AECM-90-0196, Final Part 21 Rept Re Automatic Switch Co MSIVs Failing to Close Upon Demand from Automatic & Remote Manual Actuation Signals.Initially Reported on 890914.Dual Solenoid Valves Replaced W/Two Single Solenoid Valves

Final Part 21 Rept Re Automatic Switch Co MSIVs Failing to Close Upon Demand from Automatic & Remote Manual Actuation Signals.Initially Reported on 890914.Dual Solenoid Valves Replaced W/Two Single Solenoid Valves

ML20071A011
Person / Time
Site:	Grand Gulf
Issue date:	11/21/1990
From:	Cottle W ENTERGY OPERATIONS, INC.
To:	Ebneter S NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
REF-PT21-90 AECM-90-0196, AECM-90-196, NUDOCS 9104150156
Download: ML20071A011 (8)

Text

. . ._ _.

9" ? EntCrgy i

Operations November 21, 1990 i;!":'f"

. m. Uff'7"'""*'F W. {. Cottle i

U.S. Nuclear Region II Regulatory Commission .

101 Marietta St. '

Atlanta, Georgia, 30323N.W., Suite 2900 Attention:

i Mr. Stewart D. Ebneter, Regional Administrator-

SUBJECT:

Grand Unit 1 Gulf Nuclear Station Docket No. 50-416 License No. NTF-29 RD-89/001, Main Steam Isolation Valve Failure to Close Due to Solenoid Valve Malfunction, Final Report AECH-90/0196 On September 14, 1989 Mr. Floyd Cantrell of System Energy Resources, Inc .

SERI) notified Nuclear Station (GGNS)your Unit 1. office of a Reportable Deficien(cy at Grand $11f isolation valve failure to close.The deficiency concerned a main steam

a dual valve. solenoid valve extruding through the exhaust port of theThis The extruded material blocked the exhaust port preventi solanoid valve from exhausting air which resulted inngthe MSIV remaini ng the solenoid open, j

10CFR21 for GGNS Unit I and an September 18, 1989. r the interim provisions ofreport, R0-8 was issued submitted by startup from the fourth refueling outage.The e inter

! GGNS Unit 1.

Attached is the updated

! entirety for continuity. Item 9 has been added to provica f

actions taken, and final a ons, Inc. -

n report its for E urs raly, _

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UG/WTC:be Attachment

ca (See Next Page) 9011081/SNLICFLR \

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9104150156 901121 PDFs 11:020 S ADOCK 05000416 PDR

'7 At.LM-WU/0196 Page 2 cc: Mr. D. C. Hintz Mr. R. B. McGehee(t/a) /a Mr. N. S. Reynolds(w(w/a))

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

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

Office of Nuclear Reactor Regulation '

U.S. Nuclear Regulatory Comission Mail Sten 11021 Washington, D.C.

20555 Director Office of(w/3)

Nuclear Reactor Regulation U.S. Nuclear Regulatory Comission Mail Stop P1-137 Washington, D.C. 20555 Document Control Desk U.S. Nuclear Regulatory (w/a)

Commission Mail Stop P1-137 Washington, D.C. 20555 1

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Attachment to  !

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AECM 90/0196 FINAL 10CFR21 REPORT

1. Name and address of the indi'ddual informing the comission:

l W. T. Cottle .

Vice President, Nuclear Operatiors P. O. Box 469 .

Port Gibson, Mississippi 39150 l

2. Identification of the facility ... whien ... contains a deficiency:

Grand Gulf Nuclear Station (GGNS) Unit 1 Port Gibson, Mississippi 39150

3. Identification of the fira ... supplying the basic component which ...

contains a deficie m -

l Automatic Swi6h Coinpany Florham Park, N,1. 07932

4. Nature of the deficiency ... and the safety hazard which ... could be l created by such a dificiency ...:

A. Description of the Deficiency On August 14, 1989 MainSteamIsolationValve(MSIV)821F0022B failed to close upon demand from automatic and remote manual actuation signals. Several minutes later the MSIV closed on-its .

own. An investigation later revealed that the EPDM disk material for ASCO Model NP8323A20E dual solenoid valve B21SV501B had extruded into the exhaust port of the solenoid valve. When the solenoid valve was de-energized, the disk lifted off the exhaust port and the extruded mater.al in the exhaust port was torn away from the disk material. The extruded disk material blocked the exhaust port preventing the solenoid valve from exhausting air resulting in the MSIV remaining open. The extruded disk material was later blown out hv r rmal air pressure allowing the solenoid valve to exhaust and che ESIV.to close.

! A contributing factor which caused the disk material to be extruded into the exhaust port appears to be related to the elastomer seal

being forced against the metal seat by the energized dual solenoid.

