ML20092B763
| ML20092B763 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 01/30/1992 |
| From: | Mcmeekin T DUKE POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-88-011, IEB-88-11, NUDOCS 9202110121 | |
| Download: ML20092B763 (7) | |
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Mirnetue, NC2bOTMMS (104)S75,4by914e DUKEPOWER January 30, 1992 U. S. Nuclear Regulatory Com^1ssion ATTN: Document Control Desk Washington, D. C.
20555 Subject McGuire Nuclear Station, Units 1 and 2 Docket Nos. 50-369 and 50-370 NRC Bulletin 88-11 Pressurizer Surge Line Thermal Stratification Dear Sir;
-By a letter dated August 1, 1991, the NRC issued a Safety Evaluation Report:(SER) on the Westinghouse Owners Group (WOG)
Pressurizer Surge line Thermal Stratification Generic Detailed Analysis (WCAP-12639)..The SER advised us that the Woo program results could be used to satisfy items 1.c.and 1.d of the bulletin for McGuire and Catawba Nuclear. Stations, f
provided that plant specific' applicability is demonstrated and additional evaluation requirements as specified within-the SER are performed. -Your August-1, 1991 letter also requested that we-submit the results within-30 days-of completing-the analysis.
The analysis was completed on December 31, 1991, accordingly i
please find attached a. summary of the results of our analyses i
for McGuire-Nuclear Station (attachment 1).
Briefly,-the i
results'of the analyses confirm the adequacy of the existing
-i designs for McGuire.
In addition, Pipe support drawings affected by the-stratification analysis have been revised and issued for McGuire.
Turther, lplease be advised-that all actions requested by
-Bulletin 88-11-.of licensees:of operating-PWRs (Items--1.a through 1.d) have been completed for the McGuire-Nuclear 1
Stations.
D1 tails'of the inspections, analysis and i
. evaluations performed in support of responding to this bulletin are available for inspections.
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4 Document Control Desk i
January 30, 1991 page 2 If you have any questions regarding the information provided in response to Bulletin 88-11, please contact Paul Guill at (704) 075-4002.
i I dociare under penalty of perjury that the statements set forth heroin are true and correct to the boat of my knowledge.
Ver' cruly yours, f'
I Tod C. McMookin, Vico President xc:
S. D. Ebneter Regional Administrator, Rogion II P. K.
VanDooran Senior Resident Inspector, McGuiro T. A. Reed, Project Manager ONRR l
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Document control Doak January 30, 1992 page 3 bxc R. O. Sharpo K. P. Mullen L. J. Kunka R. L. Morgan, Jr. (DE)
W. H. Taylor (DE)
R. E. Hall (DE)
P. R. Herran R. J. Deese T. D. Curtis C. R. Lewis (CNS)
R. C. Futrell (CNS)
M. E. Patrick (ONS)
W. M. Sample R.
L._ Gill, Jr.
H. A. Froebo (group file 815.02 (bulletin 88-11))
Master File 1.1.3 MNS File 815.02 (Du110 tin 88-11)
Coporate Records l
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ATTACHMENT 1
DUKE POWER COMPANY MCGUIRE NUCLEAR STATION
RESPONSE
TO BULLETIN 88-11 PRESSURIZER SURGE LINE l
THERMAL STRATIFICATION All analyses and evaluations required for NRC Bulletin 88-11, Pressurizer Surge Line Thermal Stratification, are complete.
Results of the analyses confirm the adequacy of the existing designs.
Pipe support drawings affected by the stratification analysis have been revised and issued.
A summary of the actions taken for final closure of. NRC Bulletin 88-11 for McGuire Nuclear Station follow.
The summary is presented in four parts:
Background, SER Applicability Requirements, SER Plant Specific Evaluations, and Additional Evaluations.
B a c k cy r o u n ct NRC Bulletin 88-11 required utilities to take action to confirm the structural adequacy of the pressurizer surge line considering the effects of thermal stratification and thermal striping.
Generic tasks required by NRC Bulletin 88-11 were performed under the auspices of the Westinghouse owners Group.
The results of the Westinghouse Owners Group program were summarized in WCAP 12639, "WOG Pressurizer Surge Line Thermal Stratification Generic Detailed Analysis."
The NRC transmitted the staff's SER on the WCAP 12639 with a letter to M.S. Tuckman dated August 1, 1991.
The SER stated that for McGuire Units 1~& 2, "the WOG generic detailed analysis results can be used to satisfy the requirements of NRC Bulletin 88-11, Actions-1.c and 1.d, provided that plant specific applicability is demonstrated and additional evaluations which were not included as part of the WOG program are performed.
Applicability requirem6nts include:
Review of operatirg records to ensure that system delta-T limits assumed in the analysis were not exceeded Verification of operational methods to ensure that they-are consistent with the methods assumed in the analysis.
Limits on system delta-T for future operation are recommended.
Verification of applicability of seismic OBE bsnding moments used in tho' fatigue analysis and combined deadweight and OBE moments at the hot leg nozzle.
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t Additional plant specific evaluations to be performed include Evaluation of adequacy of pipe support [s for) loads and displacements.
