ML20210S747

Forwards Rev 1 to Exhibit F of 861113 Concrete Evaluation Rept,Reflecting Results of Util Reevaluation of Generic Applicability of Concrete Issue,Per Request.Ceb 87-02, Concrete NDT Also Encl,For Info

ML20210S747
Person / Time
Site:	Sequoyah
Issue date:	02/06/1987
From:	Gridley R TENNESSEE VALLEY AUTHORITY
To:	Youngblood B NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation
Shared Package
ML20210S752	List: ML20210S747 ML20210S778
References
NUDOCS 8702170696
Download: ML20210S747 (15)

Text

_ - _ _ _ _ _ - _ _ _ - _ _ _ _ _ _ - _

i -

L 3 .- _.

TENNESSEE VALLEY AUTHORITY g

CH ATTANOOGA. TENNESSEE 374ot SN 157B Lookout Place FEB 061987 U.S. Nuclear Regulatory Consission Attn: Document Control Desk Office of Nuclear Reactor Regulation Washington, D.C. 20555 Attention: Mr. B. J. Youngblood In the Matter of ) Docket Nos. 50-327 Tennessee Valley Authority ) 50-328 SEQUOYAH NUCLEAR PLANT - CONCRETE EVALUATION REPORT On November 13, 1966 TVA submitted a report on the evaluation of concrete quality at Watts Bar Nuclear Plant. Exhibit F to that report addressed.

generic applicability of the Watts Bar concrete issues to Sequoyah and other TVA nuclear facilities. Upon review, NRC requested that a more extensive evaluation be performed for closeout of this issue at Sequoyah units 1 and 2.

TVA subsequently established and implemented a more thorough review program for Sequoyah concrete.

Enclosure 1 documents the results of this review effort. Revision 1 to Exhibit F discusses in detail the program conclusions and the basis for acceptability of concrete at Sequoyah. It supersedes and should replace the original Exhibit F to the Watts Bar Concrete Evaluation Report (CEB-86-19-C).

As enclosure 2 TVA submits CEB Report No. 87-02, which provides the results of our Mondestructive Testing Program at Sequoyah. Data serves to confirm the acceptability of in-place concrete at Sequoyah and is offered for your information.

If any questions exist regarding the enclosed, please call M. R. Harding at (615) 870-6422.

Very truly yours, TENNESSEE VALLEY AUTHORITY R. ridley, D: rector Nuclear Safet# and Licensing Enclosures cc: See Page 2 0j 0

h2]

P 6 870206 K 05000327 PCR

..m An Equal Opportunity Employer

U.S. Nuclear. Regulatory Conmission B 06 M7 cc (Enclosures):

U.S. Nuclear Regulatory Commission Region II Attn: Dr. J. Nelson Grace, Regional Administrator 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Mr. J. J. Holonich Sequoyah Project Manager U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue Bethesda, Maryland 20814 Mr. G. G. Zech, Director TVA Projects U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Sequoyah Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37319

ENCLOSURE 1 Revision 1 EXHIBIT F GENERIC REVIEWS Generic Review of Concrete Quality for Sequoyah (SQN),

Browns Ferry (BFN), and Bellefonte (BLN) Nuclear Plants 1.0 GENERAL 1.1 Background -

The evaluation of concrete quality for Watts Bar Nuclear Plant (WBN) has identified several deficiencies which are being cddressed in the following nonconformances:

NCR 6719 - Low Concrete Compressive Strength Results NCR 6720 - Use of Bedding Mortar in Structural Concrete Placements NCR 6721 - Frequency of Sampling Concrete 1.2 General Discussion of Generic Evaluations 1.2.1 WBN NCR 6719 This NCR identified periods of time when the percentage of low concrete compressive strength results exceeded the G-2 specification requirements.

A complete review of the concrete strength test records was performed for Sequoyah Nuclear Plant (SQN). Some deviations from the specification requirements were identified and a Problem Identification Report (PIR) PIRSQNCEB8691 was issued. A detailed evaluation of the deviations has been performed for SQN and is discussed in Section 2.0.

Reviews of the concrete records for Browns Ferry Nuclear Plant (BFN) and Bellefonte Nuclear Plant (BLN) were performed for NCR 6719. These reviews, which are discussed in Sections 3.0 and 4.0, indicate that the deficiency does not exist at BFN and BLN. However, detailed reviews of the concrete records will be performed for the generic evaluation of PIRSQNCEB8691. The results of these reviews will be reported independently for each of the plants as part of the PIR resolution.

