ML19276H116

Reactor Containment Bldg:Second Tendon Surveillance Test Three Yrs After Structural Integrity Test - Evaluation of Tendon H51-13. Prepared for Met Ed

ML19276H116
Person / Time
Site:	Three Mile Island
Issue date:	01/30/1978
From:	Herr J, Moreadith F GILBERT/COMMONWEALTH, INC. (FORMERLY GILBERT ASSOCIAT
To:
Shared Package
ML19276H113	List: ML19276H112 ML19276H116
References
NUDOCS 7910100518
Download: ML19276H116 (9)

Text

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THREE MILE ISLAND NUCLEAR STATION UNIT 1 REACTOR CONTAINMENT BUILDING SECOND TENDON SURVEILLANCE TEST THREE YEARS AFTER S.I.T.

EVALUATION 0F TENDON E51-13 JANUARY 30, 1978 Prepared By:

J. C. Herr, P.E.

Project Structural Engineer Power Engineering Division Reviewed by:

F. L. Moreadith, PhD, P.E.

Supervisor, Technical Services Structural Engineering Power Engineering Division Gilbert Associates, Inc.

P. O. Box 1498 Reading, Pennsylvania 19603 5/$

7910100 $ 415 59

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TABLE OF CONTENTS Section Title Page 1.0 SYNOPSIS 1 2.0 FIELD INSEECTION 2 2.1 LIFT-OFF TEST 2 2.2 BROKEN WIRE 2 2.3 SPLIT BUTTONEEADS 2 2.4 ACCEPTANCE CRITERIA 3 3.0 EVALUATION 4 3.1 LIFT-OFF TEST 4 3.2 BROKEN WIRE 5 3.3 SPLIT BUTTONHEADS 5

4.0 CONCLUSION

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1 1.0 SYNOPSIS During the Three Mile Island Nuclear Station Unit 1 (TMI-1) Tendon Surveillance Test, Three Years after S.I.T., Gilbert Associates, Inc.

(GAI) was requested to evaluate hoop tendon E51-13. Ota evaluation was necessary since inspection results indicated that tendon H51-13

=ay have one broken wire and four buttonheads with splits exceeding the acceptance criteria.

The prestress force confirnation test (lift-off force) denonstrated that the force in tendon H51-13 continues to be at an acceptable level for design load conbinations. The buttonheads of tendon a51-13 will be inspected again during the next scheduled tendon surveillance to ensure that acceptable cirett=scances continue.

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2 2.0 FIELD INSPECTION Lift-off tests and buttonhead inspections for tendon H51-13 were conducted by VSL Corp. and verified by DfI-QA. GAI inspected the tendon buttonheads when the tendon was detensioned.

2.1 LIFT-OFF TEST The lift-off test results for tendon H51-13 were:

End Lift-Off Force Shop (Buttress #1) 1259 kips Field (Buttress #5) 1171 kips An evaluation of these results is presented in Section 3.1.

2.2 BROKEN WIRE One wire protruded approxinately 5" from the shop end stressing washer after detensioning. This condition was defined as a " broken wire."

A discussion of this " broken wire" is presented in Section 3.2.

2.3 SPLIT BUTTONHEADS Splits in four (4) buttocheads exceaded the acceptance criteria of "The sum total of all splits or the opening of one split less than 2C to vertical axis shall not exceed 0.060"." The splits are approxinately parallel to the wire axis with the larger splits being dianend shaped and appearing to be the result of the buttonheading.

The recorded split widths in the buttonheads are:

1415 262 Shop End One split of 0.C530" > 0.060" Shop End One split of 0.100" > 0.060"

3 Field End One split of 0.150" > 0.060" Field End Splits of 0.010" and 0.055" for sum total of 0.065" > 0.060" A discussion of the split buttenheads is presented in Section 3.3.

2.4 ACCEPTANCE CRITERIA The acceptance criteria for wires /buttonheads is "Any tendon with one missing, broken, and/or damaged wires is subject to rejection, if at the same time four additional buttonheads do not =eet acceptance criteria for buttonheads." Tendons which do not satisfy the acceptance criteria shall be further evaluated.

The inspection results for broken wires and split buttonheads place ter. don H51-13 within the acceptance criteria limits requiring further evaluation. However, the " broken wire" appears to be a result of an error in judgement of v' cat constitutes a broken wire. As concluded in Section 3.2, there may be no broken wires in tendon H51-13 and hence the tendon may not be subject to rejection.

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4 3.0 EVALUATION An evaluation of the inspection results of tendon H51-13 is presented to denanstratu the acceptability of the tendon.

3.1 LIFT-OFF 1EST The expected prestress loss at the cine of naasuring lift-off for tendon H51-13 was calculated to be 180.3 kips.considering the actual elastic shortening experienced by the tendon due to the tendon stressing sequence. The expected lift-off force was calculated to be:

End Original Force Excected Lift-Off Shop 1463 kips 1282.7 kips Field 1395 kips 1214.7 kips The lift-off test results given in Section 2.1 are less than those expected by the following percentages and are acceptable.

End Percentage Shop 1.8% .

Field 3.6%

The average lift-off force of 1215 kips is 135 kips greater than the lower bound tendon force of 1080 kips, i.e. the average m4 4 "" design tendon force.

The lift-off test results demonstrate that tendon H51-13 is naintaining an acceptable level of prestrass force, the =ain characteristic checked by the tendon surveillance inservice inspection program.

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5 3.2 BROKEN WIRE During the tendon surveillance inspection, tendon H51-13 was detensiened to inspect for broken or damaged wires. One wire which protruded approxinately 5" from the stressing was'ar was defined as a " broken wire". Apparently steps were not .aken to verify that the wire was broken.

Undocunented discussions disclosed that the wire was drawn into the washer and its buttonhead reseated when the tenden was recensioned.

Experience has demonstrated that wires of a detensioned tendon will protrude from the stressing washer varying a=ounts and not be broken.

It is concluded that the wire nay not be broken. The tendon surveillance procedure will be revised to include definitive =eans of determining if protruding wires are in fact " broken wires".

3.3 S? LIT BUTTONHEADS The intent of the buttonhead inspection is to detect gross changes in the condition of the buttonheads. The " Tendon Buttonheading Card" for tendon H51-13 was reviewed.and found to indicate that, at installation, all splits were within tolerance and that there were no uracceptable buttocheads. If that is the case, then the splits in four buttonheads defined in Section 2.3 have occurred since installation.

Splits of the type found on the buttonheads of tendon H51-13 should allow the wire to develop the mininum guaranteed ulti= ate cens11e strength of the wire ' }.

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"Buttonheads for Tendon Wires of a Prestressed Concrete Reactor vessel",

J. F. Hildegrand, PCI Journal, Septenber-October, 1971.

" Investigation of Suttenhead Efficiency", Western Concrete Structures Co. , Inc. ,

Technical Report Number 6, July, 1968.

6 During the next scheduled tendon surveillance test, the buttenheads of tendond' 51-13 vill be inspected to deter =ine if changes are occurring in the split buttonheads.

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4.0 CONCLUSION

As described in Section 3.0, tendon H51-13.is acceptable as inspected. Its continued acceptance will be confir:ned during the next scheduled inspection.

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