ML20035F968

Forwards Response to NRC Questions Raised During 930401 Structural Meeting

ML20035F968
Person / Time
Site:	Brunswick
Issue date:	04/19/1993
From:	Mccarthy D CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NLS-93-106, NUDOCS 9304230148
Download: ML20035F968 (4)

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E Carolina Power & Light Company APR 191993 SERIAL: NLS-93-106 United States Nuclear Regulatory Commission ATTENTION: Document Control Desk Washington, DC 20555 BRUNSWICK STEAM ELECTRIC PLANT, UNIT NOS.1 AND 2 DOCKET NOS. 50-325 & 50-324/ LICENSE NOS. DPR-71 & DPR-62 RESPONSE TO NRC QUESTIONS FROM APRIL 1,1993 STRUCTURAL MEETING Gentlemen:

The purpose of this letter is to provide the Carolina Power & Light Company's (CP&L) response to NRC questions raised during the April 1,1993 structural meeting between CP&L and NRC at the NRR White Flint offk 1 provides the CP&L response to those questions.

Please refer any questions regarding this submittal to Mr. D. B. Waters at (919) 546-3678.

Yvs very truly, O\\ h D. '.'AcCarthy Manager Nuclear Licensing Section DBW/kah (nis93106.wpf)

Enclosure cc:

Mr. S. D. Ebneter M4. F. D. M;;6ao Mr. R. L. Prevatte I

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i ENCLOSURE 1 BRUNSWICK STEAM ELECTRIC PLANT, UNITS 1 AND 2 NRC DOCKET NOS. 50-325 & 50-324 OPERATING LICENSE NOS. DPR-71 & DPR-62 j

RESPONSE TO NRC STRUCTURAL QUESTIONS Ouestion 1:

I What basis exists for assuring short-term structural integrity items resulting from corrosion will continue to be qualified until the items are repaired?

j CP&L Response:

Numerous corrosion repairs have been comp!eted in the Service Water Building and Reactor Building since CP&L began a corrosion upgrade program in April 1992. Completion of this program is included in the Brunswick Nuclear Plant (BNP) Three-Year Plan. Short-term structural integrity 7

items will be repaired by the end of next Unit 2 refueling outage except for those items associated

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with the Service Water pump replacements, which will be completed by November,1994 when the j

last Service Water pump is scheduled to be replaced.

Short-term structural integrity items associated with the Service Water System were evaluated in j

February 1993 to confirm their acceptability until repairs are made. Items exhibiting corrosion were reviewed for the significance of the corrosion to structural integrity and the relative degree of corrosion. The most heavily corroded or sensitive conditions were tested with a loading of two (2) times the postulated design basis loading. The results of these tests showed that the items were capable of withstanding the applied loads without failure.

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Maintenance in the Service Water Building has been improved such that additional corrosion of l

these supports will not be significant. In addition, the testing performed adequately envelopes the expected conditions until the items are replaced.

Ouestion 2:

Provide sources for equations included in the presentation, particularly; e

Non-compact bending allowable Weld allowable Nelson Stud allowable 1

CP&L Response:

The primary source for the allowable stress limits established in Design Guide DG-il.20 is Appendix F of Section lli of the ASME Code,1986 Edition. For components and materials not specifically addressed in Appendix F, additional industry documents were consulted and engineering judgement used to establish stress limits which would ensure the structural integrity of the component under review. The basis for each of these limits is documented in CP&L calcuhtion NED-C/STRU-1002, Revision O. The source of the specific stress limits for the request 9d items are:

Non-compact bending allowable: ASME ;11, Appendix F, Article F1000: " Rules for Evaluation E1-1

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q of Service Loadings with Level D Service Limits",1986, Section F-1334.4.c.

e Weld allowable: The weld allowable stress of.48 S,is based on the AISC (Section 1.5.1.2) limit for a material in shear given by Sy/3n2 =.58 S,. The ratio of S, to S, for weld metal is approximately 1.2 (reference Design of Welded Structures, Blodgett, Table 1, page 7.4-3 1). Therefore, when given in terms of S (as is typical for weld metal), the STSI limit for l

o weld metal is.48 S.

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Nelson Stud allowable: Historically, Design Guide DG-II.20 has permitted the use of a factor of safety of 1.4 against the ultimate strength of the concrete for operability evaluations of Nelson Studs. The normal factor of safety for Nelson Studs is 2.0. The 1.4 factor of safety used in operability assessments was reviewed in accordance with the requirements of ACI 349-80 and judged to be adequate to assure the structural integrity of the Nelson Studs due to their ductile nature.

i Ouestion 3:

Address criteria used for compression in bending.

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CP&L Resoonse:

No specific check of the compression flange of a section subjected to bending is required by Design Guide DG-il.20. Evaluation of localized instability within a structure is performed at the discretion l

of the responsible Engineer.

Q]aestien 4:

i Address the loading conditions for which.48S,is appropriate for welding. (i.e., is.48 S, used for welds under Netmal Loading?)

j CP&L Resoonse:

i The allowable stress limit of.48 S used for the evaluation of weld metalin Operability o

Assessments is intended for use with all load cases (Normal - Upset - Emergency). Th3 intent of this allowable limit is to ensure structuralintegrity of the component legardless of the service l

I loading. It is, therefore, considered adequate for use for any design basis load case in an i

operability assessment.

Generic Letter 91-18 does not specify what load case should be evaluated when making operability evaluations of piping and supports. The generic letter merely references other documents to be l

used when performing these evaluations (such as IE Bulletins 79-02 & 79-14 and Appendix F of l

Section 111 of the ASME code). A review of the applicable sections of these documents indicates i

that specific load cases are not defined for use with the specified service limits.

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r Question 5:

Address the use of tested mechanical properties or mill certification.

CP&L Resoonse:

i The use of tested mechanical properties or mill certification of material properties has not been used at the Brunswick Plant for operability evaluations. In addition, there are no plans to use this information in ile : sture for structures at Brunswick for which this information may be available.

DG-il.20 will be revised to eliminate the option for use of test data to exceed minimum material properties.

1 Question 6:

Address the use of transient loading in the operability equation for piping.

CP&L Response:

Consistent with our previous procedure employed for operability determinations at Brunswick (Brunswick Procedure M-20), short-term structural integrity items are qualified for loading combinations which include design basis transient loadings. DG-il.20 wil! he revised to incorporate the requirements of Brunswick Procedure M-20.

Specific transient loading design requirements were recently investigated, and the results of this investigation are summarized in CP&L Report RLCA/P238/01-92/001.

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