ML19210B352

Forwards Summary of Rept Evaluating Concrete Placed in TMI-1 Fuel Pool Wall in Jan 1971 in Response to Arndt 710629 Request During Meeting in Bethesda,Md

ML19210B352
Person / Time
Site:	Three Mile Island
Issue date:	07/30/1974
From:	John Miller METROPOLITAN EDISON CO.
To:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
References
710730, NUDOCS 7911070680
Download: ML19210B352 (5)

Text

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Dr. Peter A. Morris 1 ACTION NECE$$ARY CONCURRENCE DATE AN$wERED:

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CD tD Dr. Peter A. Morris, Director Division of Reactor Licensing U. S. Atomic Energy Commission Washington , D. C. 20545

SUBJECT:

THREE MILE ISLAND NUC~ STATION UNIT 1 DOCKET NO. 50-289

Dear Dr. Morris:

Enclosed please find a summary of the report which evaluated the concrete placed in the TMI #1 fuel pool wall in January 1971. This subject has also been discussed with compliance personnel. The summary was requested by your Mr. Arndt during a DRL meeting held in Bethesda on June 29, 1971.

We trus t tha t this su= mary will adequately answer your questions concerning this problem.

Very truly yours ,

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John G Miller Vice President

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On January 8,1971 concrete was placed in a 5 foot thick reinforced concrete wall in the Fuel Handling Building. The ambient temperature was between 14-18* F. Die constructor had scheduled this concrete placement to be done under normal cold weather concrete conditions.

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Inadequate heating prior to concrete placanent resulted in in-place concrete surface temperatures varying from 2S* F. to 34* F. The GAI specification in reference to ACI 306, " Recommended Practice for Cold Weather Concreting',

Table 1.4.1 for moderately massive section requires fresh concrete as placed to be no t les s than 45* F . In addition all surfaces to be in contact with the new concrete should be raised to as close as practical to the temperature ,

of the new concrete, i.e. 45* F.

The west wall of the fuel storage pool is an interior wall and designed for the combined effect of dead load, hydrostatic pressure, and earthquake. This wall will therefore not be exposed to aircraf t impact. Specified minimum compressive s tr'ength of the concrete is ff = 5,000 psi. The maximum com-pressive bending stress in the concrete at the location of the constniction joint is 270 psi. The maximum shear stress at the same location is less than 10 psi.

Die concrete was placed with crane and bucket and deposited through 10" diameter chutes located 3 ' on centers. The temperature of the fresh concrete as mixed varied between 56-67* F.; m2namum required is 55* F. The lowest temperature of fresh concrete as placed was 46* F.; minimum required is 45* F.

The wall was covered with a tarp tent with propane heaters inside, maintaining a tempera ture varying between 54-62* F. for the following 3 days; minimum required is 45* F. The form was lef t in place for an extend'ed period. The concrete placenent and curing conformed to the specification.

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The critical part of this wall is the construction joint between the old and the new concrete. In order to evaluate the structural effect of the in-place concrete due to the low temperature of the old concrete surface, core drilled specimens were taken at the construction joint, which would be the primary location for any detrimental effect. The core drill specimens, approximately 4" in diame ter, were tes ted in compression and by tensile splitting. In addition microscopic examinations were performed in order to determine any signs of free:ing.

The induced compressive stress in the concrete is low. The wall is under-reinforced and therefore not dependent upon developing its ultimate capacity, ff=5,000 psi. The 5 foot wall thickness was required for biological shielding. Compressive s trength of the core drilled specimen was 4,050 psi.

Core. drilled concrete tes ts made to check adequacy of strength in-place must be interpreted with judgement. Ihe test results cannot be translated in terms of standard concrete test cylinders with any degree of confidence, nor should they be expected necessarily to exceed the specified s trength. Section 4.3.5.1 of the proposed revision of ACI 318-63, ACI Journal, February,1970, states that, n - - no single core should be less than 75% of ff". That is 0.75 x 5000 =

3,750 psi. Examining the fractured compressive stress specimen (af ter testing) showed that about 50% of the cons truction joint plane was exposed and the remaining fracture were in both the old and new concrete. This would indicate that the low temperature has no t affected the compressive s trength at this lo cation.

The entire shear can be resisted entirely by the cons truction joint shear key, withou t depending upon bond transfer between old and new eencrete.

1he ability of this concrete to resist tensile stress is not a design require-men t. However, any indication of freezing would reduce the tensile bond normal to the constmetion joint. The tensile splitting tes t of the core drilled specimen will therefore only be used as a measure of the effect of free:ing on this joint. The core drill specimen, with the cons truction joint 1584 246

i going through the vertical axis, was tested to develop maximum tengile stress normal to the joint. Ihe effect of free ing could reduce or even eliminate the tensile ability through this joint. The tensile splitting strength of the core drill specimen was 395 psi. Examining the fracture of the tensile splitting tes t specimen showed that a double split occurred during the tes t simultaneously; one in the construction joint and aaother approximately 1/2 inch parallel to the cons truction joint in the adjacent concrete. This would' indicate that the low temperature has not affected the tensile bond at this location .

The microscopic examnation of core specimens indicated no fros t printi or other indications of free:ing which wenld adversely aff ect the concrete bond.

Bending and shear stresses at the location of this cons truction joint are , ,

small. Thersfore, the construction joint as designed far exceeds jts func tional requirements . Based on the above discussion it is our opinion that the wall will fullfil all the requirements in terms of service, dura-bility and safety.

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