ML20246Q193
| ML20246Q193 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 09/05/1989 |
| From: | Blosser J UNION ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 89-10, ULNRC-2066, NUDOCS 8909110378 | |
| Download: ML20246Q193 (8) | |
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. yg,9y Et..scraic Caraway Mant Seotember 5, 1989 U. S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 ULNRC-2066 Gentlemen:
DOCKET NUMBER 50-483 1
CALLAWAY PLANT UNIT 1 FACILITY OPERATING LICENSE NPF-30 SPECIAL REPORT 89-10 STH YEAR INSERVICE CONTAINMENT VESSEL TENDON SURVEILLANCE FAILURE The enclosed Special Report is an engineering evaluation submitted to satisfy Technical Specification action stotement 3.6.1.6(b) regarding sheathing filler gresse voids in excess of 5% noted during the 5.5 year containment vessel tendon surveil 1 Lance Sinco complisnee with ell remaining surveillor.ce requirements for Technical Specific.3 tion 6
.6.1 was demonstrated, it is concluded that voids ir, excess of 5%
of tnu net duct volume have not resalted in any degradation of the L
pest-trnsioning system, thus assueug the structural integr ity of the containment vessel.
64 g
J. D. Blosser f
T Manager, Callaway Plant
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WRC/J M/DLB G/cmk Enclosure cc Distribution attached f60 8909110378 890905
{DR ADOCK 05000483 I
PDC Maang Adtfrest P.O. Box 620, Fulton MO 65251
4 cc: distribution for U1NRC-2066 l
l Mr.
A. Bert Davis Regional Administrator U.S. Nuclear Regulatory Commission Region III 799 Roosevelt Road Glen Ellyn, IL 60137 i
Mr. R. W. DeFayette Chief, Reactor Projects Section 3A U.S. Nuclear Regulatory Commission Region III 799 Roosevelt Road Glen Ellyn, IL 60137 Mr. T. W. Alexion (2)
Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop 13-E-21 Washington, D.C. 20555 Manager, Electric Department Missouri Public Service Commission P.O. Box 360 Jefferson City, MD 65102 Mr. B. H. Little NRC Senior Resident Inspector i
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1 EVALUATION OF THE FIFTH YEAR INSERVICE TENDON SURVEILLANCE FOR THE CALLAWAY NUCLEAR PLANT The Callaway Plant Technical Specification 4.6.1.6.1 requires th'e demonstration of containment vessel structural integrity through a surveillance of-the containment post-tensioning system at the end of 1.5, 5.5 and 5.5 years following the initial structural integrity test, and at 5 year intervals thereafter. The 5.5 year surveillance of the system began on July 17, 1989.
On August 10, 1989, it was discovered that the not refill volume of the sheathing filler grease exceeded 5% of the not duct volume for tendons (see Attachmnent 1, Ten-don Greasing Summary)..This void condition failed to meet Tech. Spec.
4.6.1.6.1(d)(2) which requires verification of operability of the sheathing filler material, by assuring the " amount of grease replaced does not exceed 5% of the net duct volume, when injected at +10% of the specified installation pressure."
Since a void greater than 5% was discovered after filling, restoration of the tendon sheathing filter greese, specification action statement 3.5.1.6(b), was immedi-ately satisfied with the exception af tha Special Report.
The NRC staff concurred with thic position in a meetino on the same sub;ieet for the first year surveillance on July 19, 1085.
T4s Callaway co4tainment vessel is a post-tensioned, reinforced concrete structers comprise.d of a veetical cylinder with a hemispheri-cai dome roof and is supported by ta reinforced concrete slab.
A con-tinuous access enllery is provided beneath the foundation slab for inspection of tne vertical tendons.
Three concrete buttresses are provided for anchorage of the horizontal tendons. Anchorages are designed such that the tendons can be detensioned, inspected and reten-sioned readily during the life of the plant. The vertical cylinder wall is provided with a system of vertical and horizontal (hoop) e
Evolustien Page 2 tendons. Vertical tendons are continuous to form inverted U's that extend over the dome.
The configuration of the tendons in the dome is based on a three way system consisting of two groups of vertical tendons oriented at 90 degrees with respect to each other and a horizontal (hoop) group extending from the spring line to approxi-mately 45 degrees from the horizontal. Hoop tendons in both the wall and the dome are placed in a 240 degree system in which three tendons form two completed rings using three buttresses for anchoring the tendons.
Each tendon is comprised of 170 - 1/4" wires, terminating at each end with a cold formed buttonhead at the anchorage fixture.
The essential criterion for the operability of the sheathing filler material'is to prevent corrosion of both the tendon wires and the anchorage components. The material used in the Callaway Plant post-tensioning system, Visconorust 2090P-4, accomplishes this by a charac-teristic which gives the filler grease an affinity to adhere to steel surfaces, an ability to emulsify any moisturo in the system which nullifies its rusting tender.cy, and resistance to moisture, mild acids and alkalis.
