ML18100B276

LER 92-015-00:on 920424,RCIC Sys Declared Inoperable When Sys Flow Controller Meter Indicated Approx 30 Gpm Flow W/ RCIC Not Operating.Caused by Setpoint Drift.Work Orders Initiated to Correct Meter indication.W/920519 Ltr

ML18100B276
Person / Time
Site:	Vermont Yankee
Issue date:	05/19/1992
From:	Reid D VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-92-015, LER-92-15, NUDOCS 9205290262
Download: ML18100B276 (5)

Text

VERMONT YANKEE NUCLEAR POWER CORPORATION P. 0. BOX 157 GOVERNOR HUNT ROAD VERNON, VERMONT 05354 May 19, 1992 U.S. Nuclear Regulatory Commission Document Coritrol Desk Washington, D.C. 20555

REFERENCE:

Operating License DPR-28 Docket No. 50-271 Reportable Occurren.ce No. LER 92-15

Dear Sirs:

As defined by 10 CFR 50. 73, we are* reporting the. attached Reportable Occurrence as LER 92-15.

Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION Donald.A. Reid Plant Manager cc: Regional Administrator

• USNRC Region I 475 Allendale Road /

King of Prussia, PA 19406

/

9205290262 920519 PDR ADOCK 05000271 S PDR

NRC Form 36.6 u.s. NUCLEAR REGULATORY COMMISSION APPROVED OMS NO. 3150-0104 (6-a9) EXPIRES 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST:

-* 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT*

LICENSEE EVENT REPORT (LER) BRANCH (P-530), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555,_ AND TO THE

'PAPERWORK REDUCTION PROJECT (3160-0104)' OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20603.

FACILITY NAME ( 1) DOCKET NO. ( 2) PAGE ( 3)

VERMONT YANKEE NUCLEAR POWER ..STATION o *Is Io Ia lo I2 I1 I1 0 1 OF 014 TITLE ( 4) RCIC system Declared Inoperable Due To Flow controller setpoint Drift EVENT DATE ( 5) LER NUMBER (6) REPORT DATE ( 7) OTHER FACILITIES INVOLVED (a)

MONT'H DAY YEAR YE-AR SEQ II REVll MONTH DAY YEAR. FACILITY NAMES 01 K T N s 0 5 0 0 0 014 2I4 912 912 - o I ils - olo ols 119 912 0 5 0 0 0 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO REQ'MTS OF 10 CFR §' CHECK ONE OR MORE ( 11)

MODE ( 9) N 20.402(b) 73.7l(b) 20.4osccJ ,__ 50.73(a)(2J(iv)

- 50.36(c)(l)

POWER LEVEL c 10 >Io.la o -

20.405(a) (1) (i)

- ,__ 50.73(a)(2)(V) ,__ 73.7l(c)

20. 405(a) ( 1) (ii) 50.36(c)(2) xx 50.73(a)(2)(vii)

,__ OTHER:

................ ,__... 20.405(a) (1) (iii) 50. 7 3 (a i 'c 2 l (i l ,__ 50.73(a)(2)(viii)(A)

................ ,__... ~0.405(a)(l)(iv) 50.73(a)(2) (ii) ,__ 50.73(a)(2)(viii)(B)

................. 20.405(a)(l)(V) 50.73(a)(2)(iii) 50.73(a)(2)(X)

LICENSEE CONTACT FOR THIS LER ( 12)

NAME TELEPHONE NO..

AREA CODE DONALD A. REID, PLANT MANAGER a Io I 2 2!sl1!-l1!1!1!1 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT ( 13)

CAUSE SYST COMPONENT MFR REPORTABLE CAUSE SYST COMPONENT MFR REPORTABLE TO NPRDS . . .. TO NP RDS ...

x- B N F I K G 0 a I 2 YES *-* .. I I I I I I I ...

