ML18139A805

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Forwards Updated Response to IE Bulletin 80-11,submitting re-evaluation Criteria Used to Evaluate Masonry Walls & Informing of Progress & Schedule for Completing re-evaluation Program
ML18139A805
Person / Time
Site: Surry, North Anna  Dominion icon.png
Issue date: 11/03/1980
From: Sylvia B
VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To: James O'Reilly
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
878, IEB-80-11, NUDOCS 8011070479
Download: ML18139A805 (48)


Text

.I V1B.0I.Nl:A ELECTRIC AND* Pow:s::a;CoMPANY RICHMOND, VIRGI~IA 2.3261

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    • ~!-HQYlllber 3.i 1980

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Mr. James P. O'Reilly, Director Serial No. 878 Office of Inspection &Enforcement PSE&C/RHW 1 III:bmt

u. s. i~uclear Regulitory Conm1ss1oti* .* * ~::_~'.'::a Docket Nos. 50-280 Region 11 . *,. ~-* 50-281 101 Marietta Street. Suite 3100 50-338 Atlanta. Georgia 30303 50-339 License Nos. DPR-32 OPR-37 NPF-4 NPF-7

Dear Mr. O'Reilly:

I.E. BULLETIN NO. 80-11, INTERIM REPORT SURRY POHER STATION - UNITS 1 & 2 NORTH ANNA POWER STATION - UNITS 1 & 2 This letter provides an interim report on the masonry wall reevaluation pro-gram required by I.E. 3ulletin No. S0-11. ri,e purpose of the letter is to update the response provided in our 60 day reports of July 7, 1980, Serial No. 434/050880.

to submit the reevaluation criteria being used to evaluate the masonry walls includ-ing just1f1catfcn of the criteria, and to inform you of our progress and schedule

. for completing the reevaluation program.

The 60 day reports submitted by our letter of July 7~ 1980 addressed items l, 2a. and 3 of the Bulletin and provided a partial response for item 2b. The enclo-sure and attac."lments A, B, and C to this letter update our previous response and provide the additional 1nfonnation required by item 2b of the Bulletin with the excep-tion of ~,e final results from the reevaluation program which is still fn progress.

Our letter of October 24, 1980, Serial Ho. 868, requested an extension of ttae Bulletin deadline to complete the reevaluation program by the end of July, 1981.

Analysis has been comp1eted for 41 of the 89 masonry walls at Surry and 13 of the 65 walls at North Anna. All these walls meet our initial conservative acceptance criteria. The remaining walls which did not meet our initial conservative acceptance criteria are being analyzed using more refined analytical techniques which are st111 conservat1ve and incorporate refined boundary conditions, equipment loading detann1na-t1on and the aid of computer analysis. Our current schedule estimates that analysis will be completed for at least five walls each month with the majority of the analy-sis being ,ampleted during the later part of the requested extension period.

The present available results of the reevaluation program indicate that safety*

of the plants will not be jeop4rdized by continued analy!is of the masonry walls dur-fng plant operation. If, however, during the remainder of the reevaluation p't"Ogram the operability of any safety related system 1s shown to be 1n jeopardy by the results of the analysis, the applicable technical spec1f1cations action statement will be met. 'Bo~/

j 8t11010 t.f 71 ,I,

Mr. O'Reilly It is the intent of tnts latter. w1th the 60 day responses previously 1n*ov1ded.

to adequately address all areas of IE Bulletin S0-11. Final resvlts of t!le reeYalua-t1on program will be submitted upon completion- of the program. Should you raqu1N addit1oM1 informat1on. please contact. us.

Very tnaly yours *

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a. R. -*Sylvia Manager--..uclaar Operations and Ma1ntenanca Enclosure Attactw1ents A. a, and c c~: Mr. Victor Stello, Director Off1ce of Inspection &Enforcement

~r. Harold R. uentan, D1reetor Qff1ce of Huclear Reactor Regulation

COMMONWEALTH OE VIRGINIA )

) s. s.

CITY OF RICHMOND )

Before me, a Notary Public, in and for the City and Commonwealth aforesaid, today personally appeared B. R. Sylvia, who being duly sworn, made oath and said (1) that he is Manager-Nuclear Operations and Maintenance, of the Virginia Electric and Power Company, (2) that he is duly authorized to execute and file the foregoing response in behalf of that Company, and (3) that the statements in the response are true to the best of his knowledge and belief.