In addition, protection is afforded by eae,h tendon wire being individually pre-coated with a greate, Amber 1601, prior to I
instailatron.
Results from the first and third year tenden surveillancers revealed i
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voids in excess cf 5% for el) tendons surswyed, viihout a Ipss of
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l' integrity to the system.
From lab test on the removed wires and grease, and from visual inspections of the tendon components, the filler grease l
is performing its intended function of prohibiting corrosion of the I
- tendon, j
j The void in the tendon sheathing, as indicated by the refill volume and varied from 6.83% to 19.23% (see Attachment 1),
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Evaluation Page 3 g
may be attributed to a number of factors:
1
- 1) Visconorust 2090P-4 has a coefficient of expansion which yields an expansion of about 1% per every 20 F.
Initial filling temperatures of the filler grease averaged 160 F.
Cold weather conditions can cool the filler material to 40'F, giving a' contraction of 6% of the net duct volume. During the fifth year inservice surveillance of the tendons, the temperature of insitu filler arease average 90*F, giving a contraction of 3 to.4% from initial fill.
- 2) Characteristics of the. initial filling method may induce air entrapment into the filler grease.
Pumping operations can introduce air into filler material and may add up to as much as 2% of the net duct volume. The tendons at Callaway Plant were initially greased between April and October, 1981 by INRYC0 using current industry standard filling procedures.
- 3) Calculated voids between the wires which comprise the tendon bundle are approximately 7% of the net duci volume.
During 1
the initial filling operations, the tendon bundle was c.sid tambient temperature of 6E"F) und as the heated faller g: ease Texit temperature of 140 F) was pumped intr the itwathing void, it volidefied on the surface of the tendon bund'e, leaving small voids between the wires. As the filler
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grease gradually beated the tendon bundle, it is likely that the voids between the wires allowed migration of the filler grease into the tendon bundle.
Because this process is slow and gradual, it is reasonable to expect that it took place sub-stantially after the filling operation was complete and possibly during the surveillance refill operation.
In
Evaluation Page'4 addition, this type of migration could also occur at other areas such ns where tendons are in contact with the sheathing.
In addition, visual inspection of the exterior concrete of the containment building after the initial greasing and during the surveil-lance revealed no signs of grease seepage from the tendon duct.
There-i fore, refill volumes in excess of the lost grease during the l
surveillance indicates that the void existed within the tendon duct boundary.
l The Callaway Plant tendons, requir ing net refill volume of the I
filler material in excess cf the 5% eriteria, have not shown any abnormal visual deterioration. The lift off force for those tendons i
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was found to fall within the predicted limits.
Laboratory examination of the filler grease has been performed as of this date and found i
to be within the tolerance limits as specified in the Tech. Spec.
Visual inspectic.n of the different components of the anchorage system revealed proper coverage by the filler material with no signs of 1
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corrosion or presence or water.
1 As indicated by tre above, the function of the filler trease l
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protecting ine post-tensiching systw.a was maintainry.
Ar. Ir-ng as i
l sufficJent filler yrease has been introduced into the system 4.o conplately coat t%y vires and anchorcpe syst'am, corcosion protection l
1 is assured.
Voids, can be expected due to tSe characteristics of tt.e i
I filler grease and initial filliar; sperations en noted above.
Since l
each wire is individually pre-coated with Amber 1601, ths degree of i
l filling interstitial spaces, which comprise the net duct volume, is not directly related to the degree of coating which occurs, and therefore, is not a major indicator of the operability of the post-tensioning system.
Based on the lift off results, visual inspection E _-__ _ _
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Evaluation:
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-i and results from the first and third year surveillance, we have con-
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cluded that the structural integrity of the tendon'and anchorage l
system has not been adversely'affected by the measured void.
Additionally, since' compliance with all:cemaining surveillance requirements for Tech. Spec. 4.6.1.6.1 was demonstrated, it is l
r-concluded that " voids in excess of 5% of'the net duct volume" have i
not resulted in any degration of the post-tensioning system, assuring j
the structural integrity of the containment vessel structure.
In addition, future scheduled surveillance of the post-tensioning j
. system and full. pressure integrated leak rate tests wi11' monitor the structural parameters of the containment to detect any potential abnor-mal degradation, assure continued operability of the system, and verify
-containment vessel structural integrity on a continuing basis.
This repor t has been filed to meet the 30 day action statement as specified in Technical Specification Action' Statement 3.6.1.6(b).
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Attachm2nt I
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l TENDON SURVEILLANCE GREASING
SUMMARY
TENDON
% GREASE ADDED V41 10.8 V84 6.85 12AC 7.96 20AC 12.08 42AC 10.58 52AC 9.13 2CCB 12.70 20BA 11.87 44BA 8.92 i
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