ELV-03155, Special Rept 50-425/1991-003:on 910912,vent Valve on Grease Can for Horizontal Tendon H-96 at Butress 2 Found Broken Off & Grease Leaked from 15 Locations on Exterior Surface. No Degradation Occurred in Tendons or Containment

Special Rept 50-425/1991-003:on 910912,vent Valve on Grease Can for Horizontal Tendon H-96 at Butress 2 Found Broken Off & Grease Leaked from 15 Locations on Exterior Surface. No Degradation Occurred in Tendons or Containment

ML20085C971
Person / Time
Site:	Vogtle
Issue date:	10/08/1991
From:	Mccoy C GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
50-425-1991-003, 50-425-1991-3, ELV-03155, ELV-3155, NUDOCS 9110150146
Download: ML20085C971 (7)

Text

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L f()\yOf v4 N sk-l.N o se won rwei October 8, 1991 ve u" men"cn+m ELV-03155 ,

i 1148 Docket No. 50-425 U. S. Nuclear Regulatory Commission ATTN: Document Cont ol Desk Washington, D. C. 20555 Gentlemen:

V0GTLE ELECTRIC GENERATING PLANT SPECIAL REPORT CONTAINMENT TENDON SVRV_LILLANCE DEFICLLNCIES In accordance with the rcquirements of Vogtle Electric Generating Plant Technical Specification 3.6.1.6, action statement b, Georgia Power Company submits the enclosed Special Report concerning containment tendon surveillance deficiencies.

Sincerely, L

C. K. McCoy CKM/JAE/NJS/gmb

Enclosure:

Special Report 50-425/1991-003 xc: 9_torcia Power Company Mr. W. B. Shipman Mr. M. Sheibani NORMS 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

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V0GTLE ELECTRIC GENERATING FLANT - UNIT 2 SPECIAL REPORT NO. 50-425/1991-003 A. RE0VIREMENT FOR REPORT This report is submitted pursuant to Technical Specification 3.6.1.6, action statement b. This action ctatement 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 P.eport to the Commission within 30 days in accordance with Specification 6.9.2 or be in at least HOT STANDBY 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 SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />, lhe provisions of Specification 3.0.4 are not applicable."

During the performance of the combined Unit I fifth year / Unit 2 third year tendon surveillance, two deficiencies were discovered which necessitated entry into the above action requirements. The first deficiency involved the discovery of free water in the grease can of Unit 2 horizontal tendon H-96 due to a broken vent valve. The second deficiency involved the discovery of tendon grease leakage inside the auxiliary and fuel handling buildings on the exterior surface of the Unit 2 containment cylindrical shell. It was determined that these deficiencies do not meet the acceptince criteria of Specification 4.6.1.6.1.d, which, in part, require that the operability of the sheathing filler grease be assured by verifying the following:

1. There are no changes in the presence or physical appearance of the sheathing filler grease, including the presence of free water.

2. During general visual examination of the containment exterior surface, grease leakage that could affect containment integrity is not present.

B.

SUMMARY

OF CONTAINMENT VISUAL INSPECTION A visual examination was performed on all of the exposed surfaces of the containment cylindrical shell per the requirements of Technical Specification 4.6.1.6.1.d(4) and 4.6.1.6.3, including the portion which is enclosed within the auxiliary and fuel hanJ11ng buildings. During this inspection, the vent valve on horizontal tendon H-96 was found to be broken.

Also, shrinkage cracks with small quantities of grease leakage were found at 15 locations along the bottom of the containment cylindrical shell (just above the junction of the containment base slab and cylinder).

-C. QUAL.L5 0F THE DISCOVERED DEFICIENCIES

1. Water in the Crease Can for Horizontal Tendon H-96 l On September 12, 1991, the vent valve on the grease can for Unit 2 horizontal tendon H-96 at buttress no. 2 was found to be broken off, it l

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was decided to replace the broken valve and to pump grease into the grease can through a valve in the trumpet area of the tendon to determine if any water had entered the grease can while the vent valve was broken / missing.

Da September 13, 1991, with the vent valve open, grease was pumped into the trumpet area cf tendon H-96 at buttress no. 2. Appioximately I cup of water discharged out of the grease can vent valve soon after the pumping operations commenced. This was followed by grease. No additional water was discharged after the grease started flowing from the grease can. Due to the presence of water, it was decided to remove the grease can and perform a complete visual inspection of the tendon end anchorage.

