ML19345H165
| ML19345H165 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 04/24/1981 |
| From: | Delgeorge L COMMONWEALTH EDISON CO. |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8105010119 | |
| Download: ML19345H165 (9) | |
Text
t Commonwealth Edison One First Narnal Ptaza. Chicago. Illinois Address Reply to: Post Othee Box 767 Chicago, likr.ois 60690 April 24, 1981 j, r;.; sn (..
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Mr. A.
Schwencer, Chief
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Licensing Branch 2
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y4A h7 U.S. Nuclear Regulatory Commission Washington, DC 20555
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Subject:
LaSalle County Station Units 1 and 2 Seismic Category I Masonry Walls NRC Docket Nos. 50-373/374 Reference (1):
R. L. Tedesco letter to J. S. Abel aatea March 2, 1981
Dear Mr. Schwencer:
In response to the inquiry made in Reference (1) relative to the possible differences between the NRC Staff criteria for masonry walls and that used in the design of LaSalle County Station, the enclosea report is submitted for your information.
It should be clearly understood that the LaSalle County criteria satisfied all accepted masonry wall standards and results in a masonry wall design which will accommodate all applic&ble design basis loads.
The Staff's criterir. are admittedly more conservative than those employed in the LaSalle County acsign.
However, it is not clear whether the Staff's criteria - and the adaitional conservatism imposed by them - are Justified.
What is clear to this applicant is the fact that significant expenditures of engineering resources as well as money will be requireo to fully satisfy the Staff's criteria.
As is discussed in the enclosec report, a reassessment of the LaSalle County masonry wall design in light of the Staff criteria has not altered this applicant's conclusion that masonry wall re-inforcement is unnecessary.
We recognize that further aiscussion of the bases for this conclusion will be required in oraer to justify closure of the license condition on masonry walls discussed in Section 3.8.3 of the LaSalle County SER (NURES-0519).
Although this matter need not be finally resolved until the end of the first refueling outage on LaSalle County Unit 1, discussion with the Staff at your earliest convenience is requested, to assure adequate time for a thorough airing of the issue.
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. In the event you have any questions on the enclosed report, please direct them to this office.
We will await notification by you of a future meeting schedule if necessary.
Very truly yours, a
L. O. De1 George Nuclear Licensing Administrator Enclosure cc:
NRC Resident Inspector - LSCS 4
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e DRAFT RESPONSE TO NRC ON SAFETY RELATED CONCRETE MASONRY WALLS Commonwealth Edison Company has reviewed the, "SEB Interim Criteria for Safety Related Masonry Wall Evaluation," submitted by letter dated March 2, 1981.
The following is our assessment of the differences between our criteria, submitted to the NRC by letters dated July 8, 1980 and February 4, 1981, and the SEB Interim Criteria.
e 1.
General Requirements The materials, testing, analysis, design, construction and inspection of safety related concrete masonry walls for LaSalle County, Units 1 and 2, conform to NCMA-1974, which is generally in agreement with the Uniform Building Code-1979, with the exception of the allowable stresses for unreinforced masonry.
The NCMA allowable stresses for unreinforced masonry are higher than those referenced in UBC-1979.
2.
Loads and Load Combinations The loads and load combinations for the safety related concrete masonry walls are in agreement with the LaSalle County, Units 1 and 2, FSAR, and are also in agreement with the SEB Interim Criteria.
3.
Allowable Stresses The allowable stresses for unreinforced concrete masonry walls for LaSalle County, Units 1 and 2, are in conformance with NCMA-1974.
Exhibits 1 and 2, attached, summarize the allowable stresses utilized for LaSalle County, Units 1 and 2, and the 4
2 SEB allowable stresses.
a.
No overstress factor was used in the design of safety related concrete masonry walls for LaSalle County, Units 1 and 2 for
, loading combinations containing OBE seismic loads, which is in compliance with the SEB Criteria.
b.
The safety related concrete sonry walls for LaSalle County, Units 1 and 2, were designed using NCMA allowable stresses
.l corresponding to tWe specia$. inspection category.
Common-
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wealth Edison Company's QA/QC procedures for the construction
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of safety related concrete masonry walls substantiate com-pliance with the inspection requirements of the SEB Criteria.
c.
Approximately 90% of all safety related concrete masonry walls for LaSalle County, Units 1 and 2, have been designed to span horizontally, thereby precluding the use of tension perpendicular to the bed joint.
Approximately 10% of the safety related concrete masonry walls have been designed to span vertically.
The allowable tensile stresses perpen-dicular to the bed joint in these instances have been limited to 39 psi for the normal and OBE load combinations, and 65 psi for the SSE load combinations for solid masonry units.
Tension perpendicular to the bed joint, however, also occurs adjacent to openings or discontinuities in horizontally spanning walls.
This tension stress, likewise, has been limited to 39 psi and 65 psi.
d.
Commownealth Edison Company has utilized a load factor of 1.67 for load conditions which represent extreme environ-mental, abnormal, abnormal / severe environmental, and I
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abnormal / extreme environmental conditions.
4.
Design and Analvsis Considerations a.
The analysis of the safety related concrete masonry walls for LaSalle County, Units 1 and 2, has followed established principles cf engineering mechanics, and has taken into account sound engineering practices, b.
The assumptions and modeling techniques used in the assessment of the safety related concrete masonry walls l
considered proper boundary conditions, cracking of g
sections, if any, and the dynamic behavior of the masonry I
walls.
c.
The damping values for the safety related concrete masonry walls for LaSalle County, Units 1 and 2, are in conformance with Regulatory Guide 1.61.
d.
The seismic analysis for the safety related concrete masonry walls meets the requirements of the LaSalle County, Units 1 and 2, FSAR.
e.
