ML20011F825

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LER 90-003-00:on 900201,RCIC Received Div 2 Isolation on RCIC High Steam Line Flow.Caused by Spurious High Steam Flow Signal Generated When Steam/Water Mixture Admitted to RCIC Steam Line.Isolation Logic reset.W/900302 Ltr
ML20011F825
Person / Time
Site: LaSalle Constellation icon.png
Issue date: 03/02/1990
From: Diederich G, Tennyson M
COMMONWEALTH EDISON CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-003-01, LER-90-3-1, NUDOCS 9003080087
Download: ML20011F825 (6)
v • d • e


Text

,

t- V e Commonwealth Edison

' i~' g . LaSalle County Nucl!ar Station -

Rural Route #1, Box 220 Marseilles, Illinois 61341.

Telephone 815/357-6761 March 2, 1990 I I

Director of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail station Pl-137.

Washington, D.C. 20555

Dear Sir:

l- Licensee Event Report E9-003-UO, Docket #050-373 is being l submitted to your office in accordance with l

10CFR50.73(a)(2)(iv).

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'O. J. Diederich S ation Manager l- LaSalle County station l- GJD/IGET/kg L . Enclosure-xc: Nuclear 1.icensing Administrator l NRC Resident Inspector

? NRC Region III Administrator INPO - Records Center r

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9003080087 900302 k.

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PDR ADOCK 05000373 .

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LICENSEE EVENT REPORT (LER) fim Rev 2.0 Facility Name (1) lDociet Nunt>er (2) Page (3)

LaSalle County Station Unit 1 01 51 01 01 01 31 71 3 1lof!0l5 Title (4) Reactor Core Isolation Cooling Isolation Signal During Wannup Due to Spurious High Stem f)pw Signal causen by Stem / water Mixture Trapped Between Isolation valves Event _Date (5) LER Neber (6D Report Date (7) Other Facilities involved (B)

Month Day Year Year Sequential ///j Revision Month Day Year Facility Names _

Docket Nunt>er(s)

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f

// Nunt>cr ff

/// Nunt>er 01 51 01 01 Ol l 1 Ol 51 01 01 Ol l l

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01 2 01 1 91 0 91 0 01013 01 0 0l3 01 2 9LO THIS REPORI 15 SUBM111ED PURSUANT TO THE RE%1REMEN15 0' 10CFR g) (Cnect one or more of the followine) (11) 1 20.402(b) _

20.A05(c) ,. X_ 50.73(a)(2)(iv) _

73.11(b)

POWER _ 20.405(4)(1)(1) __

50.36(c)(1) __

50.73(a)(2)(v) _

13.7)(c)

IIVEL 20.405(a)(1)(ll) 50.36(c)(2) 50.73(a)(2)(vii) Other (Specify 0l9!9 ,_ _ _ _

_(10) _ 20.405(a)(1)(iii) _

50.73(a)(2)(i) _

50.73(a)(2)(vill)(A) in Abstract

/ //,/f/,/,/,/,/,/,/,/,////j/,/,/,///,/,/, _

20.405(a)(1)(iv) _

50.73(a)(2)(li) _

50.73(a)(2)(viii)(B) below and in

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fj f /'ffj ,_

f// 20.405(a)(1)(v) ___

50.73(a)(2)(iii) _

50.73(a)(2)(x) Text) llCENSEE CONTACI FOR THIS f.ER (12) lame TEl[ PHONE NUpBER __

AREA CODE Mike fennyson. Technical Staff Engineer. extension 2704 _ _ _ _ _ _

8 l 1 15 315171-l6171611 COMPIE1E ONE llNE FOR EACH COMP 0NEW IAILURE EYSCRlBF,0_IN_THIS REPORT (13)

CAUSE SYSTEM COMP 0N MI MANUfAC- REPORIABlE CAUSE SYSIEM CDPPONENI MANUFAC- REPORTABLE TURER TO WPRDS_ TURER TO NPRDS B Bl N l l l l l l N I I l l l l l 1 1 I I I I I I 1 I I I I I SUPPLEMENTAL REPOR1 EXPECTED (14) Expected Month l Day l Year Submission Date (15) l I

-lyes (if ves, conqplete EXPECTID SUBMI5510N DATE) X l NO l l l 1 l ABSTRACT (Limit to 1400 spaces, i.e approxinutely fifteen single-space typewritten linas) (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 stem line flow.