Evaluation of effects of stratification on stress and fatigue at integrel welded attachments (lugs, plates, etc.)
Evaluation of effects of stratification on stress and fatigue of the pressurizer nozzle."
Applicability Re cru i r e mo n t es Requirement 1.
Review operating records to ensure that system delta-T limits assumed in the analysis were not exceeded.
The McGuire operating records were reviewed.
No occurrences were found of system delta-T exceeding 3200F; or, of fill and vent delta-T greater than 1500F.
The system delta-T limits assumed in the WOG generic analysis are applicable for past McGuire operation.
Requirement 2.
Verify operational methods to ensure that they are consistent with the methods assumed in the analysis.
Limits on system delta-T for future operation are recommended.
The maximum administrative 1y controlled pressurizer to RCS delta-T at McGuire.is 3700F.
Thia exceeds the 3200F assumed in the analysis.
However, as noted in requirement (1), the 3200F degree has never been exceeded.
The 3700F can only potentially occur when the pressurizer is at its mtximum temperature allowed during heatup-without an RCP running (4400F), with the RCS temperature at the minimum allowed (700F) { 440 - 70 = 370 }.
In practice the 3700F does not occur.
Normal operating practice is to turn on a reactor coolant pump while the pressurizer is in the range of 4250F to 4300F and RCS temperature is in the range of 1100F to 1300F.
Maximum system delta-T given this normal operating practice is 3200F { 430 - 110 = 320 }.
The fatigue life of the surge line will be determined by normal operating practice.- The WCAp 12639, 3200F limit on pressurizer to RCS temperature difference is a fatigue limit, not a primary stress type (ductile rupture) safety limit or a brittle fracture type safety limit.
Adequate conservatism exists in the analysis to more than compensate for a brief excursion above the 3200F limit
-should such an excursion ever occur.
Thus, the McGuire operating methods-are consistent with the methods assumed in the WCAP 12639 analysis.
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Requirement 3. - Verify the applicability of seismic OBE bending moments used in the fatigue analysis and comblard deadweight and OBE moments at the hot leg nozzle.
A unit specific analysis has boon completed for the McGuiro Unit 1 and Unit 2 surge linos.
The e.nalysos confirm that the seismic OBE bonding moments for the McGuiro Unic 1 and Unit 2 surgo lines are. loss then the 1731 in-kips usea in the WCAP 12639 analysis (roforenco pg 9-14 of WCAP 12639.)
The combined doadweight and OBE inertia moments are loss than 1847 in-kips (roforenco pg 9-21 vf WCAP 12639).
Plant S yn o c.i. f i c Evaluationra Evaluation 1.
Evaluate adequacy of pipo support [s for] new loads and displacements.
Results of the unit specific analysos confirm that all pipo support loads and displacements remain within applicable design limits.
Loads and displacements for all loading conditions woro evaluated.
The pipe support structural actachments were also ovaluated for the increased pipo s mport loads.
Each McGuire u
unit surgo line is supported by one spring, one snubber and one rigid (three supports por unit; six total for the station).
The six pipe support drawings have boon revised to reflect the now loads and movements resulting from the thermal stratification analysis.
Evaluation 2.
Evaluate the effects of stratification on stress and fatigue at integral welded attachments (lugs, plates, etc.)
Integral wolded attachments are not used on the McGuire surgo lines.
This SER ovaluation is not applicable to McGuiro Nuclear Station.
Evaluation 3.
Evaluate the ef fects of stratification on stress and fatigue of the pressurizer nozzle.
As noted in our July 15, 1991, letter to the NRC staff, Westinghouse has completed an analysis of the pressurizer surgo nozzle accounting for the offects of stratification.
The analysis confirms that the pressurizer nozzlo satisfies all applicablo stress and fatigue limits considoring the offects of stratification.
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Acict i t i o n a l E:va l u a t i o n s In addition to the applicability and plant specific evaluatiuns included in the SER, the following was also evaluated:
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the new maximum pipe movements against available rupture restraint gaps, 2.
the effect of stratified movements on rupture restraint blowdown loads; and, 3.
effect of stratification on postulated break locations.
Additional Evaluation 1.
The new maximum-pipe movements resulting from the combination-of uniform expansion, stratification, SSE and LOCA were evaluated against.the evallable rupture rostraint gaps.
Contact was-predicted at one rupture restraint.
The effects of the contact were evaluated;with respect to the pipe, the rupture restraint device, and the pipe supports.
The components evaluated are structurally _ adequate considering the effects of the predicted contact.
All other devices were found to have adequate clearance for all loading conditions.
Additional Evaluation 2.
The effect of-stratified movements on rupture restraint blowdown loadings was evaluated.. (Rupture restraint loadings are a function of the hot gap.)_ Existing-blowdown loads remain adequate when considering the new thermal expansion movements associated with thermal stratification.
Additional Evaluation 3.
The' effects of stratification on postulated break locations was evaluated.
Final stress and fatigue results, including the effects of stratification, were reviewed and resulted in no new postulated break locations.
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