ML19352A260

Responds to NRC 810211 Ltr Re Violations Noted in IE Insp Repts 50-518/80-27,50-519/80-25,50-520/80-27 & 50-521/80-23. Corrective Actions:Procedures Re Concrete Placement Initiated

ML19352A260
Person / Time
Site:	Hartsville
Issue date:	03/16/1981
From:	Mills L TENNESSEE VALLEY AUTHORITY
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19352A257	List: ML19352A260
References
NUDOCS 8104160252
Download: ML19352A260 (7)

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TENNESSEE.: VALLEY AUTHORITY CH ATTANCOG A. TENNESSEE 37401

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400 Chestnut. Street Tower II O .

O March 16,1981 Mr. James P. O'Reilly, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Conunission Region II - Suite 3100 101 Marietta Street Atlanta, Georgia 30303

Dear Mr. O'Reilly:

Enclosed is our response to your February 11, 1981, letter to H. G. Parris transmitting Inspection Report Nos. 50-518/80-27, 50-519/80-25, 50-520/80-27, and 50-521/80-23 regarding activities at our Hartsville Nuclear Plant which appeared to have been in violation of NRC regulations. If you have any questions regarding this subject, please call Jim Domer at FIS 857-2014.

To the best of my knowledge, I declare the statements contained herein are complete and true.

Very truly yours, TENNESSEE VALLEY AUTHORITY

.YM L. M. Mills, Manager Nuclear Regulation and Safety Enclosure 81041607M An Ecual Opportunity Employer j

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, . ENCLOSURE HARTSVILLE NUCLEAR PLANT A RESPONSE TO SEVERITY LEVEL IV VIOLATION 50-518/80-27-03 AND SEVERITY LEVEL V VIOLATION 50-520/80-27-03 OIE LETTER, J. P. O'REILLY TO. H. G, PARRIS DATED ,

FEBRUARY 11, 1981 Description of Violation 50-518/80-27-03 (Severity Level IV) 10 CFR 50, Appendix B, Criterion V, and the accepted QA program, TVA topical report TVA-TR 75-1A, Section 17.1A.5 requires that activities affecting quality shall be prescribed and accomplished in accordance with .

documented procedures. Criterion X of Appendix B and Section 17.1A.10 of TVA-TR 75-1 A requires inspection of activities affecting quality to verify conformance with documented instructions, procedures and drawings.

1. TVA General Construction Specification 0-2, Plain and Reinforced Concrete, provides specific requirements for placing concrete.

Specification G.2, paragraph 10.2 requires all reinforcing bars be carefully inspected for proper position and fastening prior to approval for placement of concrete. TVA Quality Control Instruction C-201, Instruction 2 requires the Civil QC inspector to verify correctness of preparations for placement, and Instruction 4 requires the materials insp^ctor to verify that reinforcing bars are not distorted or shifted. TVA Construction Engineering Procedure C.R.P.9.02 req. tires the Civil Project Engineer to verify the correctness of reinforcing and to initial and date the concrete pir. cement form.

Contrary to these requirements, placement had been authorized and was in progress in the Unit A-1 weir wall on December 10, 1980, with a long section of curved #18 rebar protruding into the 4-3/8" clearance between the inner and outer rows of #18 rebar effectively blocking the vertical passage of concrete mix. After the NRC inspector notified quality control and construction personnel of this obstructing rebar, the rebar was forced back into position with steel wedges, clearing this blockage.

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2. Specification G-2 paragraph 10.4 requires that reinforced concrete placed within forms be deposited in layers of 12 to 18 inches; that hatches be deposited vertically in a manner to avoid segregation; that the deposited concrete shall not be worked along the forms for any distance; that the concrete be compacted as close to the point of deposit as practical; and that the reinforcements shall be protected against splashing.

Contrary to these requirements, buildup in excess of 24 inches was observed in one area of the weir wall and vibration was not in progress on this buildup. Transport of mix for considerable .

distances occurred at several locations. Splitting of the plastic tube extension to the pump line caused splashing of reinforcing hara below the splits. ,

3 Specification G-2, paragraph 9.1 forbids segregation of the concrete stream by free fall through reinforcing steel and limits free fall to 10 feet without the use of a confining drop pipe.

