ST-HL-AE-4165, Suppl to 920430 Special Rept:On 920408,nonvalid Failure of Sdg 21 Occurred When Sdg Tripped When Released from Emergency Mode.Cause Not Determined.Power Supply Mfg by Beta Products.No Corrective Actions Warranted

Suppl to 920430 Special Rept:On 920408,nonvalid Failure of Sdg 21 Occurred When Sdg Tripped When Released from Emergency Mode.Cause Not Determined.Power Supply Mfg by Beta Products.No Corrective Actions Warranted

ML20113H488
Person / Time
Site:	South Texas
Issue date:	07/29/1992
From:	Jump W HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ST-HL-AE-4165, NUDOCS 9208040057
Download: ML20113H488 (4)

Text

r, The Light c o mp a ny South Texas Project Electric Generating Station P O. Box 289 Wadsworth, Texas 77483 IIouston Lighting & Power ___.

July 29, 1992 ST-HL-AE-4165 File No.:

G02 10CFR50 U.

S. Nuclear Regulatory Commission Attention:

Document Control Desk Washington, DC 20555 South _ Texas Project Unit 2 Docket No. STN 50-499 Supplemental Special Report Regarding A Non-Valid j

Failure of_ Standby Diesel Generator #21 on ADril 8.

1992 j

Pursuant to.the South Texas Project (STP)

Technical Specifications 4.8.1.1. 3 and 6.9.2, Houston Lighting & Power (HL&P) submits the attached Supplemental Special Report regarding Standby Diesel Generator #21 non-valid failure which occurred on April 8, 1992.

If you should have any questions on this matter, please contact Mr.

C.

A. Ayala at (51.2) 972-8628 or me at (512) 972-7205.

'j he& [p.

o uz ; k William J.

Jun General Manager, Nuclear Licensing MAC/ag Attachments: 1.

Supplemental Special Report Regarding A Non-Valid Failure'of SDG #21 on April 8,

1992 2.

HL&P letter dated April 30, 1992 (ST-HL-AE-4065) 300061 n

SAEP\\92.198.001 A Subsidiary of Houston industries inectporated 9200040057 920729

{DR ADOCK 05000499

/

PDR

=

1, I

I Homton Lighting & Power Ccmpany ST-HL-AE-4165 South Texai Project Dectric Generating Station File No.: G02 Page 2

cc:

Regional Administrator, Region IV Rufus S.

Scott Nuclear Regulatory Commission Associate General Counsel 611 Ryan Plaza Drive, Suite 400 Houston Lighting & Power Company Arlington, TX 76011 P.

O.

Box 61867 Houston, TX 77208 George Dick, Project Manager U.S. Nuclear Regulatory Commission INPO Washington, DC 20555 Records Center 1100 circle 75 Parkway J.

I. Tapia Atlanta, GA 30339-3064 Senior Resident Inspector c/o U.

S.

Nuclear. Regulatory Dr. Joseph M. Hendrie Commission-50 Bellport Lane P.

O.

Box 910 Bellport, NY 11713 Bay City, TX 77414 D. K. Lacker J.

R. Newman, Esquire Bureau of Radiation Control Newman & Holtzinger, P.C.

Texas Department of Health 1615 L Street, N.W.

1100 West 49th Street Washington,-DC 20036 Austin, TX 78756-3189 D.'E.-Ward /T. M.

Puckett Central Power and Light Company P.'O.

Box 2121 Corpus Christi, TX 78403 J.

C. Lanier/M.

B.

Lee

. City of Austin Electric Utility Depa tment P.O.

Box 1088 Austin, TX 78767 K. J. Fiedler/M. T.-Hardt City Public Service Board P.

O. Box 1771 l

San Antonio, TX 78296 l

L Revised 10/11/91 L4/NRC/

L l

1 9

Attachment ST-HL-AE-4165 Page 1 of 2 South Texas Project Unit 2 Docket No. STN 50-499 Supplemental Special Report Regarding A Non-Valid Failure of Standby Diesel Generator J21 on April 8,

1992 DIS _QIiTfTION OF EVENT:

On April 8,

1992, Unit 2 was in Mode 1 at 100% power.

