05000423/LER-1986-001, :on 860116,during Hot Standby Mode,Reactor Tripped Due to Safety Injection Signal from Rate Compensated Steam Line Low Pressure of Steam Generator A.Caused by Quick Opening of Atmospheric Steam Dump Valve

:on 860116,during Hot Standby Mode,Reactor Tripped Due to Safety Injection Signal from Rate Compensated Steam Line Low Pressure of Steam Generator A.Caused by Quick Opening of Atmospheric Steam Dump Valve

ML20153C903
Person / Time
Site:	Millstone
Issue date:	02/14/1986
From:	Langan J, Romberg W NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	NRC OFFICE OF ADMINISTRATION (ADM)
References
LER-86-001, LER-86-1, MP-8720, NUDOCS 8602210696
Download: ML20153C903 (4)

LER-1986-001, on 860116,during Hot Standby Mode,Reactor Tripped Due to Safety Injection Signal from Rate Compensated Steam Line Low Pressure of Steam Generator A.Caused by Quick Opening of Atmospheric Steam Dump Valve

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv), System Actuation
4231986001R00 - NRC Website

text

NaC Forat 308 U 8. NUCLE A Il REOULATORv COamesmeO80 4r431 APN40VE) DassasO. 3130 4 104 LICENSEE F1 E 'T ';EPORT (LER)

PACILITV NAmet (1)

DOCEST NUaEBER (21 Pagu (3 Mille:tnno Nucinar pnwnr statinn unit 1 0151010 lolaloI, 1 loFl ni, TITLE tes

' ~

Reactor Trip with SI Due to Low Steam Line Pressure EVENT DATE 45)

LER NUhEBER (6)

REPORT DATE (71 OTHER F ACILITIE* INVOLVED del MONTM DAY YEAR YEAR

'n' '

MONTH DAv YEAR PactLif y haMas DOCKET NUMeERIS) 0 1510101 0 1 I l 0l1 1l6 86 8l6 0l0 l 1 0l0 0l2 1l4 8 l6 oisioioici l i TMIS REPORT IS SUGasITTED PURGUANT TO THE REOutREMENTS OF 10 CFR { (Chece one er sne,e of lae %W1 III)

OPE RATHeG MODE (9) 1 20 402thi to desis) g 30,734eH2Havl 73.711hl A

30.40BieH1HO 90.3eleH1) 30.73teH3Hw6 73.714sl 39p m.0.

n,..,

m.,ei.,

gg,g.g,.4;e.

- 73,.,an.

O n.,

20 405(eH1 Hilel to.734elGHG to.73(eH2HvenHAl JosAJ 20.405leH111M 90 734al(2Hal 30.714eH2HveNHS1 30.485(sH1 Hv) 30.73telGHein 30.73teH2Hal LICENS!E CONTACT FOR THIS LER 1121

%Aug TELEPHONE NUMSER ARE A CODE Jeffrey A. Langan, Associate Engineer 21013 4141 71-11l 71 911 CoasPLETE ONE LINE FOR EACM COnaPO8eENT FAILURE DESCR10ED IN THIS REPORT (131

,O

" 'y,I,f' d

O

,T

CAUSE

SY ST E M COMPONENT "A

CAUSE

SYSTEM COMPONENT 9

R 3 yg A

5S P ICIVl-F l1131 0 N

i i i i I i i I

I I I I I I I

I I I I I I SUFFttheENTAL REPORT EXPECTED lies MONTH DAY YEAR TES (19 yee, comgvers LKPECTfD SUOMi$$10N CA Til NO l

l l

A.m ACT m,..

, e..e

._, ~,

e-e,-,

, n..

On 1/16/86, at 0344 hours0.00398 days <br />0.0956 hours <br />5.687831e-4 weeks <br />1.30892e-4 months <br />, while operating in the Hot Standby mode, the plant received a Safety Injection Signal from the rate compensated steam line low pressure off Steam Generator "A".

Plant operations verified the opening of both Reactor Trip breakers.

All Control Rods were fully inserted prior to the event. All Engineered Safety Feature Systems actuated properly.

The restoration from the SI, which was performed in accordance with plant procedures, was hampered by a fault in the "B" train Diesel Sequencer. This fault prevented the I

restoration of the Reactor Plant Component Cooling Water nonsafety supply header, as well as preventing the "B" Emergency Diesel Generator from being reset.

The "B" EDG was secureu by placing it in Emergency Shutdown.

Subsequent investigation revealed the rate compensated steam line low pressure SI resulted when the Atmospheric steam dump valve on Steam Generator "A" was opened too quickly. The rate compensated steam line low pressure SI is an anticipatory trip and safety injection to mitigate the consequences of a steam line break.

This caused a sudden drop in steam line pressure which caused the rate compensated steam line pressure circuit to generate a Safety Injection.

This report is being submitted in accordance with 10CFR50.73(a)(2)(iv).

