ML20214Q289

Summary of 861124 Meeting W/Util Re Results of Recent Investigations Performed by Util on Concrete Strength.Util Requested Meeting Re Calculation of Equivalent Concrete Strength.List of Attendees & Util Presentation Encl

ML20214Q289
Person / Time
Site:	Sequoyah
Issue date:	11/28/1986
From:	Joseph Holonich Office of Nuclear Reactor Regulation
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 8612050077
Download: ML20214Q289 (23)

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UNITED STATES 8

o NUCLEAR REGULATORY COMMISSION g h 9 $ WASHINGTON, D. C,20555

\ . . . . . *#g kOV 2 81986 i

Docket Nos.: 50-327 and 50-328 APFLICANT: TENNESSEE VALLEY AUTHORITY FACILITY: SEQUOYAH PLANT, UNITS 1 AND 2

SUBJECT:

MINUTES OF NOVEMBER 24, 1986 MEETING TO DISCUSS C0tiCRETE STRENGTH AT SE0VOYAH PLANT, UNITS 1 AND 2 On November 24, 1986, members of the staff met with representatives of the Tennessee Valley Authority (TVA) to discuss the results of recent investiga-tions performed by TVA on the concrete strength at the Sequoyah Plant, Units 1 and 2. Enclosure I is a list of attendees at the meeting. The TVA presen-tation is contained in Enclosure 2.

The meeting began with TVA presenting an overview of the program to date. This included a history of the issue of concrete strength and how it first arose.

Initially, the issue was identified as an employee concern at the llatts Bar Plant. It originally dealt with the fact that TVA did not follow the appropriate procedures for concrete strength, control and sampling frecuencies for concrete test specimens. The concern was made generic to all TVA nuclear plants since the construction procedure referenced was applicable to all units. Subsequent investigation by TVA into the problem at Sequoyah yielded a conclusion that the sampling frequencies used were acceptable. However, in several of the batch samples, over 10% of the measured strengths fell below the value specified in the procedure. It was required in the procedure that no more than 10% of the averaged test strengths of the last consecutive 30 samples be below the required strength.

As a result of this finding, TVA determined that for those concrete cours that did not meet the specified requirements, it would demonstrate that the actual strengths were acceptable for use. The TVA approach used to perform this demonstration was to calculate the equivalent specified strengths using the mean and standard deviation for the last 30 tests. This equivalent specified strength was then increased hased on an increase of strength which is expected to occur in concrete as it as~s. When this delta increase in strength was added to the equivalent specified strength, the resultant strength for most of the concrete in questien was above the minimum.value specified in the construction precedure. In addition to its discussion on the strength of concrete, TVA also discussed the sampling frequency of the strength tests and a bedding trortar evaluation it had perfonned as a result of the Watts Bar' concern.

A.ithough the staff found the method of calculating the equivalent specified strengths reasonable, it did not agree with the TVA approach of adding the additional strength which is expected to occur as a resu!t of aging. The reasons for this staff position were:

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8612050077 861128 PDR ADOCK 05000327 P PDR

NOV 2 31986 x (1) The test. data used to determine the expected increase in concrete strength were based en five test block pours. These values coulc be used for concrete that caree from the same mix; however, they ceu'd not be applied generally in the plant.

(?) The staff does not permit the use of this additional strength for concrete pours where the strengths dc, meet the required values. By allowing TVA to use this application would not be consistent with the normal staff practice. and (3) The American Concrete Institute Code spccifies that under conditions where the strength test do not meet the acceptance criteria additional non-destructive testing should be perforced in order to verify the adequacy of the inplace concrete.

Based on its review of the information presented at the meeting the staff identified to TVA two ways in which the staff believed the issue of con-crete strength could be resolved. One option was to use the equivalent strengths and verify that even with these lesser strengths the concrete could still perfonn its function. The second option was to perfonn some type of non-destructive strength test.

With respect to the other two issues discussed at the meeting, the staff concluded that, pending further arplification of the technical basis presented by TVA and submittal of additional information identified by the staff in the meeting, the TVA findings on the sampling frecuency and bedding mortar were acceptable. Additionally, the staff expressed a concern with some of the test data related to the slurrp and air content of the concrete. This staff concern arose as a result of the TVA investigation done at hatts Bor where it was discovered that there were deficiencies in the slump and air content of the concrete. The staff requested that TVA address this issue fcr Sequoyah and describe what, if any, deficiencies existed at Sequoyah and provide the basis for disposition of the deficiencies, as appropriate.

