ML20154N359

Special Rept 86-001:on 860127,net Refill Vols of Sheathing Filler Grease Exceeded 5% of Net Duct Vol for Listed Tendons.Caused by Physical Characteristics of Sheathing Filler Matl & Industry Std Installation Techniques

ML20154N359
Person / Time
Site:	Wolf Creek
Issue date:	03/06/1986
From:	Koester G KANSAS GAS & ELECTRIC CO.
To:	Martin R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
86-001, 86-1, KMLNRC-86-038, KMLNRC-86-38, NUDOCS 8603170301
Download: ML20154N359 (5)

Text

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e % KANSAS GAS AND ELECTRIC COMPANY

?>E ELECTN COMPANY OLENN L ROESTER v<a Passioteer mxtgan March 6, 1986 Mr. R. D. Martin, Regional Administrator A

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U.S. Nuclear Regulatory Commission A: : IIG @ (B [l W/ 1H ,

Region IV 611 Ryan Plaza Drive, Suite 1000 '

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Arlington, Texas 76011 J i t__ . - _ .

KMLNRC 86-038 Re: Docket No. STN 50-482 Subj : Special Report 86-01

Dear Mr. Martin:

The enclosed Special Report is submitted pursuant to Technical Specifications 3.6.1.6 and 6.9.2.

Yours very truly, Glenn L. Koester Vice President - Nuclear GLK:see cc: P0'Connor (2)

JCummins 8603170301 860306 PDR ADOCK 05000402 -

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t gl- sci 2-201 N. Market - WIctuta. Kansas - Mad Address: PO. Box 208 I Wictuta, Kansas 67201 - Telephone: Area Code (316) 261645 t

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4 SPECIAL REPORT 86-01 Inservice Tendon Surveillance Voids In Excess of 5 Percent Of Net Duct Volume This special report is being submitted pursuant to Technical Specifications l

3.6.1.6, action statement b, and 6.9.2 concerning the discovery of volds in excess of 5 percent of the net duct volume, thus exceeding the acceptance criteria of surveillance 4.6.1.6.1.e.l.

The first year tendon surveillance at Wolf Creek Generating Station (WCCS) began January 27, 1986. The surveillance inspection procedures required in part, inspection of tendon wire and anchorage components for evidence of I

corrosion and/or cracking, inspection of concrete adjacent to the bearing plates for cracks, inspection of the tendon system for signs of water intrusion, verification of tendon lift-off force and elongation, and the measurement of sheathing filler grease volds expressed as a percentage of the net duct volume. Figure 1 illustrates details of a typical vertical tendon anchorage and grease can assembly.

Technical Specification Surveillance 4.6.1.6.1.e.1 requires in part, that the OPERABILITY of the sheathing filler grease be assured by verifying that no volds in excess of 5 percent of the net duct volume exist. In order to assess the percentage of volds in the sheathing filler grease, hot grease is pumped into the tendon duct under pressure and the volume of grease added by this method, less the volume of grease removed f rom the tendon duct and grease can assembly during tendon inspection, is compared to the net duct volume. The pumping pressure was limited to assure that no damage to the containment structural integrity would occur during this process. This regreasing operation was performed on the eleven containment vessel tendons inspected during the survelliance.

During regreasing it was identified that the net refill volumes of the sheathing filler grease exceeded 5 percent of net duct volume for tendons listed below:

Percent Volds Date Tendon Number Of Net Duct Volume Discovered ICB 7.3 2/21/86 SIBA 8.1 2/25/86 45BA 6.7 2/26/86 9AC 5.5 2/26/86 9CB 6.6 2/26/86 These percentages reflect the amount of sheathing filler grease added to the tendon ducts themselves and their associated grease can.

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[ Technical Specification 3.6.1.6 Action b requires that, "With any abnormal l degradation of the structural integrity . . . at a level below the acceptance criteria of Specification 4.6.1.6, restore the containment vessel to the required level of Integrity within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and perform an engineering evaluation of the containment and provide a Special Report to the Commission within 15 days in accordance with Specification 6.9.2..."

Pursuant to this action statement Kan'sas Gas and Elcetric Company (KG&E) has determined that the process used to measure and identify the volds In the sheathing filler grease immediately, " . . . restores the containment vessel to the required level of integrity . . .", provided no other evidence of abnormal degredation is present, by filling the identified volds with sheathing filler grease.

Based on preliminary inspection and test results of additional as pect s of the post tensioning system for the inspected tendons it was confirmed that the presence of voids in excess of 5 percent of net duct volume does not degrade the structural integrity of the Containment. The amount of grease found in each can was more than adequate as all tendon wires and anchorage components had extensive grease coverage. There were no signs of water or evidence of corrosion within the tendon ducts or grease can assemblies.

Additionally there was no evidence of concrete cracking adjacent to the tendon anchorages.

Prevention of corrosion of the tendons is assured by adequately coating the tendon wires and anchorage components. The material used in the WCGS post-tensioning system, Visconorust 2090P-4, accomplishes its corrosion protection function by the filler material's affinity to adhere to steel structures, its ability to emulsify any moisture in the system nullifying its rusting ability, and by its resistance to moisture, alld acids and alkalis. As long as sufficient grease has been introduced into the system to coat the wires and anchorages completely, corrosion protection is assured. Protection is also afforded by each tendon wire being individually precoated with Amber 1601 prior to installation. The degree of filling the Interstitial spaces, which comprise the net duct volume, is not directly related to the degree of coating which occurs and, consequently, is not of significant importance as an Indicator of ope rab111 ty of the sheathing filler material.

Due to the physical characteristics of the sheathing filler material and Industry standard installation techniques, volds up to approximately 15 percent could be expected af ter the initial filling operation. Volds in the tendon sheathing may be attributed to a number of addition factors:

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 material can average 160 F. Cold weather conditions can cool the filler material to 40 F, giving a contraction of 6% of the net duct volume.

s Calculated volds between the wires which comprise the tendon bundle are approximately 7% of the net duct volume. If during the initial filling operations the tendon bundle is cold (ambient temperature of l 65 F.) and, as the filler material is pumped into the sheathing void, it solidifies on the surf ace of the tendon bundle, small volds will be lef t between the wires. As tendon bundles gradually heat and cool over time, it is likely that the volds between the wires allow migration of the filler material into the tendon bandle. In i addition, this type of migration could also occur at other areas such as where tendons are in contact with the sheathing.

Characteristics of the initial filling method may induce air entrapment into the filler material. Pumping ope rations can introduce air into filler material and may add up to as much as '2%

of the net duct volume. This void value could be higher for

! horizontal tendons due to the lower pumping head used when compared to the vartical tendons.

. In summa ry , even under optimum fliling conditions, voids of approximately l 15% could be expected af ter the initial filling operations.

Based on the above discussions it has been determined that the identification of sheathing filler grease voids in excess of 5 percent of the net duct volume alone is not evidence of degradation and does not adversely affect the structural integrity of the Containment Building. The basis for this conclusion was previously presented in letter KMLNRC 85-264, dated December 6, 1985.

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