ML20205D665

Part 21 & Deficiency Rept Re Penetration Seals Found Not to Be Watertight.Initially Reported on 880609.Water Leakage Tests Performed on Unit Upper Cable Spreading Room Seals. All Floor Penetration Seal Assemblies Repaired

ML20205D665
Person / Time
Site:	Vogtle
Issue date:	10/18/1988
From:	Rice P GEORGIA POWER CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
REF-PT21-88 GN-1449, NUDOCS 8810270168
Download: ML20205D665 (8)

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October 18, 1988 U. S. Nuclear Regulatory Corrnission ATTN: Document Controi Desk File:

X7BG03-M145 Washington, D. C.

20555 Log:

GN-1499

Reference:

Vogtle Electric Generating Plant - Unit 2; 50-425 Non-Watertight Penetration Seals GPC Letter GN-1478, dated 8/16/88 GPC Letter GN-1468, dated 7/6/88 In the referenced letters. Georgia Power Company notified the NRC of a potentially reportable condition involving certain Unit 2

penetration seals which were found not to be watertight.

Georgia Power Company has completed its reportability evaluation on this subject and has determined that a reportable condition as defined by the reporting requirements of 10 CFR Parts 21 and 50.55(e) does exist.

Based upon NRC guidance in NUREG-0302, Revision 1.

and other NRC correspondence. Georgia Power Company is reporting this condition pursuant to the reporting requirements of 10CFR50.55(e).

A sumary of our evaluaticn for Unit 2 is attached.

This correspondence contains no proprietary infortna tion and may be placed in the NRC Public Document Room.

wW P. D. Rice PDR/wkl xc: USNRC - Region !!

Suite 2900 101 Marietta Street. N.W.

Atlanta, GA 30323 H. G. Baker D. R. Altman C. W. Hayes J. P. Kane J. A. Bailey R. W. McManus R. H. Pinson G. Bockhold. Jr.

Sr. Resident (NRC)

E. D. Groover G. R. Frederick D. H. Smith (OPC)

C. T. Moore J. E. Swartzwelder J. E. Joiner (TSLA)

R. A. Thomas A. B. Gallant NORMS C. K. McCoy 8910270168 881018 i

PDR ADOCK 05000405

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PDC

Evaluation of a Potentially Reportable Condition Non-Watertight Penetration Seals Initial Report:

On June 9,

1988 C.

W.

Hayes, Vogtle Quality Assurance Manager, notified Mr. M. V. Sinkule, USNRC-Region II, of a potentially reportable condition as defined by the reporting requirements of 10CFR50.55(e).

This condition involved certain L

Unit 2 foam penetration seals which were found not to be water-tight.

Initial Condition:

Unit 1 experienced water leakage through silicone foam-sealed penetrations between the upper cable spreading room floor and the main control room ceiling.

The dripping water entered electrical cabinets causing spurious actuation of a power operated relief valve (PORV) and the pressurizer backup heater, and spurious indication of pressurizer high Javel.

A description of this event on Unit 1 is provided in Licensee Event Report (LER)88-016.

Since similar penetration seals are also utilized on Unit 2, they were identified as a potentially reportable condition.

i E n g i n e e r i n o __ E v a l u a t i oJ :

As a result of the penetration seal leakage identified on Unit 1 Georgia Power Company (GPC) performed a series of water leakage tests on the Unit 2 upper cable spreading room seals.

These testa combined with the Unit i

tests demonstrated that water could leak between the concrete and the embedded angle around the penetration, that water could seep between the foam and the structure in the corners of square or l

rectangular penetrations, and that water could soep between a tight group of cables penetrating the seal (see figure 1).

l Evaluation of the resulte of the tests performed indicate that the I

leakage between the embedded angle and the surrounding concrete can I

be attributed to the effects of heat from welding to the embedded angle.

Because this was a change in the original design, the construction work sequence resulted in the embedded angle having l

an angle extension welded to it af ter concrete placement. The heat from welding appears to have caused surface separation and bond l

breakage between the embedded angle and the concrete.

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The small water seepage i,ctween the foam and the structure in the l

corners of square or rectangular penetrations has oeen attributed L

to shrinkage of the foam seal material due to off-gassing and cooling.

This seepage was evidenced by a very slight leak in one corner of one seal that wetted a dime sized spot of the damming l

board over the half-hour of the test.

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Small water leakage through a group of cables indicates that leakage could occur where cables were grouped such that the foam did not completely surround the individual cables.

This was the result of the foam material not entering and sealing the small spaces between cables as anticipated.

A separate test showed no leakage around individual cables not grouped together.

Based on these tests, it was determined that small water leakage could occur through gaps within grouped cables in the foam seals, through the corners of rectangular or square silicone foam seals, and around the seals where welding has been performed on the i

embedded angles.

The root cause of water leakage around the embedded angles of theso penetration seals is a

design oversight by Bechtel power l

Corporation which assumed that embedded steel angles would maintain a watertight seal with the concrete floor slab after being seal welded to the penetration's upper angle iron assembly.