Upon conpletion of preventative naintenance on the RCIC system, the system was being returned to Standby per LaSalle Operating Procedure, LOP -R14)4, "Turbina Trip Recovery arid Turbine Reset," when the inboard isolation valves (1E51-F063 and IE51-F076) isolated due to a spurious high steam flow signal.

1he RCIC stem line isolation was not a valid high stem flow signal. A steam / water mixture trapped between the inboard valves and the outboard valve was raileased into the piping downstre m of the outboard valve when it was opened. The surge from this release was sufficient to exceed the trip setpoint of the high flow isolation switches.

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 the RCIC system proceeded with no further incidents.

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

Before the outboard isolation valve (IE51-F008) is opened, the equalizing valves for instruments lE31-N013AA and IE31-N013BA will be opened. After the outboard isolation valve is opened, the equalizing valve will be closed, and warming of the stem lines will continue. This procedure will continue until a penrunent resolution is nade. A modification request which addresses a perwunent resolution to the problem of returning the RCIC system to service without isolations has been submitted for review.

This event is reportable to the Nuclear Regulatory Coninission as a Licensee Event Report in accordance with 10CFR50.73(a)(2)(iv) due to an Engineered Safety Feature actuation.

a

. Lirmrr EVENT REPORT (LER) TEX 1 CONilNUATION Fom Rev 2.0 4- _ FACILITV N4pui (1)- DOCKET NUpWER (2) LER 1RD9ER (6) Paae (3)

Year /// Sequential / Revision

  1. aber 7'/'/ Number //

w ile - etv Station unit 1 0 1 5 I o'I o 1 0 1 31 71 3 910 - 01013 -

01 0 01 2 0F 01 5 1 EXT Energy industry identification System (Ells) codes are identified in the text as [XX]

a PLANT AND SYSTEM IDEN11 FICA 110N General Electric - Bolling Idater Reactor-Energy Industry identification System (Ells) codes are identified in the text as [XX].

A. CONDITION PRICR 10 EVENT Unit (s): 1 Event Date: 2/1/90 Event Time: _ 1822 Hours Reactor Mode (s): 1 Mode (s) Nme: Run Power Level (s): 995

8. DESCRIP110N OF EVENT 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) [8N] received a Division 2 (inboard) isolation signal due to RCIC high steam line flow instrumentation. This isolation was not a valid high stem flow signal. This event occurred while Unit I was in Operational Condition 1~

(Run) at 995 power.

At the time of the event, RCIC stem line was being womed up following the completion of preventative maintenance to the RCIC system. The outboard RCic steam isolation valve (IE51-F008) and the inboard stem isolation valves (1E514063 and IE514076) were closed. Upon completion of the maintenance, RCIC was being returned to standby per LaSalle Operating Procedure, LOP-Al-04. . The Control Room Operator attsupted to slowly crack open the outboard isolation valve (IE51-F008), with the inboard valves closed.

Shortly after the outboard valve apparently lifted off of its seat, the Operator aoticed a step increase in RCIC stem line pressure downstrem of the outboard isolation valve and lamediately closed the ;

outboard valve. Within 4 seconds of the pressure increase the Olvision 2 inboard RCIC stem isolation -

valves (IE514063 and IE51-F076) received an isolation signal due to a high stem flow signal from the pressure differential switch PDS IE31-N0138A.

1he inboard stem isolation valves (IE51-F063 and IE514076) 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 wamed in accordance with the sme 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 perfonnance 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. The flow elbow cannot accurately measure flow in these circianstances due to the difference in fluid density between the taps.

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

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LICEN3LE EVENT REPORT (LER) TEXT CONTINUATION Fonn Rev 2 0 ]

FAClEITY NAME (1) DOCKET NumER (2) lER NUSER (6) Pace (3) l Year /// Sequential fjf /jjj

// Revision  ;

/// Nueer /// Nu6er LA$alle County Station Unit 1 0 1 5 1 0 1 0 1 0 l 31 71 3 910 -

010l3 - 01 0 01 3 0F 01 5 :

TEXT Energy Industry Identification System (Ells) codes are identified in the text as [XX]

C. APPARENT CAUSE OF EVENT The cause of the RCIC steam Ilne isolation was a spurious high stem flow signal generated when a steam / water mixture was admitted to the RCIC stem Inne downstrem of the outboard isolation valves IE514008.

Apparently the ste.im/ water mixture becme trapped downstrem of the inboard isolation valves (IE514076 and IE514063) and upstrem of the outboard isolation valve (IE514008) during the isolation of the system for preventative maintenance.

