GO2-83-996, Amplifies 830916 Response to NRC Re Violations Noted in IE Insp Rept 50-397/83-38.Corrective Actions: Discrepancies from Design Requirements Evaluated.Structural Members Adequate for All Loads

Amplifies 830916 Response to NRC Re Violations Noted in IE Insp Rept 50-397/83-38.Corrective Actions: Discrepancies from Design Requirements Evaluated.Structural Members Adequate for All Loads

ML20086B026
Person / Time
Site:	Columbia
Issue date:	10/31/1983
From:	Carlisle C WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
Shared Package
ML20086B024	List: GO2-83-996, Amplifies 830916 Response to NRC Re Violations Noted in IE Insp Rept 50-397/83-38.Corrective Actions: Discrepancies from Design Requirements Evaluated.Structural Members Adequate for All Loads
References
GO2-83-996, NUDOCS 8311160257
Download: ML20086B026 (9)

Text

r NOV 2 Et Washington Public Power Supply System P.O. Box 968 3000 GeorgeWashingtonWay Richland, Washington 99352 (509)372-5000 Docket No. 50-397 October 31,1983 G02-83-996 Mr. J. B. Martin Regional Administrator U.S. Nuclear Regulatory Commission Region V 1450 Maria Lane, Suite 210 Walnut Creek, CA 94596 Subject  : NUCLEAR PROJECT 2 NRC INSPECTION REPORT 50-397/83-38 NOTICE OF VIOLATION Reference : (1) Mashington Public Power Supply System letter G02-83-839, dated September 16, 1983 (2) Meeting with NRC on October 14, 1983, in Bethesda, Maryland Attachment I to this letter amplifies information contained in reference (1) in response to requests made at reference (2).

If you have any questions or desire further information, please contact Hugh Crisp at (509) 377-2522, extension 4661.

. 982A Program Director, WNP-2 HAC/fl Attachment cc: Mr. R. Auluck, NRC Maryland Mr. R. T. Dodds, NRC RV Mr. R. F.-Heishman, NRC I&E Mr. A. D. Toth, NRC Resident, WNP-2 W

8311160257 j3g g PDR ADOCK PDR_ 2 .

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. ATTACHMENT I WASHINGTON PUBLIC P0hER SUPPLY SYSTEM' NUCLEAR PROJECT N0. 2 DOCKET NO. 50-397

• LICENSE N0. CPPR-93 ADDENDUM TO RESPONSE TO INSPECTION REPORT 83-38 i NOTICE OF VIOLATION EVALUATION OF CONCRETE AND REINFORCING STEEL FOR ,

WASHINGTON PUBLIC POWER SUPPLY SYSTEM UNIT 2 o Concrete Sampling Program Beams 2B3, 2Bil and 2B25 were the subject of nonconformance report (NCR)6426-1851. This NCR identified honeycombing on each beam, ,

which was subsequently repaired. When these patches were rein- '

spected and sounded (b" tapping) in 1983, it appeared patches were i deficient and it was ded ded to perform destructive examination of

these beams. Removal of these patches showed that there reinforcing steel placement deviations and honeycombing/,were voids-existed in areas of congested rebars. - Concerns were expressed by' the Construction Appraisal Team-(CAT) that similar conditions might, e exist elsewhere and additional destructive examination of concrete #' '

structural components was undertaken.- -

(

l A total of 17 members with 23 nxiNation locat s known'to have. I congestion were selected for evaluation. These structures -(with i congested rebars) are the ones most likely_ to exhibit misplaced rebars and honeycombing. The sample was thus biased in the dire'-

tion of those components and locations most susceptible to be affected by the deviations mentioned above.-

Reinforced concrete design drawings were reviewed,and it was established that the areas most likely to have a similar problem would be the beam-bioshield wall intersections where the main rebars are spliced with. dowels. There are 66/such beam-bioshield' intersections;_ six of these intersectin were excavatedi The sample was further biased by selec% 2871 and 2825,:which repre--- -

i sent all of the beams with thre !@ of bottom-reinforcement'at j the beam-bioshield intersectf'in ~

U < exc'avated were beams- 283-and 285, with two layers of.b W .om ,# :Jorcement, and beams 3B18

and 6B9, with single-1ayers'oi bottom reinforcement. In'additio'n

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to beams framing into the'bioshield wall, two beams (3810 and 4B30)'

, framing into column / exterior walls were also excavated.V The total sample excavated is representative'of the reinforced ~'

conc' rete ~in

-the remainder of.the plant. ^

- Reinforced concrete-design drawings were also reviewed in 3rder-to. ..