Contrary to these requirements, clogging of plastic drop tubes, in the space between the inner and outer layers of horizontal rebar, required splitting of the tubes to clear them. Splitting of the tubes near the pump line permitted fall of the released concrete in excess of 10 feet across the rows of rebar which could resultein segregation.

4. Specification G-2, paragraph 9.1 also prohibits imposition of limitations on consistencies and proportions of concrete by inadequate deposition equipment.

Contrary t0 d.:s 'equirement, the plastic tubes used to prevent the free fall of concr6te were inadequate to pass the concrete without clogging during the early stages of the A-1 weir wall placenent when problems with the plasticizer admix caused the mix to stiffen.

The above items constitute multiple failures to meet specification and procedure requirements during the weir wall placement.

This is a Severity Level IV Violation (Supplement II.D.1) applicable to Docket No. 50-518 only.

Admission or Denial of the Allered Violation TVA agrees with the violations as cited in sections 1, ?, and 3 Heuever, TVA does not believe that the violation, as cited in section 3, occurred.

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Peason for the Violation

1. Since installation tolerances are'not specified for the unique situation which was cited, the reba" in question was accepted based on fabrication tolerances. This bar could have remained in its original location if it had not restricted the flow of concrete.

2. Buildup in excess of 24 inches is not a violation of the specifications since there are no limits concerning buildup before

• vibration. The 24-inch (unvibrated) buildup is reasonable when trying to achieve 12- to 18-inch compacted layers. In addition, vibration is accomplished after deposition of concrete; occasionally, this may occur after several batches have been placed.

Although we are unsure what " considerable distances" are, it is likely that we were moving #.he concrete more than was necessary.

There are no exact distances allowed or prohibited by procedures; however, inspection personnel were limiting the flow to prevent segregation.

3plitting of the flexible boots caused splashing of reinforcing bars. This was caused by the low slump concrete that was clogging the boots during'the early stages of concrete placement. The ' ~

concrehr should have bt.en near an eight-inch slump but was being placed at about a one and one-half inch slump at this time. We have determined two causes for the loss of slump. The major cause was inspector error in the concrete mixing plant. The concrete mix should have had a three-inch slump before the addition of the super-plasticizer, but the concrete produced actually had about a one and one-half inch slump. The second reason was a delay in placement

( which cancelled the effects of the super-plasticizer. The mix reverted to the original slunp after the unscheduled delay.

3 When the flexible boots were split, the concrete fell more than 10 l

l feet and struck rebar. The boots were solit because of low slump concrete which was clogging them. The reason for this condition

) is stated in 2 above.

l l 4 Denial of this alleged violation is based on the section of specification G-2 referenced in the Notice of Violation. .

l Paragraph o.1 concerns inadequate placing equipment. Or the pour cited, the flexible boots in use were planned in advance and perfcrmed satisfactorily with the high slump concrete. The actual l paoblem was caused by the low sump mix described in 2 above, not the l placing equipment.

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. 4 Corrective Staos Taken and Results Achieved

1. No corrective action was taken other than t'he action stated in the Notice of Violation. Bracing the rebar cited ensures that the remainder of the concrete placement was acceptable.

2, 3. and 4 No corrective action was taken since only a minimal quantity of concrete was involved. We have determined that no detrimental segregation occurred.

Steps Taken To Avoid Further Noncompliance Item 1 In researching this situation, TVA has determined that this is a unique situation in that there is no stated tolerance for the movement of this bar in the direction it was moved. With a thicker wall, this situation would have been of little consequence. However, all Civil Quality Control Reinforcing Steel Inspectors have bec.n instructed to inspect for the ability to place concrete and to report any situation of reinforcing steel alocking the flow of concrete (that cannot be corrected) to Project Engineering. If the situation is not corrected by the day of placement, a Quality Control Investigatien Report (QCIR) wilj be initiated.