DNEl - 1265M i

1.2.2 WBN NCR 6720 This NCR identified the use of a special mix, lack of proper sampling, and low strength test results for bedding mortar.

ACI 318-71 recognizes the use of bedding mortar but requires that it be the mortar fraction of the concrete being placed.

The application and the use of bedding mortar were not specifically noted in ,TVA General Construction Specification G-2 (G-2), but were acceptable practices in accordance with ACI 318-71. ACI 318 is the licensing basis for WBN as well as the other plants.

A generic evaluation for the other TVA plants was performed to determine if the use of bedding mortar was properly controlled in structural concrete placements at BFN, SQN, and BLN. As discussed in Sections 3.0 and 4.0, it has been determined that bedding mortar was not routinely used for bedding mortar at BFN or BLN, respectively.

At SQN, mortar was frequently used for concrete pump lubrication which is an accepted industry practice. Mortar was also used in some congested areas but mortar was not used as a standard practice.for bedding on joints. The results of the SQN evaluation are discussed in Section 2.3.

1.2.3 WBN NCR 6721 This NCR identified a failure to always follow the procedure specified in G-2 and WBN QCP 2.02 for Frequency of Sampling Concrete Mixes. The investigation for this NCR showed that the sampling frequencies used at WBN substantially complied with G-2. In view of the relative small percentage of samples deviating from specification requirements (60 out of approximately 6100 total samples for less than 1 percent),

the overall offect is negligible and this NCR was not considered to be significant.

Reviews of the records cad audits for BFN and BLN indicate that requirements for sampling were met. For SQN, a detailed review of the concrete quantities and test data identified only 10 time periods from a total of 497 when the sampling frequency requirements were not met. The 10 occurrences were evaluated and determined to be acceptable. Due to the small number of deviations, the WBN deficiencies were determined to not be generic to SQN.

1.3 Variation of In-Place Concrete Between TVA Plants TVA General Construction Specification G-2 is applicable to all TVA nuclear plants. However, the implementation differed between the nuclear sites. This section describes the background for these differences.

DNE1 - 1265M

The physical properties and variability of the concrete at each of the nuclear plants are inherently different because even though the controlling specifications are essentially the same (some differences in the detailed specification provisions exist for the different plants), the materials, and the implementation procedures contain differences. Program results are directly related to the personnel and management implementing its provisions.

Interpretation of specific provisions of control documents will vary. As pointed out in Volume I of TVA's Nuclear Performance Manual, decentralization of program activities contributed to inconsistant application of requirements. Concrete specifications for all nuclear plants state that no more than 10 percent of the strength test results are to be less than the specified strength (20 percent for less than 3000 psi specifie<1 strength). This permits an individual materials engineer to use any percent between 0 and 10 as a target. All nuclear plants changed materials engineers during the course of construction, and at some plants this changed control efforts. Changes also occurred in the design personnel reviewing the control efforts. Our investigations to date indicate that while differences among the plants do exist, the in-place concrete will adequately perform its intended function.

2.0 SEQUOYAH NUCLEAR PLANT

2.1 Background

A generic evaluation was performed for SQN for the three deficiencies listed in Section 1.1 in April 1986. This review determined that the WBN deficiencies were not generic to SQN. This review was based on interviews with cognizant personnel and on a review of approximately a third of the SQN concrete records. In October 1986, the NRC performed an audit to investigate the generic implications of the WBN deficiencies and, as the result of the audit. TVA was requested to perform a more comprehensive review of the concrete records for SQN. The following sections provide the results of the expanded review.

2.2 Sampling Frequency Evaluations 2.2.1 Procedure A detailed review of the concrete sampling frequency was performed using the monthly concrete reports and the concrete testing ledger. The monthly reports include the quantity of concrete placed for several mixes placed during the calendar month covered by the report. The ledger provides a tabulation of all sampling and testing for each concrete mix. The construction procedures were also reviewed for compliance with the requirements of the specification.

DNEl - 1265M

Compliance with the specification requirements was evaluated by correlating the number of tests performed on a mix during the reported time period to the total yardage placed. A

, total of 497 time perio_ds were evaluated.

2.2.2 Results The review of the procedures showed that the requirements of G-2 were correctly incorporated into the procedures and revisions to the requirements were incorporated in a timely manner.

