ML18094A325

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LER 89-005-00:on 890312,reactor Tripped on Steam Generator 23 Feed Flow/Steam Flow Mismatch W/Low Steam Generator Level.Caused by Equipment Failure of D Vital Instrument Inverter.New Vital Inverter reinstalled.W/890405 Ltr
ML18094A325
Person / Time
Site: Salem PSEG icon.png
Issue date: 04/05/1989
From: Miller L, Pollack M
Public Service Enterprise Group
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-005-02, LER-89-5-2, NUDOCS 8904180088
Download: ML18094A325 (5)
v • d • e


Text

NACFt-1111311 U.1, NUCLEAR REQULATOllY COMll*ION (9-83)

A. .ROVED OMI NO. 311111-4104 EXPIRES: 11/311915 LICENSEE EVENT REPORT (LER) t:F:":'A~Cl~Ll~TY NAM----E~l~1)_ _ _ _ _ _ _ _ _ _ __.;._ _ _ _ _ _ _ ... ~~--.-~---"""""-.....,,r:::ooc=K:':"ET;-:::NU~Ma=E11:"::12:"'1---.....,l--irmr_UEr,..,1111....

Salem Generatinq -station - Unit 2 o 15 Io Io Io I 31 11 1 1 loFP 1*

TITLE 14)

Reactor Trip/SI From 100% Power Due To .An Equipment Failure EVENT DATI! 181 I.EA NUMllER 18) REPORT DATE 17) OTHER FACILITIES INVOLVED Ill MONTH DAY YEAR . YEAR ]f SE~~~~~~AL rt~~~~ MONTH DAY . YEAR FACILITY NAMES DOCKET NUMBERIS) .

0151010101 I I oI 3 OPERATING i I2 a 9. al c- o Io 1s - o I o oI 4 or s al THll REPORT 11 IUIMITTED PURIUANT TO THE REQUIREMENTS OF 9

io CFll §: (Ch<<:k OM Of mtHW of tll* following) 111)

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  • 20.40ll*111llll I0.311lcll1l 1111.ni.11z1M 73.71Ccl LEVEL - . ** - - -

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LICENSEE CONTACT FOR THIS LEA 1121 .

NAME TELEPHONE NUMBER AREA CODE M. J. Pollack - LER Coordinatoi COMPLETE.ONE LINE FOR EACH COMPONENT FAILURE DESCRllED IN THll llEl'ORT 1131 CAUSE SYSTEM COMPONENT MANUFAC* MANUFAC*

TUR ER TUR ER B I I I I I . I I I I I I ,I I I I I I I I I I SUPPLEMENTAL REPORT* EXPECTED 1141 MONTH DAY Y~

EXPECTED SUBMISSION CATE 116)

- - , YES (If yn, comp/or. EXPECTED SUBMISSION DA TE)

I I I AllTRACT (Limit ro r400 _,,n, I.*.* opprox/mor.ty fifr.on 1ingl..,1>>c* ty1>>.,,.itton iinnl 11 ll On 3/12/89, both Steam Generator Feed Pumps (SGFPs) reduced their turbin~ speed to idle; The reactor subsequently tripped on No. 23 Steam Generator (S/G) Feed Fiow/Steam Flow Mismatch with Low S/G Level. ~fter the reactor tripped, a Safety Injection (SI) occurred on High Steamline .Flow coincident with. Low Steamline Pressure. The root cause of this event has been attributed*to an equipment failure. A control power fuse*, in the "D" Vital Instrument Inverter low voltage power source~ came out of its fuse holder resulting in jnverter failure and deenergization of "D" _Vital Instrument Bus.

Investigations concluded the fuse more than likely had come out of the fuse holder due to improper installation at sc;>me point in the past.

The fuse assembly did not show any sign of damage or impairment which would cause the fuse to dislodge. Subsequently, the inverter fuse was reinstalled and success.fully checked for continuity and tightness.

The statid inverter was started, tested satisfact6rily and returned to service. Engineering is investigating the feasibility of separating the pressure channels to other. vital inverters thereby eliminating the possibility of the occurrence of a similarly caused SI. New Vital Inverters are scheduled to be installed during the .next Unit 2 refueling outage. These inverters have a fast transfer feature.

