ML20012D534

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LER 90-003-01:on 900201,RCIC Isolation Signal Occurred During Warmup.Caused by Spurious High Steam Flow Signal.Rcic Sys Piping Integrity Verified & Isolation Logic Reset.W/ 900316 Ltr
ML20012D534
Person / Time
Site: LaSalle Constellation icon.png
Issue date: 03/16/1990
From: Diederich G, Tennyson M
COMMONWEALTH EDISON CO.
To:
Office of Nuclear Reactor Regulation
References
LER-90-003, LER-90-3, NUDOCS 9003280019
Download: ML20012D534 (6)
v • d • e


Text

(194 Commonwe:lth Edison -

E '.

LaSalto County Nuclear Station

! . Rural Route #1, Box 220 :

. Marseilles, Illinois 61341 ,

J.  ; Telephone 815/357-6761 -

t i.'

P March 16, 1990 r

1; Director of Nuclear Reactor Regulatiott

' U.S. Nuclear Regulatory Commission

Mail Station F1-137 r Washingtoni D.C. 20555- ,

Dear Sir:

3-Licensee-Event Report-#90-003-01, Docket #050-373 is being

  • submitted to your office in accordance with 10CFR50.73(a)(2)(iv) and supersedes previous submitted report. i This suppletaent is to correct a typographical error in the Licensee Event Report number found on the cover letter of the previously submitted report, dated March 2, 1990.

O '

O. J. Diederich Istation Manager .

LaSalle County _ Station GJD/MMT/kg Enclosure xc: Nuclear Licensing Administrator NRC Resident Inspector NRC Region III Administrator INPO - Records Center l

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1 9003280019 900316  :) 4h PDR ADOCK 05000373 O,;i,

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1 1

. LICENSEE EVENT REPORI (LER) F Rev 2.0 ')

facill'ty Name fl) Docket Number (2) Paoe (3) l llof!O QSalleCountyStationUniti Ol 51 01 01 01 31 71 3 5 11tle (4) Reactor Core Isolation Cooling Isolation Signal During Wannup Oue to Sourlous High Steam flow signal caused _by SteaW Water Mixture _ Trapped Between isolation Valves l Event Date (5) lLR_Ns6er{6)

L _ _ _

Report Date,,17} _ Other f acilities_ lnvolvedj8) _ l Month Day Year Year j/j/ sequential /j/j/ Revision Month Day Year facility Names Docket Ntaber(s) f

//_ Nunber /// Nisser 0151010101 l l 01 2 01 1 91 0 91 0

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0_}013

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0,1 1 0l3 116_9LO. 0151010101 l l l1 l 1HIS REPORI IS SUBMllit0 PURSUANI 10 lill RLQUIRLMLNIS Of 10CIR {

OP M M (Check one or suore of the following) (11) '

1 20.402(h) _ 20.405(c) _XL 50.73(a)(2)(lv) ,,,_ 73.71(b)

POWER _ 20.405(a)(1)(l) _ 50.36(c)(1) _ 50.73(a)(2)(v) _ 73.71(c)

LEVEL' _ 20.405(a)(1)(ll) _ 50.36(c)(2) _ 50.73(a)(2)(vil) ,_

Other (Specify (10) 0 9 9 _ 20.405(a)(1)(lii) _ 50.73(a)(2)(1) _ 50.73(a)(2)(vill)(A) in Abstract l

/ //////,/,/,/,///,/,/,/,/,/,'/,/,/,/,//,/ _ 20.405(a)(1)(lv) _ 50.73(a)(2)(ll) _ 50.73(a)(2)(vill)(B) below and in

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//}/'j///' jjjjj/jjj

'/'//' //' '//j' ' '//// _ 20. 405 (a ) ( 1 ) ( v ) ,_ 50.73(a)(2)(lli) ,_ 50.73(a)(2)(x) Text)

LICENSEE CONIAC' IOR 1ll15 LER (12)

Name- TELEPil0NE NUMBER AREA CODE Mike Tennyson. Technical Staff Enoinee_r a extension 2704 8 l 1 15 315171-l6171611 COMPLETE ONE LINE FOR EACll COMPON N FAllDRE DISCRIBED IN lill5 R5 PORI (I3)

CAUSE SYSTEM COMPONEN1 MANUFAC- REPORIABLE CAUSE SYSTEM COMPONENI MANUFAC- REPORIABLE TURER TO NPRDS TURER 10 NPR05 e sl N I_ _ l_ _LLL N _1 __ L L L _LLL I I _1 -II I_ -_ --

1 I I I _LL_L__ _

Month l Day l Year SUPPLEMENIAL REPORT EXPECTED (I4) Expected Sutunission lyes (If yes, conclete EXPECIED SUBMISSION DME) ___

Y l,NO .

