ELV-03889, Application for Amends to Licenses NPF-68 & NPF-81,revising TS 4.6.1.6.1.d.2 SR for Containment Tendon Sheathing Filler Grease,To Replace Requirement to Verify Grease Void Fraction W/Requirement to Replace Grease Removed During Tendon Insp

Application for Amends to Licenses NPF-68 & NPF-81,revising TS 4.6.1.6.1.d.2 SR for Containment Tendon Sheathing Filler Grease,To Replace Requirement to Verify Grease Void Fraction W/Requirement to Replace Grease Removed During Tendon Insp

ML20105C007
Person / Time
Site:	Vogtle
Issue date:	09/14/1992
From:	Mccoy C GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20105C009	List: ELV-03889, Application for Amends to Licenses NPF-68 & NPF-81,revising TS 4.6.1.6.1.d.2 SR for Containment Tendon Sheathing Filler Grease,To Replace Requirement to Verify Grease Void Fraction W/Requirement to Replace Grease Removed During Tendon Insp ML20105C012 ML20105C015
References
ELV-03889, ELV-3889, NUDOCS 9209220010
Download: ML20105C007 (7)

Text

, , u m: s . ,

x , ' e_

P. ,

mA

c. x. wcoy GC0!gia power September 14, 1992 ELV-03889 004521 Docket Nos. 50-424 50-425 U. S. Nuclear Regulatory Commission ATIN: Document Control Desk Washington, D. C. 20555 _

Gentlemen:

V0GTLE ELECTRif GENERATING PLANT REQUEST (0 REVISE TECHNJC AL SPEC _1.FIC AT10N 4.6.1.M.d . 2 In accordance with the requirements of 10 CFR 50.90 and 10 CFR 50.59, Georgia Power Company (GPC) hereby proposes to ar. nd the Vogtle Electric Generating Plant (VEGP) Unit 1 and Unit 2 Technical Specifications (TS), Appendix A to

, Operating Licenses NPF-68 and NPF-81. The proposed amendment would revise the surveillance requirements for the containment tendon sheathing filler grease.

The proposed amendment and its basis are described in enclosure 1. Our evaluation pursuant to 10 CFR 50.92 showing that the proposed amendment does not involse significant hazards considerations is provided in enclosure 2. A '

mark up of the affected page is provided as enclosure 3. In accordance with 10 CFR 50.91, the designated state official will be sent a copy of this letter (

and all enclosures. Georgia Pcwer Company requests approval of the proposed amendment by December 31, 1993.

Mr. C. K. McCoy states that he is a Vice President of Georgia Power Company and is authorized to execute this oath on behalf of Georgia Power Company and that, to the best of his knowledge and belief, the facts set forth in this letter and enclosures are true.

GEORGIA POWER COMPANY By: . I C. K. McCoy Sworn to and subscribed befoce me this / 7 day of a d tt1992.

(ULLt "[ ht 10 CV,. \

N$ary Public /).

v ,,mmnuaMMMd2 p 92o922o01o 92o914 PDR ADOCK 05000424 Ch1 i

16 P PDR k l

/

Georgi:iPower d U. S. Nuclear Regulatory Commission Request to Revise Technical Specifications ELV-03889 Page 2 CKM/NJS

Enclosures:

1. Basis for Proposed Change

2. 10 CFR 50.92 Evaluation

3. Marked Up Page

~

c(w): ngorcia Power CSmpEly Mr. W. B. Shipman Mr. M. Sheibani NORMS U. S. Fuclear Reo!1]atory Commission Mr. S. D. Ebneter, Regional Administrhtor Mr. D. S. Hood, Lf:ensing Project Manager, NRR Mr. B. R. Bonser, Senior Resident Inspector, Vogtle State of Georoia Mr., J. O, Tanner, Commissioner, Department of Natural Resources u

l l

4 ENCLOSURE 1 V0GTLE ELECTRIC GENERATING PLANT REQUEST TO REVISE TECHNICAL SPECIFICATION 4.6.1.6.1.d.2 BASIS FOR PROPOSED CHANGE Proposed Chanae The Vogtle Electric Generating Plant (VEGP) Unit I and Unit 2 Technical Specifications (TS) require, in part, that the containment tendon sheathing filler grease be verified operable by assuring that the " amount of grease replaced does not exceed 5% of the net duct volume, when injected at a pressure not to exceed the designer's specifications." This surveillance requirement (TS 4.6.1.6.1.d.2) is applicable when a tendon is opened for inspection pursuant to TS 4.6.1.6.1_ The purpose of the surveillance requirement is to verify that <

there are no significant voids in the grease, thereby providing assurance of minimum grease coverage so that the tendon is protected from degradation due to corrosion.

The proposed change would replace the requirement to verify the grease void fraction with a requirement to replace the grease removed during a tendon inspection.