Engineering.is evaluating the possibility of moving the inverter's alternate power source to the same bus as the normal supply. This coupled with the high speed t:i;-ansfer feat~re of .the new Vital *~;e:- .

Inverters should prevent recurrence of this event. ~j/';:?"'C,.

89041BOOB8cu Bo2S?~~11 ,, /

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Salem Generating Station

  • DOCKET NUMBER LICENSEE EVENT REPORT (LER) TEXT CONTINUATION LER NUMBER PAGE Unit~2~-~~~~~~~~~-~~--~~500031=1o.-~~~~~8~_-_0_0_5_-_o~0.-~~~~2'---'o~f~4~~

PLANT AND SYSTEM IDENTIFICATION:

Westinghouse - Pressurized Water Reactor Energy Industry Identification System (EIIS) codes are identified in the text as {xxl IDENTIFICATION OF OCCURRENCE:

Reactor Trip/Safety Injection From 100% Power Due To An Equipment Concern Event Date: 3/12/89 Report Date: 4/05/89 This report was initiated by Incident Report No.89-148.

Mode 1 Reactor Power 100% - Unit Load 1150 MWe On March 12, 1989 at 0723 hours0.00837 days <br />0.201 hours <br />0.0012 weeks <br />2.751015e-4 months <br />, during routine power operation, both Stearn Generator Feed Pumps (SGFPs) reduced-their turbine speed to idle. The reactor subsequently tripped on No. 23-stearn Generator (S/G) Feed Flow/Steam Flow Mismatch with Low S/G Level. After the reactor tripped, a Safety Injection (SI) occurred due to High Steamline Flow coincident with Low Steamline Pressure (less than 500 psig) .

The Unit was stabilized in Mode 3 {Hot Standby), and in accordance with the requirements of the Code of Federal Regulations 10CFR 50.72{b) (2) {ii), the Nuclear Regulatory Commission was notified of the automatic actuation of the Reactor Protection System f JC} and the automatic actuation of the Emergency Core Cooling System {ECCS) fJE}. This was the tenth SI actuation cycle to date.

APPARENT CAUSE OF OCCURRENCE:

The root cause of this event has been attributed to an equipment failure of the "D" Vital Instrument Inverter.

A control power fuse, in the "D" Vital Instrument Inverter low voltage power supply, came out of its fuse holder resulting in inverter failure and deenergization of "D" Vital Instrument Bus. The fuse was found still in its fuse knob. Investigations concluded the fuse {and its knob) more than likely had come out of the fuse holder due to improper installation at some point in the past.

ANALYSIS OF OCC~RENCE:

The "D" Vital Instrument Bus provides the_ AC p6wer to the Master and

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE

_U=n=i'""""'t'---=2=--------~--------=~900 311 a9-oo s--o~o~---3=---o~f~4__

ANALYSIS OF OCCURREN~Ji.;__Jcont'd)

Slave controllers used in SGFP c.ontrol. Loss of the 120 VAC power causes the controllers to fail to minimum SGFP speed demand.

Therefore, both SGFPs went to idle speed upon failure of the inverter. With the loss of Feedwater, the reactor tripped on Feed Flow/Steam Flow Mismatch coincident with Low Steam Generator Level.

The P-4 interlock actuites when the reactor trip breakers opert. This interlock resets the high steam flow setpoin~ for SI to the no-load value. This causes the High Steam Flow bistables to.actuate until actual 'steam flow decreases to below approximately 4Q%. This occurs rapidly following a normal trip. However, in this instance, due to the deenergized bus, the low steamline pressure bistables for No~. 21 and 24 Steam Generators were actuated (Channel IV for both Steam Generators are fed from 2D Vital lnstrument Bus). Therefore, the combinatl.on of high steamline flow (greater than 40%) , which is normal following a ftill power trip, in conjunction with an indicated low stearnline pressure ori two *loops satisfied the logic for

Currently, the bus's alternate power source is administratively d~energized (tagged open~ to maintain vital bu~ electri~al separation. *The normal power source is* from "2B" 230 VAC Vital Bus*.

and the alternate source is from.the "2A" 230 VAC Vital Bus. The other vital* instrument bus's ("A", "B", and "C") have uninterrupted power sources. They get power from the same respective 230 VAC Vital

_Busses.