Item 2 At the present time, there are no specifications in which exact distances for movement of concrete along the forms are given. However, Materials Quality Control personnel have been advised that two and one-half to three-feet maximums should be used in most cases while limiting the buildup to 12 to 18 inches after all vibration, as referenced in Specification G-2, paragraph 11.2. To limit the excessive movement of concrete, enough horizontal length of concrete must be deposited before vibration to prevent the concrete from running. In some cases, an entire lift may have to be in place before it is vibrated. Materials Quality Control personnel have been instructed that they are to ensure that vibration does not occur until the appropriate time. Additional items will be considered when a vibrator is to be used. When using melment, the vibrators will be approximately two inches, as specified in ACI 30c.

Also, for concrete with less than a three-inch slump, the vibrators should be approximately three inches as specified. In all cases, ATI 309, table 5.1.4 will be referred to for specific values.

Item 1 Thu spinshing of concrete on the reinforcing steel resulted from the cloeging of the plastic drop tuben which were split to alleviate the problem. This problem was due to the insufficient slump (as addressed in item 4) and should not occur if the slump is properly controlled.

Item 4 The violation on concrete placement for the A-1 veir wall was written as a problem with the plastic tubes used in placing the concrete. TVA believes, however, that the problem was ac't'ually in the slump value of the concrete which was used. The slump was only one and one-half inches when it should have been three inches before adding melment. In the j future, when a super-plasticizer admix is being used, Materials Quality i Control personnel are to ensure that the correct amount of water is in the mix before the addition of this admix. Additionally, more coordination between pour placement personnel and batch plant personnel ,

will be initiated.

Date When Full Compliance Was Achieved Full compliance on all of the above items was achieved on February 24, 1981.

Description of Violatir- 50-520/80-27-03 (severit' Level V)

B. 10 CFR 50, Appendix B, Criterion V, and the accepted CA program, TVA topical report TV'.-TR 75-1A, Section 17.1A.5 requires that activitics affecting q'tality shall be prescribed and accomplished a accordt-ce with documer,ted procedures. TVA General Construction pecification G-2, Plain and Reinfored Concrete, paragraph 9.1 requires depositing concrete as near as possible to its final position ta preclude use of placing methods that would cause concrete to flow in the forms. TVA Ouality Instruction G-201, Concrete Placement, requires the materials inspector to verify conveying and placement of concrete is in accordance with General Construction Specification G-2.

1. Contrary to the above, concrete was not placed in accordance with TVA General Construction Specification G-2 on December 10, 1980, in that concrete was caused tc

' low horizontally up to eight feet while placing concrete in the Unit A-2 reactor pressure vessel pedestal.

l 2. Contrary to the above, Quality Instruction G-201 was not I followed in that the OC material inspector who witnessed the above placement did not stop the work or require a change in the point for depositing concrete until the MRC inspector questioned him about this violation.

This is a Severity Level V Violation (Supplement II.E.) and is applicable to Docket No. 50-520 oniv.

Admission or Denial of the Alleged Violation l

TVA agrees with the findings citad in this violation c=- -. -

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Reason for the Violation

1. Concrete was being moved more than was necessary; however, we have determined that the concrete was being moved approximately four feet and the grout used to prime the pump ~was moving in excess of eight feet. This was an open pour with no reinforcing steel in which a four and one-half-inch slump concrete mix was being used. The relatively high slump would contribute to this apparent prohlem.

2. The piacement inspector did not consider the movement of concrete in this pour to be excessive. The four and one-half-inch slump concrete mix in this unreinforced pour moved easily, and the inspector was carefully observing the movement to avoid segregation.

After the conversation with the NRC inspector, the placement inspector questioned his earlier decision and changed the point of deposition until the question could be resolved.

Corrective Steos Taken and Results Achieved We have determined that no detrimental segregation occurred; therefore, no corrective action is required.

Steos Taken To Avoid Further Noncompliance The actions necessary to prevent further noncompliance are the same as previously stated for 50-518/80-27-03, item 2.

Date When Full Connliance Was Achieved Full compliance on the above items was achieved on February 24, 1981.

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