At the close of the neeting, TVA agreed to address the latter of the staff issues in its formal submittal. However, TVA stated that the method of calculating the equivalent concrete strength anc then adding to it the additional strength which occurs due to aging was a method that was being used for all of the TVA facilities. If the staff did not approve this approach, there would be a significant impact on the Uatts Bar Plant. Because of this, TVA would not cormit to change this approach and requested a nee ing on this subject for the-Watts Bar Plant. g(

Joseph J. Holonich, Project Manager PWR Project Directorate #4 Division of PWR Licensing-A ,

PWR6 lR-A PW f / A PW p/EPWR-A PWI WR-A JHolo i h/ rad enyon CS ile BJYfuncblood 11 /86 11/ 86 11/g/86 11 86

,- ' MEETING SUtiftARY DISTRIBLITION NOV 2 81986 QDoEk~etTFilE*73 NRC Participants

.NRC POR J. Holonich L PDR G. Walton NSIC D. Jeng PRC System R. Ballard PWR#4 Reading File N. Reinhart M. Duncan H.'Asher OGC J. Partlow E. Jordan .!

B. Grires ACRS (10)

OTHERS bec: Licensee & Service List-I j

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Mr. S.A. White

., Tennessee Valley Authority Sequoyab Nuclear Plant CC: I Tennessee Departnent of Public Regional Administrator, Region II Health U.S. Nuclear Regulatory Connission, ATTN: Ofrector, Bureau of 101 Marietta Street, N.W., Suite 2900 Environn: ental Health Services Atlanta, Cecrgia 30323 Cordell Hull Building Nashville, Tennessee 37219 J. A. Kirkebo ATTN: D.L. Williams Mr. Michael H. Mobley, Director Ternessee Valley Authority Division of Radiological Health 400 West Summit Hill Drive, W12 A12 T.E.R.R.A. Building Knoxville, Tennessee 37902 150 9th Avenue North hashville, Tennessee 37203 Mr. Bob Faas Westinghouse Electric Corp. Cou'nty Judge P.O. Box 355 Hamilton County Courthouse Pittsburgh, Pennsylvania 15230 Chattanooga, Tennessee 37402 R. L. Gridley Tennessee Valley Authority SN 157B Lcokout Place Chattanooga, Tennessee 37402-2801 M. R. Harding Tennessee Valley Authority Sequoyah Nuclear Plant P.O. Box 2000 Soddy Daisy, Tennessee 37379 Resident Inspector /Sequoyah NPS c/o U.S. Nuclear Regulatory Commission 2600 Igou Ferry Road Soddy Caisy, Tennessee 37379 H.L. Abercror.bie Tennessee Valley Authority Sequoyah Nuclear Plant P.O. Box 2000 Soddy Daisy, Tennessee 37379 f

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, *: Enclosure 1 LIST OF ATTENDEES i .

NRC

__ TVA i

G.'Walton N. Perry F. Rineldi R. Cullock

, D. Jeng R. Hernandez J. Holonich M. Cones ,

i R. Ballard M. Burzynski M. Reinhart W. Massie H. Asher i

Bhl R. Philleo 4

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Enclosure 2 TVA Presentation

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TENNESSEE VALLEY AUTHORITY

. SEQUOYAH NUCLEAR PLANT CONCRETE QUALITY EVALUATION PRESENTATION TO NRC ON SCOPE AND PROGRESS OF EVALUAll! ION NOVEMBER 24, 1986, 9:30 a.m. - 3:00 p.m.

BETHESDA, MARYLAND A. INTRODUCTION B. REVIEW PROGRAM C. CONCRETE STRENGTH EVALUATION D. SAMPLE FREQUENCY EVALUATION E. BEDDING MORTAR USAGE F. STRUCTURAL EVALUATIONS G. PROGRAM RESULTS i

H. CONCLUSIONS I

t 0438h 11/21/86 GC i i t

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INTRODUCTION

• INITIAL REVIEW '

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• INTERACTION WITH NRC STAFF

• EXPANDED PROGRAM .

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• PURPOSE e

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i SCOPE OF EUALUATION

• Documented Evaluations l

• Concrete Strength Test Reports

• Concrete Production Records OBJECTIVE:

Perform detailed assessment of deviations identified at WBN i

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DOCUMENTED EUALUATIONS

• FSAR

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• Nonconformances  !