The results of this evaluation show that, for the major mixes, only 10 sample periods out of 497 did not meet the requirements of G-2. Eight of the ten periods were early in the plant construction period and involved fill concrete. An evaluation of these mixes indicated that the strength levels were sufficiently above the specified strength to offset any decrease in strength not identified as the result of inadequate sampling.

The other two periods are in October 1971 and June 1973 for the 300.75AFW. The October 1971 period was reviewed and determined that only about 54 yards of the reported 624 yards was placed in QA structures and that the sampling was

, acceptable. The strength levels for the mix in 1973 were significantly above the required strength.

2.2.3 Conclusion Only minor deviations from the sampling requirements of TVA General Construction Specification G-2. occurred.at SQN and all deviations were evaluated and determined to be acceptable.

2.3 Mortar Usage Evaluations The initial generic evaluation for use of bedding mortar was based on interviews with cognizant engineers involved in the concrete placements at SQN. These reviews indicated that mortar had been used in a few isolated areas but that the use of bedding mortar was not a standard practice as it was at WBN.

Additional data on mortar usage became available as the result of the strength evaluations discussed in Section 2.4, and specifically in development of the data base for the concrete pour cards discussed in Section 2.4.5. The pour cards provide the volumes of all mixes used in a pour including the mortar mix.

DNEl - 1265M

.The information on the pour cards shows that mortar was frequently used'in small quantities for priming and lubrication of the concrete pump. .The pour cards also frequently state that the mortar was wasted. . Occasionally, the pour cards noted that mortar was used in

' congested areas. A total of.about 800 pour cards noted the use of mortar (5500 total pour cards for Category I structures).

Approximately 680 of these pours noted a total mortar volume of 1 cubic yard or less.which was generally for pump lubrication. Only about 50 pours noted mortar volumes exceeding 20 percent of the total volume of the pour. In many of these cases, part of the mortar was likely wasted.

Since the use of mortar for pump lubrication is an accepted and necessary practice, and the use of mortar in congested areas was limited, the deficiency occurring at WBN is not considered to be generic to SQN. However, for the structural evaluations discussed in Section 2.5, if the mortar strength was less than the concrete strength the following adjustments were made: the estimated inplace strength of the pour was assumed to equal the mortar strength if the mortar volume exceeded 20 percent of the total volume of the pour.

For mortar volumes between 5' percent and 20 percent, the average strength of the mortar and concrete was used.

2.4 Compressive Strength Evaluations 2.4.1 Background and Purpose The design drawings for SQN specify the concrete mix to be used in the structures. The requirements for obtaining these required strengths were given in G-2. G-2 specified that no more than 10 percent of the strength test results could fall below the specified strength.

The purpose of the compressive strength evaluation was to identify and evaluate any mixes and time periods when the G-2 requirements for strength were not met.

2.4.2 Data Base Development A computerized data base was developed that consisted of all concrete strength test results obtained for structural concrete mixes which were produced during the construction period and which were placed in Category I structures. This data base consists of approximately 3800 tests on a total of 40 mixes. The data was obtained from the compressive strength test report (TVA Form 331) and the concrete ledger, which was a laboratory worksheet summarizing all strength test results. Both documents were obtained from QA record storage.

The data base showed that approximately 5 percent of the tests did not meet the specified strength requirement at the specified age. This compares to 13 percent for WBN.

DNEl - 126SM

2.4.2 Strength Evaluation Procedure Compliance with the requirements for compressive strength was evaluated by determination of an equivalent specified compressive strength for each six for all periods of time that mix was used. The equivalent specified strength is the strength level below which a statistical calculation indicates no more than 10 percent of the strength tests would be expected to fall. This calculation was based on methods provided in ACI 214 and used the mean and standard deviation for the last 30 tests. The equivalent strength by the ACI 214 method is equal to the mean minus 1.28 times the standard deviation.

The method discussed above is not generally applicable to less than 30 tests. Therefore, for the first 30 tests of a mix, the equivalent specified strengths were based on the ACI 318 criteria. The ACI 318 criteria is that the average of three consecutive tests must exceed the specified strength for the mix and no individual test is more than 500 psi less than the specified strength.

2.4.4 Strength Evaluation Results The strength evaluation identified 7 mixes which had one or more time periods when the G-2 requirements for strength were not met. As the result of this determination, the deficiency identified at WBN was determined to be generic to SQN and PIRSQNCEB8691 was written.

The following mixes were identified as having " low strength" periods: 300.75AFW, 301,5AFW (2 periods), 401,5AFW, 401.5AFWR1, 500.75AFW (3 periods), 500.75AFWG, and 800.75BFW (2 periods). Two of the mixes had previously been evaluated for lower strength as documented in the Section 3.8 of the FSAR (mixes 401.5AFWR1 and 800.75BFW).

