ML20137W423
| ML20137W423 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 01/24/1986 |
| From: | Gahan M BALTIMORE GAS & ELECTRIC CO. |
| To: | Varela A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| IEB-80-11, NUDOCS 8602200137 | |
| Download: ML20137W423 (3) | |
Text
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BALTIMORE GAS AND ELECTRIC CHARLES CENTER. P.O. BOX 1475 BALTIMORE. MARYLAND 21203 l
l January 24, 1986 Mr. Anthony A. Varela United States Nuclear Regulatory Commission Region 1 631 Park Avenue King of Prussia. PA 19406
SUBJECT:
Calvert Clif f s Nuclear Power Plant Units 1 and 2 FCR 80-1024: Masonry Walls NRC I&E Bulletin 80-11
Dear Mr. Varela:
During your recent on-site review of concrete masonry walls in connection with our response to NRC Bulletin 80-11. a cone rn was noted by your staff with regard to three walls located at el.ra t i o n 45'-O' in the auxiliary building. The walls in question surround stair AB-5 adjacent to the Unit I containment building,.ind are identified as walls "T",
"U" and "W".
l The concern stems from the apparent absence of steel dowels l
used to connect the top of the walls to the underside of the slab at l
clevation 69'-0".
Since the original evaluation of these walls was based on the lateral support provided by these dowels, an apparent inconsistency l
exists between the assumptions made for the evaluation of these walls and the actual fteld conditions.
This inconsistency resulted in an unresolved item at the exit meeting held on January 17, 1986.
i To formulate a comprehensive plan of action leading to the
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resolution of this concern, a detailed review of the boonrh ry rnnell' inna I
geomet ric propert ies, and assumptions made to perf orm the original evaluation of these walls, was undertaken.
Our review indicates the approach used in the evaluatlon, conservatively neglected the stiffening effect allorded by the steel l
framed concrete landings cormected to the walls at elevations $1'4".
57'-0" and 63'-4".
f l
9602200137 4
PDR A00CM 0 317 0
DR I
lb N
Page 2 Thus, the original evaluation considerably underestimated the capacity of the walls, since the boundary conditions assumed, yielded conservations above those outlined in our response of June 12, 1985.
i In light of the apparent margins available in the design of g
the walls in question, we do not believe that a safety implication _.
exists. However, in order to ettect a comprehensive approach to the
resolution of your question and document the satety margins we have l
previously outlined, the following options will be considered:
l 1.
Quantif y all available margins by reperf orming i
detailed analysis of the walls.
The analysis would consider plate action of the walls. the support afforded by the stair landings and the
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as-built condition of the walls.
l 2.
Restore the extreme conservations inherent in the original evaluation by providing lateral support at the top of the walls. This option would involve the addition of steel shapes at the top of the walls to transfer lateral loads to the concrete floor stab.
i i
3.
Depending on the accessibility of certain portions of the walls, a combination of options 1 and 2 will also be considered.
l Upon completion of this work, a report summartaing the options used and outlining the results will be transmitted for your review. This report should be completed by Aprt! 1, 1986.
We further reaffirm your conclusion at the Exit Hecting that this is not a generic Issue. Several reasons suppnrt this conclusions i
A.
The mirror-image wall in Unit 2. "EL" which i
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seen similar operating conditions, anpears to be in excellent shape.
i B.
Numerous walls viewed during the walkdowns
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typically show high quality workmanship.
C.
The walkdown survey package for Wall "T" wan the only one representing a concern.
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l' age 3 Should you have turther questions, please call me at (301) 234-5549 Very tiuly yours,
?
e Af i c h a e l
.I. Gahan. !!!.
I'. E.
Senior Engineer Nuclear Engineering Services Depa rt ment MJG/ps cc:
W.J.
Lippold R.F. Ash / File D.T. Ward L.E.
Satyards M. Nitzel, EG & G D.E.
Stewart
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