• Design Evaluations 2 -

• Memorandums, Design Deviations i

's. Requests, Etc.

Objective:

Identify all previous evaluations that have been performed.

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i CONCRETE STRENGTH TEST REPORTS 100 % Review Test Reports -

Objectives Identify all mixes and s. periods time when deviations from ~

specification requirements occurred.

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! CONCRETE PRODUCTION RECORDS

• Concrete Pour Card (4900+)

• Monthly Concrete Reports Objectives:

Identify all concrete pours made during periods that mix did not meet

., , specification requirements.

Determine if concrete sampling frequency requirements were met.

Investigate use of bedding mortar in concrete pours. , i

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4 STRENGTH EUALUATION ,

1 METHODS

• Determination of Equivalent Specified Strengths Same tec'hniques as used for WBN evaluation .

use mean and standard deviation for last 30 tests N s.

Calculate equivalent specified strength Special techniques

for less than 30 tests l

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. BOO.75BFW CReview 95 % Complete)

• FSAR documents evaluation for 7350 psi 8000 psi - 24 QA Pours -

7000 psi - 33 QA Pours 6800 psi - 20 QA Fours i

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500.75AFW CReview SS % Complete)

N. 5000 psi - 210 QA Pours

( 4800 psi - 41 QA Pours

] 4600 psi - ES QA Pours i

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i 500.75AFWG CReview S5 % Complete) 5000 psi - 118 QA Pours.

4800 psi - 17 QA Pours

' ' 401.5AFW CReview 80 % Complete)

'w. 4000 psi - 53 QA Pours 3300 psi - 8 QA Pours 1

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.i 301.SAFW CReview 80 % Complete) 3000 psi - SOS QA Fours 2700 psi - 17 QA Pours 401.SAFWR1 CReview 100 % Complete)

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• FSAR documents deviation from specification was evaluated.

3500 psi - S11pformed #2 Shield Wall J #

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3OO.75AFW 1

(Review 80% Complete) 3000 psi - S18 QA Fours 2500 psi - 135 QA Pours i

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OTHER MIXES CReview SO % Complete)

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No Strength Reduction 2000+ QA Pours Note: Totals may not add up because some pours used 2 or more mixes.

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i SAMPLING FREQUENCY EUALUATION METHODS

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• Review Monthly Concrete Reports -

Determine quantities placed per month

' Correlate to number of tests performed per mix

• Perform detailed review from pour cards for some critical mixes

• Results i

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l BEDDING MORIAR EUALUATION l

METHODS.

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• Evaluate mortar using,same a

methods as for WBN i

• Tabulate mortar (grout)

{ quantities in all concrete pours

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i RESULTS s.

• Mortar used for pump lubrication Can l

acceptable practice)

• Mortar used in some congested, areas

• Not used as standard practice for, i bedding on joints i

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STRUCTURAL EUALUATION EUALUATION OF POURS WITH STRENGTH LOWER THAN SPECIFIED METHODS

• Determine estimated inplace strength

• Determine appropriate concrete strength gain with age j -

Include affects of drying and l N. concrete temperature

CMethods developed for WBN)

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Add conservative strength gain to

! equivalent specified strength Factor in mortar strength l

into evaluation

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. i STRUCTURAL EUALUATION EUALUATION OF POURS WITH STRENGTH LOWER THAN SPECIFIED RESULTS

• Evaluation on 8000 psi concrets

• Evaluation of 4000 psi concrete 4 . Shield Building ,

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• Reevaluation of 5000 psi concrete

for which designs used strength

's. increase with age as allowed by Design Criteria

• Most 4000 psi concrete and all 3000 ,

psi will not require structural

. evaluation (Sufficient strength gain with age)

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i COMPARISON TO WBN RESULTS

• Compressive Strength Some deviations but only 5 % low tests

• Sampling Frequency Problem does n6t exist to significant degree ,

• Bedding Mortar N s' Mortar used differently.

. Lower volumes for pump lines, limited use in. congested areas.

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i CONCLUSIONS

• As identified in initial generic review, some deviations from concrete specification requirements occurred at SON

• The extent of the deviations at SQN ,

- while greater than initially identified was much less than at WBN

• Some deviations had previously been evaluated

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• Inplace concrete strengths are acceptable and no modifications or

physical testing will be required.

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