ML19323D328
| ML19323D328 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 04/08/1980 |
| From: | Eric Turner HOUSTON LIGHTING & POWER CO. |
| To: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| IEB-79-02, IEB-79-2, NUDOCS 8005210439 | |
| Download: ML19323D328 (6) | |
Text
NSIC 6MgM cz"ra^t r tzs Company a-sm ueso-e-m a.aoo s==.nxas nooumms-92ii April 8,1980 ST-HL-AE-438 SFN:
V-0540 Director, Region IV Nuclear Regulatory Comissior.
611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76102
Dear Sir:
South Texas Project Units 1 & 2 Docket Nos. STN 50-498, STN 50-499 Revised Response to IE Bulletin 79-02 Houston Lighting & Power Company is revising the response to Bulletin No. 79-02, Revision 1, which was sent to the NRC July 5, 1979.
Changes have been made in the responses to Items 1, 2 and 4 of the Bulletin.
Two minor design requirements in the response to Item 2 have been revised, while the other changes are clarifications of the original respor ses.
These changes and clarifications are consistent with the guidel'nes of the Bulletin.
Change bars have been added to the attached repo-t to identify those areas where revisions have been made.
In additian, the responses to Items 5 and 6 of Revision 2 of t"e Bulletin have bien added to the report.
If you have any questions, please contact Mr. S. S. Rodgeis at (713) 676-7953.
Very truly yoirs, (4
C E. A. Turner Vice Preside::t Power Plant Construction
& Technica? Services PLW/dlk Attachment 8005210
h @'s & W cmpany ST-HL-AE-438 Paga 2 cc:
D. G. Barker C. L. McNeese H. R. Dean R. L. Waldrop G. B. Painter A. J. Granger R. A. Frazar M. D. Schwarz (Baker & Botts)
R. Gordon Gooch (Baker & Botts)
J. R. Newman (Lowenstein, Newman, Reis, Axelrad & Toll)
Director, Office of Inspection & Enforcement Division of Reactor Construction Inspection Nuclear Regulatory Commission Washington, D. C.
20555 j
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Revised R sponse to NRC IE Bulletin 79-02 Rev. 2 Item 1.
The flexible behavior of a base plate causes the concrete expansion anchor bolt to experience a higher load than an externally applied tensile load.
HL&P procedure to assess the prying force is as follows:
a.
The prying force is calculated using the equation for A490 bolts given on page 4-81 of the AISC Manual of Steel Con-struction (Seventh Edition),
b.
The design prying force is determined by multiplying the above force by a factor of 1.5.
However, in no case is the prying force more than the externally applied load per bolt.
Item 2.
Only wedge and sleeve-type anchors are allowed to be used at the South Texas Project.
The minimum factor of safety used between the bolt design load and the bolt ultimate capacity from static load tests is 4.0.
This is consistent with the requirement of the IE Bulletin 79-02 Rev. 2.
l The effects of shear-tension interaction minimum, edge distance and bolt spacing are taken into account in the following manner:
a.
Shear-Tension Interaction Allowable working loads for combined tension and shear are checked to satisfy the following interaction equation:
T 3
applied
+
aoplied 1.0 g
T S
allowable allowable Where T and S are allowable pure tensile and shear forces,aQgg9vely. aggag$t the allowable working loads are not increased for accidental or severe environmental conditions.
b.
Edge Distance and Bolt Spacing The minimum concrete edge distance (i.e., the distance to the edge of the concrete from the center-line of the expansion bolt) is determined from the following considerations:
i) Tension:
f Edge distance =
2D ut 56 (f' P2 c
ii)
Shear:
Edge distance =
0 fut 7.5 (f' b c
Where:
0 = nominal diameter of anchor, in.
f' c specified compressive strength of concrete, psi.
f
= minimum specified tensile st.ength of anchor ut steel, psi.
If the bolt is under combined shear and tension, the higher of the above two values governs. The expressions of edge distances are obtained from Section 8.7.1.1 of Reference 1.
AHow e Des more, the minimum e$ge bskan!n Load When the ratio is equal to 10.0 or ace is at least 5.0 times the bolt diameter.
The minimum spacing between two expansion bolts is normally twice the embedment length. Minimum embedment length is 4.5 times the bolt diameter.
Under such conditions no reduction in ultimate bolt strength is deemed necessary.
Bolt strength is reduced on a straight-line basis down to 50% at a spacing equal to the embedment length (see Ref. 2).
In no case will spacing less than the embedment depth be allowed.
Item 3.
Safety-related piping systems are analyzed for dynamic loads such as seismic loadings, water hammer, steam hammer, safety relief valve discharge, etc.
Equivalent stati.c pipe support design loads are then determined for the above loads as applicable. The anchor bolts are thus designed to withstand these loads.
A test program for wedge and sleeve type anchor bolts (Ref. 3) has concluded that the dynamic load capacities of such expansion bolts are about the same as their corresponding static load capacities.
However, as an added measure of conservatism, on safety-related piping systems the factor of safety of 4.0 given in response to Question No. 2 above is increased to 5.0 to account for the effect of cyclic loads.
Item 4.
On STPEGS, no expansion anchor bolts have been installed on safety-related piping systems at the present time.
A technical reference document (Reference 4) has been established to consider various design requirements.
Preloading due to the presence of cyclic loads is not an essential requirement.
No adddi-tional torque / tension has to be provided other than that which is required for setting the bolt.
Each bolt will have a special marking which specifies its desian size and type. This special marking is permanently stamped on the top end of the bolt so that it can be read when the bolt is in place.
Note that no shell type anchor belts are used on STPEGS.
A v Ttic Testing Program was conducted in the field to determine the torque values required to verify manufacturer's predetermined
' cad "apacities.
ne +.istallation of expansion anchors for safety-related piping sye ems will not commence until the QC Program is established.
l Item 5.
No expansion anchors bolts will be used in concrete block (masonry) walls for attaching pipe supports in Seismic Category I systems.
Item 6.
No pipe supports with expansion anchor bolts will use structural steel shapes in lieu of base plates for anchoring.
1 -
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References :
1.
Proposed Addition to:
Code Requirements for Nuclear Safety-Related Concrete Structures (ACI 349-76), Reported by ACI Committee 349; as published in ACI Journal, August 1978.
2.
Standard for Testing Anchors in Concrete., Expansion Anchor Manufacturers Institute, Inc., New York.
3.
Drilled-In Expansion Bolts Under Static And Alternating Load, a report prepared for Hanford Engineering Development Laboratory, Richland, Washington by Bechtel Power Corporation, San Francisco, California, Report No. BR-5853-C-4, January 1975.
4.
Design, Installation, Testing & Inspection of Concrete Expansion Anchor Bolts, Technical Reference Document No. 5A0195Q010, Brown & Root, Inc.
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