\

Given under my hand and notarial seal this  ?, "° 0 My Commission expires (SEAL)

e ENCLOSURE VEPCO letter to NRC dated November 3, 1980, Serial No. 878 This enclosure update.s the information on IE Bulletin 80-11 provided in the 60 day reports and provides addit'.ional information required to be submitted within 180 days of the the date of the Bulletin for Surry and North Anna Power Stations. The 60 day reports addressed items 1, 2a, and 3 of the Bulletin and provided a partial response for item 2b. The information provided herein completes the response to the Bulletin items with the exception of the final results from the reevaluation program which is still in progress.

This information will be submitted in the final report upon completion of the reevaluation program. For clarity, the item numbers below correspond to the items of IE Bulletin 80-11.

1. Item 1 of the Bulletin requires the identification of all masonry walls which are in proximity to or have attachments for safety-related piping or equipment such that wall failure could affect a safety-related system. It further requires the description of systems and equipment, both safety and non-safety-related, associated with these masonry walls.

This information was provided in our 60 day report.

Since the submittal of this report an "as-built" verification program has been conducted to provide the necessary details for analysis of the walls in the reevaluation program. This as-built verification program has been completed.

During this program some of the wall identification numbers were changed and the physical limits of some walls were redefined by subdividing or combining wall sections in order to facilitiate analysis. On-going work associated with the steam generator replacements at Surry and THI modifications for both stations required the removal of some existing walls. Also, based on the as-built details obtained, some walls previously defined as being within the scope of the Bulletin were found to have no safety-related equipment within the proximity of the wall and were deleted from the reevaluation program.

Four additional walls at North Anna which were not included in the 60 day report, were identified by the field forces during the as-built program. All other additions reflect wall redesignations during the as-built program to better reflect existing wall conditions in the analysis of the reevaluation program. These changes to the reevaluation scope alter the information provided in the appendices of the 60 day reports in that the scope of the reevaluation program has been reduced from 91 to 89 walls for Surry and from 67 to 65 walls for North Anna. In order to provide you with the latest information, Attachments A and B to this letter update the information provided in the 60 day reports. Attachment A updates the information provided for Surry and Attachment B updates the information provided for North Anna.

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2. Item 2 of the Bulletin requires a reevaluation of the design adequacy of the walls identified in item 1 to determine whether the masonry walls will perform their intended function under all postulated loads and load comblnations. The information required as part of this evaluation program is addressed in the subitems below:
a. The prioritized program for reevaluation of masonry walls describe~ in the 60 day reports is still in affect. Those walls located in critical plant areas and with a high probability of striking a significant amount of safety-related equipment if wall failure results are given the highest priority for reevaluation. As stated in Vepco's letter to the NRC dated October 24, 1980, Serial No. 868, the current schedule is to complete all analyses by the end of July 1981.

Following the multi-level analyses program described in item 2b (iii) below it was projected that analyses will be completed on at least 5 walls each month with the majority of the analysis being completed during the later part of the requested exten~ion period. During the course of the reevaluation if the operability of any safety-related system is found to be jeopardized the applicable technical specifi-cations action statement will be met.

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b. Item 2b requires that a written report be submitted upon completion of the reevaluation program. Subitems (i) and (ii) were addressed in the 60 day reports and are updated below.

Subitem (iii) below addresses the details of the reevaluation program and includes the justification for the reevaluation criteria submitted in Attachment C. Results of the reevaluatio;11 program will be submitted upon completion of the program.

(i) Concrete masonry walls at Surry and North Anna have been used primarily to provide barriers for shielding, fire protection, and personnel separation. Those walls utilized in the con-struction of seismic Class I structures are not designed, nor intended to act as bearing walls or for transmitting building shear forces. Additional information describing details of wall functions, configurations, materials, and reinforcement was provided in the 60 day reports.

(ii) Construction practices employed in the construction of the masonry walls were addressed in the 60 day reports.

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-s-(iii) Reevaluation of the masonry block walls is being performed based on the "Criteria for Reevaluation of Concrete Masonry Walls" submitted as Attachment C to this letter. In order to expedite completion of the analyses the reevaluation program is structured in the multi-level format utilizing conservative assumptions, simplified analysis techniques and conservative acceptance criteria. In the initial phases of analysis, the walls are analyzed using the most conservative criteria and simplified analytical techniques to screen those walls where more complex analyses is not warranted. Where additional analysis is warranted more exact analysis techniques, which are still conservative, are applied to incorporate refined boundary conditions, more precise loading definition, and computer aided analysis.