Had the "D" Vital Instrument Bus alternate source been energized, the loss of "D" Vital Inverter would have resulted in the_transfer of the "D" Vital Instrument Bus power source from the inverter output to the alternate source. However, t.he trip would still have occurred since the present transfe~ scheme takes approximately 3 seconds and the' trip occurred in less than a-second of inverter failure.

Due to the increased charging flow associated with the. SI, Pressurizer pressure increased to the Power Operated Relief Valve fPORV) .setpoint resulting in several lifts of valve 2PR2 (PORV).

This event involved no undue risk to the health or safety of the public. However, because of the automatic actuation of the Reactor Protection System, it is reportable in accordance with the Code of Federal Regulations 10CFR50.73(a) (2) (iv). tn addition; due to the ECCS actuation, this report also fulfills the requirements of the ninety (90) d~y Special Rep6rt required by Technical Specification*

3.5;2 (Action b).

  • CORRECTIVE ACTION:

The fuse knob and fuse holder assembly did not show any sign of damage or impairment which would cause the fuse to dislodge.

Subsequently, the inverter fuse and fuse knob was reinstalled and successfully checked for continuity and tightness. The static inverter was started, tested s~tisfactorily and returned to service.

Salem Generating Station

-* DOCKET NUMBER LICENSEE EVENT REPORT (LER) TEXT CONTINUATION LER NUMBER PAGE U~n_i_t_._2~~~-----~-----~500031_1~~~~~-8_9_-~~5--_~.0~~~~~4'---"o~f=---4~_

CO~RECTI~E ACTION:_~(c_q_!l t 'dj_

The Unit was returned to power operation on March 14, 1989.

Salem Generating Station System Engineering is investigating the feasibility of separating the pressure channels to other vital inverters thereby elimin~ting the possibility of the occurrence of a similarly caused SI.

Since the current inverter manufacfurer (Garrett) is no longer in business, new Vital Inverters (Cyberex) have been scheduled for installation during the next Unit 2 refueling outage. These inverters have a power source "fast normai to alternate transfer" feature. System Engineering is evaluating the possibility of moving the instrument bus's alternate power source to the same Vital Bus as the normal source. This will allow t~e new "D" Vital Inverter to automatically transfer from the normal to the alternate power source if the vital inverter fails thereby ensuri'ng uninterruptable "D" Vital Instrument Bus power. Salem Unit 1 has the same vital bus and inverter- arrangement as Unit 2~ However; during the current Unit 1 refueling outage, new vital inverters, with the high speed transfer feature, will be installed.

POST SAFETY

- INJECTION

- DATA:

Final Pressurizer Level 26%*

Initial Pressurizer Pressure 2250 psig Final Pressurizer Pressure 2250 psig*

Initial Average Reactor Coolant Temperature 570. 59 F Final Average Reactor Coolant Temperature 547° F*

Refueling Water Storage Tank Temperature 7 5. 9° F Duration of Safety Injection 28 minutes

  • - The Pressurizer Level had peaked to 100%

The Pressurizer pressure had peaked at 2340 psig The minimum average Reactor Coolant Temperature during the event was 530°F General Manager -

Salem Operations MJP:pc SORC Mtg.89-028

PSEG *

  • Pui:i:ic Service Electric and Gas Company P 0. Box E Hancocks Br*idge, f\Jew Jersey 08038 Salem Generating Station April 05~ 1989 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Dear Sir:

SALEM GENERATING STATION LICENSE. NO. DPR-75 DOCKET NO. 50-311 UNIT NO. 2 LICENSEE EVENT REPORT 89-005-00 This Licensee Event Report is being submitted pursuant to t~e requirements of the Code of Federal Regulations 10CFR 50.73 (a} (2) (iv). This report is being submitted within thirty (30} days of discovery.

Sincerely yours, L. K. Miller General Manager -

Salem Operations MJP:pc Distribution

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