Date (15)  ; lg lg ABSTRACT (Limit to 1400 spaces, i.e, approxinkitely fif teen single-space typewritten lines) (16)

On February 1,1990, at- 1822 hours0.0211 days <br />0.506 hours <br />0.00301 weeks <br />6.93271e-4 months <br /> with Unit 1 in Operational Condition 1 (Run) at 99% power, the Reactor Core Isolation Cooling system (RCIC) received a Division 2 (inboard) isolation on RCIC high steam line flow, Upon conpletion of preventative psiintenance on the RCIC system, the system was being returned to Standby per

l. LaSalle Operating Procedure, LOP-RI-04, " turbine Irlp Recovery and lurbine Reset," when the inboard isolation valves (IE51-f 063 and 'IE51-F076) isolated due to a spurious high steam flow signal.

The RCIC steam line isolation was not a valid high steam flow signal. A steam / water mixture trapped between the inboard valves and the outboard valve was released into the piping downstream of the outboard valve when it was opened. The surge from this release was sufficient to exceed the trip setpoint of the high flow Is31ation switches.

L When the isolation signal was received, the inboard isolation valves and the outboard isolation valve were

, already closed. RCIC system piping Integrity was verified and the isolation logic was reset. Wanning up of l the RCIC system proceeded with no further incidents.

The RCIC system high steam flow isolation switches will be bypassed during the system return to service.

Befors the outboard isolation valve (IE51-F008) is opened, the equalizing valves for instruments IE31-N013AA (nd IE31-N013BA will be opened. After the outboard Isolation valve is opened, the equalizing valve will be cicsed, and wanning of the steam lines will continue. 1his procedure will continue until a per m nent rss31ution is made. A modification request which addresses a permanent resolution to the problem of r3 turning the RCIC system to service without isolations has been sutxnitted for review.

This event is reportable to the Nuclear Regulatory Conmission as a t.lcensee Event Report in accordance with 10CFR50.73(a)(2)(lv) due to an Engineered Safety feature actuation.

e , at 19 .,

-LICENSEE EVENT REPORT (LER) TEXT CONilNUATION form Rev 2.0 FACll'1,1Y NAME '(1) < 00CKEl NUfeER (2)- .LER NtpBER (6) Pace (3)

Year. Sequential Revision g// g/// Number i / Weber ..

n ine County station unit l' oI5101010131713 910 -- 01013 -

0 I -1 01 2 Or 01 5 TEXT. Energy Industry identification System (Ells) codes are identified in the text as (XX]- l' 'lI

.j PIANT AND SY$1EM IDLNiillCA110N General Electric - Bolling Water Reactor Energy Industry identification System (Ells) codes are Identified in the' text as (XX).

~

.A.; . CONDlil0N PRIOR 10 EVENI [

Unit (s): I Event'Date: 2/1/90' Event ilme: 1822 Hours I L' Reactor Mode (s): 1 Mode (s) Name: Run Power Level (s): 991 j

8. DESCRIPil0N OF EVENI.

l On february 1,1990, at 1822 hours0.0211 days <br />0.506 hours <br />0.00301 weeks <br />6.93271e-4 months <br /> the Reactor Core Isolation Cooling system (RCIC) [DNJ received a ,

Division 2 (Inboard) Isolation signal due to RCIC high steam line flow instrumentation. 1his isolation i was not a valid high steam flow signal. This event occurred while Unit I was in Operational Condition 1 "

(Run) at 99% power.-

  • At the time of the event, RCIC steam line was being wanned up followlng the conpletion of preventative maintenance to the RCIC system. The outboard RCIC steam isolation valve (IE51-F000) and the inboard steam isolation valves (IE51-f063 and IE51-f076) were closed. Upon coupletion of the maintenance, RCIC was being returned to standby per LaSalle Operating Procedure, LOP-RI-04. 1he control Roum Operator cttupted to slowly crack open the outboard isolation valve (IE51-F008), with the inboard valves closed.

Shortly after the outboard valve apparently l'lfted off of its seat, the Operator noticed a step Increase  ;

in RCIC. steam line pressure downstream of the outboard isolation valve and inmediately closed the '

outboard valve. Within 4 seconds of the pressure increase the Division 2 inboard RCIC steam isolation valves (IE51-f063 and IE51-f076) received an Isolation signal due to a high steam flow signal from the

. pressure differential switch PDS IE31-N013BA.

