ML18017A775

Ack Receipt of NRC 791030 Ltr Re Placement of Concrete Omitting Rebar.Caused by Human Error.Repairs on Affected Walls Will Commence After NRC Approval of Corrective Action

ML18017A775
Person / Time
Site:	Harris
Issue date:	11/01/1979
From:	Jackie Jones CAROLINA POWER & LIGHT CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML18017A774	List: ML18017A773 ML18017A775 ML18017A776 ML18017A777
References
NUDOCS 7912130452
Download: ML18017A775 (6)

Text

I~~pe 2 197%P.O.sex,1551~Raleigh, N.C.27602.J.A 4ONES Senior Execu~VRs Pseddmt Chlat C peratlng CNcer Ha@ember.1, 1979 Hr.James P O'Reilly>>Diractor Region 11 UeSe Nuclear Regulatory Coauaission 101'fariatta.

Street, HeVe Atlanta, Georgia 30303 SHEAROti BAR~:HJCLKKR

?0'4TR?LQFZ>>

UBITS DOS~1>>2>>3>>ADD+DOCKET DOS~30&00~.5~1>>5~2>>.AULD 50-403 IHVESTMATIONS Ai%)CORBECTIVc ACTIONS 5'OLLO>L'aQ QiilSGXOH OZ RZ3AR AT TWO LOCATIONS Gear kW O'Railly Me concux'n your understanding that.Carolina?ower 0 Light Company will not place Class I concrete containing rebaLr at thaa Shearou Harry ttuclear Power Plant construction site without tha concurrence of your office~This i" as discuss'.'between:ir C>>Ei Hurphy oi your staff and:hi ili,~HcDutfie of my staff on October 29, 1979 ancL further docuaganM in your conzi~tion o"" action.letter ta me dated October'0>>.

1979 Yhe following investigations.

and.corrective actions have baca completed or are ia progress as.indicatada (1)On October 30 1979 4 P Q Eowe 8z'.S D Smith and 8z~H~Je Qdansi were dispatched to conduct an indepth audit ox the circmastancaa surrounding tha omission of the rebar at two locations~the subsequent acceptanca of tho installation by the quality control staff~?rocedures relative to installation and inspection of xebar, inspection foras, concrete pour cards,.personnel quasi ications, craft supervision ratios and actuaL documents of record for omissmn of rebar at, the two locations were reviewed in detail In sunaary>>our indepth review, has convinced us that the program and procedures are sound, that tha occurrences are not, related and that the ouission of 52 reinzorcing.

oars M a short section of the RM!fo" south exterior shear wall was an isolated incident attributed ta hualan er or which was subsequently identified and reported by the saae.inspector Hz James PE O'Reilly November 1, 1979 The detailed chronology, marked up drawings and documents associated with the omissioa of RAB Ho 2 reinforcing bere were delivexed to ead discussed with your scarf at your office oa October 31, 1979 by Mri P.M>>Howe, Oi~S>>D.Smith and Hr>>A>>i1 Lucas of my staff In summary, the required number of bars and correcc spacing existed in the lower 5'-9" of the 10'W" h~h sectioa of wall prepared for coacxete placemeat>>

Likewise~the 12'-0" high sect on or this well immediately below this area contained the correct number and spacing of hers and was previously poured>>The number and spacing ox bere had been vex'ified when the foundatioa mat oelow the wal3.was poured, when the first (12'W")section ox the wall was poured and again when the secoad (10'H")section of wall was placed>>Izx this 3.ast section of waLL poured, the inspector failed to check projection ox baxs relative to the scheduled pour hei~ht and missed the fact that alternate bars were to'oe lap spliced starting at the bottom of this pour aad pro]ecting oa up the well>>As a result, alternate bars ended in the middle oz the pour rather than being extended by Lap splices>>Tne souch side of this wa3.1 is adjacent to e seismic ap and is forced by special movable metal plates which are greased on the exterior face and installed immediately prior to concrete placement which prevents pour height from being as obvious as it is with coaventioaa3.