The analysis of the safety related masonry walls considered both in-plane and out-of-plane loads.
f.
The average shear stress for the safety related concrete j
masonry walls due to interstory drif t is approximately 36 psi under SSE conditions.
The NCMA allowable shear stress for solid masonry units is 57 psi for SSE load combinations.
g.
All safety related concrete masonry wall construction has been completed for LaSalle County, Units 1 and 2.
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h.
There are no concrete masonry shear walls at LaSalle County, Units 1 and 2.
i.
All multigthe safety related concrete masonry walls meet the minimum UBC-1979 requirements.
j.
QA/QC information for the' safety related concrete masonry walls is available for NRC review at the LaSalle County site.
The QA/QC information which is available includes:
1.
Masonry Material Receiving Reports 2.
Masonry Material Storage Reports 3.
Masonry Work Check Lists 4.
Compression Strength Test Reports for Masonry Units j.
and Mortar i
k.
There are no safety related concrete masonry walls at i
LaSalle County, Units 1 and 2, which are sabject to accident pipe reaction (Y ),
et impingement (Y ), or r
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missile impact (Y,).
.l It is Commonwealth Edison Company 's opinion that the NCMA Code
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allowable stresses are appropriate for the safety related concrete masonry walls for LaSalle County, Units 1 and 2.
The NCMA Code was formulated by the concrete masonry industry, and is, therefore, specifically c concrete masonry code.
The Uniform Building Code and the Applied Technology Council Recommendations, on the other hand, are primarily seismic codes, and do not necessarily represent the concrets masonry industry.
It is Commonwealth Edison Company's judgement that the Uniform Building Code provisions for concrete masonry walls are primarily intended
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5 for walls which form an integral part of a structure's vertical and/or lateral load resisting system, such as bearing walls and shear walls.
The safety related concrete masonry walls at LaSalle County, Units 1 and 2, are considered to be non-load bearing, interior partition walls, and do ~not form an integral part of the building's lateral or vertical load resisting system.
The safety related concrete masonry walls at LaSalle County, Units 1 and 2, have been properly analyzed and designed for all attachment and inertial loadings.
It should also be emphasized that the attach-ments to safety related concrete masonry walls have been limited to very light items (typically less than 180 pounds per attachment),
such as small-bore. piping, instrumentation lines, conduit, and electrical junction boxes.
Also, the concrete shear wall system for the LaSalle County, Units 1 and 2 safety related structures is very stiff, resulting in average interstory displacements of approximately 0.02'.
This corresponds to an average shear strain in the concrete masonry walls due to interstory drift of approxi-mately 0.00016" per inch.
It is Commonwealth Edison Company's opinion that shear deformations of this magnitude will not impair the structural integrity of the safety related concrete masonry walls.
It is, therefore, Commonwealth Edison Company's judgement that the concrete masonry design criteria, submitted to the NRC by letters dated July 8, 1980 and February 4,1981, is appropriate for LaSalle County, Units 1 and 2, and no further modifications to the safety related concrete masonry walls are justified.
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EXHIBIT 1 ALLOWABLE STRESSES FOR CONCRETE MASONRY INSPECTED WORK?tANSIIIP UNREINFORCED MASONRY (Table Values based on NCMA-1974)
Allowable Stresses (PSI)
Normal / Severe Extreme Environmental Type of En i "tal Re a n
Type of Stress Load Combination
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,d Combina overs Type M Mortar Type M Mortar p,e or Comoression Flexural F, 0.3 f'm~
All 405 676 1.67 a.
b.
Axial F, EQ. 1 All EQ. 1 1.67 x EQ. 1 1.67 Bearing Pb I
a.
On full area 0.25 f'm All 337 563 1.67 1
I b.
On 1/3rd area or less 0.375 f'm All 506 845 1.67 Tension in Flexure a.
Normal to bed joints f p g None H
23 38 1.67 L
S& G 39 65 1.67 b.
Parallel to bad joints f H
46 77 1.67 t0 S&G 78 130 1.67 l
Shear All 34 57 1.67 i
Reinforcement Tension - Jt. Wire 0.5 Fy } 30,000 0.9 Fy = 58,500 1.95 (Fy = 65 kai)
= 30,000 EQ. 1 = 0.2 f'm [1 - (h/40t)*]
(a, 11 = Ilollow Units, G = Grouted Units, S = Solid Units
EXIIIBIT 2 ALLOWABLE STRESSES / STRAINS FOR CONCRETE MASONRY I
INSPECTED WORKMANSIIIP UNREINFORCED MASONRY (Table Values are based on SED Interim Criteria)
Allowable Stresses (PSI)
N rmal/ Severe Extreme Environmental Type of E"
"t Load Combination Type of Stress Unit,)
ad Co ination g
Type M Mortar Type M Mortar Overstress 2,500 psi Factor Used m
= 2,500 pai m
=
g g
Compression H
170 425 2.5 2.5 j38 S
5 Flexural and Axial F,and F, g
H 255 637 2.5 Bearing Under Concrete Loads S
262 655 2.5 G
337 842 2.5 l
f Tension in Flexure l.
Normal to Bed Joint F H
0 0
0 tl A
S 0
0 0
G 0
0 0
H 6
1.5 2.
Parallel to Bed Joint Ftll S
24 36 1.5 2
i G
50 75 1.5 Shear H
12 12 1.0 0
i Out-of-Plane Loads and In-Plane Loads G
25
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Reinforcement Plain 60 120 2.0 Bond Deformed 140 280 2.0 Grade 40 20,000 40,000 2.0 Tension Grade 60 24,000 48,000 2.0 Jt. Wire 30 000 0.9 Fy = 58,500 Compression 0.4 Fy 24,000 (a) 11 = llollow Units, G = Grouted Units, S = Solid Units
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