_x B N p D T G 0 a I 2 YES .... I I I I I SUPPLEMENTAL REPORT EXPECTED ( 14 )- EXPECTED MO DAY YR SUBMI-SSION

--i YES (If yes, complete EXPECTED SUBMISSION DATE) Fxl NO DATE ( 15)

ABSTRACT (Limit to 1400 spaces, i.e., approx. fifteen single-space typewritten lines) (16)

At 07 45 on 4/24/92, with the reactqr operating at 80% power, the. plant's Reactor Core Isolation Cooling System (RCIC)(*BN) was declared inoperable when it was identified that the system's flow controller (*FIK) meter was indicating approximately 30 gpm flow with RCIC not operating. Investigation into the event revealed that the zero reference for the RCIC pump output flow transmitter (*PDT) had drifted high. The zero was adjusted downward to within specifications. At 1321, during post-maintenance testing, pump output flow was approximately 360 gpm versus the 400 gpm required by Plant Technical Specifications.

Investigation into the cause of the low flow condition revealed that flow controller FC-13-91 upper limiter setpoint had drifted downward and was limiting the flow controller output current. The upper limiter setpoint was increased slightly. At 1552, RCIC pump output flow was tested and verified satisfactorily, RCIC was declared operable.

The cause of both events is setpoint drift. The flow controller and transmitter_ were recalibrated. Monitoring of the flow controller's limiter_setpoint is being performed to ensure stability. Due to an increasing incident rate with this style flow controller, Vermont Yankee will investigate available replacements and consider upgrading these units.

The High Pressure Cooling Injection (HPCI)(*BJ) System was operational throughout this event. A similar event was reported to the Commission under LER 91-007.

• Energy Industry Identification System (EIIS) Identifier

NRC Form 366A U.S. NUCLEAR R~GULATORY CO~MISSION APPROVED OMS NO. 3150-0104

( 6-89) . EXPIRES 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION ~OLLECTION REQUEST:

50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT.

LICENSEE EVENT REPORT (LER) BRANCH (P-530), U.S. NUCLEAR REGULATORY TEXT CONTINUATION COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3160-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20603.

FACILITY NAME ( 1) DOCKET NO ( 2) LER NUMBER ( 6) PAGE. ( 3)

YEAR SEQ II REV II VERMONT YANKEE NUCLEAR POWER STATION ol5lololol2l1l1 I 9 2 - o I 115 - olo 0I2 OF ol4 TEXT (If more space is required, use additional NRC Form 366A) (11)

DESCRIPTION At 0745 on 4/24/92, with the reactor operating at 80% power, the plant's Reactor Core Isolation Cooling System (RCIC)(*BN) was declared inoperable when it was identified that the system's. flow controller (General Electric.. Hodel 50-540) *meter . (*FIK) was indicating approximately 30 gpm flow with RCIC not operating. A Vork Order was initiated to determine the cause of the erroneous_flow controller meter reading.

Investigation into .the event revealed that the RCIC pump output flow transmitter FT 58 (General Electric Hodel 50-555)(*PDT) zero reference was approximately 0;24 milli-amp (ma) high, this deviation was consistent throughout the transmitters calibration band. The zero reference was* adjusted downward to within specifications. The output of the loops square root converter, and the reading on the controller's flow indicator were verified correct. At 1300, with FT-13-58 returned to within specifications, RCIC was started as part of the post-maintenance operability test. At 1321 RCIC was secured, as the pump output flow was approximately '360 gpm. The Plant Technical Specifications require RCIC System flow to be a minimum of 400 gpm ..

At 1408, a second Vork Order was released to investi.gate flow controller FC-13-91 to determine the cam~e of the low pump output flow condition. Trouble-shooting efforts on the flow controller revealed that an electronic governor (upper limiter) setpoint was preventing the controller from supplying sufficient current to achieve rated pump flow. The upper limiter setpoint was increased approximately 3.5 ma. At 1552 RCIC was started for a second post-maintenance operability run and flow was verified satisfactory at 410 gpm, RCIC was declared operable.

CAUSE OF EVENT The erroneous meter indication and subsequent inability of RCIC to meet the required flow both appear to have been*caused by setpoint drift. The exact cause of the setpoint drifts are not known. The transmitter zero shift drifted outside of the calibration tolerance by 0.08 ma high. The flow controller upper limiter setpoint needed tri be adjusted from 48 ma to 51.5 ma to meet required flow. In the course of trouble-shooting all components within the instrument loop were checked for proper response and found acceptable.

A Nuclear Power Reliability Data System (NPRDS) search was performed on the controller and setpoint drift was found to be a frequent failure for this controller.

