ML18136A240
| ML18136A240 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 11/28/1979 |
| From: | Spencer W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7911300547 | |
| Download: ML18136A240 (2) | |
Text
Vepco VIRGINIA ELECTRIC AND POWER COMPANY, RICHMOND, VIRGINIA 23261 November 28, 1979 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Mr. Denton:
SEISMIC ANALYSIS OF PIPING SYSTEMS SURRY POWER STATION UNITS 1&2 Serial No. 972 PSE&C/CMRjr:mac:wang Docket Nos. 50-280 50-281 License Nos. DPR-32 DPR-37 The conduct of piping system stress analyses during most of this year has demonstrated sever a 1 1 es sons learned which are nm, being emp 1 oyed to upgrade piping systems at Surry Power Station Unit~ 1 & 2. - The purpose of this letter is to inform you of our experience in p~rforming these analyses and the methods being used to conform to the requirements of the Nuclear Regulatory Commission.
This letter also confirms the teleohone ca.11 between Mr. Russell of the NRC and Messrs. Robinson and Spencer of Vepco.
It has been shown that initia.1 stress evaluations of pip*ing systems are preliminary in nature and the results generally differ notic~ably from final calculations.
More modifications result from initial stress evaluations than from final calculations ai the analyses become sufficiently refined to reflect actual conditions.
It has been found from experience that a parallel approach to stress and support calculations results in the most expeditious upgrading of systems; with support modifications being designed based on preliminary evaluations while analyses continue to conc1usion.
This may result in thi'.:
installation of modifications at the time that final calculations are completed.
The installed modifications will remain even if final calculations show they are not required. A check will be made of system flexibility prior to installation of morlifications.
In cases where system, seismic, or analytical boundaries are not clearly defined for completion of stress analysis, the analysis t1ill be resolved by the addition of supports in order to bound the analytical model and, in so doing, upgrade the plant design.
Supports tho.t are added for this purpose will be designated in our supporting documentation as "supports for analysis". These supports will be designed and installed, if possible, in parallel with the continued stress analysis. These supports for analysis",
since they do not impact operability criteria, will not be evaluated as a significant item.
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- ., With* regard to reporting requirements for a.n operating unit, t1Jhen a significant item has bee~ determined tb impact system operability, per the plant Technical Specificitions, the NRC w1*11 be notified within the 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> stipulated by the NRC's order of August 22, 1979.
The notification process is through an LER.
If the modifitation to correct that significant item *1s accomp 1 i shed within the time frame imposed by the Techn'ica l Specifi cati ans, continuous plant operation shall be maintained.
Pipe support redesign-will continue* in parallel with pipe support analysis. This will allow installation of preliminary suppor:t modifications prior to completion of analysis.
Pipe support modifi cat i ans may be accomp 1 i shed to. upgrade supports that may. upon completion of analysis, be deemed not to be required.
If it is deteimi~ed *that an o~erlo~ded or overstressed co~dition exists, but a review of the plant Technical Specifications reveals that operability
- ,muld not be affected, mod"ifications to correct the overload or overstress may be performed while the plant is operating or during outages.
No notification to the NRC will. be made since-.all such design packages will be documented and referenced on LER's.
We believe that experiences_ gained to date with pipe stress analyses has provid~d us with the rnethodolo~y destribed herein to expeditiously install modifications and upgrade piping systems. All NRC requirements are fully and completely met with the only disadvantage being installation of more supports than actually being required by final detailed. analyses.* The large. scope of work \\,,,llich is covered*by this program justifies expenditure of these design efforts*and installation efforts in otder to expedite m~eting the required schedules.
This is acceptable to Vebco to facilitate the analysis and enhance
.tile safety systems at Surry Power Station Units 1 & 2.
. -_ Ver~trul yours,.,
. '.d't.
. '::) <---1~
I W. C. Spencer Vfce.President - Power Station Engineering and Construction _Services cc: Mr. Victor Stello~ Director Office of Inspection and Enforcement Mr. James P. O'Reilly, Director Office of Inspection and Enforcemerit Region II
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