Item 2b (iii) requires justification of the criteria used, an evaluation of all loads and load combinations, and a description of the mechanism for transferring local loads into the masonry walls.

The development of the reevaluation criteria was based on a review of existing test data and published literature. The basis of the acceptance criteria, as described in Attachment C is, in part, the allowable stresses specified in the American Concrete Institute's

e ACI 531-79 "Building Code Requirements for Concrete Masonry Structures". The review of the test data and literature substantiates our use of these allowable stresses. The review alsb included research of acceptable damping percentages, analysis techniques, in plane effects, arch action and local stress values. This research forms the remainder of the basis for the reevaluation criteria.

The reevaluation criteria considers loads from both safety and non-safety-related attachments as well as relative interstory displacements between building elevations where applicable.

All applicable loads and load combinations specified in the Surry and North Anna FSAR's for concrete design have been included in the reevaluation. A review of the walls determined that the walls are not subjected to tornado mi.ssiles or depressurization, pipe whip or jet impingement loads. The global review of the walls includes seismic inertia loads, interstory displacement loads for both in plane and out of plane effects, equipment loads and wind loads where applicable.

e The local review includes discontinuities such as openings and the mechanism for local load transfer into the walls.

This includes a review of potential local block pull out as well as possible overstress within individual blocks due to attached equipmen~. Multiwythe walls were also reviewed to ensure the integrity of the collar joint. Calculated shear and tension stresses across the collar joints were compared against

.allowable values that were conservatively chosen to account for potential small areas of voids or other discontinuities.

3. As described in item 2b (iii), the use of allowable stresses as specified in ACI 531-79 and applied to the reevaluation criteria is substantial.

Based on the review of existing test data and the conservative assumptions applied in the reevaluation criteria it is believed that additional confirmatory testing is not necessary to justify the acceptance criteria being applied.

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e October 1980 ATTACHMENT C VEPCO LETTER TO NRC DATED NOVEMBER 3., 1980 SERIAL NO. 878 CRITERIA FOR REEVALUATION OF CONCRETE MASONRY WALLS SURRY POWER STATION UNITS 1 & 2 NORTH ANNA POWER STATION UNITS 1 & 2 VIRGINIA ELECTRIC AND POWER COMPANY STONE & WEBSTER ENGINEERING CORPORATION BOSTON, MASSACHUSETTS

e TABLE OF CONTENTS

1.0 INTRODUCTION

1.1 Purpose 1.2 Scope 2.0 LOAD AND LOAD CONDITIONS 2.1 Loads 2.2 Load Combinations 3.0 MATERIAL PROPERTIES 4.0 ANALYSIS PROCEDURES 4.1 Elastic (uncracked) Section 4 .1.1 Frequency 4.1.2 Inertial Loads 4.1.3 Equipment Loads 4.1.4 Interstory Displacements 4.2 Ultimate Strength of Unreinforced Section 4.3 Ultimate Strength of Reinforced Section 5.0 ACCEPTANCE CRITERIA 5.1 Permissible Stresses 5.2 In-Plane Effects

'I CRITERIA FOR REEVALUATION OF CONCRETE MASONRY WALLS

1.0 INTRODUCTION

1.1 Purpose This document establishes design requirements and criteria for use in reevaluating the structur~l adequacy of concrete masonry walls as required by the Nuclear Regulatory Commission (NRC) I&E Bulletin 80-11, Mas_onry Wall Design, dated May 8, 1980.

1.2 Scope The reevaluation as covered by this *document pertains to existing masonry walls in the operating plants. These walls are not used as major load-bearing walls and not included as part of the overall building shear wall system. Primary purposes of these walls are to provide radiation shielding, fire protection, and act as personnel barriers.

Reevaluation of the masonry walls shall include local transfer effects. The local transfer of equipment loads into the masonry wall panel, as well as the global response of wall, will be reevaluated for all loads and load combinations defined herein; however, the review of anchor bolts and supporting systems is not considered to be within the scope of this reevaluation.

