ML19343A191

Final Deficiency Rept Re 84 Reinforcing Bars Left Out of Wall Pour C1-F1 Located in Control Bldg.Caused by Inspector Error &/Or Rebar Removed for Other Installations.Missing Rebar Replaced.Detail Checkoff List Initiated to Aid Insp

ML19343A191
Person / Time
Site:	Yellow Creek
Issue date:	09/11/1980
From:	Mills L TENNESSEE VALLEY AUTHORITY
To:
References
10CFR-050.55E, 10CFR-50.55E, NCR-YC-090, NUDOCS 8009160368
Download: ML19343A191 (3)

Text

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cncicacd 13 cur final report.

If you have any cueaticnc eencernind this =ttor, plasse get in cuch 'iith S. c. Lancert at FTS 657-2c51.

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L. M. Milla, t'anager I.uclear Ee;;1acion tna Safety i..cic.a ure 2c: .w. Victor Stello, J.'., Director uff;ce of Inspection ar.c Ecfercoc:ent U.S. !;uclear 3cc';1atcry Cc:r.miccion

'sachinC en, EC 20535 lo/7 3

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A ENCLOSURE YELLOW CREEK NUCLEAR PLANT REBAR IN CONTROL BUILDING WALL NCR YC-090 10 CFR 50.55(e)

FINAL REPORT Description of Deficiency Eighty four reinforcing bars (rebar) were left cut of wall pour C1-F1 loca ted in the control building. The apparent cause of the missing retar was because of inspector error and/or rebar being recoved for other installations after the concrete pour card had been signed.

This report also references NCR's YC-055, YC-085, YC-073, and YC-096.

Although these NCR's on missing rebar by themselves were not determined significant, they appear to represent a generic concern at YCN.

Safety I=clications Failure to install rebar could result in the concrete structure not meeting the tinicum structural strength required to provide its safety function. This could have resulted in degradation of plant structures and affected adversely the safety of operations cf the plant.

Currective Action The 84 missing rebar for this NCR (YC-090) will be installed by drilling in the appropriate location and grouting the: into place using nonshrinking grout. This will be co=plete by Nove=ber 1, 1980.

As a result of this nonconformance, a plan was prepared for invest. gating the extent of missing rebar in the centrol building.

The investigation results are:

(1) All exposed rebars in the control building (approximately 5,500 rebars) were inspected, and four missing rebars were discovered.

These are identified en and the subject of NCR YC-096.

(2) The craf t rebar fabricatien records were reviewed and compared to our detailed rebar listings made from drawings review (takeoffs); however, no usable information was obtained.

(3) A review of cur control building NCR's shows that we have had three similar cases where rebar was left out of pours. In ene of the cases, the six missing rebars were due to crafts and inspector error and were identified and dispositioned en NCR YC-055. The other two cases were due to rebar being recoved to accommodate other installations af ter final acceptance. One of the cases censisted of four rebars and was identified..and dispositiened en NCR YC-085. In the other instance, eleven rebars were recoved to allow another installation and cnly ten were replaced resulting in ene rebar being cuitted. This was ~

identified and dispositioned en NCR YC-073 -

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This investigation has shown the adequacy of rebar placement in concrete pours at Yellow Creek with the results of the study indicating that although occasi :nal rebar was cdssed, they were identified during preparaticn for subsequent pours.

Corrective action taken to prevent recurrence of rebar being =issed in concrete pours in safety-related areas will include the following:

(1) The use of detailed takeoff checklists will be supplied for inspec tors . Quality Control-Materials and Civil personnel will cake a detailed takeoff for each concrete pour and record it en record sheets. This record sheet will subsequently be used by rebar inspectors as a checklist while inspecting rebar installation. This record sheet will be retained as further verificatien of ccrrect rebar installation in addition to the concrete pour card. -

(2) Final inspection and signoff of the pour card for rebar inspection will be held until all other craft work (except cleaning) has been completed and will be the last inspection and signoff ic=ediately before releasing the pour by the shift

<ngineer.

TVA has initisted the above corrective actions and was in compliance as of September 8,1980.

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