ML19329F331
| ML19329F331 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 07/14/1976 |
| From: | Seyfrit K, Shewmaker R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | |
| Shared Package | |
| ML19329F317 | List: |
| References | |
| NUDOCS 8006250419 | |
| Download: ML19329F331 (5) | |
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DETAILS I
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Prepared by:
NM7C f
At/ E. Shewmaker, Senior date Structural Engineer Reactor Technical Assistance Branch Headquarters Dates of Inspection:
June 24 and 25, 1976 Location of Inspection:
Bechtel Associates, Midland, Michigan Reviewed by:
/b b h 7[/4/7C ff.V.Seyfrit, Chief date VReactor Technical Assistance Branch Headquarters The material contained in these Details applies to both Units 1 and 2, unless specifically identified with a single unit.
1.
Individuals Contacted K. D. Bettke-Consumers Power Company-QA Engineer D(d Bechtel Associates R. L. Castleberry-Project Engineer J. L. Hurley-Asst. Project Engineer J. C. Hink-Asst. Project Engineer C. V. Newton-Senior QA Engineer f
i R. P. Narang-Civil-Structural Engineering Supervisor j
W. F. Holub-QA Engineer J. C. Arora-Civil-StructuralGroupLeaderforAuX.hidg.
T. R. Thiruvengadam-Civil-Structural Group Leader for Contain. Bldg.
P. V. Regupathy-Civil-Structural Engineer on Aux. Bldg.
A. Almuti-Civil-Structural Engineer A. Boos-Field Engineering l
2.
Purpose of Special Inspection The review of Nonconformance Reports submitted by the licensee l
undu the ALAB-106 Order of March 26, 1973 revealed several items l
related to the reinforcing steel in several locations in reinforced concrete structures.
Bechtel, the licensee's architect-engineer, had completed investigation and evaluation of the nonconfor=ing items l
and concluded that minor corrections were adequate or none were l
needed at all. The inspection was to ascertain whether the conclusions I
and actions taken by Bechtel did in fact maintain the margins u
associated with the original design criteria.
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Conduct of the Inspection i
The Bechtel resolution for each of the 16 Nonconformance Reports was reviewed during discussions with the design, quality assurance and field engineering personnel to determine whether the resolution was acceptable.
Each of the items was reviewed. The comments on the items are listed below.
Items "a" through "o" related to the Aux. Bldg. and Item "p" to the containment.
n.
NCR C-18:
Examination of Bechtel drawings C-210 and C-219 indicated that #11 bars had been required at 18" centers along
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a diagonal line and the fabricator's shop drawings supplied i
rebar for 18" ctrs. on the orthogonal.
The result was that i
4-#11's were omitted in the steel shipment indicating that all rebar shipped to the site for use in this area was placed.
l Jhe oversignt occurred in the checking of shop drawings against the engineering drawings and the fact that at this
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time rebar placement check-off'by QA was completed from shop J
drawings which were to have been approved.
Currently rev-i isions are being made to the QA procedures related to rebar i
and concrete placement which should reduce nonconformances i
such as this.
Since in this case the rebar spacing was T
excessive and 4 pieces were missing, 8 pieces were added by j p) drilling and grouting the rebar into place with a 3' embedment.
1 A double, number was used to account for a shorter embedment.
j This adequately addressed the north face of the wall.
The addition of 3-#11's in the south face corrected 3 missing y
rebars. The discrepancy in concrete cover was corrected by A
thickening the wall.
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NCR -158 :
The missing horizontal dowels from the north and south walls were installed by drilling and grouting. The i
vertical dowels in the G-line header were also drilled and grouted.
This adequately repaired the structure.
The cause of this missing rebar was not determined but was apparently related to openings in valls.
A c.
NCR-172: Vertical #11 bars were noted as missing during a
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field inspection and repair of these 351ocations was ace-g omplished by adding 35 drilled and grouted vertical dowels.
i The repair is acceptable.
The'cause was rebar displacement due to openings being relocated.
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d.
NCR -260:
Some discrepancies in documenting this NCR were noted and the licensee agreed to revise and correct the NCR.
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The technical adequacy of the repairs completed was examined y
and found to be acceptable. The missing horizontal' dowels yG vere placed by drilling and grouting.
It was not determined d
why the horizontal reinforcing steel was omitted. The repairs completed will return the structure to a condition which satisfies the original criteria.
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NCR-290:
This item involved the omission of 8-#11's at an opening and resulted from an engineering change being made i
which did not get incorporated into the shop drawings prior to concrete placement.
