ML20137P592
| ML20137P592 | |
| Person / Time | |
|---|---|
| Site: | 05200003 |
| Issue date: | 04/03/1997 |
| From: | Bagchi G NRC (Affiliation Not Assigned) |
| To: | Quay T NRC (Affiliation Not Assigned) |
| References | |
| NUDOCS 9704090278 | |
| Download: ML20137P592 (3) | |
Text
. _ _
April 3, 1997 MEMORANDUM T0:
Theodore R. Quay, Director
[3'#d Standardization Project Directorate Division of Reactor Program Management O PJ T T M O T O FROM:
Goutam Bagchi, Chief Civil Engineering and Geosciences Branch Division of Engineering
SUBJECT:
INCLUSION OF LIVE LOAD AND DESIGN CHANGES DUE TO 72 HOUR ACTIONS IN THE REVISED SEISMIC MODEL 0F THE AP600 NUCLEAR ISLAND STRUCTURES Westinghouse's response to the staff's concerns related to the post 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> action requirements and the inclusion of live load masses is not acceptable. We believe that it is necessary for us to develop a staff position on these two issues. Our position is attached.
Please forward the attached staff position to Westinghouse by a letter from Mr. T. Martin.
If you have any questions please contact Thomas Cheng of my staff on (301) 415-2270.
Attachment:
As stated cc:
B. W. Sheron Distribution:
G. C. Lair.as ECGB R/F D. Jackson Central: Files:1 -
PDR CONTACT:
T. Cheng, ECGB/DE 415-2770 DISK / DOCUMENT NAME: G:\\CHENG\\LIVELOAD.S of.,.'cdi' ' *
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%,,, g April 3,1997 MENORANDUM T0:
Theodore R. Quay, Director Standardization Project Directorate 4
Division of Reactor Progra anage ent FROM:
Goutam Bagchi, Chief Civil Engineering Geos ences Branch Division of EnpMeering
SUBJECT:
INCLUSION OF LIVE LOAD AND DESIGN CHANGES DUE TO 72 HOUR ACTIONS IN THE REVISED SEISMIC MODEL OF THE AP600 NUCLEAR ISLAND STRUCTURES Westinghouse's response to the staff's concerns related to the post 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> action requirements and the inclusion of live load masses is not acceptable. We believe that it is necessary for us to develop a staff position on these two issues. Our position is attached.
Please forward the attached staff position to Westinghouse by a letter from Mr. T. Martin.
If you have any questions please contact Thomas Cheng of my staff on (301) 415-2770.
Attachment:
As stated cc:
B. W. Sheron G. C. Lainas D. Jackson CONTACT:
T. Cheng, ECGB/DE 415-2770 i
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r, The Staff Position on the Live Load and Desian Chanaes of the Shield Buildina Roof Structures Due to j
the Post 72 Hours Actions The seismic design modei for the complete nuclear island structures, the internals and supported. systems for the AP600 never included any provision of live loads. The staff raised concern regarding the lack of consideration of any live load masses in the seismic model of the nuclear island structures in the draft safety evaluation report (DSER) and in a series of seismic design review meetings that were conducted between NRC and Westinghouse.
In each of these review meetings, the staff repeatedly raised its concern about the lack 2
of live load masses in the seismic analyses and stated that the change of mass i
properties due to the inclusion of live load masses could significantly affect the seismic responses of the nuclear island. On this basis, the staff concludes that the elimination of live load masses from the seismic model is not acceptable. However, no information was provided either in the latest revision (Revision 11) of the SSAR or for the staff review.
Recently, as a result of the post 72-hours-action requirements cited in SECY-96-128, Westinghouse revised the shield building roof structure by:
(1) in-creasing the mar.imum water level from Elevation 298 feet to 303 feet, (2) raising the top of the tank by one foot, (3) reducing the thickness of the tank roof from 24 in:hes to 15 inches, (4) decreasing the thickness of the inner tank wall from 24 inches to 18 inches, and (5) adding a 9-inch deep fire water tank composed by two stainless steel plates underneath the PCS tank roof.
Based on its estimation that the affected structural mass decreases by 2 percent in the horizontal direction and increases by 5 percent in the vertical direction, Westinghouse concludes that these changes are small enough to have only a negligible effect on the global seismic analyses of the nuclear i
island structures, and will only have a small effect on the structural design of the shield building roof.
The staff does not concur with the conclusion drawn by Westinghouse, because the global effect of the design change must be evaluated and demonstrate its insignificance through a comparison of in-structure response spectra and design of critical sections.
From the discussion above, it is the staff's position that Westinghouse should:
[
1.
Revise the existing 3D lumped-mass stick seismic model to include the mass effects due to the live loads and the increase of water inventory in the PCS tank at each mass degree of freedom.
2.
Incorporate the changes of the PCS tank structure design and revise j
stiffness properties of the shield building roof structure stick model.
3.
For each of the design site conditions, develop in-structure response spectrum envelopes, and determine the impact of the design changes and 4
live loads to the. seismic responses and the design of the nuclear island.
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