70 Fisher butterfly valves which have been divided into six groups of esrentially identical valves Differential pressure testing was performed on a total of four valves in the eight inch valve group to justify the use of the analytical methodology utilized to determine the torque requirements. There is a concern that the methodology has not been adequately justified for use on the larger valve sizes.
Status To provide additionaljustification to support the methodology utilized to predict butterfly valve torque requirc.ments, differential pressure tests were performed on two NSCW pump discharge valves. Valves 1HV-11600 and 1HV-i1605 are 18 inch Fisher butterfly valves which operate against a design-basis differential pressure of 173 psid, which is the highest design differential pressure of any butterfly valve in the VEGP GL 89-10 program. The valves were opened at differential pressures of 164 psid and 165 psid respectively, and each valve operated successfully. The dynamic opening loads measured in the tests were 68% and 102% of the predicted opening loads respectively. The measured load for valve 1HV-11605 is slightly higher than the predicted load, however, the apparent difference is insignificant relative to the overall accuracy of the test process.
Minor errors in either the torque measurement or differential pressure measurement
would be sufficient to account for this slight discrepancy. Based on the results of these tests, as well as those tests perfonned previously on the eig,ht inch valves, it can be concluded that the current VEGP methodology provides a reasonable approximation of the actual loads required to operate Fisher butterfly valves under differential pressure conditions.
Issue No. 3 The thrust calculations for the Anchor-Darling gate valves in groups AD-1, AD-2 and AD-4 and for the Velan globe valves in groups V-1, V-2 and V-3 were performed utilizing the EPRI Performance Prediction Program Methodology (PPM). Subsequent to the use of this methodology at VEGP, the NRC issued a Safety Evaluation Report (SER) on March 15,1996 documenting their review of Topical Report TR-103237 covering the EPRI PPM. There is a concern that the SER has not been revie"<ed in sufficient detail to ensure that the Conditions / Limitations outlined in the document have been adequately addressed relative to the VEGP calculations.
Status The SER covering the EPRI PPM has been reviewed in detail for applicability to the calculations performed relatis e to the Anchor-Darling and Velan valves, as well as those performed on certain Westinghouse valves. A summary of this review is included in the VEGP Thrustfrorque Calculation, X4C1000UO2.
The only significant issue identified in conjunction with this review was the evaluation of cracking loads for gate valves in the opening direction. The EPRI PPM includes a manual calculation for estimating cracking loads as a function of the differential pressure and the final closing thrust. This evaluation was not performed in conjunction with the initial implementation of the methodology, primarily due to the fact that the final closing thrust is a variable, and an evaluation of this type would only be applicable to the as-lef1 configuration of the valve.
The cracking loads for the Anchor-Darling and Westinghouse gate valves, which were evaluated utilizing the EPRI PPM, have been calculated based on the ma mal methodology included in the PPM All of the valves have been determined to be acceptable i., their current configurations. In addition, a methodology has been
. developed to assess cracking loads in conjunction with the periodic static test program.
The actual measured pullout load will be combined with the predicted load due to differential pressure, and this total load will be compared to the allowable opening thrust.
This will ensure that the cracking loads associated with subsequent valve setups are within the opening capabilities of the MOV. The procedural revisions necessary to implement this methodology will be completed prior to 2R6, which is scheduled for the spring of 1998.
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hivtEnd The thrust calculations for the Anchor-Darling gate valves in group AD-3 were performcd utilizing the Industry Standard equation with a 0.5 valve factor, since the EPRI PPM does not apply to valves operating in air systems. There is a concern that the Industry Standard equation with a 0.5 valve factor is not adequatelyjustified for this valve group.
Status Valves 1/211V-9380A/B have been re-evaluated, utilizing the EPRI NMAC equation with a 0.7 friction coefficient, to provide a more conservative prediction of thrust requirements. The revised calculations resulted in a margin of 15% in the opening direction, which is the safety direction for these valves. To provide additional assurance that these valves will be capable of performing their safety functions, the operators will be modified during 2R6 and 1R8 to provide additional opening margin.