$23 h

PDR g)

=--

p l

1 NRC Fonn 3,4A U 5 NUCLE AR KEGULATOAV COMMIES 404 UCENSEE EVENT REPORT (LER) TEXT CONTINUATION AmowO ove No uso-om EXPimES 8 318B FACILITY NAME (1)

DOCK E Y NUMSE R th LER NUMGER 46)

1. AGE (3 Millstone Nuclear Power Station

" W,it' W,0 ua Unit 3 4 2l3 8;6 0 0 l1 0; 0 0 l2 0 l3 o so o a or TEXT t# auwe ansce e seused esse edicoonef N#C Fene JE4 si(th On 1/16/86, at 0344 hours0.00398 days <br />0.0956 hours <br />5.687831e-4 weeks <br />1.30892e-4 months <br />, while operating in the Hot Standby mode, the plant received a Safety Injection Signal from the rate compensated steam line low pressure off Steam Generator "A".

The rate compensated steam line low pressure SI is an anticipatory trip and safety injection to mitigate the consequences of a steam line break.

Plant operations verified the opening of the Reactor Trip breakers.

All Control Rods were fully inserted prior to the event.

All Engineered Safety Feature Systems actuated properly.

The restoration from the SI, which was performed in accordance with plant procedures, was hampered by a fault in the "B" train Diesel Sequencer. This fault prevented the restoration of the Reactor Plant Component Cooling Water nonsafety supply header, as well as preventing the "B" Emergency Diesel Generator from being reset. The "B" EDG was secured by placing it in Emergency Shutdown.

An investigation revealed the rate compensated steam line low pressure SI resulted when steam line pressure experienced a step decrease of approximately 80 psi while initiating steaming through the Atmospheric Steam Dump valve on Steam Generator "A".

Based on a report received from a Stone and Webster crew working near the Main Steam Valve Building, and visual observation by a Plant Equipment Operator on outside rounds, it was thought that a Main Steam Safety valve had lifted concurrently with the opening of the Atmospheric Relief valve. However, a review of "A" steam line pressure showed a maximum pressure well below safety valve settings.

Furthermore, a check by the Maintenance Department on January 19, verified that the two lowest set safety valves were not lifting early.

It is therefore concluded that the rate compensated steam line pressure SI resulted from opening the Atmospheric Relief valve on Steam Generator "A" too quickly.

Plant heatups are performed in accordance with Operating Procedure 3201.

In order to allow operators maximum flexibility during startup, this procedure does not give specific detailed instructions on the use of the Atmospheric Steam Dump valves (e.g.,

manual control versus changing the setpoint with the valve controller in automatic).

Since this procedure has been used in the past without similar events occurring, it is not felt that detailed instructions are needed in the procedure. However, to ensure operators are made aware of the potential for Safety Injection actuation while operating the Atmospheric Steam Dump valves, a precaution has been added to the procedure to exercise extreme care while operating the valve controls.

In addition, the response of the lead / lag unit in the rate compensated steam line low pressure circuit was reviewed to determine whether it was responding properly to inputs. This review showed the circuit responded properly to the step decrease in steam line pressure. No adjustments were judged to be necessary.

An investigation into the problems with the "B" Diesel Sequencer revealed the problem to be a diode that had shorted out. This failure caused 4 cards within the sequencer to burn out, and prevented the sequencer from being reset. The "B" Emergency Diesel Generator was secured by placing it in Emergency Shutdown. After replacing the diode and cards, the Reactor Plant Component Cooling Water nonsafety supply header was restored.

F,"."*'"'

l haC Form 304A.

U S NUCLEAR 5 EQULATO3Y COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Areaovto ous =o siso-oios enmats e ai a F ACsLITY NAME Of DOCKET NUMSta Qt LER NUMSER ISI PAGE(31 "R'W"

"'##2 Millstone Nuclear Power Station Unit 3 o l6 lo lo lo l 4 a 3 8l6 01011 0l0 013 0F 0l3 rm n -

M.. -., - une w s

,,nn There were no safety implications to the public as all equpment performed its intended safety function. The single failure within the "B" Diesel Sequencer resulted in the sequencer failing in a safe condition.

This report is being submitted as required by 10CFR50.73(a)(2)(iv).

msAC FOsw 3esa 19 83

I NOltTHEAST IFFII. FRIES E

555555EI2 bS[$"b ""' "'"*

= : = =!

t <L February 14, 1986 MP-8720 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 50-423/86-001-00 Gentlemen:

This letter forwards Licensee Event Report 86-001-00 required to be submitted within thirty days pursuant to 10CFR50.73 (a) (2) (iv); any event or condition that resulted in manual or automatic actuation of any Engineered Safety Feature (ESF), including the Reactor Protection System (RPS).

Yours truly, NORTHEAST NUCLEAR ENERGY COMPANY FOR: Wayne D. Romberg Station Superintendent Millstone Nuclear Power Station Y

v BY:

James C. Kelley Station Services Superintendent Millstone Nuclear Power Station WDR/JAL:se Attachment: LER 86-001-00 cc: Dr. T. E. Murley, Region I o

h

)\\

1 l