ML20043B983

LER 90-016-00:on 900424,automatic Isolation Signal Closed Suction Valves from Reactor Water Recirculation Sys.On 900425,suction Valves Closed & RHR Pump Tripped.Caused by Chattering Pressure Switch.Switches replaced.W/900523 Ltr

ML20043B983
Person / Time
Site:	FitzPatrick
Issue date:	05/23/1990
From:	Fernandez W, Fish H POWER AUTHORITY OF THE STATE OF NEW YORK (NEW YORK
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
JAFP-90-0428, JAFP-90-428, LER-90-016, LER-90-16, NUDOCS 9006010141
Download: ML20043B983 (5)

Text

.J James A. Fit #elflok '

>g ., > . : g ; w m w pw

(?

i

P.Oi Box 41 :

• y

. Lycoming. Neo Yc k 13093 = ~

31$ 342-3840 '

WrkPower 0%. Resident Manager-May-23, 1990- I JAFP-90-0428 United States Nuclear Regulatory Commission .;

Document Control Desk. ~1 Mail Station P1-137 '

Washington, D.C. 20555

SUBJECT:

- DOCKET NO. 50-333 <

LICENSEE EVENT REPORT: 90-016-00 i Shutdown'CoolingiSystem Isolations

Dear Sir:

This Licensee Event Report is submitted in accordance'with 10'CFR 50.73(a)(2)(iv). n _

Questions concerning this. report may be addressed to.  !

Mr. Hamilton Fish at (315) 349-6013. q Very trul yours,  !

WILLI D.

FERNAN EZ 6b <&

't q

WF:HCF:lar Enclosure cc: USNRC, Region I USNRC Resident Inspector INPO Records Center American Nuclear Insurers IVgp0 f 0 '

1 9006010141 900523 PDR .ADOCK 05000333 S PDC

1 1

l

.se .,. me va mmena neonaven emessen 1

• • 8 -

a,suoveeeseem 3,s.mes UCENSEE EVENT REPORT (LER) ****

enou n mese ni esean masen ei _ i.

J ANES A. FIT 2PAftlCE NICLEAR P0NER PL ANT o is io io ioi:is ,a i lop ei 4 Shutdown Cooling System Isolation Caused by Pressure Switch chatterino eve n m es a saa maman e nemen o.n m orusa ..eures evetve m tenerTM QAY veAA veAA '

hMh'" bl M- a Idosefw 0.y veam f aciuTy naasse DocEtt ssJessene 0Isicioio sii l 0l4 2l4 90 9l 0 0l1l6 0l 0 0l 5 2l3 9l0 ,,,,,,,,,, ,,

! ,,,,,,,,,,, j rue e mnne,unsu.=1.ve r -- awiseentm . ., eoo anos m m m.,s.

_ 3 .m,s g.,,

pe,,,,

y O00

.ms.n _

.m n, E,, .

n. i i mmemnm suswa Erm uim g

mmewonu ErmiseMo es.rewomeMas

_ nwa y g g 7 _ _ _

mee

( emH, Hist a =

~

EFel tSNel W.FetstGHumle I

$Ik .

B.4WhH, Hul EFeWeem EPeh6SMal uceasse convaev een two ten nm

= '

n- ,,u Hamilton C Fish '"""

compten oneons on 3:1 5 3 i 4iti-isp i :l3 n = - ,utu esees. rue . ,nei cause evere. cou,o=ent q ;,'o ag,aj,'ge  : ' qq caves ey ,re , co ,s,, ge,as ng,, ga

-^

X Bi O PiSI I Si318i2 Y  ?" ' d' ' I i i ; i i i k i i i i i i ,

._e_,,.......

N i i i , i i i MM

,,,,e,,,

_ ,. mv ,

sumamo=

~k'] vn tu q e;retens suomesson uns '^'""

sm ce io.. . , m. _ _ , mis = = _ _

~~]=o nei O7i 1;5 9;O

! EIIS Codes are in []

The reactor was shutdown for refueling on March 31, 1990. The reactor vessel head has been removed for refueling. The. Shutdown Cooling (SDC) mode of the Residual Heat Removal system (RHR) [BO) isolated during startup on April 24 and again during pump transfer on April 25. The system was successfully restarted. There was no significant interruption in the removal of decay heat from the reactor core which had been shutdown for 24 days.

Subsequently, a series of six test runs using additional instrumentation, controlled variables, and duplicate pressure switches were conducted from May 9 through May 14. A chattering pressure switch caused the isolation. Test results showed a possible cause of the chattering may have been a small quantity of air in one of the two pressure switches which initiate the isolation signals. The tests showed that starting of the pumps does not produce a pressure transient of sufficient magnitude to initiate an isolation signal when the instrument lines are filled with water.

The switch which was found to be chattering prior to venting was 1 replaced and sent to the manufacturer to determine if a defect in the switch, rather than an air bubble, could have caused the chattering.

Related LERs90-002 and 90-011 describe similar isolations of the l SDC which may also have been caused by air in the pressure switch )

instrument line.

l mac e== see a

L e s. u asac she asea u.s. mucLain aseut; tony communesces UCENSEE EVENT REPORT RER) TEXT CONTINUATION - waovio onie =o sino.e.

Expent8 er3tet pacobifV Nan 85110 00casi asunete tts Lem Nundgem lei past m 1AMES A. FITZPATRICK ma "t!r.W "'d.?: -

IlWCLEAR POWER PLANT o o ojo 3 3 3 90 __ 0 jll6 __

0l0 0l2 oF 0l rentn- . .nem.mm.wi EIIS' Codes are in~()

Description .

