ML20072A032
| ML20072A032 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 06/03/1983 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| REF-SSINS-6820 IEB-80-11, NUDOCS 8306090331 | |
| Download: ML20072A032 (3) | |
Text
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TENNESSEE VALLEY AUTHORITY CH ATTANOOGA. TENNESSEE 37401 400 Chestnut Street Tower II June 3, 1983 Mr. Harold R. Denton, Director-Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission
-Washington, D.C. 20555 Dea: Mr. Denton:
In the Matter of the
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Docket Nos. 50-259 Tennessee Valley Authority
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50-260 50-296 By my letter to you dated April 22, 1983 we submitted a response to NRC request for additional information regardin6 IE Bulletin 80-11 masonry wall investigations for Browns Ferry Nuclear Plant. In that letter we committed to submit the results of a wall displacement analysis by June 30, 1983 Enclosed is that response.
Very truly yours, TENNESSEE VALLEY AUTHORITY L.
. Mills, Ma' age Nuclear Licensing Subscribgd g sworn to efore me this 0 - - day of 1983 Gadat M #A22 Notary Public g
My Commission Expires /"
Enclosure cc (Enclosure):
U.S. Nuclear Regulatory Commission Region II ATTN: James P. O'Reilly, Regional Administrator 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30303 Mr. R. J. Clark Browns Ferry Project Manager U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue Bethesda, Maryland 20814 9
gh 8306090331 830603 PDR ADOCK 05000259 C
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An Equal Opportunity Employer
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ENCLOSURE U
l IE BULLETIN 80-11, MASONRY WALL DESIGN WALL DISPLACEMENT ANALYSIS BROWNS FERRY NUCLEA5 PLANT Item 8 According to' Reference 5, page 4,.the differential floor displacement was found to be less than 0.01 ft for a'11 floor elevations below the operating floor. Provide the criteria by which this displacement was judged to be insignificant, and justify.
Response
The effects of differential floor displacement on masonry walls were evaluated by performing a finite element analysis of the wall judged to be the most severely affected by building displacement using the computer program SUPERB developed by Structural Dynamics Research Corporaticn.
Masonry wall 71B was selected for the analysis because it has a.
significantly greater ratio of width to height than any other masonry wall and it is located at an elevation in the reactor building having a horizontal displacement due to earthquake per unit height as great Wall 71B is an as any other level where masonry walls are located.
unreinforced-mortared wall 25-feet high and extends 22 feet 7 inches in the north-south direction. There is a 7-foot-6-inch-high opening at the base of the wall beginning i foot 4 inches from the northern The wall is adjoined edge and extending 6 feet 4 inches to the south.
on its north and south ends by the concrete building structure and is restrained at the top by steel angles attached to the bottom of the floor above on the east and west sides of the wall. (Please refer to Appendix A enclosed in the letter from L. M. Mills to James P.
O'Reilly dated October 1,1981, for the location and description of all masonry walls that are near safety-related systems.)
Since Design Criteria BFN-50-D709 allows the same stresses for the operating basis earthquake and the design basis earthquake in unreinforced masonry walls, the wall was analyzed for the effects of building displacement due to the controlling design basis earthquake.
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The differential displacements for which wall 71B was analyzed were determinsd by deubling the building displacements for an operating basis earthquake obtained from the seismic report prepared by John A.
Blume and Associates and do not exceed 0.0026 foot. The stresses due to displacement in the east-west direction were found to be low and, when combined with'other stresses caused by the design basts earthquake, did not cause allowable stresses to be exceeded.
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l Two conditions of end restraint were investigated when avarining the effects of north-south building ' displacement. First, the top of the wall was assumed to be bonded to the floor above while small gaps exist between both sides and the adjacent building structure.
Secondly, the concrete building structure was assumed to be in direct contact with the wall and thus was loading the block wall in the directica of the building displacement while no bond was assumed to exist between the top of the wall and the floor above. For this i.
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2' condition a uniform horizontal load resulting in the design displacement was applied along one side of the wall. The bottom of the wall was assumed to be bonded to the floor below for both conditions.
The shear stress in the mortar was found to be less than the allowable 2
of 40 lb/in.when the wall was subject to,the north-south displacement. The normal stresses in the mortar were generally found to be within allowable limits for this loading condition. However, in limite d areas the tensile stresses in the mortar exceed the 10 j
allowable.
The regions of tensile stress exceeding 10 lb/in lb/in2 are limited to the vicinity of the opening and in the lower southern corner of the wall and have a total area never exceeding 8 percent of the area of the wall. Even chough the allowable tensile stress is exceeded in these regions and cracking can occur, the wall is in no danger of collapsing because of the nature of the loading.
Since the masonry walls are not needed by the building structure to resist seismic forces, the maximum building displacements wi)1 not be ef fected by their performance. Since the masonry walls will be distorted only a set amount, they will not collapse due to this distortion regardless of the development of cracks.
It should also be noted that wall 71B, as wis11 as all other masonry walls which have support conditions that could cause in plane distortion of the walls due to differential buildicg displacement and whose failure could effect safety-related features, are to be restrained by steel members with spacings not exceeding 4 feet because of loading conditions defined in design criteria BFN-50-D709 R2.
In summary, TVA's investigation has determined that the masonry walls will maintain their stability (will remain standing) when subjected to the maximwn differential building displacement and other loads caused by the design basis earthquake.
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