Equivalent specified strengths were assigned to each of the mixes for " low strength" time period. The value assigned was the lowest equivalent strength calculated during the time period that the G-2 requirements were not met. The equivalent specified strengths for the 7 mixes (and each time period) are provided in Attachment 1 (ESS28 for class A mixes and ESS90 for all mixes),

f i

l i

DNE1 - 1265M f

4

2.4.5 Id:ntific:tien cf Pcurs Affceted by "L:w Stesngth" Time' Periods An additional data base was developed that consisted of the data from all pour cards for each structural concrete pour in Category I structures. The pour card is the QA record of the placement and, in addition to providing documentation of the inspections, it identifies the concrete mix used and the date of placement. A total of 5500 QA concrete pours were identified with 420 having mixes with " low strength" time periods.

The pour card data base was sorted by concrete mix and placement date to allow determination of all concrete pours made during " low strength" time periods. A computer summary was developed that listed all concrete pours with concrete having an equivalent specified strength that did not meet the G-2 strength requirement at the specified age. This sununary along with the construction pour drawings was used for identification of concrete members that required additional evaluation.

2. 5' Structural Evaluations j 2.5.1 Concrete Structures i All Category I concrete placements were identified where the equivalent specified strength was less than that specified on

the drawings. Based on this information, average estimated

inplace strengths were established using the method described in Section 2.4 of this report for all such placements. (The rtrengths used were verified as detailed in Section 2.6.)

I Approximately 9,900 cubic yards of concrete, representing 6

percent of the concrete placed in Category I structures was

identified as having an equivalent specified strength less than the specified strength at 28 or 90 days.

{

l All design calculations for the affected Category I j structures were reviewed. If the inplace strength was less

! than the strength used for the existing design, an evaluation l_ using the estimated in-place concrete strength was done to

! determine if the structure or feature meets the design requirements. The estimated in-place strengths satisfied structural requirements since either the originally specified l strengths were higher than required, the original loads are

, larger than up-to-date loads, or more reinforcement was provided than was originally required. This evaluation confirms that all concrete placements with estimated in-place i strengths less than specified on the design drawings or used in the design calculations are structurally adequate to perform their intended function.

I DNE1 - 1265N

All design calculations have been checked and documented.

Design criteria revisions and FSAR revisions to incorporate the results of this evaluation are being developed. All concrete design drawings for Category I structures where the estimated in-place strength is less than the specified strength are being revised to incorporate a reference to ensure the use of proper concrete strengths in future design evaluations. .

2.5.2 Anchorages to Hardoned Concrete The design of concreto expansion anchors is based on a specified compressive strength of 3000 psi. Exceptions to this occur where increased concrete strength was used in a reevaluation for higher loads. Only two cases were identified. Calculations for these supports were reviewed using the estimated in-place strength and were found to be acceptable.

In summary, it is concluded that the designs for anchorages to hardened concrete are adequate for the in-place strength of the concrete.

2.5.3 Embedments All design calculations for embedded plates and bolt assemblies (including some grouted bolts) in the reactor buildings and steam valve room were reviewed. Where estimated in-place strengths were less that those used in the design calculations, the embedment calculation was revised.

All revised calculations demonstrated that the embedments are adequate to carry their design loads.

In addition to the review of all embedded plate calculations completed as discussed above, all Sequoyah Reactor Building and East Steam Valve Room pours with estimated in-place concrete strengths less than the estimated in-place strengths for corresponding Watts Bar pours were identified. All embedments in these lower strength pours were identified, reviewed, and found to be acceptable.

For all other Category I structures (auxiliary, control, diesel generator, and intake pumping station) estimated in-place strengths in this report were compared to specified strengths. Only a few nonstructural elements in the auxiliary building had estimated in-place strengths less than the specified strength. Embedments in these areas were reviewed and found to be acceptable.

In summary, the designs for embedded plates and anchorages are adequate for the in-place strength of the concrete.

DNEl - 1265M

.l 1

2.5.4 Emb:dddd Pleto Rsvitw Prcgrams ,

Three review programs using independent. calculations and unrelated to this investigation have been performed at SQN.

Each of.these programs was reviewed to' determine if in-place strengths were less than the strength used for the calculations. Several cases were found, and revised calculations were generated.- All cases were found to be acceptable. These programs were found to be satisfactory.

