ML19325E697

LER 89-008-02:on 890523,two Redundant Secondary Containment Isolation Dampers Failed to Close within 4 Time Limit of Tech Spec 3.6.6.2.Caused by Malfunction of Exhaust Valves. Exhaust Valve replaced.W/891031 Ltr

ML19325E697
Person / Time
Site:	Grand Gulf
Issue date:	10/31/1989
From:	Byrd R, Cottle W SYSTEM ENERGY RESOURCES, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
AECM-89-0304, AECM-89-304, LER-89-008, LER-89-8, NUDOCS 8911080290
Download: ML19325E697 (6)

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.U.S. Nuclear Regulatory Commission  !

. Mail Station P1-137

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D.C. 20555

Attention

Document Control Desk i g ..

f~ Gentlemen: I I

SUBJECT:

Grand Gulf Nuclear Station r Unit 1 Docket No. 50-416 l License No. NPF-29 l

, Update on The Failure of Redundant ,

Isolation Dampers i LER 89-008-02 i

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AECM-89/0304 )

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Attached is Licensee Event Report (LER) 89-008-02 which is a final j report, i Yours truly, e

WTC:cg-Attachment l cc:. Mr. D. C. Hintz (w/a)

Mr. T. H. Cloninger (w/c)

Mr.'R. B. McGehee (w/a)

Mr. N. S. Reynolds (w/a) '

Mr.11. L. Thomas (w/o) l Mr. H. O. Christensen (w/a) )

Mr. Stewart D. Ebneter (w/a) l i

Regional Administrator l U.S. Nuclear Regulatory Commission  !

Region II I 101 Marietta St. , N.W. , Suite 2900 I

. Atlanta, Georgia 30323 l l

Mr. L. L. Kintner, Project Manager (w/a) .

Office of Nuclear Reactor Regulation i U.S. Nuclear Regulatory Commission l

, Mail Stop 14B20 i Washington, D.C. 20555 l 891108'0590 89103L k

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on May 23, 1989 two redundant secondt.ry containment isolation dampers.

Q1T42F019 and QlT42T020, failed to close within the 4 second time limit of Technical Specification 3.6.6.2. It was suspected that the internal disk of each exhaust valve, which shuttleu *o vent or admit air on the actuator i cylinder f ailed to properly lif t tc, vent air pressure during initial attempts to close the dampers. The exhaust valve associated with the actuator of each damper was replaced. SERI will remove these type exhaust valves on all safety-related Bettis actuators and replace existing solenoid valves with valves having larger orifices and air tubing to achieve the same required stroke time.

On June 16, 1989, the QlT42F020 damper again failed to close within the 4 second time limit. The damper actuator was disassembled and no obvious r failures or defects were observed. The actuator containrd Mob 11 grease 28 which was previously identified in a 10CFR21 report as having a tendency to cause seals to swell and produce slower stroke times. Ilowever, this model of actuator was not projected to degrade in stroking time. This was not initially considered a potential contributor since the QlT42T019 had been refurbished and ,

lubricated with the approved Molykote 44 during the third refueling outage.

Grand Gulf has a 5 year program to refurbish 3ettis actuators which ensures that Molykote 44 is used. All except 2 actuators in this program have now been rebuilt. An evaluation found rose variance between the seals removed from the actuators and new seals, but it could not be conclusively determined if interaction with Mob 11 grease 28 was a factor. After consultation with the vendor, it is SERI's judgement that seal swelling was not c cause of the event.

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I A. REPORTABLE OCCURRENCE Oa May 23, 1989, two redundant secondary containment isolation f dampers failed to close within the 4 second time limit of  !

Technical Specificar,1on 3.6.6.2. This condition is reported l pursuant to 10CTR50.73 (a)(2)(v).

B. INITIAL CONDITIONS i l

The plant was in Operational Condition 4. Cold Shutdown, at the  !

time of the occurrence. [

i C. DESCRIPTION OF OCCURRENCE i On May 23, 1989 at 0235, operators manually initiated Sta.ndby Gas l Treatment Systems (SGTS) A and B. This planned initiation was ,

taken as a precautionary measure while transporting the contaninated 'B' recirc pump upper shroud from the cask washdown .-

area to the refueling floor. The 'B' recirc pump had been  !

l recently removed for disassembly and inspection to determine the cause of high vibration.

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k' hon the SGTS (E11S System code BH) was initiated two secondary containment isolation dampers failed to close within the allowed i stroke time. The two dampers, QlT42r019 and QlT42F020 are .

installed in series to isolate the outside air supply to the fuel l pool sweep fans (EIIS System code: VG). QlT42F019 is powered from i electrical division 1 and QlT42T020 is powered from electrical division 2.

Approximately 15 seconds after initiation, the Control Roon l operator placed both damper handswitches to the closed position.  ;

The QlT42F020 damper closed slowly, but the QlT42F019 damper did ,

not initia.11y close. The operator cycled the handswitch for QlT42F019 from AUTO to CLOSE repeatedly. The damper closed approximately 30 to 45 seconds after the last closure attempt '

(approximately 1 minute after the SGTS initiation).

D. APPARENT CAUSE Initial investigations into the occurrence included the initiation of SGTS "A" and "B" again to aid in the investigation. However, both dampers closed in less than 4 seconds with no work having been performed on the dampers, actuators, or controls.

