ML20092C868
| ML20092C868 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 01/30/1992 |
| From: | Tuckman M DUKE POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-88-011, IEB-88-11, NUDOCS 9202120144 | |
| Download: ML20092C868 (6) | |
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January 30,1992 U. S. Nuclear Regulatory Commission ATrN: Document Control Desk Washington, DC 20555
Subject:
Catawba Nuclear Station, Units 1 and 2 Docket Nos. 50-413 and 50-414 NRC Bulletin 8811 Pressurizer Surge Line Thermal Stratification Gentlemen:
By a letter dated August 1,1991, the NRC issued a Safety Evaluation Report (SER) on the Westinghouse Owners Group (WOO) Pressurizer Surge Lino Thermal Stratification Generic, Detailed Analysis (WCAP 12639). The SER advised Duke Power that the WOG program results could be used to satisfy items 1.c and 1.d of the bulletin for Catawba Nuclear Station, provided that plant specific applicability is demonstrated and additional evaluation requirements as specified within the SER are performed. The August 1,1991 letter also requested that Duke submit the results within 30 days of completing the analysis.
The analysis was completed on December 31,1991. Accordingly, please find itaiched a summary of the results of Duke's analyses for Catawba Nuclear Station. The results of the analyses confirm the adequacy of the existing design for Catawba.
Please be advised that all actions requested by Bulletin 8811 of licensees of operating PWRs (Items 1.a through 1.d) have been completed for Catawba Nuclear Station. Details
.of the inspections, analysis and evaluations performed in support of responding to this bulletin are available for inspection.
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U. S. Nuclear Regulatory Commission January 30,1992 Page 2 If there are any questions regarding the info mation provided in response to Hulletin 8811, please contact Chuck Ixwis at (803) 831-3076.
I declare under penalty of perjury that the statements set forth herein are true and correct to the best of my knowledge.
Very truly yours, t %.-~
M. S. Tuckman Attachment CRUll8811RSP.NRC xe: S. D. Ebneter Regional Administrator, Region il W. T. Orders Senior Resident Inspector, Catawba R. E. Martin, Senior Project Manager ONRR
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DUKE POWER COMPANY CATAWilA NUCLEAR STATION RESPONSE TO IlULLETIN 8811 PRESSURIZER SURGE I.INE TIIERMAL STRATIFICATION All analyses and evaluations required for NitC llulletin 8811, Pressuriter Surge 1.ine Thermal Stratification, are complete. Itesults of the analyses confirm the adequacy of the existing designs. A summary of the actions taken for final closure of NitC llulletin 8811 for Catawba Nuclear Station follows.
The summary is presented in four parts:
llackground, SElt Applicability Requirements, Siilt Plant Specific Evaluations, and Additional Evaluations, ilA C K G U 9 U N D NRC llulletin 8811 required utilities to take action to confirm the structural adequacy of i
the pressurizer surge line considering the effects of thermal strati 0 cation and thermal striping. Generic tasks required by NRC llulletin 8811 were performed under the auspices of the Westinghouse Owners Group. The results of the Westinghouse Owners Group program were summarized in WCAP 12639, "WOG Pressuriter Surge Line Thermal Strati 0 cation Generle Detailed Analysis." The NRC transmitted the staff's SElt on the WCAP 12639 with a letter to M.S. Tuckman dated August 1,1991. The SER stated that for Catawba Units 1 & 2, "the WOG generic detailed analysis results can be used to satisfy the requirements of NRC llulletin 88-11 Actions 1.c and 1.d, provided that plant speci0c applicability is demonstrated and additional evaluations which were not included as part of the WOG program are performed.
Applicability requirements include:
- Review of operating records to ensure that system A T limits assumed in the analysis were not exceeded,
- Verification of operational methods to ensure that they are consistent with 'he methods assumed in the analysis (Limits on system A T for future operation are recommended), and
- Verification of applicability of seismic OBE bending moments used in the fatigue analysis and combined deadweight and OBE moments at the hot leg nozzle.