-with all designs being' adequate for the estimated in-place strengths.

2.6 Verificationlof Compressive Strenath Adequaev from Later Aae Standard Cylinder Tests 2.6.1 Background Section 4.2 of.the main report describes the method used for application of concrete strength gains with age to the equivalent specified compressive strength. The strength gains are based on tests on cores and cylinders from test blocks. These blocks, although of the same nominal proportions as the mixes evaluated, did not use the same materials as the concrete which did not meet the specification strength requirements.

To further verify the adequacy of the compressive strengths utilized in the structural evaluations, an additional investigation was performed. The purpose of the investigation was to determine the equivalent specified strengths based on the 90-day compressive strength for the standard cured cylinders, and to compare these values to the concrete strength used.for the. structural evaluations. The 90-day compressive strength is sometimes used in the concrete industry. The investigation was performed on the 6 class A mixes that had " low strength" periods. The class B mir (800.75BFW) used the 90-day equivalent specified strength as the inplace strength with no additional strength increase with age.

2.6.2 90-Day compressive Strength A review of the 90-day compressive strength test results for the " low strength" mixes and time periods was performed. The review showed that 9.0-day standard cured cylinders were tested for over 90 percent of the samples made for class A concrete during these periods.

The 90-day compressive strengths for the standard-cured cylinders from the concrete made during periods of low strength document the strength gain with age expected to occur except for very thin members. Using 90-day results, an equivalent specified strength was calculated.

DNEl - 1265M

~

2.6.3 Equivelant Cancreto Strangth at 90 Days Theequivalentspecifiedstrengthat90dayswascalculahd

• using the same methods used previously for the 28-day ~ " ,, ' '

strengths (calculated from the average and standard _ deviation ,

for the last 30 tests or using the ACI criteria for less.than .

30 tests). The calculated values are tabulated on Attach 5ent i 1 (ESS90 for class A mixes). '['

Attachment 1 shows the*6 class A mixes that had " low strength" timo periods and with the equivalent specified strength at 28 and 90 days. The summary shows that for each period the specified strength is achieved or exceeded at 90 days. A review of the structural evaluations shows that the'- f estimated inplace strength used for the evaluation wrs always~

less than or equal the equivalent specified strength at 90 ,

days.

2.6.4 Identification of " Thin" Structural Members As discussed previously, the strength gain indicated by 90-day cylinders for concrete with specified 28-day strength is appropriate if an evaluation for thin members is performed. Therefore, an additional review of the e calculations was performed to verify that the strength gairis used for thin members was conservative.

All concrete pours placed during " low strength" time. periods -

have previously been identified for the evaluations discussed-in Section 2.5.1 and the volume-to-surface ratio (V/S) for' '

each pour calculated. Also, all pours were previously  ?

identified which used later age strength in the analysis as '

specified in the design criteria.

1 For the previous evaluation using estimated inplace t , ,

strengths, no strength gain with age was used for members ,

with V/S less than or equal to 0.25 feet (6 inch wall for,, '

example). The full strength gain with age was added iffene, 4 3 V/S was 1 foot (2-foot-thick wall for example). A lincat' i ,

interpolation was used for V/S between 0.25 and 1.0 feet /.' 'r '

6 7 To provide a consistent comparison and verification of the strengths used for the structural analyses, a similar -

approach was used except that the interpolation was between '

the equivalent strength at 28 days and the equivaluat strength at 90 days. < ,;.c

~

Allstructuralmembersplacedduring"lowstrengt[* time periods and all structural members with long-terni strength specified on the drawings were ident'.fied which have V/S less than 1 foot. The smallest V/S was 0.31 feet.., '

DNEl - 1265M 1 >

.'?

% .,, . u . ,

t' y Fce occh cf thzsa p:urs en equivslant strength wzs calculatsd based on interpolation between the equivalent strengths at 28 and 90 days. These values were generally higher than the

. strength used for the structural evaluation and were never more than 100 psi less. Therefore, the structural m evaluations based on the estimated in-place strength are

.  ; adequate.

2.7 Conclusions , i T!ie generic evaluation has determined that the WBN deficiencies for j sampling frequency and bedding mortar usage do not apply to SQN.

i Some deviations from specification requirements dealing with the

'.* strength level of some concrete mixes were identified and PIRSQNCEB8691 has been issued. The evaluation of the deficiency has

- been completed and all structures were determined to be acceptable.

