ML17252B625

Dresden Unit 2 Seismic Evaluation Effort and Analyses Recommendations

ML17252B625
Person / Time
Site:	Dresden
Issue date:	05/25/1979
From:	Stevenson J D Woodward-Clyde Consultants
To:	Jabbour K N Office of Nuclear Reactor Regulation
References
Download: ML17252B625 (9)

Text

{{#Wiki_filter:3645 Warrensvi I le Center Road Cleveland, Ohio 44122 216-991-8841 Woodward-Clyde Consultants May 25, 1979 Mr. K. N. Jabbour Division of Operating Reactors Mail Stop 542 Washington, D.C. 20555

Dear K:

As you requested during our site visit to Milstone in support of the Dresden #2 seismic evaluation effort, I recommend that EGG perform the analysis of three piping systems, recirculation, LPCI suction and seismic example problem #1 identified as being typical of the three methods used to seismically qualified Dresden 2 piping systems. Specifically, I recommend the following analyses be performed: A. Recirculation System 1. Analyze system using best estimate of support stiffness and analysis methods with seismic input from the J. Blume response spectral curves shown in Figure 1 assumed acting first in the nominal N-S and then in the E-W horizontal directions plus 2/3 this spectrum in the vertical direction. Moment resultants are to be combined.on both the SRSS and ABS bases. Resultant seismic stresses to be compared to J. Blume resultant seismic stresses at at least 3 common points. Seismic reaction forces in supports should also be determined and compared to J. Blume results if available. Stress intensification factors of NC 3600 should be used. This effort has essentially been already completed in the summary report by M. E. Nitzel except that the response spectra used as shown in Fig. 1 has been smoothed and ened somewhat from the original Blume curves shown in Fig. 2 and the response spectra has been normalized to a 0.2g ZPGA rather than O.lg QBE ZPGA which was used by Blume. The purpose of this analysis is to evaluate the adequacy and accuracy of the original Blume analysis which is also applicable to steam and feedwater systems. 2. Analyze recirculation system as in (1) above except assume supports are rigid and compare results with J. Blume. 3. Analyze recirculation system using best estimate of support stiffness and using current multi-degree of freedom model and modal analysis methods for the revised EDAC SSE consulting EngineJrQ. response spectral curves shown in Figures 3 and 4 and Environmental Scientists 7 Offices in Other Principal Cities Mr. K. N. Jabbour May 25, 1979 Page 2 Woodward*Clyde Consultants (with torsion-interpolated) for 3 percent damping assumed acting both in the nominal N-S and E-W horizontal directions plus 2/3 of Figure 3 spectrum in the vertical directions. Seismic moment resultants are to be combined on a SRSS basis. Total stresses in the piping system to be determined in accordance with Eq. 9 of NC 3600 for Condition D stress limits. Total reaction forces in the supports should also be determined. Resultant stress or load ratings in the pipe and supports should be compared with Condition D ASME code allowables. In the analysis the stresses and reaction loads induced by deadweight, pressure and seismic should be identified separately. B. LPCI Suction 1. Analyze the LPCI Suction system using seismic coefficient of 0.7g applied statically to the system in the horizontal plane perpendicular to the piping local longitudinal axis. Simultaneously apply a seismic coefficient of 0.067g to the system in the vertical direction. Determine resultant seismic stresses in piping using the stress intensification factors of NC 3600 plus seismic reactions in pipe supports. Assume all supports are rigid. 2. Analyze the LPCI suction system using best estimate of support stiffness and using* current multi-degree of freedom model and modal analysis methods for the revised EDAC SSE (0.2g ZPGA) response spectral curves shown in Figures 5 and 6 (with torsion-interpolated) for 3 percent damping assumed acting both in the nominal N-S and E-W horizontal directions plus 2/3 of the Figure 6 spectrum in the vertical direction. Seismic moment resultants to be combined on a SRSS basis. Total stresses in the piping system to be determined in accordance with Eq. 9 of NC 3600 for ASME Condition D stress limits. Total reaction forces in the supports should also be determined. Resultant stresses or load ratings in the pipe and supports should be compared with Condition D code allowables. In this analysis the stresses and reaction loads induced by deadweight, pressure and seismic should be identified separately. C. Seismic Test Example #1 1. Analyze system in test example 1 shown in Figure 7 attached assuming supports rigid and using current degree of freedom model and modal analysis methods for the revised EDAC SSE (0.2g ZPGA) response spectral curves shown in Fig. 6 (without torsion) for 2 percent damping assumed acting both in the normal N-S and E-W horizontal directions plus 2/3 of the Figure 6 spectrum in the vertical direction. Mr. K. N. Jabbour May 25, 1979 Page 3 Woodward*Clyde Consultants Seismic moment resultants to be combined on a SRSS basis. Seismic stresses .in the piping system to be determined in accordance with Eq. 9 of NC 3600 for Condition D stress limits. Seismic reaction forces in the supports should also be determined.

2. Repeat the analysis of (1) above assuming (a) vertical supports as not active (b) all supports have a stiffness equal to 10 times the bending stiffness of the pipe spaning between adjacent supports.

The analyses described herein will provide quantitative assessment of seismic design margins and thereby should support the qualitative judgement in Chapter 6 of the seismic design adequacy of the Dresden 2 Category I piping systems required for safe shutdown of the RCS and engineered safeguards. I will complete Chapter 6 of the Dresden report assuming that the results of the EGG piping analysis outlined herein will be available as an Appendix to the report which serves to further substanciate the condlusion reached in Chapter 6 that the seismic Category I piping are capable of withstanding SSE seismic loads plus other applicable loads using current analysis and evaluation methods without loss of safety function.

• Please advise if you require any clarification of my dations. Please also note by copy of this letter, I have transmitted this same information to Mr. Saffell of EGG in order to expedite this piping evaluation effort assuming you concur with my recommendation.

JDS/ijz Sincerely, ln. Stevenson General Manager cc: Mr. B. c. Saffell, Jr. 1179 Cresent Ave. Idaho Falls, Idaho 83401 H. Levine -NRC l l \ I I ! f 9 l j i I I 11

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