Contributing Cause:

A contributing cause to this event appears to be the age of the equipment. Th~ flow controller has been in operation for the majority of the plant's life and has operated satisfactorily. For this style of flow controller, Vermont Yankee as well as other nuclear facilities are experiencing higher incident rates than experienced earlier in the equipments life. *

• Energy Industry Identification System (EIIS) Identifier

NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMS NO. 3150-0104 (6-89) EXPIRES 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY

. WITH THIS INFORMATION COLLECTION REQUEST:

50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT LICENSEE EVENT REPORT CLER) 'BRANCH (P-530), U.S. NUCLEAR REGULATORY TEXT CONTINUATION COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3160-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20603.

FACILITY NAME ( 1) DOCKET NO ( 2) LER NUMBER (6) PAGE ( 3)

YEAR SEQ ff REV ff VERMONT YANKEE NUCLEAR POWER STATION ol5lololol2l1l1 912 - ol 115 - olo ol3 OF ol4 TEXT (If more space is required, use additional NRC Form 366A) (11)

ANALYSIS OF EVENT There were negligible safety implications resulting from these events.

The affect of the transmitter zero being out of tolerance was not significant.* The 0.24 ma increase in the loops zero reference represents an approximate flow Indicator deflection of 35 gpm. However, due to the nature of the square rooting function in this instrument loop the affect of this 0. 24 mA shift near pump rated output flow would correspond to the pump discharge flow being slightly degraded, 398.13 gpm versus the rated 400 gpm.

The downward drift of the flow controllers upper limiter setpoint is significant in that it limited the rated RCIC pump output flow by 40 gpm.

The net affect of these events is that if called upon, RCIC would have been functional but would not have reached rated flow in automatic mode. By placing the controller in manual operators could have increased the current output to achieve rated flow. Considering the effects of both the transmitter zero change and the upper limiter setpoint drift, the calculated RCIC output pump flow would have been approximately 358 gpm, a 10% reduction in the required pump output flow. It should be noted that RCIC was successfully flow tested five days earlier on 4/19/92.

The High Pressure Cooling Injection (HPCI)(*BJ) System was operational throughout this event.

CORRECTIVE ACTIONS:

Immediate:

1. RCIC was declared inoperable and York Orders were initiated to determine and correct the erroneous meter indication. The flow transmitter was recalibrated and the flow controller upper limit setpoint was raised to 51.5 ma in order to achieved sufficient pump output flow and return RCIC to operable status.

2. Daily monitoring of the flow controller limiter setpoint was initiated to determine the stability of the setpoint.

Long-Term:

1. To date the limiter setpoint has remained within the calibration tolerance. Based upon this information, a weekly check will be performed for the next two consecutive weeks, at which time an assessment will be made if further monitoring is warranted.

2. Vermont Yankee, will investigate if a suitable replacement/upgrade is available for the flow controller. Based upon the results of this investigation, consideration will be given to replacement.

3. Vermont Yankee had previously identified a replacement for the GE Transmitter. Replacement of these transmitters is continuing as part of the maintenance/surveillance program.

• Energy Industry Identification System (EIIS) Identifier

NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMS NO. 3150-0104 (6-89) EXPIRES 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFOR~ATION COLLECTION REQUEST:

50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT LICENSEE EVENT REPORT (LER) BRANCH (P-530), U.S. NUCLEAR REGULATORY TEXT CONTINUATION COMMISSION, WASHINGTON, DC _20555, AND TO THE PAPERWORK REDUCTION PROJECT (3160-0.104), OFFICE OF MANAGEMENT AND BUDGET; WASHINGTON, DC 20603.

FACILITY NAME (1) DOCKET NO ( 2) LER NUMBER ( 6) PAGE ( 3)

YEAR SEQ ff REV ff.

VERMONT YANKEE NUCLEAR POWER STATION* ol5lololol2l1l1 I 9 2 - ol 115 - olo 014 OF ol4 TEXT (If more space is_ required, use additional NRC Form 366A) (11)

ADDITIONAL INFOR11ATION:

A similar event was reported to the Commission under LER 91-007, in which the upper limiter setpoint on the HPCI flow controller drifted downward and result in degraded pump output flow.

• Energy Industry Identification System (EIIS) Identifier