On September 16, 1991, the grease can was removed from tendon H-96 ct buttress no. 2, and a complete visual examination of the end anchorage was performed. Approximately 2 tablespoons of free water were found in the grease can, and the inspection revealed that a small area of the anchor head was of reddish brown color. However, there was no evidence of pitting or active oxidation, and this was determined to be an acceptable condition.

Following inspection of the tendon end anchorage, the grease inside the can was removed and replaced with new Visconorust 2090 P-4 material.

The tendon end anchorage was stripped of the existing grease and was hand coated with new grease. The grease can was reinstalled, and new Visconorust 2090 P-4 material was pumped into the tendon trumpet area and the grease can,

2. Grease Leakage Through Containment Cylindrical Shell Concrete Prior to performing any regressing for the Unit 2 tendon surveillance, a {

visual examination of the exterior surface of the containment cylindrical shell was performed. It was discovered that grease had leaked from 15 locations on the exterior surface. Four of these locations are in the_ fuel handling building encapsulation vessel rooms.

The remaining 11 are located in or adjacent to the encapsulation vessel rooms in the auxiliary building. All of the leaks occurred at vertical cracks in the concrete just above the junction of the containment base slab and cylindrical shell. The location of the leaks, concrete crack width, quantity of grease collected at each location, and other observations are shown in table 1.

A containment entry was not made to inspect the liner plate for the following reasons:

a. Regreasing of tendons inspected for the Unit 2 tendon surveillance had not been started.

b. None of the cracks are located near the tendons which were inspected and regreased during the Unit 2 first year surveillance in November l 1989.

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'l Therefore, there is no possibility of existing damage to the liner plate due to the grease pumping process. The concrete surfaces at all of the 15 grease leakage locations have been cleaned and will be monitored for further leakage.

D. [NGINEERING EVALUATION

1. Water in the Grease Can for Horizontal Tendon H-96 The procedure used by the Georgia Power Company (GPC) Construction Department for installing the tendons ensured a high degree of corrosion protection for the tendons. The tendons were hand corted with Visconorust 2090 P-4 material as they were pulled intc the sheathing.

Additionally, the tendons were hand coated at the fcctory with a

temporary corrosion preventive material. During the greasing procedure, i vents were opened to allow the release of air bubbles. Hot grease was pumped until a clear-flow of grease was observed exiting the appropriate vent. Inspections were made to identify any grease leakage from the tendon duct. This process ensured that the tendons originally received a thorough coating of grease.

Visconorust 2090 P-4 material, which is manufactured by the Viscosity 011 Com.oany, provides an effective barrier to moisture and air which retards the effect of 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 l

aids in retarding corrosion introduced by water soluble ions from (

l chlorides, nitrates, and sulfides. Samples of grease were taken from i the grease can of horizontal tendon H-96 in which a cup of free water t was found during the surveillance, as well as from the grease which leaked out of the cracks in the exterior surface of the containment shell. These samples-are being tested to determine the reserve alkalinity of the grease. Test results are expected by the end of October 1991. If the test results are not satisfactory, a supplemental report will be submitted to the NRC.

Approximately I cup of water had infiltrated into the grease can of L horizontal tendon H-96 through a broken vent valve. However, visual l inspection determined that this small amount of water did not cause any damage to the tendon end anchorage components. A small area of the anchor head was found to be of reddish brown color. It appears that

' this anchor head was initially installed in this condition during construction since the anchor head surface displayed no evidence of active oxidation or pitting. The broken vent valve has now been replaced, and the end anchorage components have been recoated with new grease. In addition, the grease in the grease can has been replaced with new Visconorust 2090 P-4 material. These actions will ensure that horizontal tendon H-96 will perform its intended design function.

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A visual examination of. the grease cans for all other tendons.in the Unit 2 containmerit-has been performed, and no other broken vent valves have been found.: Therefore, it can be concluded that the end anchorages

'of all tendons in the. Unit 2 containment are not subjected to a corrosive environment. -

2,: Grease Leakage Through Containment Cylindrical Shell Concrete ,

t Based upon the location'of the leakage and the quantity of grease that has leaked into the fuel handling and auxiliary buildings as listed in table 1,-it is likely that this grease is leaking from the taped joints of the sheathing for several vertical tendons. The leakage has occurred through vertical cracks in the exterior surface of the containment shell located just above the base mat. This location is where the hydraulic -

head of the grease is at-its highest for vertical tendons'along the cylindrical shell. In addition, no horizontal tendons are located in

-this area of the containment shell which would be beneficial in sealing shrinkage _ cracks that normally occur in concrete structures. Since the j

-tendon sheathing is. not designed to be leak tight, the reduced flow l resistance caused by high summer temperatures has apparently allowed the grease, driven byL a high hydraulic head, to-leak from the taped joints into the' hairline cracks in the concrete adjacent to the tendons.