! pressure-(not spring pressure .

have been separated from rthe )emaining seat material due to theThis extru friction forces created by movement of the seat away from the exhaust port when the solenoid coils were de-energized on August 14, 1909.

A9011081/SNLICFLR

mecnsent to l; ; l, AECM 90/0196 i

TI,e extrusion process leading to ultimate failure may be both temperature and force dep(ndent. It a softening allows the process to begin.ppears that seal materialSeal soften:

ambient temperature, and extreion depends on the softening and the ,

force applied by the solenoid on b the seal material. If seal l softening has not occurred,-then the amount of protrusion of=the

! seal material into the exhaust port is so small that it has no '

l affect on valve operation. ,

The effect that ambient temperature has on the seal material softening is complex in nature. While ambient temperature is known to be a controlling factor in chemical reaction rates and its effects can be predicted utilizing Arrhenius methodology, it appears l

that the softening or extrusion process can occur at temperatures below those specified by the ASCO cualification reports.

The ASCO qualification report specifies a life of eight years at 140 degrees Fahrenheit ambient temperature for ASCO valves tested in an energized condition. A review of the available temperature data indicated that the average ambient temperature in each of the-inboard and outboard MSIV areas at GGNS Unit 1 has been below this temperature. However, evidence of substantial extrusion has been found on all eight MSIV dual solenoid valve seats. GGNS had no history of problems with these NP8323A20E MSIV solenoid-valves until the time of failure. These NP8323A20E dual. solenoid valvea weic installed on all eight MSIVs in March 1985 to replace the ASCO Model HTX8323A20V solenoid valves after three MSIVs failed to close due to the failure of three HTX8323A20V solenoid valves. In October 1985-and during the first refueling outage solenoidvalvewas--removed, disassemble (d,andinspec)ted. No- Fall of 1986 degradation or other problems were found during either inspection.

Successful completion of fast closure of the MSIVs had been documented as recently as startup from the third refueling outage (April 29,1989). Previous to this, successfu% fast closures were achieved on January 5,1989 and August 16, 1988.

System Energy Resources, Inc. (SERI) contacted ASC0iin August, 1989 for additional information relating to potential thermal aging l

effects on the EPDM seal material. utilized in the NP8323A20E valves.

i ASCO provided new, more conservative _ heat rise values than those previously received by SERI.

SERI performed an-evaluation of the themal endurance service life of these solenoid valves using the more conservative ASCO heat rise velues and the thermal endurance test data from tests perfomed for Cleveland Electric's Perry Plant. ' The' tests were performed on three groups of ASCO solenoids with both Viton and EPDM elastomers in each test group. Test-data from one group shows that a solenoid with '

EPDM elastomers functioned after 60 days at 225r~ ambient (oven -

l temperature). Conservatively assuming 135F ambient temperature (equal to-maximum anticipated dr resulted in an expected thermal ywell temperature),

endurance level of at least this evaluation-5.17 A9011081/SNLICFLR i

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Attacnment to 4 .

AECM 90/0196 years. This represents strictly a the'nal life without consideration to other aging effects included in an IEEE 323 test program.

It should be rearesentative cf the installed life at GGNS in that the failed valve lad been eposed to a themal environment with an insignificant cumulative radiation dose. However, all eight of the MS!v solenoid valves had been in service less than this period, one [B21F028A) approximately three years, and were all In similar condstion. Therefore, it is expected that strictly from a thermal endurance standpoint this failed valve should have '

functioned and all the valves should not have been in similar condition.

SERI also performed a design calculation to determine the qualified life based on the new, more conservative ASCO heat rise data and the '

ASCO test data which accounts for the cumulative aging effects and the DBE conditions. This calculation was performed for the Drywell as well as the Auxiliary Building Steam Tunnel applications, assuming 13SF and 12SF, respectively for the ambient conditions.

This calculation results in a qualified life of 2.84 years for the core disk and 4.17 years for the lower disk (GGNS failed part) in the Orywell (B21F022A-D) and 4.37 years for the core disk and 6.56 years for the lower disk in the Auxiliarv Buildino Steam Tunnel (821F028A-D). All of these calculations provide lives less than the e

ASCO reported life of eight years at 140F.

B. Analysis of Safety Implications:

The ASCO NP8323A20E dual solenoid valves are utilized as three-way, normally energized, dual solenoid operated main pilot control valves to reposition the main control valves in the pneumatic control units. The pneumatic control unit for each MSIV is attached to the valve's air operated cylinder and are utilized to control positioning of the MS!vs.

