ML18058B964
| ML18058B964 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 07/20/1992 |
| From: | Zeringue O TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| TAC-M80618, TAC-M80619, TAC-M80620, NUDOCS 9207240138 | |
| Download: ML18058B964 (5) | |
Text
.UID Tennessee Valley Authority, Post Office Box 2000, Decatur, "Alabama 35609
- 0. J. "Ike" Zeringue Vice President, Browns Ferry Operations JUL 2 0 1992 U.S. Nuclear Regulatory Commission ATTN:
Document Control Desk Washington, D.C.
20555 Gentlemen:
In the Matter of Tennessee Valley Authority
)
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Docket Nos. 50-259 50-260 50-296 BROWNS FERRY NUCLEAR PLANT (BFN) - RESOLUTION OF THE THERMAL GROWTH ISSUE (TAC NOS. M80618, M80619, M80620)
Reference:
NRC letter dated May 12, 1992, Summary of the April 30, 1992 Meeting with the Tennessee Valley Authority Regarding Thermal Growth of Steel Structures As documented in the referenced letter, TVA and NRC met to discuss the methodology used to evaluate the effects of thermal growth on structural steel configurations at BFN.
In response to the verbal agreements reached during that meeting, Enclosure 1 to this letter provides the results of TVA's previous analysis of thermal loads on structural steel configurations and its plan for developing the additional analyses.
In addition, a discussion of the referenced meeting notes is provided.
A summary list of commitments contained in this letter is provided as. If you have any questions, please telephone R. R. Baron, Manager of Site Licensing, at (205) 729-7566.
Sincerely, Enclosures cc:
See page 2
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2 U.S. Nuclear Regulatory Commission JUL 2 0 1992 Enclosures cc (Enclosures):
NRC Resident Inspector Browns Ferry Nuclear Plant Route 12, Box 637 Athens, Alabama 35611 Mr. Thierry M. Ross, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. B. A. Wilson, Project Chief U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323
ENCLOSURE 1 BROWNS FERRY NUCLEAR PLANT (BFN)
RESOLUTION OF THE THERMAL GROWTH ISSUE PLANS FOR RESOLUTION OF THE THERMAL GROWTH ISSUE In order to address the thermal growth issue for Unit 2 Cycle 6 restart, approximately 300 structural configurations were reviewed.
Approximately 230 were evaluated and determined to remain elastic.
The remaining structural configurations exhibited some degree of thermal restraint and required further evaluation.
The approximately 70 remaining structural configurations were categorized into six groups.
This grouping was based upon the configurations of the structures.
The worst cases from each of these groups was identified based upon the highest thermally induced growth and stresses.
The critical elements were evaluated for member behavior, welded connections, and anchorages.
Of the six groups evaluated, two remained within elastic limit, two groups required modifications (resulted in approximately 60 modifications), and two groups went beyond the elastic limit.
Approximately 20 structural configurations were contained in the last two groups.
As part of the April 30, 1992 meeting, TVA verbally committed to provide an explanation, or make the information available, of why the two cases it selected for analysis were the most limiting of the approximately 20 structural configurations that behaved in a non-linear fashion.
A summary of the approximately 20 structural configurations will be tabulated.
This tabulation will describe the critical parameters: unbraced length, width to thickness ratio, depth to thickness ratio, maximum stresses or strains for linear and nonlinear analyses and maximum deflections for linear and nonlinear analyses (including appropriate dead weight loadings).
TVA will also perform ANSYS linear analyses from the approximately 20 nonlinear structural configurations that exhibit the highest level of thermally induced stress.
A comparison between the results of the two analyses and an evaluation of the acceptability of the nonlinear analysis results will be prepared.
This summary report will be submitted to NRC and the supporting calculations made available for NRC review at TVA's Rockville office by September 30, 1992.
ENCLOSURE 1 BROWNS FERRY NUCLEAR PLANT RESOLUTION OF THE THERMAL GROWTH ISSUE (CONTINUED)
Page 2 of 2 TVA continues to pay close attention to lateral deflections of structural configurations and weld behavior.
The behavior of structural steel inside the drywell was also discussed during the meeting.
In the NRC's meeting notes, it states:
"In this meeting, TVA stated that structural steel within the drywell and torus were able to expand without restraint."
Thermal growth and thermal loads were not considered as an explicit load case as part of the original load cases for the drywell platform steel.
Thermal growth was considered during the development of the drywell platform steel as evident by the outboard beam seated connections for the radial beams, which rest on lubrite sliding plates.
During the Unit 2 restart effort, a sample of the drywell platforms, including the radial beams, were re-analyzed and thermal growth was considered.
In addition, a study of the thermal loads on the radial beams due to the thermal expansion of the tangential diaphragm beams was also performed.
These studies were reviewed by NRC and supported the closure of the thermal growth issue for Unit 2 restart.
Consequently, it was concluded that the drywell was thermally unrestrained.
TVA will:
ENCLOSURE 2 BROWNS FERRY NUCLEAR PLANT (BFN)
SUMMARY
OF COMMITMENTS TVA will prepare a summary of the calculations used to address the thermal growth issue and will also perform linear analyses for those structural configur~tions that exhibit the highest level of thermally induced stress.
A summary report will be submitted to NRC and the supporting calculations made available for NRC review at TVA's Rockville office by September 30, 1992.