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include other type structures in the sample program. Again, con-gested areas were selected in order to obtain representative samples of columns, walls, slabs and mats.

The pour records were examined for each structure included in the sample to insure that RFIs and NCRs, which might have been issued 1

on the structure, were considered in the analysis, i

The selection and extent of each excavation also included evalua-tion of each member for the excavated condition to assure that the

excavation did not weaken the member.

.I

! The sample selected for investigation was not based on a random nor a statistical .ipproach. Rather it was selected to provide a con-servative biased sample of representative types of construction. It included beams, columns, walls, slabs and mats. Each excavation was

i. selected at an area most susceptible to construction problems wherc l

rebar congestion might lead to honeycombing, voids, rebar spacing deviation or misplacement of rebar.

Visual reinspections were made of the beam-bioshield wall connections for 37 beams (framing into the bioshield wall), which represent 56%

of the principal beams in the Reactor Building. Eight minor-questions recorded were dispositioned " accept as is" by the engineer.

o Clarification of Lap Splice (SK-17 of Reference 1)

{ ACI Co'de.318-71, per paragraph 7.5.4, allows the'use of non-contact lap splices, provided the bars to be spliced are not spaced trans-i i versely farther apart than one-fifth the required : length of lap nor-six inches. At column line M on the East Exterior Wall, the wall thickness is 3'-0" on the north side of the pilaster and 2'-6" on the south side of the pilaster. The horizontal -bars for 3'-0'.' and 2'-6" walls were terminated within the pilaster with C-1 splice, which is in full conformance with code requirements', because the.

difference in wall thickness is six inches and the horizontal bars are spaced transversely only six in'ches-apart.

o Rebar Alignment Paragraph 7.4.l'of ACI 318-71 stipulates that where parallel reinforcement is placed in two or more layers, the bars .in the upper layers shall be placed directly above those in the bottom .

layer. The commentary to ACI 318-71 code further clarifies that these spacing limits were developed from successful practice to permit concrete to flow readily into spaces between bars and

j. between bars and forms without honeycomb. Rebar placement with some misalignment in layers (bars in~ different layers not directly:

above each other) ineets the intent of the code and is acceptable,;

l Page 2 of 5l- ATTACHMENT I I

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as long as rebars are placed to allow concrete to flow readily through the spaces without honeycombing. The excavation of beam 2B5 (SK-2 of Reference 1), which originated this concern, showed fully-consolidated concrete tightly bonded to the rebar with no honeycomb.

o Rebar Spacing l The spacing of rebar has received considerable attention among structural engineers and constructors for decades. The ASCE has a committee to study the problems related to nuclear power plants.

The various codes (ACI 301, ACI 318, ACI 349, and ACI 359) specify clearances that are desirable. It is desirable that the maximum size aggregate pass between the rebar. This is rarely practical on all parts of the plant. Sometimes the spacing between bars is actually designed to be zero. This " bundling" has been studied and tested.

Some results of tests have been published in the 1960 ASCE Trans-actions in Paper No. 3047, " Concrete Beams and Columns with Bundled Reinforcement", by N. W. Hanson and Hans Reiffenstuhl. As the title states, both beams and beam-columns were tested. Bars were placed with zero clearance, both vertically and horizontally, so that " bundling" occurred in part of the cross section of the member.

In all cases, "no significant difference in behavior or ultimate strength was found for bundled as compared to spaced reinforce-ment".

The tests showed that "there was no systematic difference in ultimate bond stress developed between spaced and bundled bars".

