ML20081M873

Requests NRC Review & Approval of Three Alternative Seismic Analysis Methodologies Described in Attachment

ML20081M873
Person / Time
Site:	Mcguire, Catawba, McGuire
Issue date:	03/16/1995
From:	Tuckman M DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9504030115
Download: ML20081M873 (6)

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.F% > ;~f I Ddel%werCompany . I M S Dxxw P.O. Box 1006 Senior VicePresident .

Owlane,NC2820M006 NuclearGeneration

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March 16,1995 -

L .U. S. Nuclear Regulatory Commission L . Attention: Document Control Desk -

Washington, DC '20555

Subject:

Catawba Nuclear Station, Units 1 & 2, Docket Nos. 50-413'and -414 McGuire Nuclear Station, Units 1 and 2, Docket Nos. 50 369 and-370 Request for Approval of Seismic Analysis Methodology The existing steam generators (S/G)'at Duke's Catawba Unit 1 and McGuire -

Units 1 and 2 will be replaced during scheduled outages beginning in June 1996. As a part of the engineering evaluations performed in support of the'.

S/G replacement activities, the seismic analysis of the main steam (SM) lines was reviewed. It was concluded that use of the previously approved seismic ;

analysis methodology would result in major hardware changeouts for existing pipe supports, significant radiation exposure to personnel, reduced access to critical components inside containment and substantial expenditures in -

resources with minimalincrease in plant safety.

The_ p,urpose of this letter is to request NRC review and approval of three alternative seismic' analysis methodologies as described in Attachment 1. It is requested that approval be provided by September 1,1995.

' Please contact R. O. Sharpe at (704) 382-0956 if you have any questions.

Very truly yours, wsrTC M. S. Tuckman n'40070 9504030115 950316 gDR ADOCK 05000369  !

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e [. [4 U. S. Nuclear Regulatory Commission March 16,1995 Page 2

- Attachments .

. xc: S. D. Ebneter Regional Administrator, Region II U. S. Nuclear Regulatory Commission 101 Marietta Street, NW, Suite 2900 Atlanta, GA 30323 R. J. Frudenburger Senior Resident Inspector Catawba Nuclear Station G. F. Maxwell

. Senior Resident Inspector McGuire Nuclear Station R.E. Martin Project Manager, ONRR V. Nerses Project Manager, ONRR

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-- Attachment 1"

.i k- Duke Power Company

• Steam Generator Replacement Project - l Main Steam Line Pining Seismic Analysis - 1

-Purpose- "

This attachment describes alternative seismic methodologies to be used to re-qualify the main steam (SM) piping. Requalification is required to account 1 for changes associated with the replacement steam generators. The new steam generators weigh approximately 20% more than the original steam i generators at operating conditions. Furthermore, the location of the center of gravity has moved up 10 5/8". i i

Current Pioine Analysis The current seismic analysis methodology for the main steam (SM) piping is described in Section 3.7 of the Catawba and McGuire Final Safety Analysis -

Reports. The SM piping is modeled by decoupling from the reactor coolant ,

loop (RCL) at the steam generator / SM connection. The modelincludes the i piping from the four steam generators to the turbine passing through the Reactor Interior Structure, floating penetrations, the Interior / Exterior  :

Doghouses, over the Main Steam Yard Supports and finally into the Turbine ,

Building. The pipelines from the four steam generators are included in a i

_ single model.

• The current seismic analysis considers inertial loads using modal _

superposition with response spectra loadings. Anchor motions are considered .

using psuedostatic loads. The combination ofinertia and anchor motions are used in the qualification of the piping, the development of support loads and other design checks. Response spectra at attachment points to the RCL and building structures are enveloped and used to generate seismic forces, displacements and accelerations on the piping. Anchor motions at structural attachment locations are also calculated and input into the analysis. t For the analysis, modes are combined in accordance with RG 1.92.

Directional responses are combined by square root of the sum of the squares I (SRSS) of the individual responses - also in compliance with RG 1.92. j Critical damping values for the OBE and SSE earthquakes are 2%. Seismic  :

I anchor motions are statically applied at the steam generator / SM nozzles and support attachment points on the building structures. Development of l

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y these static cases are based on the following assumptions. Anchor motions

' for each structure move in phase.1 Adjacent structures move out of phase.

Load combinations between the inertia and seismic anchor motion cases are combined as described in Section 3.7.3.7 of the Catawba FSAR and Section 3.7.3.4 of the McGuire FSAR.

