ML20043G103

LER 90-016-00:on 900513,steam Generator B lo-lo Signal Generated Reactor Trip Signal,Causing Automatic Start of motor-driven Auxiliary Feedwater Pumps a & B.Caused by Inadequate Guidance.Procedure revised.W/900612 Ltr

ML20043G103
Person / Time
Site:	Millstone
Issue date:	06/12/1990
From:	Hulme N, Scace S NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-016, LER-90-16, MP-90-585, NUDOCS 9006190060
Download: ML20043G103 (4)

Text

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6 'T2 E *IE E' I IE'E= U o"maa",, HARTFORD, CONNEcTIOUT 06414-0270 Nortneast Nuce.ar Energy company (2031665-5000 June 12, 1990 MP-90-585 Re: 10CFR50.73(a)(2)(iv)

U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555

Reference:

Facility Operating License No. NPF-49 Docket No. 50-423 Licensee Event Report 90-016-00 Gentlemen:

This letter forwards Licensee Event Report 90-016-00 required to be submitted within thirty (30) days pursuant to 10CFR50.73(a)(2)(iv), any event or condition that resulted in manual or automatic actuation of any Engineered Safety Feature (ESP), including the Reactor Protection System (RPS).

Very truly yours,.

NORTHEAST NUCLEAR ENERGY COMPAh"t' A~

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Step en E. Scace Director, Millstone Station SES/NDH:mo

Attachment:

LER 90-016-00 cc: T. T. Martin, Region I Administrator W. J. Raymond, Senior Resident inspector, Millstone Unit Nos.1, 2 and 3 D. H. Jaffe, NRC Project Manager, Millstone Unit No. 3 0

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T NRC Form 344. V.S. NUCLE AR REGULAT ORY COMM:SSION APPROVED OMB NO. 3160-0104 (6-60)

• E XRRE S: 4/3042

. Esiimated tiuroen per response to comoty with tNs information cotiection rooses1: 60.0 nrs- Forwerc LICENSEE EVENT REPORT (LER) lWo"is'E' n$",' eye'n%r'a'nE$e',$0')"* u IS YEear Regulatory Commission WasNnoton. DC 20666. anc to the Papewsk Reduction Proiset (3160-0104 L Office of .

Management and Buocet, Washincton. DC 20603 DOC 41 NVMb4R (2) WM '

F ACILIT Y NAME (1)

Millstone Nuclear Power Station Unit 3 ol 5101 of old 1213 1lOF 0l 3 inLE m

• B" Steam Generator Low-Low Level Actuation Due to inadequate Guidance EVE NT DATE f6) L F A NUMP F R f O AEPOAT DATE (h OTHE A F ACit fTIE E. INVOLVED (8)

MONT F DAY YEAR YEAR MONTH DAY YEAR F ACtLITY NAME6 of 5l of of of I l

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0 5 1l3 9 0 9 10 0l1l6 0l 0 o l6 1h 9l0 of sl ol ol of I l QPERATING THIS REPOAT is BEING SUBM:TTED PURSUANT TO THE REQUIREMENTS OF 10 CFA i (Chop one or mete of tne foliowingyii) 0 60.73(a)(2)(iv) 73.71(D) 20 402(b) _

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20 406(a)(1)(1) 60.36(cH1) 60.73(aH2)(v) 73,7)(c)

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vik 0l0l0 20 406:a)(1)(48) 60.36(c)(2 > 60.73 (a)(2Hvii) _ (THR (6ceci Text. N Form 366A, 20 406(a)(1)(iii) 60.73(aH2Hi) 60.73(a H2)(viii)l A) q4 J tN . 20 405(a)(1)(iv) 60.73(aH2Hlin 60.73(aH2)IvillHB) 20 406ta)(1)avi 60.731a)(2Hiii) 60 73taH2itx)

LICENSEE CONT ACT FOR THIS LER f12)

NAME TELEPHONE NUMBE A AREA CODE Nelson D. Hulme, Senior Engineer, Ext. 5395 2l0l3 1l4l7l-l1]7l9l1 COMPLETE ONE LINE FOA E AC6i COMPONENT F AILUAE DESC AIDED IN THIS REPORT (13i w

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On May 13,1990, at 0351 hours0.00406 days <br />0.0975 hours <br />5.803571e-4 weeks <br />1.335555e-4 months <br /> with the plant shut down in Mode 5 (Cold Shutdown) at a temperature of 136 degrees Fahrenheit and a pressure of 350 psia, a "B" Steam Generator (S/G) low-low level signal generated a reactor tnp signal, caused an autorratic start of "A" and *B" Motor Driven Auxiliary Feedwater (MDAFW) Pumps, and closed "B" SIG Blowdown isolation valve. The low-low level signal also generated signals for closing "B" S/G sample valve, and aligning the MDAFW pumps to transfer water from the Demineralized Water Storage Tank to the S/Gs. Aside from the "B" S/G Blowdown Isolation valve, no other valves actuated as they were already in the required positions. The event occurred as a result of improperly isolating the level transmitters for *B" S/G in preparation for draining the generator to repair a leaking hand hole cover.