forming systems concainiag grade strips Shen the section of wel1 adjacent and to the west of this wal3.was befng inspected, the iaspector"ound every other bars missing and had them installed prior to siga~ff At the same time, he reverified the previous placement, verified the omissioa and issued a discrepancy report which was subsequently reviewed and determined tu be a reportable icam As previously requested to your scaff, several rebars ware omitted from the Unit Noi 1 containment

'ouilding exterior wall The detailed"as-built" drawings aad documents associated with che omission of Unit No>>1 coacainme'at building exterior wa3.1 reinforcing

'oars were de1ivered to and discussed with your staff at your office on October 31, 1979 by Hr Pi.U>>Howe, id>>S 0 Smith and'Ari A';f Lucas of my staff The coacaiament exterior, wall dowels originate in the foundation mat aad have.to be inserted through the top met ox reinforcing steel which consists of three Layers of iso>>1S reinfox'cing bars each over 2 1/4-inches in diameter>>.

Two of these Layers are radial and one is circumferential>>

Fabrication.

aad placing tolerances do aot, allow dowels to be placed ia the theoretical position and therefore drawings allow shirting dowels to xLiss roundacion met reinforcingi In the case of the containment exterior well, well penet ation sleeves are restraints that dictate rebar locations at higher elevations Hr>>James P O'ReQ.ly&3 W:november 1, 1979 The containment building exteriox'all 8th row contains 701 dowels at the top of the foundation mat (El>>216)and 694 at the cuxrent concxete elevations ox 226'nd 236'TypicalLy, one or more dowels terminate under each penetration and each dowel is extended by mechanical splices (cadwelds)>>

In addition, dowels terminate at various e3.evations as design loads decrease progressing up the wall>>Dowels also terminate at various elevations to al.low cadwelds to be staggered and not create unacceptab3.e congestion"As-built" dxawings have been submitted to the engineer several times to evaluate bar spacing, location and quantity as concxete placement and inspection proceed upward In this case,.inspection revealed a total of five vertical bax's of 694 in the 8th row which had not been extended to the required e3.evation This omission is attributed to the complexity of the installation and difficulty of inspecting and accounting for bars in the circular geometry>>The as-built drawings (6 sheets)of this row delivered to your staff demonstxate this complexity There are a total of 2,714 No.18 dowels in the containment building exterior wall at the foundation mat.This does not include horizontal, cizcumferential bars Corrective actions to minimize chances of reoccurrence axe discussed in Item 4>>(2)An audit of previous Class I concrete placements was initiated on October 30, 1979 to determine if there had been previous occurrenc s of this type The audit initiated includes a 100'udit of Class I concrete in place with pzo)ecting dowe3.s as well as an audit of documents such as discrepancy zeports (DR), permanent waivers/field change requests (PQ/9'CR)for pzeviously identified conditions of rebar omissions The audit of previous3.y identified cases of rebar omission shows that in each case the condition was documented in accordance with prospect procedures and submitted to the Engineer (Ebasco)for evaluation and that the required corrective action to meet design requirements was implemented prior to the work proceeding on the pazticulax wal'r column>>The 100K audit of Class I.concx'ete inplace with pro]ecting dowe3.s is continuing with over 21,700 dowels representing over 6,200 linear feet of wall checicad on October 30, 1979 Resu3.ts of this portion of the field audit show less than 0>>4X missing bars ox 0 6~~, iI the 52 bars in RA3 bio>>2 are included>>There are etrn bars 8 some walls also."-or example, in RAB No 1 there were 5,000 dowels checked with 18 missin oars identified and 36 extxa bars identified In general, the vertical dowels aze spaced every six inches on each side ox the wall with a two f.nch installation tolerance on this spacing as 3.ong as the number of bars in any 10 foot section's maintained>>

