ELV-03200, Special Rept 1-91-5:on 911008,discovered That Amount of Grease Injected Into Vertical Tendon V10-102 Significantly Larger than Amount of Grease Removed from Tendon.Caused by Voids in Tendons.Tendon Retensioned

Special Rept 1-91-5:on 911008,discovered That Amount of Grease Injected Into Vertical Tendon V10-102 Significantly Larger than Amount of Grease Removed from Tendon.Caused by Voids in Tendons.Tendon Retensioned

ML20085N052
Person / Time
Site:	Vogtle
Issue date:	11/07/1991
From:	Mccoy C GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
1-91-5, ELV-03200, ELV-3200, NUDOCS 9111140029
Download: ML20085N052 (5)

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n C. K. McCoy y e Pmi.w N .de as Georgit Potser yggtf Pf;geil II4' h'.~ Aif ' t' d 'Ii ff ! % l F (th / I November 7, 1991 ELV-03200 1187 Dockat No. S0-424 l.

O. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555 Gentlemen:

l V0GTLE ELECTRIC GENERATING PLANT l SPECIAL REPORT CONTAINMENT TENDON SURVEILLANCE DEFICIENCIES In accordance with the requirements of the Vogtle Electric Genere'ing Plant Technical Specifications, section 3.6.1.6, action statement b, Georgia Power Company hereby submits the en:loted Special Report concerning containment tendon surveillance deficiencies.

Sincerely, C. K. McCoy CKM/NJS/gmb

Enclosure:

Special Report 1-91-5 xc: Georaia Power Company Mr. W. B. Shipman Mr. M. Sheibani NORMS l

l U. S. Nuclear Reaulatory Commission

! Mr. S. D. Ebneter, Regional Administrator Mr. D. S. Hood, Licensing Project Manager, NRR Mr. B. R. Bonser, Senior Resident Inspector, Vogtle 1

l 911114o029 +11107 j@f* g >

l PDFi ADOCK 05000424 / '\

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V0GTLE ELECTRIC GENEPATING PLANT - UNIT 1 TECHNICAL SPECIFICATION SPECIAL REPORT l-91-5 C.ONTAINMENT TENDON SURVEILLANCE DEFICIENCIES A. REQUIREMENT FOR REPORT This report is required in accordance with Technical Specification (TS) 3.6.1.6, action statement b. This action statement contains the following requirements:

"With the indicated abnormal degradation of the structural integrity other than ACTION a. at a level below the acceptance criteria of Specification 4.6.1.6, restore the containment (s) to the required level of integrity or verify that containment integrity is maintained within 15 days; perform an engineering evaluation of the containment (s) and provide a Special Report to the Commission within 30 days in accordance with Specification 6.9.2 or ' e

' in at least HOT STANCBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHU1DOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. The provisions of Specifit.ation 3.0.4 are not appl icable. "

During the performance of the combined Unit 1 fif th year / Unit 2 third year tendon surveillance, two Unit 1 tendons were discovered to have sheathing filler grease voids which exceeded the acceptance criteria of Specification 4.6.1.6.1.d (i .e. , 5 percent of the net duct volume). These deficiencies were discovered during regreasing of the tendons.

B.

SUMMARY

OF REGREASING OPERATION DURING THE TENDON SURVEILLANCE For horizontal tendcns, hat grease is pumped in one end of the tendon until grease exits the opposite end. If no grease exits, the pumping operation is transferred to the other end of the tendon. For vertical tendons, hot grease is pumped in one end of the tendon until grease exits at the high point vent on top of the containment dome. Then the pumping operation is transferred to the other tendon end, and hot grease is again pumped in until it exits at the high point vent. If no grease is emitted at the dome when pumping from either or both ends, then grease is poured (or pumped if necessary) into the high point vent to completely fill the void. Pumping pressure is limited to 150 psig on vertical tendons and 100 psig on horizontal tendons to prevent sheathing damage. The void is calculated by taking the total grease added, subtracting the total grease removed, and dividing by the net tendon duct volume.

C. DETAILS GF DISCOVERED DEFICIENCIES On October 8, 1991 during regreasing of Unit 1 vertical tendon V10-102, it was observed that the amount of grease being injected into tendon end 10 was significantly larger than the amount of grease which had been removed from that tendon end during the inspec"lon. After 118.5 gallons of grease were injected (55.5 gallons had been removed from tendon end 10), the pumping operation was stopped and a walkdown of the corresponding portion of the containment exterior surface was conducted. No grease leakage or

other abnormality was observed and the grease pumping operation was continued on the morning of October 9, 1991. No additional grease could be injected ir.to tendon end 10, and the pumping operation was transferred to tendon end 102. An amount of grease equivalent to the volume of grease which had been removed from that end (110 gallons) was injected into tendon ,

end 102. At this point, the combined net volume of grease injected l indicated that a grease void of approximately 10 percent of the theoretical net duct volume had existed prior to the start of the tendon surveillance.

Another walkdown of the corresponding portion of the containment exterior surface was conducted and again no grease leakage or other abnormality was noted. On October 10, 1991 the regreasing operation for tendon V10-102 was completed by injecting grease at the high point vent of the tendon. An  !

additional 17 gallons of grease were added at the high point verit. This l provided a final estimated grease void of 13.2 percent of the theoretical net duct volume. Since the amount of grease injected had significantly exceeded the amount removed, a walkdown of the corresponding portion of the containment interior surface was also perform d. It was verified that no grease leakage or damage to the containment :iner plate had occurred due to I the grease pumping operation.

