ML20132D897

Safety Evaluation Supporting Use of Pvrc Damping Values (ASME Code Case N-411) for Response Spectrum Seismic Piping Analyses

ML20132D897
Person / Time
Site:	Vermont Yankee
Issue date:	07/22/1985
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20132D893	List: ML20132D889 ML20132D897
References
NUDOCS 8508010512
Download: ML20132D897 (2)

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTORS REGULATION VERMONT YANKEE NUCLEAR POWER CORPORATION VERMONT YANKEE NUCLEAR POWER PLANT PIPING REPLACEMENT ANALYSES - MECHANICAL ASPECTS DOCKET NO. 50-271 1.0 Introduction By letters dated April 22, May 14, and July 10, 1985, Vermont Yankee Nuclear Power Corporation provided information describing the scope of the Recirculation System Pipe Replacement Program at Vennont Yankee and requesting approval fo the Pressure Vessel Research Comittee (PVRC) recomended damping valves (ASME Code Case N-411) for response spectrum seismic piping analyses of the Recirculation and portions of the Residual Heat Removal (RHR) Systems at the plant. The staff review and evaluation of the mechanical aspects of the above stated submittals follows.

2.0 Evaluation Code Case N-411. " Alternative Damping Values for Seismic Analysis of Piping Section III, Division 1, Class 1, 2 and 3 Construction" is a conditionally acceptable Code Case and is approved by the staff for specific plant applications pending revision of Regulatory Guide 1.61. Utilities wishing to use this Code Case shall submit in their request the following information or comitments:

(a) Comit to use the case for piping systems analyzed by response spectrum methods and not those using time-history analysis methods.

(b) Indicate if the case is to be used for new analyses or for reconciliation work and for support optimization.

(c) Due to the increased flexibility of the system, comit to check all system predicted maximum displacements for adequate clearance with adjacent structures, components and equipment, and that the mounted j equipment can withstand the increased motion.

(d) When the alternate damping criteria of this Code Case are used, they l will be used in their entirety in a given analysis and shall not be a mixture of Regulatory Guide 1.61 criteria and the alternate criteria of this Code Case.

1 The licensee in the abov; eferenced letters has stated that the Recirculation and porte ...i of the RHR Systems will be analyzed by response spectrum methods. Therefore, item (a) above is satisfied. The licensee 8508010512 850722 PDR ADOCK 05000271 P PDR

has stated the analyses perfonned are new (for the replacment piping) and, therefore, item (b) is satisfied. In the above referenced letters the licensee has stated that systems will be free of interferences to restrict free motion during a seismic event and that acceptance criteria have been developed and implemented to ensure that adequate clearance exists to allow for all piping replacements and that mounted equipment can withstand the increased motion that would be present with a more flexible piping system.

Therefore, we find that item (c) has been satisfied. The licensee has stated that PVRC damping would be used for the replacement program piping system analyses and, therefore, item (d) above is satisfied. Based on the previous discussion, we find the use of PVRC damping (ASME Code Case N-411) is acceptable for the Recirculation and portions of RHR Systems. Further, the licensee's use of ASME Code Case N-411 should be documented in a future

, Amendment to the FSAR.

In addition the licensee has stated that for the replacement piping system analyses, the following will be utilized:

(a) the B 31.1 Power Piping Code which was also used for the original piping system analyses.

(b) the replacement system analyses will be performed with a three directional earthquake and a cutoff frequency of 33 Hz as compared to the original analyses which used a two directional earthquake and a cutoff frequency of 20 Hz.

The use of the Power Piping Code is consistent with the original design criteria for the plant and is thus acceptable. The use of the three dimensional earthquake and the 33 Hz cutoff frequency is consistent with design methodology being accepted by the staff for plants currently undergoing licensing review and is thus acceptable.

3.0 Conclusion The staff has completed the mechanical engineering aspects of the Vermont Yankee Recirculation System Pipe Replacement Program and find the program as described by the licensee is acceptable.

Principal Contributor: R. Kirkwood Dated: July 22, 1985 L