Issue No. 5 Fisher globe valves 1/211V-3548 have as-left closing margins ofless than 5% based on the current torque switch settings and calculated required closing thrust. There is no differential pressure test data available to support the analytical methodoF,gy utilized for the valves in this group, therefore, there is a concern regarding the low as-le!1 margins for these valves.
Status Valves 1/211V-3548 have been repacked with a revised packing configuration which reduced the packing loads to a value substantially lower than that previously assumed in the calculations. As a result of the reduced packing friction, the design packing load has been revised from 1000 lbs to 500 lbs, the value originally specified by Fisher. The revised calculations resulted in a margin of 243% in the opening direction and as-letl margins ranging from 57% to 95% in the closing direction.
Issue No. 6 A total of three Velan globe valves have as-left closing margins ofless than 5% based on the current torque switch settings and calculated required closing thrust. The closing thrusts for these valves were determined utilizing the EPRI PPM and are supported by extensive in-situ differential pressure testing. However, there is a general concern that maintaining margins ofless than five percent above design is not a good long-term pmetice.
Status Procedure 26871-C," Static Testing of Motor Operated Gate / Globe Valves Using Votes Analysis and Test System" has been revised to include an additional 5% bias in the c:;tablishment of target minirc.um thrust requirements for all torque switch controlled valves. The additional 5% will be considered a " good practice" and will not be considered relative to valve operability. The additional 5% margin may be reduced based on a valve specific engineering evaluation.
Issue No. 7 Differential pressure tests were performed on Westinghouse gate valves in groups W-2A, W-2B and W-8 to justify the analytical methodology utilized to determine the thrust requirements for these valves. Ilowever,in certain cases the calculations do not bound the difTerential pressure test results. There is a concern that the analytical methodology has not been adequatelyjustified for these valve groups.
Status The thrust requirementc for the Westinghouse gate valves in groups W-2A, W-2B and W-8 have been recalculated utili-ing friction coeflicients which bound the VEGP differential pressure test data. The revised calculations utilize the following friction coefficients:
Groun Onening Closing W-2A 1.5 0.8 W-2B 0.7 0.6 W-8 0.65 0.65 Evaluating the current valve setups with respect to the revised thrust requirements indicates that all of the valves have positive margins with the exception of the following valves:
Vah e Descrintion Close Margin lilV-8716A IUIR Crosstic Isolation
-4%
211V 8719A RIIR Crosstie Isolation
-5%
lilV-8804A RilR to CCP Suction
-1%
llowever, further evaluatian of these valves utilizing measured packing loads demonstrated that positive closing margins exist. The torque switch settings for these valves will be adjusted during 1R8 and 2R6 respectively to provide additional closing margin.
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Issue NoJ Differential pressure tests were not perfonned on Westinghouse gate valves in groups W-9, W-11 and W-12. There is a concern that the analytical methodology has not been adequate." justified for these valve groups.
Status The Westinghouse gate valves in groups W-9, W-11 and W-12 have been re-evaluated utilizing the EPRI Performance Prediction Methodology. Evaluating the current valve setups with respect to the revised thrust requirements indicates that all of the valves have positive margins in their current configuration.
Issue No. 9 The Fisher, Velan and Westinghouse rising stem valves utilize a stem friction coefficient of 0.15 in the opening direction and in the closing direction on limit switch controlled valves. There is a concern regarding thejustification of the 0.15 stem friction coefficient for these valve functions.
Status The calculations for the Fisher, Velan and Westinghouse rising stem valves have been revised to incorporate a 0.18 stem friction coefficient for all valves in the opening direction and for limit switch controlled valves in the closing direction. The 0.18 stem friction coefficient is based on a statistical evaluation of VEGP test data and represents a 95% confidence value. Evaluating the current valve setups with respect to the revised thrust capabilities indicates that a total of three valves have close torque switch settings which are in excess of the operator capabilities, based on the revised stem friction coefficient. Ilowever, a re-evaluation of each valve utilizing actual stem friction coefficients, derived from test data, concluded that the current torque switch settings are within the operator capabilities. Therefore, the valves are acceptable in their current configuration.