ML20081K337
| ML20081K337 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 06/17/1991 |
| From: | Parker T NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML19302E705 | List: |
| References | |
| IEB-88-011, IEB-88-11, NUDOCS 9106260325 | |
| Download: ML20081K337 (7) | |
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Northem States Power Company 414 Nicollet Mall Minneapots, Minnesota $54011927 1elephone (612) 334b500 June 17, 1991 NRC Bulletin 88 11 U S Nuclear Regulatory Comn.ission Attn:
Document Control Desk Washington, DC 20555 PRAIRIE IS1AND NUCLEAR CENERATING PIANT Docket Nos. 50 282 License Nos. DPR 42 1
50 306 DPR 60 Response to NRC Bulletin No. 88-11 Pressurizer Surre Line Thermal Stratification
Reference:
Letter dated February 12, 1991, T M Parker (NSP) to U S Nuclear Regulatory Commission, " Response to NRC Bulletin 88-11, Pressurizer Surge Line Thermal Stratification" Thn purpose of this letter is to provide information regarding the status of f
activities taken by NSP in accordanco with Action 1.d of the Bulletin.
Backr.round The referenced letter described the preliminary resalts for Prairie Island Unit 1 and the final acceptable results for Unit 2.
This letter provides the final results for Unit 1 and submits the Westinghouse l
report WCAP 12877, " Technical Justification for Eliminating Pressurizer Surge Line Rupture as the Structural Design Basis for Prairie Island 1" for NRC review and approval to support the required modifications of the surge line pipe whip restraints.
i Prairie Island Unit 1 l
Results of the pressurizer surge line evaluation indicate that ASME stress and fatigue requirements can be met for the design life of Prairie Island Unit 1, contingent on making modifications to whip restraint gaps in 1992 based on utilizing leak-before-break technology.
Modification of whip restraint gaps subsequent to demonstration of leak-before break, as opposed to iterative methods of removing further conservatisms from the stratification analysis, was determined by NSP and Westinghouse to be the more technically prudent, as well as cost-effective, means to effect fatigue qualification of the Prairie Island Unit 1 surge line.
Specific details of the evaluation are described below.
ATTACHMENT 4 CONTAINS PROPRIETARY INFORMATION TO BE WITHHELD FROM PUBLIC DISCLOSURE IN ACCORDANCE WITH 10 CFR PART 2, SECTION 2.790
e USNRC Northern States Power Cornpany June 17, 1991 page 2
- 1) Using, the Wectinghouse owners Gro p work as a base, plant specific applicability analysea have been performed, including:
a.
Transient development utilizing monitoring data from ten plants, including Kewaunee (which is similar in design to Prairie Isla.4 Unit 1), and past operatir.: records for Prairie Island Unit 1 to determine the distribution of system delta-T's for unit heatups and cooldowns b.
Stress and fatigue evaluations, accounting for global loadings resulting from two configurations, before and after the whip restraint gap modifications assumed to occut in 1992 Results of these evaluations showei Equation 12 stress acceptable for the post modification configuration, and fatigue usage f actor value within the ASME allowable for the design life of the plant Analysis Allowable Equation 12 stress (ksi) 52.3 53.0 Fatigue usage 0.90 1.0 m
- 2) The results of the pressurizer surge nozzle stress and fatigue evaluation for thermal stratification loadings are:
Analysis Allowable Maximum stress intensity range (ksi) 38.4 57.9 Fatigue usage 0.69 1.0
=
- 3) To justify the whip restraint gap modification in 1992, leak-before-break evaluation of the Prairie Island Unit 1 surge line was done, using i
the loads resulting from the global analysis. The results of the leak-before break evaluation are attached for NRC approval, to support the 1992 modification.
As Attachment 4 contains information proprietary to Westinghouse Electric Corporation, it is supported by an affidavit signed by Westinghouac, the owner of the information. The affidavit sets forth the basis on which the information may be withheld from public disclosure by the Commission and
..ddresses with specificity the considerations listed in paragraph (b)(4) of Section 2.790 of the Comrnission's regulations.
I
USNRC Northern States Power Company June 17, 1991 Page 3 i
Please contact f you have any questions related to our response.
6}lb N. Thomas M Parker Manager Nuclear Support Services c: Regional Administrator - Region III, NRC (w/o Attachment 4) Senior Resident Inspector, NRC (w/o Attachment 4) NRR Project Manager. NRC (w/o Attachment 4) J E Silberg (w/o Attachmen 4) Attachments 1. NSP Affidavit 2. WCAP-12876 " Technical Justification for Eliminating Pressuriner Surge Line Rupture as the Structural Design Basis for Prairic Island 1" (NON PROPRIETARY) l 3. Westinghouse authorization letter, CAW 91 143 Proprietary Information j Notice, and accompanying Affidavit 1 4. WCAP-12877, " Technical Justification for Eliminating Pressurizer Serge Line Rupture as the Structural Design Basis for Prairie Island 1" (PROPRIETARY) i i
ATTACILMENT 1 UNITED ST/fES NUCLEAR REGULATORY COMMISSION NORTilERN STATES POWER COMPANY PRAIRIE ISIAND NUCLEAR GENERATING PLANT DOCKET No. 50 282 50-306 3 PRESSURIZER SURGE LINE TilERMAL STRATIFICATION i i Northern States Power Company, a Minnesota corporation, with this letter is submitting information requested by NRC Sulletin 88-11. This letter contains no restricted or other defense information. NORTilERNSTIES/'OyE)COPAtP! By / ]M9 IW I-Thomas M Parker E Manager, Nuclear Support Services On this /7/ hay of 2 efore me a notary public in and for said b e County, personal 1 appeared Thom s M Parker, Manager, Nuclear Support Services, and being first duly sworn acknowledged that he is authorized to execute this document on behalf of Northern States Power Company, that he knows the contents thereof, and that to the best of his knowledge, information, and belief the statements made in it are true and that it is not interposed for delay. h w-eW 7 r'; p' e w:::::::::::::::v:::::::::: ! 8' JUDY L KLAPPCRTCK NOTARY PUBtIC-M:NNESOTA l ANOKA COUNTY h Wy Comm. won inpnes Sept 29,1991 l nw::::::::mww,v.v:::::,xa l
ATTACllMENT 2 VCAP 12876 " Technical Justification for Elirninating Pressurizer Surge Line Rupture as the Structural Design Basis for Prairie Island 1" (NON PROPRIETARY) i t t
ATTAC)lMENT 3 Westinghouse authorization letter, CAV 91 143 Proprietary Infortnation Notice, and accotepanying Affida'.it u ) J I
ATTACllMENT 4 k' CAP 1287 7, " Technical Justification for Eliminating Pressuri::er Surge Line Rupture as the Structural Design Basis for Prairie Island l" (PROPRIETARY) l l 1 M}}