Basit Surveillance requirement 4.6.1.6.1 specifies a number of inspection activities to be performed on randomly selected tendons. These activities typically require the tendons to be opened (i.e., the grease can covering the end anchorages.is removed) and many of these inspection activities require detensioning of the tendon, strand removal, etc. As a result, a certain amount of sheathing filler grease is removed during the process, and this grease must be replaced when the inspection of the tendon is completed. The existing TS imposes an additional requirement to assure that the sheathing filler grease void fraction does not exceed 5 percent of the net duct volume.

In order to assess the grease void fraction, the grease is heated and injected into the tendon duct under pressure. The pressure at which grease is injected is limited to 150 psig for vertical tendons and 100 psig for horizontal tendons.

For horizontal tendons, hot grease is_ injected until it exits the opposite end i

of the tendon duct. If grease cannot be forced from the opposite end, the-pumping operation is transferred to that end. For vertical tendons, grease is injected into both ends of the tendon until it exits the high point vent. If greane cannot be forced from the high point vent, the_ operation _is moved to the

top of the containment and grease is in,iected at the vent. The void fraction consists of the ratio of the volume of grease _actually added to the duct (accounting for any grease that may be forced out of the vent for vertical tendons or out of the ends for horizontal tendons) to the net duct volume.

i El-1

ENCLOSURE 1 V0GTLE ELECTRIC GENERATING PLANT REQUEST TO REVISE TECHNICAL SPECIFICATION 4.6.1.6.1.d.2 BASIS FOR PROPOSED CHANGE The 5-percent void fraction limit has been exceeded on several occasions during containment tendon surveillances at VEGP. (See Special Report I1-424/1987-002, dated May 18. 1988, SL-4577; Special Report 50-424/1989-003, dated November 29,1989, ELV-01105; and Special Report 50-424/1991-005, dated November 7, 1991, ELV-03200.) In each of these cases. the grease voids were attributed to one or more of the following factors. -

1. The grease (Visconorust 2090-P4) has a coefficient of expansion of about I percent per 20 0F. The initial filling temperature of the grease averaged approximately 180 0F. Cold weather conditions can cool the grease to approximately 40 0F, resulting in a net contraction of Innroximately 7 percent of the net duct volume. As the grease cools it 4 rinks and adheres to the steel surfaces, creating voids which are distributed along the entire length of the duct. [In fact, these voids are required to accommodate the grease as it expands due to increases in temperatur9rrom plant operation and/or increases in the temperature of the outsi R uir. This is illustrated by the following experience. On June 22, 1990, grease was observed leaking from four horizontal tendon end

% caps (three on Unit 2 and one on Unit 1). The grease leaks occurred at the 0-rings of each tendon and were attributed to the regreasing of the tendons during a surveillance completed in the Fall of 1989. Apparently, the grease that was injected during the regreasing operation completely filled the voids in the horizontal tendon ducts and left no room for thermal expanrion of the grease. Subsequently, outside ambient air temperatures reached 100 plus degrees in June of 1990, resulting in internal pressures that were greater than the capacity of the 0-rings.)

2. Calculated voids between the strands which comprise the tendon bundle are approximately 3 percent of the net duct volume. If during the initial operation the tendon bundle is cold, the grease will solidify on the -

surf ace of the tendon bundle as it is being pumped into the sheathing.

Small voids will be left between the strands. During the segreasing

• process, 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. The initial filling method could have resulted in air entrapment within the grease, accounting for voids up to 2 percent of the net duct volume.

El 2

4 i

ENCLOSURE 1 V0GTLE ELECTRIC GENERATING PLANT REQUEST TO REVISE TECHNICAL SPEClflCATION 4.6.1.6.1.d.2 DASIS FOR PROPOSED CHANGE

4. The machining tolerances on the wires, trumpets, and sther components could account for as much as 1 percent of the void volume. This would af fect the calculation of the net duct volume, assuming nominal dimensions for the components making up the tendon.

The procedure used by GPC for installing the tendons ensured a high degree of _

corrosion protection for the tendons. The tendons were handcoated with Visconorust 2090-P4 as they were pulled into the sheathing. Additionally, the tendons were coated with a temporary corrosion preventive material at the factory. During the greasing procedure, vents were opened to allow the release of air bubbles, and hot grease was pumped into each tendon duct until a clear flow of grease was observed exiting the appropriate vent. Inspections were made to identify any grease leakage from the tendon ducts. This process ensured that the tendons originally received a thorough coating of grease. ,

Visconorust 2090-P4, manufactured by the Viscosity 011 Company, provides an effective barrier to moisture and air which retards the effect of a corrosive atmosphere. The protective film provided by the grease is not easily penetrated by free water, and the grease has a reserve alkalinity for long-term acid neutralization. The film aids in retarding corrosion due to water soluble ions from chlorides, nitrates, and sulfides. As part of the tendon surveillance (as required by the TS), grease samples (which are from the anchorhead region of the tendons) are chemically analyzed for water content, chlorides, nitrates, sulfides, and reserve alkalinity. The analyses of these samples have always conservatively yielded results well in excess of the TS limits. Furthermore, _

visual inspections of tendon components, lif t-off force testing, and actual strand removal have not revealed any degradation due to corrosion and cracking.