The inboard steam isolation valves (IE51-f 063 and IE51-IO76) were closed at the time of the isolation signal, and the outboard isolation valve had already closed due to the Operator's response. After the isolation, the outboard valve was re-opened and the RCIC steam line was wanned in accordance with the

'same procedure, LOP-RI-04, this time without incident.

The water which accumulated in the RCIC steam line piping between the inboard and outboard isolation valves during the perfonmnce of the maintenance appears to affect the differential pressure instruments when it is pushed past one tap of the flow elbow by the trapped steam. 1he flow cibow cannot accurately measure flow in these circumstances due to the difference in fluid density between the taps.

This event is reportable to the Nuclear Regulatory Conmission as a Licensee Event Report in accordance with 10CFR50.73(a)(2)(lv) due to an Engineered Safety feature actuation. j 1

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1

- L CENSEE EVENT REPORT (LER) TEXT CONilNUAil0N f orm' Rev 2.0 FACILITY NAME'(1) DOCKET NUteER (2) LER PMBER (6) Pace (3)

Year fj/j Sequential /jj

// f

// Revision  !

/// Nunber /// Nunber LaSalle County Station Unit 1 0 l 5 1 0 1 0 1 0 l 31 71 3 '9 l 0 -

0l0l3 - 0l 1 01 3 0F 01 5 l

. TEXT Energy Industry identification System (Ells) codes are identified in the text as [XXJ C.- APPARENT CAUSC OF EVENT 4-The cause of the RCIC steam line isolation was a spurious high steam flow signal generated when a steaWwater mixture was adnitted to the RCIC stem line downstream of the outboard Isolation valves IE51-F008.

Apparently the steam / water mixture became trapped downstream of the Inboard isolation valves (IE51-F076 l and IE51-F063) and'upstrem of the outboard isolation valve (IE51-F008) during the isolation of the system for preventative maintenance.

  • Upon reopening of the' outboard isolation valve, the trapped steam expanded into the downstream piplug causing a surge of the.steaWwater mixture which actuated RCIC system high flow isolation logic. The j' isolation logic for high RCic stem line flow has a four second tine delay built in to prevent spurious l Isolation when RCIC fast starts. This four second change was approved as part of the corrective actions from previous isolations. The basis for the flow measurements used in the isolation logic is that the elbows would sense stem, not a steam / water mixture. 1he isolation was reset satisfactorily after it occurred.

l The cause of this isolation was that the spurious signal lasted greater than 4 seconds.

D. SAFETY ANALYSIS OF EVENT Upon receiving the high steam line flow isolation signal, the RCIC steam line inboard isolation valves isolated satisfactorily. Ihis action was conservative from the standpoint of Prin6 ry Contaltunent (PC)

[NH] Integrity.

All the valves were already closed. (IE51-F008 was closed due to operator action prior to the automatic closure signal.) ~ 1herefore the isolation function of these valves had ben net.

~Since the valves'were already closed, the isolation signal did not cause any challenges to the valves.

-RCic.was already inoperable due to preventative maintenance. Satisfactory operation of the high flow differential pressure switches was observed during subsequent testing.

Consequences of this event were minimal since the High Pressure Core Spray (HPCS) [BG) and other Emergency Core Cr inng systens were fully operable.

E.. CORRECilVE ACTIONS

-RCic system piping integrity was verified and the isolation logic was reset. Warming up of the RCIC system proceeded with no further incidents, and RCIC was returned to standby per LOP-RI44 at 1901 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.233305e-4 months <br /> on February 1,1990. .

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' Fonn Rev 2.0 LICENSfE EVENT REPORT (LER) 1 EXT CONTINUAll0N

.PACIL11Y NAME (I) : 00CKEI NUtWER (2) ILR NUMBER (6) Pace (3)-

> Year /// Sequential ///

jff Revision '

fjf

/// Nunber /// Nunber Lasalle County Station unit I- ol510IoIo131713 910 - o I o 1 3- - 01 1 ol 4 or 01 5 lJ TEXT: Energy Industry Identification System (E'IS) codes are identifled in the text as [XX]