The root cause of the event was inadequate guidance to the operators on the affects of isolating the transmitters.

- To prevent recurrence, a procedure change has been implemented which provides guidance for isolating the level transmitters.

s U.6 NUOLE AN REGULATORY CoMMISSloN APPROVE o 60-0i04 Nggorm 366A

~' Estimat.d burD.n p r respons. to Comply with this LICENSEE EVENT REPORT (LER)  ;"g'm*#,,",gg'4"4*ni er nen in-e.aoh. Nucl U SglL6h0,,"','g n

TEXT CONTINUATION .no n.pera uan. p m D@o.m.ni uan .no suons w smnoton oc rosc DOCKET NUMBER (2) l F A NUME4F A fci PAGE 13)

FACILITY NAME (1)

YEAR N Millstone Nuclear Power Station Unit 3 0j0 0l 6l 0l 0l 0l4 l2 l3 9l0 0]1l6 0l 2 OF 0l3 Text os more spec. s 1.auir o. us. .aoit,onei NRc Form 366A si cir, I. Descrintion of Event On May 13,1990, at 0351 hours0.00406 days <br />0.0975 hours <br />5.803571e-4 weeks <br />1.335555e-4 months <br /> wah the plant in Mode 5 (Cold Shutdown), at a temperature of 136 degrees Fahrenheit and a pressure of 350 psia, a spurious "B" Steam Generator (S/G) low-low level signal generated a reactor trip signal, caused an automatic start of "A* and "B" Motor Driven Auxiliary Feedwater (MDAFW) Pumps, and closed "B" S/G Blowdown Isolation Valve. The low-low level signal also generated signals for closing "B" S/G sample valve, and aligning the MDAFW pumps to transfer water from the Demineralized Water Storage Tank to the S/Gs. Aside from the "B" S/G Blowdown Isolation salve, no valves actuated as they were already in the required positions.

The event occurred as a result of improperly isolating the level transmitters for "B" S/G in preparation for draining the S/G to repair a leaking hand hole cover. The root valves were closed, but the pressure differences between the "high" and " low" sides c' me transmitters were not equalized. Consequently, the pressure differences started to increase, conw t with the indication of decreasing levels. One of the transmitters had previously been declared inopemle, so its low level histable was in the tripped condition. One of the remaining three transmitters drifted to the point where its bistable tripped on low-low level. This 2-out-of-4 trip condition resulted in the generation of a low-low S/G level signal.

The operators reviewed the emergency procedures for a low-low S/G level condition. As the reactor was already shut down and the affected vahes were already in the desired condition for plant conditions, the only immediate action taken for this event was to put the MDAFW pumps controls in pull-to-lock in order to override the emergency signal and stop the pumps. The transmitters were then properly equalized and isolated.

11. Cause of Event The root cause of the event was inadequate guidance to the operators on the effects of isolating the transmitters.

Ill, Annhsic of Event This event is reportable in accordance with the requirements of 10CFR50.73(a)(2)(iv), as an event that resulted in automatic actuation of an Engineered Safety Feature, including the Reactor Protection System, immediate notifications were performed in accordance with 10CFR50.72(b)(2)(ii).

There were no significant safety consequences because of this event as the reactor was already shut down, and there were no Technical Specification requirements to have the MDAFW pumps in service.

IV. Corrective ActiGD The operators reviewed the emergency procedures for a low-low S/G level condition, and placed the MDAFW pumps controls in pull-to-lock in order to override the emergency signal and stop the pumps.

The transmitters were then properly equalized and isolated.

In order to prevent recurrence, procedural guidance was provided for isolating the level transmitters.

The procedure has been revised to require the transmitters be equalized at the time they are isolated.

H orm M6

NRC Form 366 A U.S. NUCLEAR REGIAATORY COMMiS$10N APPROVED OMB NO. 3160-0104 y .- ,

(6-80) EXPIRE S: O/30/82

=d i Estimated maoburoen co'* per resconse to compiy 0 " 5- 'wi'h**'d this

• a '*o  : 60 LICENSEE EVENT REPORT (LER)- c'a'"ments"recaro"ing om beoe"**e' n stimate 'to tneRecoras TEXT CONTINUATION ano Reports uan oement eranen (p-63o). U 6. Nucoser.

Regulatory Commission. Washington, DC P0666. anc to the Paperwork Rooxtion Proiect (316D-0104) Office et ,

Management and Bueget. Washington. DC 20603 F ACILITY NAME (1) DOCKET NUMBER (2) tFm Ntmeern vei PAGE (3)

YEAR N Millstone Nuclear Power Station- - -

Unit 3 ol 6l ol ol oja l2 l3 9l0 0]1l6 0l0 0l 3 OF 0l3 TEXT (it more space is reavireo. use accitional NRC Form 366A's) (t?)

V. Additional Informntion There have been no similar events where improper isolation of a transmitter has resulted in generation of a low-low S/G safety signal.

EIIS Codes System Comnonents Engineered Safety Level Indicating Features Actuation System - JE Transmitter - LIT g4 gam 366

. . . ...._______________ _