ML20206F068

Safety Evaluation Supporting 850514,0710,860327,0411 & 0513 Requests for Approval to Use Pvrc Damping Values (ASME Code Case N-411) for Piping Sys Reanalysis

ML20206F068
Person / Time
Site:	Vermont Yankee
Issue date:	06/13/1986
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20206F062	List: ML20206F057 ML20206F068
References
NUDOCS 8606240121
Download: ML20206F068 (2)

Text

. . . - _ _

l y

ff ,%,

p, UNITED STATES NUCLEAR REGULATORY COMMISSION 1

5. aj WASHINGTON, D. C. 20555

\...../

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION VERMONT YANKEE NUCLEAR POWER CORPORATION PVRC DAMPING VALUE APPLICATION DOCKET N0. 50-271

1.0 INTRODUCTION

The Vermont Yankee Nuclear Power Corporation (the licensee), in its letters dated May 14,1985, July 10,1985, March 27,1986, April 11,1986, and May 13, 1986, requested the NRC's approval to use the Pressure Vessel Research Council (PVRC) damping values for piping system re-analysis for the Vermont Yankee Nuclear Power Station. The licensee intended to use the PVRC damping values for purposes of support optimization and to verify the as-built piping / support configuration, where unnecessary seismic restraints can be eliminated.

2.0 EVALUATION i

+

For the dynamic analysis of systems in nuclear power plants the NRC has recommended a set of damping values which was delineated in the Regulatory Guide 1.61. However, based on operational experience from many systems, the PVRC Piping Committee in 1984 developed an alternative set of damping values to be used for piping analysis.Section III of the ASME Boiler and Pressure Vessel Code endorsed these values in 1984 by the issuance of Code Case N-411.

This Code Case was also recommended by NUREG-1061.

The NRC staff has considered Code Case N-411 on the PVRC damping values conditionally acceptable. The licensee has explained in its letters that:

1. The damping values will be used for piping system re-analyses only.

2. These damping values will not be used intermingled with other damping values, such as those delineated in Regulatory Guide 1.61, in the same piping analysis.

3. System analyses will be performed by the response spectrum method only. .

4. I Detailed walk-down of the systems will be performed to assure that ,

no interference caused by system movements .to their environments 1 will exist. l h

P Nk 1

i 1

In addition, the licensee assured that the analyses will employ the Regulatory i Guide 1.60 spectrum, that system models will end at suitable anchors such that heavy equipment will not be included in the piping model, and that the system model and load combinations will be performed according to Regulatory Guide 1.92.

The restrictions imposed by the licensee on the use of the PVRC damping values are consistent with the conditions for NRC endorsement of the Code Case.

3.0 CONCLUSION

Because the proposed application of the Code Case fulfills all NRC

< restrictions. we find that the use of PVRC damping values for piping system j re-analysis at the Vermont Yankee Nuclear Power Station is acceptable.

a 1

i Principal Contributor: H Shaw l Dated: Juric 13, .1986  :

I 4 .

I I

i I

1 1

i 4

I 1

!