ML20149E508
| ML20149E508 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 01/08/1988 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| NUDOCS 8801130369 | |
| Download: ML20149E508 (6) | |
Text
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TENNESSEE VALLEY AUTHORITY CH ATTANOOG A, TENNESSEE 374o1 SN 157B Lookout Place JAN 0819BB U.S. Nuclear Regulatory Commission ATTN:
Document Control Desk Washington, D.C.
20555 Gentlemen:
In the Matter of
)
Docket Nos. 50-327 Tennessee Valley Authority
)
50-328 SEQUOYAH NUCLEAR PLANT (SQN) - ENHANCED CALCULATIONS FOR PLATFORM THERMAL LOADING CONDITIONS During the review of calculations related to thermal growth of platforms, NRC verbally requested that additional calculations be provided regarding the magnitude and nature of the thermal stresses for a representative structure.
The structure shown on 48N937-1 was selected as representative because, of the structures that have been evaluated, it is the most compir,x with regard to thermal loading and offers the oppearance that thermally induced stresses could be a concern.
It is a structure made up of two platforms at different elevations that are interconnected by column framing. The platform framing is composed of relatively small steel members varying in size from W8X20 to W12X36.
Corrective action identified by Significant Condition Report (SCR)
SCRSQNCEB86103 was perfotv.ed in January 1987 to evaluate platforms that contained members that appeared to be constructed in such a manner that thermal movement was constrained.
In that evaluation, certain connection modifications on the representative str.ucture were identified to release thermally constrained connection locations.
These modifications were constructed in June 1987.
To qualify the effects of thermally induced loading on the as-modified structure, a linear clast.ic analysis was completed (Calculation SCG1S81X7). The structure was nubjected to a temperature rise of 216 degrees Fahrenheit, which represents the difference between the operating temperature inside containment and the design basis accident temperature.
The resulting member stresses and connection reactions were reviewed to determine the worst case locations. The magnitude of those thermal stresses is as shown on the enclosures. The maximum flexural 2
stress because of thermal is 15 kips per square inch (k/in ).
The critical connection locations for the thermal condition were determined to be at concrete expansion anchors.
The concrete anchor evaluations indicate that the anchors meet design criteria requirements.
8801130369 080108 PDR ADOCK 05000327
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. U.S. Nucicar Regulatory Commission Thermally induced stresses are generally secondary and self-limiting in nature; therefore, they are not additive to the other stresses in the structure. However, for comparative purposes, thermal stresses were added to the primary stresses such as deadioad, piping support reaction loads, and seismic inertia loads.
The results indicate that, at only one location shown in the enclosed attachment A, the combined maximum primary and secondary stresses would exceed the elastic yield stress of the
-material.
The magnitude of this combined stress is 43.75 k/in2 in minor axis bending and 1.87 k/in2 in major axis bending.
It is postulated that, since some local yielding at extreme corner fibers of the member flange would take place, some thermal stress relief would occur; and the net resulting primary stresses will be within elastic allowable criteria.
For this condition, the ability of the section to develop the plastic moment capacity was ensured because the member meets the compact shape criteria and the maximum unbraced length requirement.
f Similarly, the connections for the member were checked to ensure that the plastic section capacity could be developed if required.
In accordance with NRC's request, the extreme corner fiber strain for the I
combined primary and secondary stress was calculated to be 0.001585.
Yield strain for A36 steel is 0.00124 The ratio of the calculated strain to yield strain is 1.28.
Therefore, it is concluded that, based on the calculated maxim.na member stresses and relatively low ratio of calculated strain to yield strain, the demonstrated ability of the end connections of the critical member to i
resist forces created by the postulated thermally induced stresses, and the demonstrated ability of the member to develop full plastic capacity, 4
the representative structure is adequate to withstand thermally induced loads and stresses and will continue to perform its safety-related l
functions in the event of design basis occurrences.
If you have any questions, please telephone M. R. Harding at (615) 870-6422.
r Very truly yours, TENNESSEE Y AUTHORITY R. Gridley, D rector Nuclear Lice ing and i
Regulatory Affairs t
Enclosures i
l cc: see page 3 i
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. U.S. Nuclear Regulatory Commission sl14N 081988 Enclosures cc:
Mr. K. P. Barr, Acting Assistant Director for Inspection Programs TVA Projects Division Office of Special Projects 2
U.S. Nuclear Regulatory Commission Region II i
101 Marietta Street, NW, Suite 2900 l
Atlanta, Georgia 30323 l
Mr. G. G. Zech, Assistant Director for Projects Mail Stop 7E23 l
TVA Projects Division Office of Special Projects U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue Bethesda, Maryland 20814 Sequoyah Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379 i
O ENCLOSURES Attachment A - Stresses at PLAN-EL 705'-0" Attachment B - Stresses at PLAN-EL 711'-1" l
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