2.0 LOAD AND LOADING CONDITIONS 2.1 Loads The reevaluation will include all relevant loads specified in the station FSAR for concrete design. A survey of all the masonry walls under consideration concluded that they are not subjected to loads from tornado, missile, pipe whip, or jet impingement. Thermal and pressure differential loads, where applicable, being carried by the wall or transmitted by supports anchored to the masonry walls will.be included in the reevaluation.

Inertial loads due to Operating Basis Earthquake (OBE) and Design Basis Earthquake (DBE), as defined by the station FSAR, will be used and applied as described in Section 4.1.

Masonry wall damping values for unreinforced walls will be a maximum of 2 percent of critical damping for severe environmental (OBE) case and 4 percent for extreme environmental (DBE) case.

2.2 Load Combination The reevaluation of masonry walls will consider the following load combinations:

e e 2

Load Category Load Factors D L w p T 0

T a

E E' Severe Environmental Load Case I 1.0 1.0 1.0 1.0 1.0 Severe Environmental Load Case II 1.0 1.0 1.0 Extreme Environmental Load Case 1.0 1.0 1.0 1.0 1.0 where D = gravity load of masonry walls and attachments L = live load where applicable P = pressure differential load W= wind load, where app.licable T0 = thermal load from attachment associated with plant operating conditions Ta = thermal load from attachment associated with accidental conditions E = OBE loads including attachments E'= DBE loads including attachments 3.0 MATERIAL PROPERTIES Material properties will be taken as the minimum specified for the masonry, mortar, grout, and steel in the project specifications and contract documents.

Testing for material properties in situ may be employed to define actual properties to be used in lieu of the values specified. Such testing will follow procedures defined in .American Concrete Institute (AC!), "Building Code Requirements for Concrete Masonry Structures" (AC! 531-79).

4.0 ANALYSIS PROCEDURES Masonry walls shall be reevaluated for earthquake on the basis of determining the effects of: (1) inertial loads, (2) equipment loads, and (3) interstory displacement effects. Initial analysis shall assume an elastic (uncracked) section, ignoring the effects of horizontal joint reinforcement. Further analysis, utilizing the reinforcing steel and ultimate strength of the wall, will be performed as appropriate.

The resultant of the combination of the various types of statistically independent seismic loads will be determined by SRSS.

4.1 Elastic (uncracked) Section The reevaluation analysis shall be performed assuming elastic behavior, comparing the results against the acceptance criteria defined in Section 5.0.

4.1.1 Frequency - Fundamental frequencies of the masonry walls shall be calculated based on elastic plate or beam theory. To account for variations in material properties and assumed boundary conditions the seismic response of masonry walls will be calculated using amplified response spectra which has had its peak broadened.

3 4.1.2 Inertial Loads - Transverse loads will be calculated using the acceleration of the appropriate dampened amplified response spectrum in a simplified dynamic analysis using the funda-mental modes.

More refined analysis may be used in some cases.

4.1.3 Equipment Loads - Equipment loads will be calculated based on a load distributed uniformly over part or all of the area of wall, depending* on the arrangement of the supports. The

~sultant may be applied as a single concentrated load or a line load, as appropriate.

Equipment support loads imposed on the walls will be determined on the basis of a simplified dynamic analysis based on fundamental modes, as described in the FSAR.

4.1.4 Interstory Displacement - Relative interstory displacements between building elevations from the seismic analysis of the structure will be imposed on the wall panel, where required and its effects accounted for in the reevaluation analysis.

4.2 Ultimate Strength of Unreinforced Section If the elastic out-of-plane moments cause higher than allowable stresses, the ultimate strength of an unreinforced wall section may be calculated using arch action analysis, see Figure 1.

The procedure for this analysis will be to postulate a crack perpen-dicular to the span of the wall, occurring at the point of maximum calculated elastic moment. The wall capacity will be calculated based on the moment P(u) r(u) (see Figure 1) where:

P(u) = compressive force developed at cracked boundaries r(u) = moment arm between two compressive forces Maximum compressive and shear stresses at the cracked section in the wall shall be in accordance with the acceptance criteria defined in Section 5.0.

No Category 1 pipe support (large or small bore) is fastened to the masonry wall.

4.3 Ultimate Strength of Reinforced Section If the elastic out-of-plane moments cause higher than allowable stress and joint reinforcement consisting of 3/16 in or greater, truss type reinforcing exists; the ultimate strength of one-way reinforced wall sections can be calculated using classical techniques for reinforced concrete masonry.