Zero spacing in bundled areas was determined to be satisfactory for both tension and compressive areas. Examination of the struc-tures after testing indicated mortar had penetrated into and filled the cavity between thn bars of the bundle.

Thus, it is concluded that the spacing of rebar can be less than specified if' adequate concrete consolidation (without honeycomb) is

. obtained.

In examining the various structural members, there were only two cases where lack of bond was experienced. These were in the com-pressive areas on beams 2B11 and 2B25. The detailed structural evaluation showed that construction loads dominated and the beams had been " tested" by the construction loads, which indicated that the systems met the design requirements.

O Mix Substitution Contract drawing S749, note #2, specified concrete mixes. 'The mix for use in beams cast integral with floor slabs is based on the Page 3 of 5 - ATTACHMENT I I

i 1

F slab thickness. For beams 4B30 and 6B9 the required mix was 4SA-P. ,

(maximum size of aggregate equal to 3/4") based on the adjacent slab thickness of 12 inches. The beams and slab were constructed

. using mix 4MA-P (maximum size aggregate equal to 1-1/2"). The mix '

i substitution was approved by the Burns and Roe Field Engineer prior to concrete placement.

This substitution in no way affected the structural integrity of

• the beams because of the following:

i (a) Both classes of concrete (i.e., 4f1A-P and 4SA-P) have the same

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required minimum 28-days' strength of fc'=4000 psi. (The actual 28-day strength of these pours was over 5000 psi.)

(b) Concrete bond and consolidation in the excavations made in these two beams was excellent, without honeycomb and voids, i

(c) Beams 4B30 (3'-0" x 3'-0") has seven bottom bars and beam 6B9

(2'-0" x 3'-0") has four bottom bars, which provides a minimum average clear space of four inches between the rebars. -This i spacing meets the requirements of paragraph 3.3.2 of the ACI

Code 318-71.

o Westinghouse Charter The Westinghouse Corporation was given direction under a Basic Ordering Agreement with the Supply System to provide an independent overview of the Supply System effort to resolve the questions raised by the NRC CAT. Westinghouse reported their assessments through the Director.of Technology to the Managing Director; however, there was daily contact between project people and the Westinghouse Team. Westinghouse was specifically asked to provide a third-party review of the concrete issue. . Initially, this review was to have been a broad overview of the facts and conclusion reached by the Supply System. Direction to Westinghouse was expanded, however, after the inspection conducted by Messrs. Albert and.

4 Herring on July 25-27, 1983, to provide for a more detailed review of.the facts being developed by the excavations related to the concrete issue. The detailed scope of the Westinghouse review is stated in their September 15, 1983, letter tc the Supply System (Appendix D to reference (1)).

o Conclusion The-Supply System has confirmed the adequacy of. concrete construc-tion at WNP-2 by performing.a detailed investigation of selected as-built structural members. The investigation included 23_excava-tions in.17 structural members at locations of congested rebar:in i

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1 representative beams, columns, walls and slabs. Such iocations are difficult to construct and therefore provide a conservative sample of the plant structures. The investigation included three structural beams (2B3, 2Bil and 2B25) where the congestion had been so severe that honeycombing and voids had been identified during construction and had been repaired in accordance with approved construction procedures.

Results of the evaluations are sumarized in Table 1. The excavations demonstrated acceptable construction quality in columns, walls, slabs and mats. The excavations in beams indicated a significant number of locations where the spacing of rebar was less than that specified in the code. This occurred primarily in areas where the main reinforcement was lap spliced. The code requirement on clear spacing between reinforcement is primarily imposed to assure good concrete consolidation. With the exception of the three beams where honeycombing and voids had already been identified during construc-tion, all excavation locations showed good consolidation of the concrete, thereby demonstrating the adequacy of concrete construc-tion in these locations.

All discrepancies from the_ design requirements were evaluated. In every case the structures were found to be adequate. The results-show that for two cases some bond was not available on all the bars. This inadequacy occurred in. beams at dowel splice locations where honeycomb and voids were most likely. Both of these beams have already experienced construction loads in excess of those specified during plant operation, and performed well. Of all the cases studied, only one dowel that should have been located in the excavation was not uncovered. This beam was conservatively evalu-ated assuming the dowel was missing and not just misplaced, and was found to be adequate. In summary, all structural members excavated during the investigation were demonstrated to be adequat'e for all specified loads.