While Standby Diesel Generator (SDG)

1. 21 Operability Test was being performed, the SDG-tripped when released from the emergency mode.

No alarms or relay flags, which would indicate the cause of the trip vere-detected.

In addition, when SDG #21 was started, none l

ofLthe usual starting alarms (i.e.,

low starting air pressure, l:

jacket water standpipe level low) were received.

Troubleshooting of tho SDG #21 electrical trip circuitry was performed with no problems found. The applicable fuses, relays and timers were verified for proper operatinn.

Various connections were inspected which revealed a loose connector to the input side of-the annunciator. power supply.

This connection was repaired.

A failed annunciator power supply (PS-2) was also identified. This power supply was subsequently replaced three times before the cause for the power supply failures could be determined.

The failure of l

thie power supply was originally thought to have been the cause of the trip uponi relcase from emergency mode.

However, after extensive troubleshooting, this conclusion could not be supported.

A functional check of the engine speed monitor and its associated trip setpoints were verified.

No abnormalities were noted.

The high jacket water temperature trip valve and the test mode safety trip pilot valve were also tested and disassembled.

No discrepancies that could cause an engine trip were detected.

l CAUSE OF EVJJiT:

The cause of the SDG #21 trip upon release from the emergency mode can not be determined.

Previous occurrences of both SDG #21 and

1. 23 trips upon release frcm the emergency mode have been attributed to a loss of air pressure in the pneumatic shutdown header.

This event is described in the attached correspondence ST-HL-AE-4065 dated April 30, 1992.

There have been no diesel trips without indication since the last reported non-valid failure of SDG #21 on SAEP\\02-198.001

~

Attachment ST-HL-AE-4165 Page 2 of 2 South Texas Project Unit 2 Docket No. STN 50-499 Su t lemental Special Report Regarding A Non-Valid Failm. of Standby Diesel Gen.grAt.g.r #21 on ADril 8.

1992 C_AUSE OF EVENT: (con't) i April 8,.1992.

This includes the performance of 4 valid tests on l-

'SDG

1. 21 since April 8,

1992.

An extensive, thorough troubleshooting ef fort, including on site consultation with the control panel vendor representative in conjunction with telephone consultation _ with the factory established no apparent cause.

Should another engine trip without indication occur, a special report will be submitted in accordance with Technical Specifications.

ANALYSIS OF EVENTi This event has" been classified as a non-valid failure sin :e the SDG

1. 21 operated satisfactorily in the emergency mode and if challenged, would have performed its safety function.

r L

CORRECTIVE ACTIONS:

No further corrective actions are warranted.

ADDITIONAL INFORMATIOJ:

At the time of the event, there were no valid failures in the last 20 valid tests and less-than 4 valid failures in the last 100 tests for.SDG #21.

Therefore, the testing frequency will remain at once l

per 31 days, l

306930.

The power supply is manufactured by Beta Products, Part No.

SREP\\92 198.001 l'

1

c

__ ATTACHMENT 2.

ST-HL-AE- % 5 aM i

F G The Light t

company P. O. Itos 289 Wadworth, Teias 77483

- liouston Lighting & Power. South Texas Project Elcettic Generating Station..

j April 30, 1992 ST-HL-AE-4065 File No.:

G02 j

10CFR50 i

U.

S.

Nuclear Regulatory Commission Attention:

Document Cyttrol Desk Washington, DC 20555 South Texas Project Unit 2

. Docket No. STN 50-499 Supplemental Special Report Regarding Two Diesel Generalor Non-Valid Failiges Pursuant to the South Texas Project Electric Generating Station (STPEGS) Technical Specifications 4.8.1.1.3 and 6.9.2, Houston Lighting &- Power submits the attached Supplemental Special

~ t.

Report regarding Standby Diesel Generators (SDG) /23 and /21 non-valid failures which occurred on December 6

and 7,

1991, respectively.

A Special Report regarding the failure was provided

... F to the NRC on January 3,

1992, reference letter ST-HL-AE-3955.

Please find attached'a supplement to that report which provides additional information concerning investigative findings, Change

. bars have been added to highlight supplemental information.