Dowels were drilled and grouted into place so that adequate lap length was provided for closure of the construction opening.
This item was a Drawing Change J
Notice which was not integrated into all drawings before 1
placement was completed. The corrected situation will satisfy j
the original criteria for the structures.
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f.
NCR-295:
Beam shear reinforcing was reduced by 50% from design by the omission of double bundles of #6 ties at y
9" ctrs. the beam was originally reinforced as a normal j
beam was originally reinforced as a normal beam and reanalysis
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was completed using deep beam provision applicable to the l
section (2' X 8 nominal). The reanalysis indicated the as built capacity satisfied the original design conditions.
i The use of 2-#6's instead of 3-68's and the lack of
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4-#6's was analyzed and the conclusion reached was that J
no repairs were needed. The information and documentation i
review resolved this item satisfactorily. The cause of this
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nonconformance is not known.
g.
NCR-296:
One #8 rebar was missing and the situation was corrected by drilling and grouting a #8 dowel in place.
1 No an'alysis needed in this case and the item is considered resolved since the embedment was more that adequate.
h.
NCR-326: Auxiliary reinforcing in the area of the pipe tunnel wall penetration in the form of double bundles of 4;
ties were not placed.
Int,tead single ties were placed, reducing the effective steel areas by 50%. A total of 42 j
ties were omitted.
The cause was apparently due to detailing
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errors by the fabricator in preparing shop drawings from the l
.j engineering drawings. Tae original design of the penetration
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area had been based on conservative hand computations
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using simplifying assumptions. A reanalysis was performed
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modeling more exactly the actual case at hand. On the basis
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of the SIARDYN 3 analysis the existing as-built condition y
meets the original design conditions. This iten is- - __.. _.__._
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NCR-396: A total of 12-#8's were omitted from the area formed j
by the intersecti:n of two orthogonal valls. Normally the duplication of the steel is not used since normal pra:tice is u --.-
to carry steel in one wall and stop the other wall's iertical l
steel as that wall intersects the outer face of the orthogonal
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wall.
Consequently this omission was judged to have no l
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detrimental effect on the structure. This item is considered I
closed.
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NCR-398: A total of 20-#11 horizontal rebars were missing in 2 walls above Elevation 614' and correction was made by using equivalent steel area by use of 40-#8's since the embedment i
length could not be achieved through the wall thickness for
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Corrections were made by drilling and grouting bars j
s irc_o place.
This rework brings the structure back to the J
condition as originally designed.
Cause was not determined.
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This nonconformance is considered resolved.
k.
NCR-135:
Reinforcing steel was located too far inside outer l
concrete surfaces to comply with rebar placement tolerances
.I in a wall section. A review of the design indicated the i
design concept was based on a shear wall system so that the j
location was not critical.
It would only be critical if the g
wall were designed to resist loads as flexural member. This 1
item is considered resolved.
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NCR-168:
Six vertical #11's were mislocated in a doorway to i
be built above. The corrective action was to drill and grout 3-#11's on each side of the opening. This was completed and i
should have no adverse effect on the structure. This item is i
considered resolved.
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NCR-254: This ites involved 14-#11's and there was no rework i
required for the same reasons as. item k above.
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NCR-256: A dowel was cut near a wall penetration and had l'.
insufficient length remaining to complete a field bend of
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180* hook.
Repair consisted of a bent dowel drilled and grouted
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into place.
This item is resolved.
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,h o.- - NCR-258:
Three #9 bars were short and had short embedment -
4 lengths. A review of the resulting stresses in this auxiliary j
rebar indicated to the licensee that no repairs were needed.
J; A review of the reduced embedment shows the structure is unaffected by this reduction.
This item is resolved.
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NCR-276:
In the haunch of the reactor containment building
!j there were 8-#11's which had portions of the e= bed =ent cut l7 short as a result of wall penetrations. An evaluation based IJ on the redundancy of reinforcing steel.in this area of the
' !l containment indicated that the original criteria could still 4
be met. This item is resolved.
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4.
General Comments
, a i a l1 A review was made of the technical aspects of the drilling and grouting lj of reinforcing steel which was utilized to correct several of chese non-ll conformances.
This included a review of the diameter of holes versus
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rebar diameter and the length of embedment to develop the ultimate strength of the reinforcing steel Embeco 636 grout used in this repair vork has common usage for this purpose and is acceptable.
5.
Summary a
j A review of the correction actions taken by the licensee on the non-g conformances listed indicated that the structures involved will still satisfy the leading criteria specified in the SAR and that the function of these structures will be maintained during all design con-j ditions.
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