The design intent was to provide a watertight seal in the room under flood conditions of four inches of water on the floor.

These penetrations leaked under minimal flooding conditions tiess than 2 inches of water), and therefore did not meet design requirements.

The root cause of the water leakage within tightly grouped cables was due to the application of a design outside of its qualification in that the vendor's qualification tost report for the penetration seal detail did not envelope all upper cable spreading room penetrations.

This potential leak path was not identified by Insulation Consultant and Managemont Scrivces, (ICMS), the vendor /

installer of the silicone foam seals or Bechtel during their review of the qualification test report.

The detail that was qualified for water leakage did not contain a tight group of cables within the penetration, whereas tne typical upper cable spreading room penetration contains cables grouped together.

The fire tests for these seals were reviewed to determine if the tested configuration was similar to these seals to assure that the seals were demonstrated to be effective three hour fire seals.

The fire tested configuration (different from the leak tested configuration) did consist of a substantial mass of cables and is suf ficiently similar to demonstrate the fire rating of the existing upper cable spreading room penetration seals, groadness Review A broadness review was conducted to determine whether there exists elsewhere in the plant, other seals, which because of slight leakage could cause an unanalyzed event.

Although the design criteria makes no distinction, the seals in the upper cable spreading room were a critical application because of the existence of sensitive electical equipment below.

This makes the slightest leakage of water a

concern, whereas in most applications, seepage of very small quantities of water would not be a concern.

The review was to find other applications where leakage could affect equipment required for the safe shutdown cf the plant.

2

All areas of the plant were reviewed to ensure that redundant trains of water sensitive 1E electrical equipment, located in separate rooms, could not both be damaged due to an internal flood or a fire protection system actuation, and subsequent seal leakage.

Extensive walkdowns were performed to verify the location of water sensitive components in potentially affected rooms.

This review identified approximately 30 penetration seals outside the upper cable spreading room that require rowerk to prevent the potential leakage of water onto water sensitive, safety related equipment.

i'or Unit 2, there are no other known applications of welding to the f ace of an embed where the embed / concrete interf ace is required to be completely watertight for plant safety.

Consequently the broadness aspects outside of the approximately 110 seals in the upper cable spreading room are limited to the penetrations sealed with tilicone foam.

Insulation consultant and Management Services, Inc.

(ICMS) is the vendor / installer of the silicone foam seals used at Vogtle.

Analysis _of Safety Implica t ior} :

Leaking penetration seals can allow water from one room to affect equipment in another room.

A single water source leaking through penetration seals could potentially affeet both trains of safety-related equipment.

J Therefore, the capability to prevent or mitigate consequences of accidents could be affected by certain penetration seals not being watertight.

Georgia Power Company considers this concern to be reportable under both 10CFR21 and 10CFRSO.55(e).

Evaluation of a_QA_ Program _BreakdowI}:

An evaluation was conducted to determine.it a eignificant breakdown had occurred in either the 1

Bechtel or the ICMS quality programs.

This evaluation concluded that a significant quality program breakdown did not occur.

The penetration seals leaks were the result of two problems.

First, the seal designer dio. not anticipate a potential flow path under an embedded angle.

Second, the sealing material did not perform as anticipated.

Georgia Power Company Quality Assurance audits and field surveillances found that ICH3 has 11 stalled the penetration seals in accordance with approved procedures.

The qualification tests for water leakage which we. e originally conducted on the seal material apparently did not adequa'.ely assess the effects of foam i

shrinkage nor envelope the accati plant condition completely.

The failure to anticipate a potential flowpath during the seal design is considered to be a case of design oversight and not a significant breakdown of the project quality assurance program.

The second area of this evaluation is a material properties question not a failure of the ICMS quality program.

3 I

==

Conclusion:==

Georgia Power Company has concluded that the leakage of water through these penetration seals could potentially have adversely affected the safety of the plant operations.

Therefore this condition is considered to be reportable under the require-ments of 10CFR50.5S(e) and 100FR21.

Based on guidance in NUREG-0302, Revision 1,

concerning duplicate reporting of an event, Georgia Power Company is reporting this condition per the criteria of 10CFR50.55(e).

Corrective Action:

All floor penetrations seal assemblies in the Unit 2 upper cable spreading room have been repaired to a watertight condition.

This includes approximately 110 seals.

Other potentially affected seals have also been identified as discussed in the broadness review.

These seals will be repaired to a watertight condition by November 15, 1938.

There are npproximately 30 seals outside of the upper cable spreading room that require repair.

The seal assembly repair utilizes two materials.

The adequacy of these materials to provide a watertight seal has been verified through on-site testing of a worst case configuration of tightly grouped cables.

The repair consists of:

1.

A flowable silicone based sealant material placed in and around electrical cable bundles that bonds to the foam and the electrical cable jacket.

2.

A caulk installed around the seal perimeter and between the seal an6 penetrants (other than electrical cable).

This caulk is also placed around the embedded angle or angle extension assembly as applicab'e.

Figures 2 & 3 illustrate where these corrective actions will be utilized on a typical penetration seal.

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