The investigation demonstrated that structural members specifically selected for their difficulty in construction met the intent of the code for all design conditions. This biased sample provides confi-dence that the conclusion may be extended to all Category I concrete structures of WNP-2 since they were designed and constructed to the same quality procedures as those included in this investigation.

Page 5 of 5 - ATTACHMENT I

TABLE 1 Page 1 of 3 .

SUMMARY

OF STRUCTURAL MEMBERS EVALUATED Design: Margin (See Footnote) Observed Discrepancies ,

SK.# Member Maximum Maximum Rebar Rebar/

+ive . -ive Spacing Dowel Honey- Remarks Conclusions Moment Moment . Shear Missing / combing

+M -M Mis @ aced SK-1 '283 2.l' .l .4 1.5- Yes None None Concrete consolidation is Meets the intent of excellent, the code.

SK-2 2B5 - 3.5 1.5. 1.2 None .None None Rebars were placed in 3 layers Meets the intent of instead of two layers. the code.

SK-3 '2B11 3.6 1.9- 1.3 Yes None Yes Honeycombing and rebar spacing Meets the intent of deviations were found ir con- the code, gested area where main bars were spliced with dowels.

SK-4 2B25 3.0 1.5 1.1 Yes None- Yes- Honeycombing and rebar spacing Meets the intent.of deviations were found in con- the code.

gested area where main bars were spliced with dowels.

SK-5 3810 2.5 1.4 .l.5 Yes -None None Concrete consolidation is Meets the code excellent. requirement.

3 SK-6 3B18 2.5 .l.0 1.6- .Yes- Yes None One dowel not found. Dowel not Meets the intent of needed per code. Consolidation the code.

is excellent.

s SK-7 4B31 4.3 2.4 :2.1 None None None Meets the code requirement.

Footnnte to Table:~-Designmarginasusedhereinisthe. capacity.providedabovethatoftheorig{ngldesignrequirementg5.) licens ng commitmen e  : (.A design margin of 1.0 signifies compliance with ACI 318 code requirements y y - - - - - - ___ _ _ _ _ _ _ _ _

7 TABLE 1 Page 2 of 3 .

SUMMARY

OF STRUCTURAL MEMBERS EVALUATED Design Margin (See Footnote) Observed Discrepancies ,

SK.# Member Maximum Maximum Rebar Rebar/

+1ve -ive Spacing Dowel Honey- Remarks Conclusions Moment'- Moment Shear Missing / combing

+M -M Mispaced SK-8 689 4.8 4.2 2.1 Yes None None Concrete consolidation is Meets the intent of excellent. the code.

SK-9 Pilaster Not' Not Not None None None None. Meets the code:

Calcu- Calcu- Calcu- requirement, lated lated- lated SK-10 Wast Not Not' Not None None None None Meets the code Exterior Calcu- Calcu- Calcu- requirement.

Wall lated lated lated SK-11 Dryer Not- Not Not None None None None Meets the code Separa- . Cal cu-~ Calcu- Calcu- requirement.

tor. Pool lated lated lated SK-12 Fuel' Not 5.6- Not Yes None None Construction aid rebars at El. Meets the code Pool 'Appli- -Appli- 588'-2h" were not placed per requirement for Wall (N.) cable cable- drawings. operating conditions.

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SK-13 Mat at' Not Not Not Yes None None Trim additional rebar deviate Meets the code El-. Calcu- Calcu-- Calcu- spacing requirements. Concrete requirements.

422'-0" lated lated lated consolidation excellent.

SK-14 Mat at' Not. Not .Not None None None None Meets the code El . - Calcu- Calcu- .Calcu- requirements.

422'-0" . lated lated lated Footn:te'to Table: . Design margin as,used herein in the capacity provided above that of the original design requirements.

(A' design margin of 1.0 signifies compliance with ACI 318 code requirements and licensing commitments,)

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