ML20042G450

LER 90-013-00:on 900405,discovered That Control Bldg Chiller Motor Current Limiter C Set Incorrectly at 56% Instead of 100%.Caused by Incorrect Setting & Maint Activities.Loop Calibr Data Sheet revised.W/900507 Ltr

ML20042G450
Person / Time
Site:	River Bend
Issue date:	05/07/1990
From:	England L, Odell W GULF STATES UTILITIES CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-013, LER-90-13, RBG-32799, NUDOCS 9005140248
Download: ML20042G450 (4)

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GULF STATES UTELETIES COMB *ANY ove no sma eu,w,;n m :,, o <n.s. m ia o w m aa m m Aftf A i pt'l t'.4 03b ILOPd 34 tihM May 7 , 1990 RBG-32799 File Nos. G9.5, G9.25.1.3 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 Gentlemen:

l River Bend Station - Unit 1  !

Docket No. 'i0 458 l

Please find enclosed Licensee T. vent Report No.90-013 for 8 River Bend Station - Unit 1. This report is beir.9 submitted pursuant to 10CFR50.73.

Sincerely, I.

W. H. Odell Manager-River Bend Oversight River Bend Nuclear Group TFP/hDG/RGW J /RTD/pg cc: U.S. Nuclea Regulatory Commission 611 Ryan Plaza Drive, Suite 1000 Arlington, TX 76011 NRC Resident Inspector P.O. Box 1051 St. Francisville, LA 70775 INPO Records Center -I 1100 Circle 75 Parkway Atlanta, GA 30339-3064 i

9005140248 900507 PDR ADOCK 03000456

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At 1100 on'04/05/90 with the reactor at 100 percent power (Operational Condition 1), it was discovered that the control building chiller C motor current limiter was set incorrectly at 56 percent current instead of 100 percent current. This lower current limiter setting would have prevented the chiller from fully loading and removing design heat load from the control building. Investigation revealed that the current limiter had been albthis setting since December 20, 1989 and that the other 100 percent chiller in Division I (chiller A) I was out of service for maintonance f rom February 26, 1990 until March  !

31, 1990. The combination of the 1* correct current limiter setting on chiller C and the maintenance activities on chiller A rendered an entire independent train inoperable for a time period in excess of the  !

seven day action statem'ent specified in Technical Specification 3.7.2.

The incorrect setting was caused by an inadequate job plan. The loop calibration data sheet for the capacity control model has now boon revised to include motor current calibration. There was no impact on health.and safety of the public as a result of this event. ,

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REPORTED CONDITION At 1100 on 04/05/90 with the reactor at 100 percent power (Operational '

Condition 1), it was discovered that the control building chiller C

(*EM*) motor current limiter setting of the capacity control module ,

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• VI * ) was incorrect. The limiter was found to be set at 56 percent current instead of 100 percent current. This lower current limiter setting would have prevented the chiller from fully loading and removing design heat load from the control building.

Purther investigation revealtd that the current limiter had been at this setting since December 20, 1989 and the other 100 percent chiller in Division I (chiller A) was out of service for maintenance from February 26, 1990 until March 31, 1990. The combination of the incorrect current limiter setting on chiller C and the maintenance activities on chiller A rendered an entire independent train inoperable for a time period in excess of the seven day action statement specified in Technical Specification 3.7.2. Therefore, this report is submitted pursuant to 10 CFR50. 73 (a) (2) (1) (D) as an operation or condition prohibited by the plant's Technical Specifications.

INVESTIGATION On 03/29/90, control building chiller C tripped on low refrigerant temperaturo and prompt maintenance work order R056509 was written to determine the cause of the trip. During the trouble shooting process on 04/05/90, it was discovered that the motor current limiter setting of the capacity control module was set for 56 percent current instead of 100 percent current. The capacity control module maintains design chilled water temperature by opening and closing the chiller compressor guide vanes. The motor current limiter prevents guide vane opening when 100 percent full load motor current is reached and closes the vanes if motor current should increase to 105 percent full load.

On 12/20/89, the capacity control module of control building chiller C was replaced. The module was calibrated to maintain 52.5 P chilled l water temperature, but was not calibrated for motor current because the loop calibration procedure did not specify this calibration. This is considered the root cause of the event.

With the current limiter get at 56 percent full load current, the chiller maintained 52.5 F water during the colder winter months.

Iloweve r , as the weather got warmer and the load increased, the lower current setting prevented the chiller from producing design temperature water and ultimately led to the trip on 03/29/90.

Since the control building chiller A was inoperable from 02/26/90 l until 03/31/90 due to maintenance, both chillers in Division I were considered inoperable for that same period of time. Prior LERs were

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=v . - . e w aar.,im reviewed for similarity to this event. There were no other operation or condition prohibited by the plants' Technical Specifications involving two inoperative trains (or channels) that were caused by an omission in the work order job plan.

CORRECTIVE ACTION The current limiter setting was set to 100 percent por the chiller vendor manual. The loop calibration data sheet for the capacity control module was revised to include motor current calibration. The motor current calibration on the other control building chillers has been checked and verified to have the proper (100 percent) setting.

SAFETY ASSESSMENT During the time that the current limiter was improperly set, the chiller was not required to remove design heat load. If design heat load had been present the chiller would have attempted to load up but >

the current limiter would have prevented full load operation and area temperatures would have increased. High area temperature alarms would have alerted the control room operators and another chiller could have been manually started. Therefore, there was no impact on the safe operation of the plant nor the health and safety of public as a result of this event.

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NOTE: Energy Industry Identification System Codes are identified in the text as (*XX*). ,

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