Hr~James P.O'Reilly tfavember l, 1979 This IOOX audft fs being cazrfed aut by a two~a team in each building.The team consists of the area engineer aad the lead construction inspector assigned to the particular building.Znspectfoa priority is shear walls, columns, interior walls and thea slabsi Each condftfon fdeatffied whfch does aot conform to drawing requirements will be documented on a discrepancy report.(DR)and will be submitted to the Engineer (Ebasco)for evaluation and determination of corxectfve action required Za summary, there have been previous cases of vertical dowels beiag omitted in concrete piacements and subsequently identified as mfssfag by the established iaspectfon process prfor to the next incx'emeat of work Xa each case the omission was identified, documented and evaluated by the Engineer (Ebasco)~Ve are confident that there axe aot cases of omissions covered by concrete which could have safety significaacei (3)The Engineer{Ebasco)is performing an analysis of the effects of the omitted rebax'n the integrity of the structures At this time, the Engineer has not verfffed all calculations associated with the existing conditfon and proposed repairs The Unit!toi I containment building exterior wall and the Unit Ho 2 reactoz auxiliary building south exterior wall ax'e automatically oa gA hold pendiag resolution of outstaadfng discrepancy repozts{DR's)issued As requested, the pz'opose zo osed repairs and repair px'ocedures will be discussed with youz oxfice aad your concurrence obtained pr'or to placing concrote on these two walls or adjacent structuxes that could be affected by repairs ox madfffcatfoas (4)The following corrective actions have been taken to mfafmf e recuxreace of these types, of events: a meetings have been held (IO/31/79) and ll/Ol/79)by the contractox with all levels of supervision to reemphasize commitment ta quality construction aad the associated quality program.The fol1owfng points were emphasized:

-Responsibility approved plans-Responsibilf ty cards+-Responsibility

-Responsibility supervisione

>>Responsibility productivity i of all supervfs"on to build gab accordfng to aad specfficatiuns for persona1 verification pxior to sign~ff oi poux ta report nonconformance conditions to management to stxess quality to personnel under their to" et it right" regardless of pressure"or Mr.James P>>O'Reilly November 1, 1979 b>>A, meeting was held by Seaior Resident Eagiaeer oa 10/29/79 with ax'ea engineers, construction iaspectioa personnel and their supervisors>>

The foll.owiag points were emphasi-ed:

Pork such as concxete placementa do not pzoceed until inspections are complete-Responsibility fox'epoztiag nonconforming coaditions

-Management commitmeat to q~ty-Resident Engineering Unit"respoaiibi3.ity for finished plant in accozdaace with plans aad specificatioas

-Responsibility for personal verification>>

c>>Training sessions were conducted (10/31/79 and 11/01/79)by site priacipal quality assuzance specialist for site discipliae engiaeexs, construction iaspectoxs, ax'ea engineers aad quality assurance to explain 10CFR50 55(e)Reporting time requirements were emphasi ed A traveler system is being implemented to ensure reporting sequence is not compromised by the unavailability of key pezsoanel.

d.Construction work proceduze MPW5"Conczete Placement" was revised, approved aad issued on 11/01/79 to incorpoxate a third verification of x'ebar quaatity, progectioa and type by the field ea ineezs Previously, bax'uaatities were verified by the craft and coastructioa inspector e Quality Assurance will increase frequency of monitoring rebar installations f>>A lOOX audit of exposed vertical dowels is ia progress as discussed in (2)above>>g>>The results of audits discussed in Item 2 above will be reviewed in detail by sita management as well as senior management and additional actions will'oe taken'f appropriate Ia summary we conclude that the omission of the rebars from the 82 RAB South Sall was attributable to human error and that suitable corrective actions have aad are being taken to substantially mid+-'xe a reoccurrence oi this type of omissioa>>Based upon the corrective actions ake , we zequest youx aathorixatioa to resume placement of Class I concrete, containing reinforcing steel, except.in the two walls noted above Me recognixe that the repaizs on these affected walls cannot commence until MC approval is-'obtained for the proposed corrrective act'oa

~p~}ir~James P.O'Reilly November 1, 1979 We appreciate your cooperation in this matter;and should you have any questions, please contact Mri Mi A McDuffie, (919-836+663).Yours very truly, CRRSSL SEN9 N J.A.JONES Ji Ai Jones Senior executive Vice President Chief Operating Officer JAJ:pfb bcc: Mr.Dr.Mr.Mr.Mr.Mr.iir.iir.Mr.iir.Mr.i%.N.J.Chiangi T.S.Elleman G.Forehand P.W..Howe W.B.Kiacaid A.M.Lucas M.A.McDuffie S.McManus R.M.Parsons Sheldon Smith T.H.Wyllie S.R.Zimmerman A.L.~iurris