E. . CORRECTIVE AC110NS (Continued)

$1milar events occurred on May 15, 1989, at 2156 hours0.025 days <br />0.599 hours <br />0.00356 weeks <br />8.20358e-4 months <br /> and on August 10, 1989, following conpletion of Unit 1 Steam Line flow RCIC isolation Functional Test. Action item Record (AIR) 313-200-89-04801 was initiated to track conpletion of the corrective actions for the events. A sunmary of the corrective actions taken after the RCIC isolations follow: 1 LaSalle Special Test, LST 89-019, Pressure / Differential Pressere Observation of RCIC Steam Line Hi-Flow Isolation Switch, was perfonted to observe the pressore and differential pressure transients, and also to detennine whether another isolation would occur on returning RCIC to Standby per taSalle Operating Procedure, LOP-RI-04. There was no RCic isolation when the system was returned to Standby, b A second special test was perfonned during return to Standby following isolation for maintenance of the RCIC high steam flow instruments. The pressure differential switches, PDS *

-IE31-N013AA/AB/BA/BB, the time delay relays associated with these switches, and the RCIC steam header pressure indicator IE51-N001 downstream of outboard isolation valve IE51-I000 were monitored during system isolation, and on return to standby.

During the RCIC system return to Standby there was no RCIC isolation. The test equipment remained connected and was monitored for three weeks to detennine the possible drift that would occur to the

. pressure differential switches while RCIC was in service. it was detennined that the drift in the t

switches was not sufficient to contribute to a RCIC system isolation during return to a Standby condition.

l The pressure differential switches PDS 1E31-N007AB/BB and PDS lE31-N013AB/BB have been placed out of service until they are permnently removed by modification M01-1-88-052. These switches are-piped."In reverse" and cannot sense a legitimate high steam flow condition.

! LaSalle Special lest, LSI 89-062 was performed again on .luly 11, 1989 inconjunctionwithaRCIC instrunent' surveillance. Upon RCIC return to service there was no RCIC isolation.

After evaluation of the tests, LaSalle Operating Procedure, LOP-RI-03 was revised. The revision instructed the Control Room Operators to reduce the steam line pressure downstream of inboard isolation valve IE51-f063 to 400 psig before closing outboard Isolation valve IE51-f008. 1he.

pressure reduction in the steam line would be acco,plished by waiting a period of 45 to 50 minutes l after closure of the inboard isolation valve.

l

! All LaSalle Instrunent surveillances and procedures that required the isolation of the RCIC system l have been revised to reflect that all system isolations would be perfonned in accordance with the specific Operating procedure that is discussed in the above paragraph.

The setpoint for the tine delay relays have been increased to 4 seconds. A Drawing Change Request was submitted for the schnnatic drawings as they currently indicate the time delay relays actuate at 3 seconds. The lechnical Specification limit is 5 seconds. 1he conpletion of this corrective action will be tracked in AIR 373-200-89-01202.

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t.- .-y.

- LICENSFE EVENT REPORT-(IER) 1 EXT CONilNUATION Form Rev 2.0  !

FACIL1,TY NAME'(I)- DOCKET NUSER (2)- LER NUMBER (6) Pace (3) ,

Year ///

j/j/f Sequential //j j//

f

/ Revision  !

/ Nisdier / Ned>er Lasalle County Station Unit I- 0 I s'l 0 1 0 1 0 l al 71 3 9l0 ,

Ol013 -

0_l 1 01 5 0F 01 5 l TEXYn Energy Industry Identification System (Ells) codes are identitled in the text as [XX]

E. .
CORRECilVE AC110NS (Continued)' -;

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To prevent spurious isolations, LOP-RI-04 and LOP-RI-05, " Preparation for Standby Operation of the RCIC System," will be revised to bypass the RCIC system high steam flow isolation switches to be bypassed during the system return to service.. Before the outboard isolation valve (1051-I008) is opened, the l' equalizing valves for instrisnents IL31-N013AA and IE31-N013BA will be opened. - After the outboard Isolation valve is opened, the equalizing valve will be closed, and wanning of the steam Ilnes will continue. - This procedure will continue until a pennanent resolution is made. Action item Record 373-200-90-01502 will track conpletion of these procedure revisions.

'A m6dification request which addresses a pennanent resol'.tlon to the problem of returning the RCIC system to service without Isolations has been submitted for review. Action item Record (AIR)'

373-200-90-01501 will track cunpletion of this review. i F. PREVIOUS EVEN15 7

LER Nuniper Title 373/85-022-00_ RCIC Steam Line High Flow Isolation During Wannup 373/84-060-00 RCIC Steam Line Differential Pressure High Isolation

-373/83-122/03L- RCIC Steam Line Isolation During Wannup 373/89-018-00 RCIC isolation During Wannup Due to Spurious High Steam flow signal 4 373-89-022-00 RCIC lsolation During Warmup '

G,. COMPONENT'FAlLURE DATA None.-

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