The MSIVs utilize air to open and spring to close with air assist actuators. The air supply to the pneumatic operated cylinder is controlled by a four-way pilot operated valve which applies air pressure to either the top or bottom end of, the air cylinder operator. This four-way pilot operated valve is in turn controlled by a three-way normally energized dual solenoid operated valve. To open the MSIV, either or both solenoids on the three-way dual solenoid valve are energized to feed air pressure to the piston of the four-way pilot operated valve which in turn shifts position to feed a'? pressure to the bottom side of the air operating cylinder and (at the same time) exhaust air from the top side of the air operated cylinder. To close the MSIV both solenoids on the three-way dual solenoid valve must be de-energized to allow the four-way valve to shift position to feed air pressure to the top side of the air operating cylinder and air from the bottom side of the air oper(ated cylinder.at the same time) exha A9011081/SNLICFLR

-AECM 90/0196 At GGNS there are four_ main steam lines and each steam line is equippet: with two MSIVs. One in each line is placed as close as possible to'the inside of the drywell and the other valve is just' outside the containment. The MSIVs are designed to close fast enougn to limit release of radioactivity to the environment to less than the limits of 10CFR100 in the event of a guillotine break of one steam line outside the primary containment.

Based on the deficiency described above, a potential' existed for i

both ASCO NP8323A20E dual. solenoid-valves to fail and not allow the two MSIVs to fast close on a main steam line in the event of a guillotine break on that line.

i Therefore, based on the redundant basic component guidelines, as-i it is conservatively postulated that a defined in NUREG-0302,in failure of both MSIVs a steam line potentially existed.

This- ..

l failure, coincident with a postulated main steam line break outside the primary containment could have resulted in a reduction in the j

degree of protection provided to public health and-safety.

! 5. The date on which the information of.such deficiency ... was j

j obtained:

System Energy Resources, Inc. received information of the deficiency i

' on August 28,1989. = An evaluation under the cuidelines of 10CFR21 was completed on September 13 1989.

i s

6. In the case of the basic component. ... the number and location of

all such component

j There currently are six NP8323A20E dual solenoid valves at GGNS Unit i 1, one located on each of the four Main Steam Isolation Valves in

the drywell, one on the 'A' steam line- (821F028A) outside -

containment and one spare located in the warehouse.- 1

(

We do not have knowledge of the location of other defective l equipment.

!L 7. The. corrective action which has been taken ... the name'of the j individual responsible for the action; and the length of._ time that-i has been ...-taken to complete the action: '.

j A. Corrective Actions Taken 4

j The NP8323A20E dual solenoid valves-on all eight MSIVs were replaced or refurbished prior to_ plant restart. Five of~the i

eight were replaced with new, iaentical valves 4

i .the other three were rWurbished with Viton tomerElas(NP8323A20 rebuild kits,_ making them NP8323A20V.

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. Attachment to AECM 90/0196

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8. R_e,sponsible Individual W. T. Cottle Vice Pteside,it, Nuclear Operations System Energy Resources, Inc.

C. Length of Time to Complete Actions SERI will continue with an accclerated replecement or refurbishment schedule for the NP8323A20E dual solenoid valves and in parallel is pursuing design change options such as the use of two single solenoid valves in place of the single dual solenoid valve design.

The length of time to complete this action is indeterminate at this time. However, SERI will provide a status update by startup from the fourth refueling cutage,

d. Any advice related to the deficiency ... that has been, is being, or will be given to purchasers or licensees:

As the deficiency did not origrate with SERI, we have no further advice to offer.

9. Status Update A. Corrective Action Taken Duringthefourthrefuelingoutage(RF04),MinorChangePackage (MCO) 89/1126, Rev. I was implemented to replace the dual solencia valves with two single solenoid valves. The removed dual solenoid valves were disassembled and the seats examined.

Engineering Report GGNS-90-0023 was updated with infonnation gained from the solenoid valve seat examination. The report also includes the most recent failure of a MSIV/ASCO solenoid vahe on July 27, 1990 which was determined to be temperature and seating force induced with the presence of a liquid substance (probably a lubricant) on the seat as a contributing factor. The report is considered a final resolution of solenoid valve failures due to elastomeric part degradation and is available for review at GGNS.

The factors contributing to solenoid valve failures were judged to be: higher than expected ambient temperature, high heat rise generated by the dual coil tolenoids, susceptibility of the EFDM to thennal degradation, a possible interaction of unknown liquid substance with the EPDM seat material, and high seating forces, y A9011081/SNLICFLR e

B #

4LCCnment to i

,. , AECM 90/0196 l This new design reduces the expected heat rise by using two single. solenoid valves.- The seating force on the seating material is also reduced. The seating and gasket material has been changed from EPDM to viton which provides better temperature characteristics and is less-susceptible to interaction with lubricants. ,

This is considered Entergy Operations - GGNS's final resolytion and response to Reportable Deficiency (RD)-89/001.

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