A separate Special Report regarding a non-valid failure of SDG..#21 on December 24, 1993 was provided to the NRC on January 23, 1992, reference letter ST-HL-AE-3985.

The attached report also provides additional information for HL&P letter ST-HL-AE-3985 that was due to the NRC by July 30, 1992.

If you should have any questions on this matter, please contact Mr.

C.-A.

Ayala at (512) 972-8628 or myself at

-(512) 972-7205.

)Ihes,,t y

7 -

William J.

Jump j(A@W. m--*'W L

'u

Manager, 9

Nuclear Licensing

'~) 1I '

l JMP/sh t

l

Attachment:

Supplemental Special Report Regarding Two SDG Non-Valid Failures SRfr\\92-098.001

,g m.Mun M IlmNon Imlustries incorpor.u cil

ATTACHMENT 2.

ST HL AE 4 / /oG '

PAGE >

0F 6

Ilouston Lighting & Power Company ST-HL-AE-4065 f

South Texas Project Electric Geocrating Station File No.: G02 Page 2

cc:

' Regional = Administrator, Region IV Rufus S.

Scott Nuclear' Regulatory Commission Associate General Counsel Gil Ryan Plaza Drive, Suite 400 Houston Lighting & Power Company

. Arlington, TX 76011 P.

O.

Box 61867.

Houston,-TX 77208 George Dick, Project Manager U.S. Nuclear Regulatory Commission INPO Waship'ston, DC 20555 Records Center 1100 Circle 75 Parkway J.

I. Tapia Atlanta, GA 30339-3064 Senior Resident-Inspector c/o U. S.

Nuclear Regulatory Dr. Joseph M. Hendrie Commission 50 Bellport Lane P.

O.

Box 910 Bellport, NY 11713 Bay City, TX-77414 D.

K. Lacher J. R. Newman, Esquire Bureau.of Radiation Control Newman & Holtzinger, P.C.

Texas Department of Health 1615 L Street,.N.W.

1100 West 49th Street Washington, DC 20036 Austin, TX 78756-3189-D.:E. Ward /T. M.-Puckett central Power and Light Company P.

O.. Box _2121 Corpus Christi,.TX 78403 J. C. Lanior/M.

B.

Lee City of Austin Electric Utility Department

- P.O.

Box 1088-

-Austin,_TXE 78767 K. J. Fiedler/M. T.

Hardt City Public. Service Board P.

0.

Box 1771

-- San Anton10,.TX.78296 Revised 10/11/91 4

L4/NRC/

j 4

er-+

v.

ATTACHIAENT 1 ST HL-AE-H W

~

PAGE 3 0F 5 __

[

Attachment ST-HL-AE-4065 Page 1 of 3 South Texas Project Unit 2 Docket No. STN S0-499 i

Supplemental Special Report Regarding Two Diesel Generatior Non-Valid Failures DESCRIPTION OF EVENT:

)

On December 6, 1991, at 2301 hours0.0266 days <br />0.639 hours <br />0.0038 weeks <br />8.755305e-4 months <br />, Standby Diesel Generator

/23 was started in the emergency mode following release of Equipment Clearance Order 2-91-3261 which was associated with a work document.

Unit 2 was in Mode 4 during a refueling outage.

SDG #23 came up to rated speed,-voltage, and frequency within 10 seconds.

When the engine was released from emergency mode, SDG

/23 tripped with no test mode trips indicated. The engine was then restarted at 0030 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> on December 7 in the test &.:de with I&C, Electrical, and Mechanical Maintenance personnel present.

The engine'came up to rated speed, voltage, and frequency within the 10 second limit and was running satisfactorily.

The engine was then__ started a third time at G059 hours in the emergency mode. The

(

diesel generator was released from the emergency mode to the test mode without a trip.

The Control Room then commenced the Standby Diesel Generator /23 Operability Test.

The diesel performed satisfactorily during the one hour surveillance run and SDG /23 was declared operable at 0250 hours0.00289 days <br />0.0694 hours <br />4.133598e-4 weeks <br />9.5125e-5 months <br />.