4 Maximum stresses in the panel will be in accordance with the acceptance criteria defined in Section 5.0. All masonry walls qualified on the basis of this ultimate strength criteria will have positive restraint against out-of-plane translation at the side supports.

5.0 ACCEPTANCE CRITERIA 5.1 Permissible Stress Permissible stresses for masonry construction will be based on the American Concrete Institute "Building Code Requirements for Concrete Masonry Structures" (AC.l 531-79). A one-third increase of the permissible stress values in Chapter '10, AC! 531 will be ~aken in consideration of severe environmental loads (OBE). For extreme environmental loads (DBE), the permissible stresses will be increased a factor of l._67.

The permissible collar joint stress for either shear or tension shall be taken as 8 and 12 psi, for severe and extreme environmental loads, respectively, with no additional increase permitted.

Other applicable codes (i.e., AISC "Specification for the Design Fabrication and Erection of Structural Steel for Buildings") are as referenced in the FSAR and shall be used in the reevaluation program, as necessary.

Permissible stresses represent levels of stress for which significant damage to the wall will not occur.

5.2 In-Plane Effects The walls considered by this procedure are not lateral load-carrying walls. In addition, because of the complex interaction between masonry walls and confining primary structural elements, in-plane stresses cannot be properly described. As a result, strain or displacement is a more meaningul index of in-plane performance.

The in-plane shear strain defined by

= .t1T -AB H

where L) T = displacement* at the top of the wall Ll B = displacement* at the bottom of the wall

  • from the building displacement profile, inches H = height of wall, inches

5 shall be limited to 0.001 inch/inch, for walls which are confined at least top and bottom, or on three sides by concrete or steel primary structural elements. All other walls (unconfined) shall be limited to in-plane shear strain of 0.0001 inch/inch.

5.3 Proximity Envelope The initial proximity envelope was conservatively assumed to be the space enclosed by a rectangle of height equal to the elevation of the blocks and" a width on either side of the wall also equal to the height of blocks.

A proximity envelope for~ failure of the masonry wall may be further defined on the basis of plastic hinge formation and boundary conditions.

. " -~*-

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3 J'ii. l 11ltilllate Vall Ca.pacit:,

./

  • VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGIN XA. 23261 October 31, 1980 Mr. Harold R. Denton, Director Serial No. 885 Office of Nuclear Reactor Regulation NO/SWB:jmj Attn: Mr. Steven A. Varga, Chief Docket Nos. : 50-280 Operating Reactors Branch No. 1 50-281 Division of Reactor Licensing License Nos. : DPR-32 U.S. Nuclear Regulatory Commission DPR-37 Washington, D.C. 20555

Dear Mr. Denton:

SUR..~Y POWER STATION FIRE PROTECTION MODIFICATIONS The Fire Protection Safety Evaluation Report of Surry Power Station Units 1 & 2 dated September 19, 1979 required implementation of fire protection modifica-tions by various target dates. Attachment I of Vepco letter dated October 29, 19.80 (Serial No. 869) listed the completed fire protection modifi-cations and the status of modifications required to be completed by October 31, 1980.

  • All modifications associated with Unit 2 required by October 31, 1980 with the exception of item 3.1.16(1)(2), COz High Pressure System, are now complete or functional as anticipated in the previous letter, including item 3.1.12, fire dampers. The status of the CO2 High Pressure System is as indicated in Vepco letter dated October 29, 1980. All modifications associated with Unit 1 required by October 31, 1980 will be complete prior to startup after the Steam Generator Replacement Outage.

Atttachment I of this letter is the Safe Shutdown Evaluation required by the Surry Safety Evaluation Report. This report should resolve the open items discussed in your letter dated October 9, 1980.

Attachment II is an updated Project Status Surmnary of all fire protection modifications for your information. Attachment III transmits additional design information and includes the design information on the charging pump service water system modification which addresses specific concerns expressed in your October 9, 1980 letter. Attachment IV is a copy of the proposed Technical Specification Changes for fire protection modifications completed to date. Additional Technical Specification changes required will be submitted prior completion of the modifications, r

VIRGINIA ELECTRIC AND POWER COMPANY TO Mr. Harold R. Denton, Director 2 If you have any questions or comments, please contact us.

Very truly yours, vdL'

-i*,R.:tl=

Manager - Nuclear Operations and Maintenance Attachments cc: Mr. James P. O'Reilly, Director Office of Inspection and Enforcement Region II