The reactor was shutdown for a refueling outage on March 31, 1990. The '

reactor vessel head was removed for refueling.- The Shutdown Cooling

\(SDC) mode of the ResidualLHeat Removal (RHR) (BO) is used during:the outage to remove decay heat to maintain ~ the: reactor coolant below -

212 F.

The piping system and heat exchangers offthe SDC are rated for-low pressure (compared to normal reactor operating pressure) service. The low pressure RHR-system must be protected from exposure 1to' normal reactor operating-pressure because the system takes: suction from and "

discharges to the reactor water recirculation: system (RWR) (AD) piping .

which is connected directly to the reactor vessel. This overpressure protection.is accomplished by isolation signals which close suction isolation valves (10MOV-17 and -18) on the SDC system when. reactor pressure exceeds a setpoint of less than or equal to 75 psig reactor -

dome pressure'(Technical Specification Table 3.2-1). '

Startup of the A side of the RHR system was.in progress on April 24, 1990. Upon start of the pump and' opening of.the discharge '

valve (10MOV-27A), an automatic isolation signal closedithe' suction. 4 i

valves from the reactor water recirculation system at 2200. The cause l of the high pressure signal was false because with the reactor vessel

head removed, the reactor pressure couldLnot exceed.0 poig compensated-L for static head. The SDC was placed in service 2. hours, 51 minutes i later at'0051 on April 25.

Later on April 25 it was necessary to transfer from RHR pump A to RHR t pump C for collection of test data on. pump operation. Both pumps'are in the same subsystem. Following transfer to pump C, as flow +was being increased by opening the RHR system discharge valve-(10MOV-27A), the >

suction valves 10MOV-17 and -18 closed and the pump tripped at 1207.

SDC was restored to service 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, 18' minutes later at 1625.

An investigation of the root cause involved numerous test runs of the L system from May 9 through May 14, 1990. Venting of a dead leg-ended.

l .the chattering of a pressure switch which initiated the isolations. To l determine whether or not there was some problem within the switch itself which caused the chattering, it was replaced and returned to the i . manufacturer for failure analysis.

l

[ Cause 1

A series of six test runs using controlled variables and identical

. pressure switches installed in parallel produced repeatable results.

The test results showed that isolation signals were being caused by a l0E*~~'

y ,- , e

J '

e wana ve muetum ..vutony ca LICENSEE EVENT REPORT (LER) TEXT CONTINUATION - ***aovio one i.o me-m.

Expents grat.n pacesity maaet tip oceRET 8 VaSta las Lee asuusen tai *Act tai JAutS A. FITZPATRICK "^a 22. 'h.# .

NUCitAR POWit PL ANT run-- . e, an.,nm o 15 l o l o l 013 l 3 l 3 9l0 -

0l1l 6 -

0j 0 0 13 oF 0 14 -

l- chattering pressure switch. The system pressure oscillation at pump discharge as measured by test instrumentation _was only.5 psi. A pressure transient of at least_45 to 60 psi above reactor pressure at 7

the time of the SDC-system initiations would have been required to isolate the system. A duplicate switch connected in parallel did not-chatter. Venting of a dead leg to the chattering switch eliminated the chattering condition during the next test run. No isolation signals were received on succeeding test runs. Therefore, the aresence of-a

-small air bubble in the pressure switch may have'been t2e cause 4of the .

SDC system isolations for'the two events of this LER'and of the isolations reported in LERs90-002 and 90-011. Final determination will be made following vendor examination of the switch which was chattering.

Analysis Shutdown cooling system isolation logic _ actuation is reportable under the provisions of 10CFR50.73(a)(2)(iv) as an activation of an engineering safety feature [JE). This high reactor pressure. permissive safety feature was not needed'because the reactor vesselihead was removed. Thus, reactor pressure (compensated'for static; head) could not exceed atmospheric pressure. There were no system or equipment failures. The shutdown cooling system isolation was_ performed in accordance with design. The SDC was restarted'at 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, 51 minutes-( after the first isolation and 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />,118 minutes after the second I isolation. The system could have been restarted more rapidly if it had

! been required. Because the reactor had-been shutdown for 24 days, l

there was no significant interruption in the removal of decay heat.

Corrective Action '

1. The SDC was restarted after each isolation.

2. A testing program was initiated to assist with determination of the cause of the isolation.

3. As a result of the test program, one of the two pressure switches-l that initiate isolation signals was replaced. The switch which' was removed was returned to the manufacturer to determine if a root cause within the switch could have resulted in the chattering. This LER will be revised upon receipt of-the report.

4. Instrument Surveillance Test procedures will be revised to include venting of the pressure switches 02PS-128A and B.

1 l

c ronu sees

. . .g i

i mac sure ase4 - u& muctsan Resutt.vony commmesson

't

. , ilCENSEE EVENT REPORT (LER) TEXT CONTINUATION- aaeaovio ous =o sino-oiw so,ans emw FAcetsty haast til Docaat spuesta m LER nutega tel pass (3 -

1 A11!5 A. FITZPAf tlCR - viaa a mp,*- m;;

NgCLEAR POWER PLANT ois{0lo10-l3l3l3 910 -

0 l1] 6 -

010 0l4 0F e l4 1 Additional Information Component _ Pressure Switch Functions- .RHR Interlock - Protect RHR from Reactor. >

l' Pressure Plant Identification - 02PS-128A c Manufacturers  : Static-0-Ring Company Model: 6N6-BB5-NX-CIA-JJTTX6 1 Design Data: 1500 psig, 125 VDC, 0,8.' amp ,

l Setpoint: . 97 psig (Nominal)

NPRDS Component Code: IBISSW-  :

NPRDS Vendor Code: S382 i

Related LERs:

90-002 and 90-011 describe similar isolationsLof the Shutdown Cooling system due to the RHR interlock pressure switch- -f

. signals'.

e c

f

[

i l

4 7,... ~

u

. . , _