3.0' BNOWNS FERRY NUCLEAR PLANT

' Discussions were held with H. S. Sheppard and J. Davenport, who were e -

directly involved in the concrete placement during the construction of

[' BFN as materials engineers, and S. Carr, who was assigned to SME.

[g' In addition, a partial review of concrete records was conducted at BFN (Attachment 2). Cylinder tests results show acceptable strengths at the specified age. These revealed the following:

0 '/ There were fewer mixes used on BFN in comparison to WBN. The maximum strength mix was 401.5 AFW. The average strength of this

(/ mix was 5170 psi with less than 2-percent low tests.

0 fe'r a 300.75 AFW . * :. here were no low tests.

0 ' Based on the above and other records, cylinder test results show

~

acceptable strengths at the specified age.

O Concrete mix designs were prepared by SME.

1 0,

'~

Congested areas were encountered in the fuel pool and in columns for the turbine and reactor buildings.

0 4 A high mortar volume, 3/4-inch-maximum aggregate size concrete mix

, was developed by SME and used in congested areas and around water

,. seals.

,/ q 0

[, t here was no knowledge of the use of grout as bedding mortar.

/ r 0 The frequency requirement for test sampling specified in G-2 were s

• adhered to. Since this was TVA's first nuclear plant, the NRC

, performed an extensive audit on TVA concrete procedures at the time

, , + 'of construction.

l Basad upon the above, the concerns identified for WBN do not apply to BFN.

Howher, a more detailed evaluation of strength test results will be performed and documented for the generic review of PIRSQNCEB8691.

' " DNE1 - 1265M v ,

3 % ,s

n

," I

. . u

~

4.0 3ELLEFONTE NUCLEAR PLANT Discussions were held with D. Nixon and R. Norris, who are assigned to BLN as materials / civil engineers, and other personnel knowledgeable of concrete design, placement, and testing for BLN and a partial review of BLN concrete records was conducted (Attachment 3). This assessment revealed the following:

i 0

An effective working relations, hip existed between the DNC materials

, engineers and DNE concreting specialists along with very good experience levels at both positions.

O The required monthly reports were submitted by DNC and evaluated by e

DNE.

O Concrete mix adjustments were frequently made by DNC to maintain strength levels and major adjustments were reviewed by DNE.

O Concrete compressive strength test records show strengths in excess of requirements.

O Concrete mix designs were prepared by SME or by BLN DNC with DNE g approval.

O Congested areas were encountered.

O High mortar volume, 3/8-inch-maximum aggregate size concrete mix was developed. This was used in congested areas.

- 0 Mortar mixes were developed to correspond to each class of concrete. These specialized mortar mixes were used to lubricate concrete pump lines.

O Informal reviews of the WBN NCRs were performed by BLN DNC personnel under the direction of the onsite nuclear licensing unit. In addition, an internal audit was performed in 1985 on the concrete unit.

Sampling frequencies for concrete were reviewed during the audit and no major deficiencies were noted.

Based upon the above, the deficiencies identified for WBN do not apply to BLN. However, a more detailed evaluation of strength test results will be performed and documented for the generic review of PIRSQNCEB8691.

5.0

SUMMARY

As a result of these discussions and reviews, it is concluded that the deficiencies discovered at WBN in regard to bedding mortar and sampling frequency are plant-specific to WBN and that similar deficiencies do not exist at BFN, SQN, and BLN. The WBN deviations with respect to compressive strength also occurred at SQN but to a lesser degree.

Reviews of compressive strength results at BFN and BLN indicate compliance with specification requirements, however, additional reviews will be performed for the generic review of PIRSQNCEB8691.

DNEl - 1265M

ATTACHMENT 1 Sequoyah Nuclear Plant Equivalent Specified Strengths The following table summarizes the strengths for the 7 mixes with " low strength" time periods. ,.

MIX f'c ESS28 ESS90 psi 28 days 300.75AFW 3000 2600 4000 301.5AFW 3000 2700 4300 2500 4000 401.5AFW 4000 3300 4800 401.5AFWR1 4000 3500 4900 500.75AFW 5000 4800 6800 4600 6200 4800 6500 500.75AFWG 5000 4890 6500 800.75BFN 8000* N/A 7600 N/A 7000 N/A 6800 ESS28 = Equivalent specified strength at 28 days.

ESS90 = Equivalent specified strength at 90 days.

• Specified strength at 90 days.

l l

l DNE1 - 1265M i

I

-- . . - - , . , _ - , . . - . . , . . _ - . , - - - . - - -.