Standby Diesel Generator /21 was started on December 7,

1991, at 0313 hours0.00362 days <br />0.0869 hours <br />5.175265e-4 weeks <br />1.190965e-4 months <br /> in the emergency mode to verify operability in accordance with Technical Specification Action Statement 3.8.1.1 and came up to rated speed, voltage, and frequency within 10 seconds. _ When the engine was released from the emergency mode, SDG #21 tripped with no' test modo trips indicated.

SDG #21 was restarted in the emergency mode a second time at 03*'1

hours, released from the emergency mode to the test mode, and the engine functioned properly.

At 0603 hours0.00698 days <br />0.168 hours <br />9.970238e-4 weeks <br />2.294415e-4 months <br />, the Control Room commenced SDG /21 operability test and declared SDG /21 operable at 0820 i

l-hours.

Subsequent troubleshooting was performed on SDG #23 and

-SDG #21 on February 28, 1992, and January 15, 1992 respectively.

All electrical circuitry pertaining to the 86S relay trip circuit was verified for termination tightness, condition of lugs, and proper termination.

In addition, a chart recorder was set up to monitor the 86S trip circuit loop voltages.

No abnormal l.

Indications were observed.

I&C personnel also inspected the I

pneumatic control system by monitoring performance with test gauges, but did not disassemble any piping or components.

Again, no problems were noted on either diesel.

SMP\\92-098.001 I

ATTACHMENT 2 ST HL AE4/ 6S PAGE 4 0F _ _ 5 Attachment ST-HL-AE-4065 Page 2 of 3 DEscUTTION OF_ EVENT:

(Continued)

The 86S relay on SDG /21 was again tested on March 3,

1992.

The voltages were monitored with a chart recorder during operation of the generator.

One set of contacts were found to have a slightly out of tolerance resistance measurement.

The relay was subcoquently replaced.

Evaluation of the 86S relay shows that the chance of circuit malfunction would be unlikely with the as-found value of resistance.

The conservative approach was to replace the

relay, as a considerably higher value of contact rasistance (leading to contact failure) could cause this mode of dio.cl trip.

Inspection of the pneumatic control circuits on both engines revealed foreign material in check valves SD-3207 (#21) and SD-3209

(#23).

These check valves prevent reverse airflow from the shutdown control air line into the reset air line.

Foreign material under the seat of these check valves causes a decrease in air line pressure and at 20 psig, a shuttle valve will change state and cause the engine to trip with no indications.

(

CAUSS OF EVENT The cause of these events can reasonably be attributed to foreign material under the seat of the check valves allowing a decrease in air pressure, and ultimately causing the trips with no apparent indication.

ANALYSIS OF EVENT:

These two events have been classified as non-valid tailures since the diesel generators operated satisfactorily in the emergency mode and if challenged, would have performed their safety function.

SDGs #21 and #23 were started in test mode on December 15, 1991 and both engines operated satisfactorily.

Diesel generator /21 also successfully conpleted a valid test on December 19, 1991.

SDGs /21 and /23 started and ran in the emergency mode when responding to a recent reactor trip and Safety Injection signal on December 24, 1991.

SDG /21 tripped when released from the emergency mode during the run on December 24.

Subsequently, a separate report for this apparent non-valid f ailure was submitted addressing the cause of the SDG

trip, reference letter ST-HL-AE-3985.

Since these SDGs have operated correctly in the emergency mode, the diesel generators are considered capable of fulfilling their required safety functions.

tEtF\\92-098.001

r.

' ~AIT56iiMENT A ST HL-AE til6 6 PAGE E OF Attachment ST-HL-AE-4065 Page 3 of 3

. CORRECTIVE ACTIONS:

1.

Troubleshooting for SDG /23 and SDG /21 have been completed.

2.

Preventive maintenance instructions will be developed to clean the subject check valves periodically.

This activity will be corapleted by July 15, 1992.

ADDITIONAL INFORMATION:

At the time of the event, there were no valid failures in the last 20 valid tests and less than 4 valid failures in the last 100 tests for SDG #21.

The testing frequency remained at once per 31 days.

At the time of the event, there were no valid failures in the last 20 valid tests and less than 4 valid failures in the last 100 tests for SDG #23.

The testing frequency remained at once per 31 days.

(.

L l

su n 92 096.001

!