As aa additional consideration, the tendon ducts are not designed to be '

leak-tight. Since the regreasing operation involves injecting the gre ase under relatively high pressure (100 - 150 psig), the very method of meisuring the void fraction could cause grease to be forced out through weak locations in the duct (the taped joints, for example), and this in turn could result in cracking of the surrounding concrete.

While it cannot be attributed to a regreasing operatirq, it should be noted that there has been some minor grease leakage through the vait 2 containment cylindrical shell concrete. (See Special Report 50-424/1989-003, dated November 29,1989, ELV-01105 and Special Report 50-425/1991-003, dated October 8, 1991, ELV-03155.) The leakage has occurred through vertical cracks in the exterior surface of the containment shell located just above the baserat. Based upon the location of the leakage, it is likely that this grease is leaking from the taped El-3 l

ENCLOSURE 1 VCGILE ELECTRIC GENERATING PLANT REQUEST TO REVISE TEC 11 CAL SPECIFICATION 4.6.1.6.1.d.2 BASIS FOR PROPOSED CHANGE joints of the sheathing of several vertical tendons. This is also where the hydraulic head of the grease is at its highest for the vertical tendons. Since the tendon sheathing is not designed to be leak-tight, the reduced viscosity of the oil caused 'yo high summer temperatures apparently allowed the grease, driven by the high hydraulic head, to leak from the taped joints into the hairline cracks in the concrete adjacent to the tendons. This leakage has been monitored regularly since it was idontified, and the grease leakage at the worst location has remained below 1 percent of the net duct volume of any vertical tendons in the area. Existing leakage will continue to be monitored, and new leakage will be identified and documented in accordance with existing plant procedures, if the cumulative leakage at any location approaches a significant quantity, an engineering evaluation will be performed to determine the appropriate level of corrective action required to ensure the continued operability of the sheathing filler grease. This leakage through the concrete illustrates the susceptibility of the ducts to leakage even though the involved tendons have not been subjected to regreasing.

Finally, by letter dated April 19, 1990, to Mr. hans Asher of th' NRC, Mr. C. W. Novak of Viscosity Oil makes the following points regarding the matter of grease voids in tendon ducts and the action of the Visconorust 2090 P-4 corrosion preventive.

1. The original design of their system took into account that there would be voids, and, given the different variables, a total void fraction of 20 percent is possible. -

2. The key to their system is that each tendon is fully coated with grease with some initial penetration into the tendon bundle during the original pumping process. Once the tendan is coated with hot grease in this manner, the Visconorust 2090 P-4, on cooling, contracts but leaves a heavy film up to 20 mils or more on the tendon surf ace, providing ample corrosion protection.

3. During a surveillance, the attempt to pump grease into one end of a tendon duct and out the other could do more harni than good. The system was well coated initially and pressurizing the ducts in an attempt to break through the solid Viscenorust 2090 P-4 could potentially force grease through weak locations in the tendon sheathing, or damage vent caps or seals.

4. Pumping an excessive amount of grease into the ducts could overfill the system, leaving no room for expansion of the grease due to an increase in ambient temperature.

A copy of the referenctj letter is attached for your information.

El-4

ENN 0SURE 1 V0GTLE ELECTRIC GENERAlING PLANT j REQUEST TO REVISE TECHNICAL SPECIFICATION 4.5.1.6.1.d.2 BASIS FOR PROPOSED C!lANGE Based on the above discussion, GPC believes the following conclusiens can be l drawn regarding the grease void fraction -limit specified- by the TS.  ;

i

1. The void fraction is not a good indicator of corrosion protection as-evidenced by the number of variables which can affect measurement of the void fraction. This is further supported by the fact that visual inspections, lift-off force testing, chemical analyses of grease samples, and tendon strand removal (and subsequent inspection and testing)- have -

revealed no evidence of degradation due to corrosion, in spite of the fact that the void fraction limit has been exceeded on several occasions.

In addition, as cited above, the vendor supports our argument that the void fraction is not a good iridicator of corrosion protection.

2. The method required for measuring the void fractior is difficult and inherently imprecise since it involves forcing hot grease under pressure into a duct filled with solidified grease in an effort to fill all voids.

Furthermore, damage can actually result by forcing grease out the joints in the sheathing and into the concrete, or by filling the voids and not allowing for thermal expansion of the grease.

3. Surveillarice requirements involving lift-off force test:ng, visual inspection of tendon components and containment interior and exterior surfe.ces, and chemical analyses of the sheathing filler grease provide definitive indication of degradation of the tendons due to corrosion or other causes.

Therfore, GPC proposes to delete the grease void fraction limit of surveillance requirement 4.6.1.6.1.d.2 and replace it with a requirement to restore as a minimum the grease removed-during the surveillance.

El-5

_ _ _ . - , _