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l Each isolation damper is held open by air pressure on the l actuator cylinder and is closed by spring force. The most likely cause of this failure was believed to be a simultaneous malfunction of the exhaust valves which help vent the air from i each actuator. One of the shuttle disks was inspected and found to have some deformation where contact is made with the outlet i port of the exhaust valve. It was concluded that the internal l disk of each exhaust valve which shuttles to vent or admit air on  !

the actuator cylinder, failed to properly lift to vent air  !

pressure during the initial attempt to close the dampers. The ,

exhaust valve associated with the actuator of each desper was  :

replaced. A removed exhaust valve was shipped to the vendor for [

an assessment of possible malfunction. l t On June 16, 1989, the Control Room Operator manually initiated i Standby Gas Treatment System (SGTS) B as a retest following  !

scheduled maintenance. Upon initiation, the QlT42F020 isolation  ;

damper again failed to close within the required Technical ,

Specification stroke time. The damper closed slowly (approximately 45 seconds later).  !

Following the second occurrence. the QlT42F020 damper actuator  ;

was disassembled for inspection. The inspection did not reveal f any obvious failures or defects which would have caused the slow i closure. However, it was determined that the actuator contained .

l Mobilgrease 28. The GH Bettis Company reported in February 1984 l l per 10CTR21, that Mobilgrease 28 as a lubricant could cause swelling l of the ethylene propylene seals in the actuator. The model of actuator installed on these dampers was not projected to degrade in stroking time.

The lubricant was not considered to be a potential contributor  !

at the time of the first incident since the QlT42F019 actuator had  !

previously been refurbished and lubricated with the approved i Molykote 44 lubricant during the third refueling outage. The '

actuator for QlT42F020 was subsequently reassembled with the approved Molykote 44 lubricant.

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E. SUPPLEMENTAL CORRECTIVE ACTIONS [

l The QlT42F019 and QlT42F020 dampers are normally cycled on a >

quarterly basis to confirm that the 4 second isolation requirement  !

of Technical Specificatien 3.6.6.2 is met. In addition, the dampers i are typically stroked every month during the SGTS functional surveillance. l

, As a result of this event, QlT42F019 and QlT42F020 dampers were cycled on  ;

an increased frequency of at least one:e every 15 days. After obtaining }

acceptable results, the test frequency was reverted to once per quarter.

Operation of the dempers will continue to be monitored during the monthly .

SGTS functional surveillance, j System Engineering dimensionally compared the actustor seals to new seals obtained from warehouse stock to determine what affect, if any. ,

the Mob 11 grease 28 may have had on the seals and the closing of the dampers. Although there were some differences in seal diameters, no  !

comparative data could he obtained from G. H. F.ettis or Enertech to  ;

substantiate that the difference was caused by seal swelling due to l interaction with Mob 11 grease 28. After consultation with the vendor, it  !

is SERI's judgement that seal swelling was not the cause of the problem I with the QlT42F020 damper.

At the time of the submittal of LER-89-008-00 there were eight (8)

Bettis actuators that had not been rebuilt under the $ year refurbishment (

program. This program ensures that approved Holykote 44 is used as a i lubricant. These eight (8) actuators were not projected to degrade in '

stroking time as described in the 10CFR21 report. Two of these actuators are normally closed and only stroke tested during cold shutdown. These  ;

two (2) actuators will be stroke tested and refurbished prior to startup [

from the next refueling outage (RF04). The other six (6) actuators have  ;

now been rebuilt using the approved Holykote 44 lubricant and retested  ;

satisfactorily. The previous stroke tests prior to refurbishment were  ;

also acceptable. t System Engineering conducted a review which included system l walkdowns and inspections to identify any potential conson mode failure mechanisms. The only other potential common mode failure i mechanisms identified which could have contributed to the slow stroke '

times were the solenoid valves. The solenoid valve in the air supply '

for QlT42F020 was disassembled and' inspected by engineering personnel.  ;

There was no evidsnee of any abnormality or defect which would have '

caused a malfunction. Testing of the solenoid prior to disassembly demonstrated that it was functioning properly. System Engineering is reviewing industry experience with ASCO Solenoid Valve Model NP831655E to determine if there are any previously identified problems that could ,

cause abnormal operation. ,

PCOM LER 89-008-02 4

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The exhaust valve vendor, parker Hannifan, reported that there were no I known generic problems associated with this type of exhaust valve.

However SERI will discontinue using the exhaust valves in safety-related applications to eliminate the possibility of their failure. These type exhaust valves will be removed from all safety-related Bettis actuators and existing electric solenoid valves will be replaced with valves having j larger orifices and air tubing to achieve the required stroke time.  ;

The change will be completed prior to startup from the fourth refueling 1 outage (RF04).

Namco recently informed customers of potential problems with Model )

EA740 and EA750 limit switches sticking due to lubrication problems. The QlT42F019 and QlT42F020 dampers utilize Namco Model EA740 limit switches which may have caused an erroneous indication of damper position. However,  !

since dual indication of damper position was not received in the Control  !

Room and since the probability of a double failure of the contacts in the ,

signal circuit is low, the limit evitches are not a likely contributor to i the occurrence. Investigation of this possibility is in progress. f I

This report is submitted as a final report. Although the root cause was ,

not conclusively determined, the actions taken to date and the actions  ;

planned are considered adequate to pr'eclude recurrence. There have been  !

no recurrences since June 16, 1989. t F. SAFETY ASSESSMENT  ;

The QlT42F019 and QlT42F020 dampers are the only secondary 3 containment isolation dampers in the outside air supply i penetration to the fuel pool sweep fans. The concurrent failure of both dampers to isolate within the required 4 seconds could l adversely affect the required drawdown time of secondary

• containment by the SGTS. Secondary containment, including the j SGTS, was not required to be operable at the time of the first ,

occurrence.

After the second occurrence on June 16, 1989, QlT4?F019 was secured in the isolated position in accordance with Action b of  ;

Technical Specification 3.6.6.2. The valve properly operated to 16olate the penetration within the required 4 seconds. '

f W"pCOM LER 89-008-02

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