At the worst leakage location, the quantity of grease leakage to date is less than 1.0 percen: of the net duct volume of any vertical tendons in the area. - This is well within the acceptance limit of 5 percent of the net duct volume as specified by Technical Specification 4.6.1.6.1.d. At the other leakage locations, the quantity of grease leakage to date is .

insignificant in comparison to the net duct volume of any vertical i tendons in the area of those leaks. Therefore, no'immediate action is L -necessary. . All leakage locations will be monitored, and additional grease will be injected if the cumulative leakage at any location approaches the grease void acceptance limit of 5 percent of the net duct volume, n The width ~ of the crack at' the worst leakage location in the concrete

shell is 0.020 inch or less. At the other 14 leakage locations, the maximum width of the crack in the concrete is no more'than-0.010 inch.

All concrete structures, including prestressed concrete structures,- are subject to shrinkage cracking. -The crack widths found at the leakage L locations do not pose any threat to:the structural integrity of the concrete structure.- In addition; visual examination of the concrete surfaces did not-identify any spalling, scaling, D-cracking, or surface deterioration or disintegration. Therefore, the structural integrity of the Unit 2 containment has not been affected by the grease leakage L

-occurring'through these cracks.

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To prevent further grease leakage and any possible surface deterioration or disintegration, some repairs may be required to seal'the concrete' L cracks which are leaking grease. Details for sealing the cracks will be l- developed-if the data. collected from monitoring the grease; leakage at the 15 leakage-locations indicate that such repairs are warranted.

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E, [0NCLUS10N Based upon the inspections performed for corrosion, characteristics of the grease, the construction process used to initially fill the ducts, quantity of grease leakage, and width of the surface cracks, it can be concluded that the grease is providing adequate corrosion protection and no abnormal degradation has occurred in the tendons or the concrete containment. The structural integrity of the Unit 2 containment has not been affected by the discovered discrepancies.

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.+ a-TABLE 1 GREASE LEAKS IN THE EXTERIOR SURFACE OF UNIT 2 CONTAINMENT CYLINDRICAL SHELL ANGLE IN CRACK WIDTH QUANTITY Of GREASE PLAN FROM .

(INCHES) COLLECTED N0. BLDG ROOM NO. PLANT NORTH +

1 FUEL R-001 2460 0.010 To 0.020 4 GALLONS

• 2 FUEL R-C01 2480 0.010 NEGLIGIBLE **

3 FUEL R-C02 2310 0.005 TO 0.010 NEGLIGIBLE **

4 FUEL R-C02 2340 0.010 1 QUART 4+

5 AUX R-Cl29 1460 < 0.005 1 QUART 6 -AUX R-Cl29 1510 < 0.005 NEGLIGlBLE**

7 AUX R-Cl28 1550 0.005 TO 0.010 NEGLIGIBLE **

8 AUX R-Cl28 1650 0.005 TO 0.010 1 QUART 9 AUX R-Cl24 1690 < 0.010 NEGLIGIBLE **

10 AUX R-Cl24 1710 < 0.010 NEGLIGIBLE **

11 AuA R-Cl24 1750 < 0.010 NEGLIGlBLE** i 12 AUX R-Cl24 1760 < 0.010 NEGLIGIBLE **

13 AUX R-Cl24 1790 < 0.010 NEGLIGIBLE **

i l 14 AUX R-Cl24 1830 < 0.010 NEGLIGIBLE **

15 AUX R-Cl24 1860 < 0.010 NEGLIGIBLE **

2 GALLONS OF GREASE WERE COLLECTED DURING THE 1989 SURVEILLANCE AS REPORTED IN SPECIAL REPORT 50-424/1989-003 (ref.: GPC letter ELV-01105, dated i November 29, 1989). THE REMAINING 2 GALLONS LEAKED BETWEEN NOVEMBER OF 1989 I AND SEPTEMBER OF 1991.

• • LEAKAJE AT THESE POINTS IS VERY SMALL. A TOTAL-0F 1 PINT OF GREASE WAS COLLECTED FROM POINTS 9 THROUGH 15.

+ ANGLE IS MEASURED ALONG CONTAINMENT SHELL CYLINDRICAL SURFACE IN A COUNTERCLOCKWISE DIRECTION.

++ THE 1 QUART COLLECTED WAS DURING THE 1989 SURVEILLANCE. ONLY NEGLIGIBLE LEAKAGE WAS OBSERVED DURING THE CURRENT SURVEILLANCE.