On October 12, 1991 during the regreasing operatia for Unit I horizontal tendon H-162, it was observed that the net volume of grease being injected was slightly exceeding the 5 percent net duct volume acceptance limit which is considered a hold point for the regreasing operation. However, since the ,

grease was beginning to pump through and exit at the opposite end of the tendon, the regreasing was continued until a clean flow of grease (free of air) was exiting at the opposite tendon end. The net volume of grease injected was measured to be 29 gallons while a total of 11.5 gallons had been removed at the beginning of the tendon inspection. This indicated that a grease void of 5.4 percent of the theoretical net duct volume had existed prior to the start of the surveillance. Since the duct void acceptance limit had been exceeded by only 1.5 gallons and the grease had pumped through to the opposite end of the tendon, this indicated that the grease pumping operation had not forced any significant amount of grease out of any cracks or leakage point which might exist in the sheathing for tendon H-162.

Therefore, a walkdown to inspect the corresponding exterior and/or interior surfaces of the containment was not performed at this time. However, on October 17, 1991 after completing the regreasing of all tendons included in the tendon surveillance, a final walkdown of the Unit I containment exterior surface was performed. No grease leakage or abnormality was found.

D. ENGINEERING EVALUATION The procedure used by the Georgia Power Company Construction Department for installing the tendons assured a high degree of corrosion protection for the tendons. The tendons were hand coated with Visconorust 2090 P-4 as they were pulled into the sheathing. Additionally, the tendons were hand coated with a temporary corrosion preventive material at the factory. During the greasing procedure, vents were opened to allow the ielease of entrapped air.

Hot grease was pumped until a clear flow of grease was observed exiting the appropriate vent. Inspections were made to identify any grease leakage which might occur from the tendon duct. This process ensured that the tendons originally received a thorough coating of grease.

Visconorust 2090 P-4, which is manufactured by the Viscosity Oil Company, provides an effective barrier to moisture and air which retards the effect af a corrosive atmosphere. The grease provides a protective film which is not easily penetrated by free water and which has a reserve alkalinity for long-term acid neutralization. The film aids in retarding corrcsion introduced by water soluble ions from chlorides, nitrates, and sulfides.

During performance of the tendon surveillance, grease samples were taken from each of the selected tendons. These samples are being tested to determine the reserve alkalinity of the grease. Test results are expected at the end of November 1991. If the test results are not satisfactory, a supplemental report will be submitted to the NRC.

Grease voids of 13.2 percent and 5.4 percent of the net duct volume were found in vertical tendon V10-102 and horizontal tendon H-162, respectively, exceeding the 5 percent acceptance limit specified in Technical Specification 4.6.1.6.1.d. However, voids in excess of 15 percent of the net duct volume have been observed in tendon sheathing ducts of containments at other operating nuclear power plants. Extensive investigations performed by other utilities have concluded that voids of this magnitude are not detrimental to containment integrity since installation procedures are effective in completrly coating the tendons.

There are several major factors that could have contributed to the grease void for tendons V10-102 and H-162 exceeding the 5 percent duct void acceptance limit:

1. Visconorust 2090-P4 material has a coefficient of expansion which yields an expansion of about 1 percent per 200F. Initial filling temperatures of the filler material can average 1800F. Cold weather conditions can cool the filler material to 400F, resulting in a contraction of 7 percent of the net duct volume.

2. Calculated voids between the strands which comprise the tendon bundle are approximately 3 percent of the net duct volume. If during the initial filling operation the tendon bundle is cold, the filler material will solidify on the surface of the tendon bundle as it is being pumped into the sheathing. Small voids will be left between the strands.

During the regreasing process of the tendon surveillance, hot grease is again pumped into the tendon sheathing. As this hot grease comes in contact with the cool grease around the tendon and warms it, it is likely that grease will enter the tendon bundle voids. This migration can also occur in areas where tendon strands are in close proximity to the tendon sheathing.

3. Pumping operations can introduce air bubbles in the filler material which may account for as much as 2 percent of the net duct volume.

4. The grease may not completely fill the voids in the duct when injected at high velocity.

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During the tendon surveillance, vertical tendon V10-102 was detensioned and a strand was removed for visual examination and tensile testing. Visual inspection found the strand to be free of corrosion and cracks. Tensile test results are expected by the end of November 1991. If the test results are not satisfactory, a supplemental report will be submitted to the NRC.

The tendon was subsequently retensioned and a lift-off test performed. The lift-off force was found to be within the prescribed limits, confirming that the structural integrity of the tendon had not been adversely affected by the presence of voids in excess of the 5 percent acceptance limit. In addition, the end anchorages of both of these tendons were inspected for corrosion, grease coverage, and anchorage cracking. No indications of corrosion or anchorage cracking were identified.

A complete visual inspection of the Unit I containment exposed concrete surface and liner plate was performed following the regreasing of tendon V10-102. No evidence of any grease leakage or damage to the liner plate was found during this inspection. Additionally, a complete visual inspection of the Unit I containment exterior surface was performed following the regreasing of all tendons included in the surveillance. No grease leakage or abnormality was found by that inspection.

E. CONCLUSION Based on the construction process used to initially fill the ducts, characteristics of the grease, results of the lift-off tests, visual inspections of the tendon end anchorages, visual examination of the containment liner plate and exposed concrete surface, and previous industry experience, it can be concluded that no abnormal degradation has occurred in tendons V10-102 and H-162 as a result of the presence of grease voids which exceeded the 5 percent acceptance limit specified in Technical Specification 4.6.1.6.1.d. Therefore, the integrity of the Unit I containment has not been adversely affected by the discovered deficiencies.

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