Proposed Analysis Methodologies As an alternative to the method described in Section 3.7.3.8 of the Catawba -

FSAL and in Section 3.7.3.6. of the McGuire FSAR, a coupled analysis or the independent support methodology may be used. A coupled methodology is a refined analysis which incorporates primary structures, typically the building -

structure but may also include the RCL, with the secondary system, i.e.

piping. Two different coupling methodologies may be used in the analysis of piping systems.

Coupled Analysis of RCL Piping This seismic methodology extends the primary RCL model which includes the building structure to include additional piping. Model boundaries are extended to other subsystems through the use of decoupling, overlapping,-

isolation or the use ofintermediate anchors. Modal combinations, damping and codirectional combinations associated with the RCL model (described in References 1,2, and 3) are applied to the added piping.

Coupled Analysis of Piping Using CREST Methodology This seismic methodology considers the coupling of two structural systems: a primary structure, e.g. that which includes the Reactor Interior Structure and the RCL piping / components and a secondary structure, e.g. that which includes the Main Steam piping with correlated building structures. The seismic analysis is prformed using the CREST computer program which was developed at the Cet er for Nuclear Power Plant Structures, Equipment and Piping, North Carolina State University. This program performs the seismic analysis of a secondary system by coupling with the primary system. In the formulation of the program, the coupled primary-secondary system's equation of motion is linearly transformed using the mode shapes of the uncoupled systems. This transformation is exact. The coupled frequencies, damping ratios and mode shapes are evaluated using a modal synthesis procedure. A response spectrum analysis of the coupled systems is performed. A detailed description of the CREST methodology is given in References 4,5, and 6, 2

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The basic formulation for the modal coupled response, the development of the coupled modal properties, and the calculation of the coupled response is provided in Reference 4, Articles 6.1 - 6.5. See also Section 4 of Reference 5.

Modal combinations are performed using a double sum methodology as given in Chapter 5, Article 5.6 of Reference 4. Correlation coefficents associated with modal combinations are provided in Reference 5. The effects of residual-

- rigid response are considered as described in Reference 6. The total seismic response is obtained by the SRSS of the X, Y and Z directional responses.

6 Independent Support Motion Methodology A piping subsystem which is supported in more than one building structure and / or is supported at varying elevations within a single structure may be

, analyzed using the independent support motion (ISM) methodology. Inertial response as well as relative anchor motion effects are combined to determine the total response of the piping. For the inertial response, the ISM methodology allows the specific input of response spectra at the support locations. Supports are classified into groups or levels based on structure and.

elevation. X, Y and Z direction spectra are correlated to each group and input in the analysis as applied loadings. For each direction, the response is calculated based on the absolute sum of the group responses and a SRSS modal combination method including missing mass effects. The total inertial response is determined by the SRSS of the directional responses. For the

- relative anchor motion effects, a static analysis is performed. The inertial and anchor motion responses are developed by the SRSS combination. This methodology conforms to that described in NUREG-1061 (Reference 7).

References

1. Letter from H. B. Tucker, Duke Power Company, to the NRC dated October 15,1992, Methodology for' Analysis of the Primary Coolant Loops for Steam Generator Replacement. >

2. Letter from D. L. Rehn, Duke Power Company, to the NRC dated November 13,1992, Methodology for Analysis of the Primary Coolant Loops for Steam Generator Replacement, Supplement 1.

3. Letter from D. L. Rehn, Duke Power Company, to the NRC dated February 3,1993, Response to NRC Request for AdditionalInformation.

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4. .Gupta, A. K., Response Spectrum Method, Blackwell,1990,- CRC Press, 1992; Chapter 5: Article 5.6; Chapter 6: Articles 6.1 - 6.5

, 5. Gupta, A. and Gupta, A. K.', Recent Improvements in the CREST-IRS ^

. Program, Center for Nuclear Power Plant Structures, Equipment and i Piping, December,1993; Sections 2,3 and 4.

6. Gupta, A. and Gupta, A. K., Coupled Analysis of Piping Systems Including the Effect of High Frequency Modes, Center for Nuclear Power Plant Structures, Equipment and Piping,1994.

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7. NUREG 1061, Volume 4, Report of the U. S. Nuclear Regulatory Commission Piping Review Committee, Evaluation of Other Dynamic Loads and Load Combinations, Section 2.4.1.

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