Additional plant specific evaluations to be performed include:
- Evaluation of adequacy of pipe support [s for) loads and displacements, CNS Bulletin 88-11 Page 1 i
d
- Evaluation of effects of stratification on stress and fatigue at integral welded attachments (lugs, plates, etc.), and
- Evaluation of effects of stratification on stress and fatigue of the pressuriter nozzle.
APPLICAHILITY REQUIREMENTS Requirement 1. Reglew operating records to ensure that system 4-T limits assumed in the annlysis were not exceeded.
The Catawba operating records were reviewed. No occurrences were found of system A-T execeding 320'F; or, of fill and vent 4 T greater than 150'F. The system 4 T limits assumed in the WOG generic analysis are applicable for past Catawba operation.
Requirement 2. Verify operational methods to ensure that they are consistent ulth the methods assumed in the analysis. Limits on system 4-T for future operation are recommended.
The maximum administratively controlled pressurizer to RCS 4-T at Catawba is 260*F. This value is enveloped by the 320*F assumed in the analysis. The Catawba operating methods are consistent with the methods assumed in the WCAP 12639 analysis.
Requirement 3. Verify the applicability of seismic OBE hending moments used in the fatigue analysis and combined deadweight and OBE moments at the hot leg nozzle.
A unit specific analysis has been completed for the Catawba Unit I and Unit 2 surge lines. The analyses confirm that the seismic OBE bending rnoments for the Catawba i
Unit 1 and Unit 2 surge lines are less than the 1731 in-kips used in the WCAP 12639 analysis (reference pg 9-14 of WCAP l2639.) The combined deadweight and OBE inertia moments are less than 1847 in kips (reference pg 9 21 of WCAP 12639).
PLANT SPECIFIC EVALUATIONS Evaluation 1.
Evaluate adequacy of pipe support [s for] new loads and displacements.
Results of the unit specific analyses confirm that all pipe support loads and displacements remain within applicable design limits. Each Catawba unit surge line is supported by one spring, one snubber and one rigid (three supports per unit;six total for the station).
Loads and displacements for each support under all loading CNS Bulletin 88-11 l _
Page 2
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-4 conditions were evaluated. Supporting structural attachments were also reviewed. All applicable design limits were satisfied.
Evaluation 2.
Evaluate the effects of stratificatlan on stress and fatigue at integral welded attachments (lugs, plates, etc.)
Integral _ welded attachments are not used on the Catawba surge lines. This SER evaluation is not applicable to Catawba Nuclear Station.
Evaluation 3.
Evaluate the effects of stratification on stress and fatigue of the l
pressurlier nozzle.
J As noted in our July 15,1991, letter to the NRC staff, Westinghouse has completed an analysis of the pressurizer surge nozzle accounting for the effects of strati 0 cation.
The analysis con 0rms that the pressurizer nozzle satis 0cs all applicable stress and fatigue limits considering the effects of stratification.
ADDITIONAL EVALUATIONS sin addition to the applicabRity and plant specific evaluations included in the SER, the following was also evaluated:
~1.: The new maximum pipe movements against available rt.pture restraint gaps,
- 2. : The effect of stratified movements on rupture restraint blowdown loads; and, 3
3.
Effect of stratification on postulated break kications.
Additional Evaluation 1.
The new maximum pipe-movements resulting from the combination of uniform expansion, stratincation, SSE and LOCA were evaluated against the available rupture restraint gaps. For Catawba Unit 1, 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 on unit 1 and all devices on unit 2 were found to have adequate clearance for all biding 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 l
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blowdown loads remain adequate when considering the new thermal exliansion movements associated with thermal stratincation.
Additional Evaluation 3.
The effects of stratincation on postulated break locations was evaluated. Final stress and fatigue results, including the effects of stratificatior, were reviewed and resulted in no new' postulated break locations.
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CNS Ilulletin 8811 Page 4'
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