Upon reopening of the outboard isolation valve, the trapped stem expanded into the downstrem piping causing a surge of the steam / water mixture which actuated RCIC system high flow Isolation logic. The isolation logic for high RCIC steam line flow has a four second time delay built in to prevent spurious

[

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 simse steam, not a steam / water mixture. The isolation was res2t satisfactorily after it l

occurred.

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

l D. SAFETY ANALYSIS OF EVENT Upon receiving the high stem line flow isolation signal, the RCIC stem line inboard isolation valves -

Isolated satisfactorily. This action was conservative from the standpoint of Primary Containment (PC)

[NH] Integrity.

1 All the valves were already closed. (IE514008 was closed due to Operator action prior to tne automatic closure signal.) Therefore the isolation function of these valves had ben met.

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 operatien 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 Cooling systems were fully operable.

E. CORRECTIVE ACTIONS RCIC system piping integrity was verifled and the isolation logic was reset. Wanning up of the RCIC system proceeded with no further incidents, and RCIC was returned to standby per LOP-RI-04 at 1907 hours0.0221 days <br />0.53 hours <br />0.00315 weeks <br />7.256135e-4 months <br /> on February 1, 1990.

LICENSEE EVENT REPORT (tER) TEXT CONTINUATION Fom Rev 2.0 FACILITY NAME (1) DOCKET NU SER (2) LER WUSER (6) _ , Pace (3)

Year- /// Sequential t,/,/ Revision fff

/// Wusber W/ thsiber 1

LaSalle County Station Unit 1 0 l 5 1 0 1 0 1 0 l 31 71 3 9l0 -

010l3 - 01 0 01 4 0F 01 5 F TEXT Energy Industry identification System (Ells) codes are identified in the text as [XX) i E. CORRECTIVE ACTIONS (Continued)

Similar events occurred on May 15,1999, 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 coupletion of Unit 1 Stem Line Flow RCIC isolation Functional Test. Action item Record (AIR) 373-200-8944801 was initiated to track completion of the corrective actions for the events. A sunnary of the corrective actions taken after the RCIC isolations follow:

LaSalle Special Test, LST 89-019, Pressure / Differential Pressure Observation of RCIC Stem Line i' H141ow Isolation Switch, was perforined to observe the pressure and differential pressure transients, and also ta detemine whether another isolation would occur on returning RCIC to '

Standby per LaSalle Operating Procedure, LOP-RI-04. There was no RCIC isolation when the system was returned to Standby.

l A second special test was perfonned during return to Standby following isolation for maintenance of the RCIC high stem flow instruments. The pressure differential switches, PDS I IE31-N013AA/A8/8A/98, the time delay relays associated with these switches, and the RCIC stem I header pressure indicator IL51-N007 downstrem of outboard isolation valve IE51-F008 were monitored during system isolation, and on return to standby.

l l During the RCIC system return to Standby there was no RCIC isolation. The test equipment remained

' connected and was nonitored for three weeks to detemine the possible drift that would occur to the pressure differential switches while RCIC was in service. It was detemined that the drift in the switches was not sufficient to contribute to a RCIC system isolation during return to a Standby condition.

The pressure differential switches PDS lE31-N007A8/BB and PDS IE31-W013nB/BB have been placed out of service until they are pennanenth, removed by modification M01-1-88-052. These sw!tches are piped "In reverse" and cannot sense a legitimate high stem flow condition.

l l LaSalle Special test, LST 89-062 was perfonned again on .luly II,1989 in conjunction with a RCIC instrument 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 stem line pressure downstream of inboard-isolation valve IL51-F063 to 400 psig before closing outboard isolation valve IE51-F008. The pressure reduction in the steam line would be accomplished by waiting a period of 45 to 50 minutes after closure of the inboard isolation valve.

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

The setpoint for the time delay relays have been increased to 4 seconds. A Drawing Change Request

- was submitted for the schematic drawings as they currently indicate the time delay relays actuate at 3 seconds. The Technical Specification limit is 5 seconds. The completion of this corrective

, action will be tracked in AIR 373-200-89-07202.

L L

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. LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Form Rev 2.0 FACILITY NAME (1) DOCKE1 NUSER (2) LER NU SER (6) Pace (3)

Year /// Sequential /j//j Revision fff f

/// Nueer /// Nueer LaSalle County Station Unit 1 0 l 5 1 0 1 0 1 0 l 31 71 3 910 - 010l3 -

0l0 015 0F 01 5 1EX1 Energy Industry Identification System (Ells) codes are identified in the text as (XX]

E. CORHEC'lVE AC110NS (Continued) 10 prevent spurlous isolations, LOP-R144 and LOP-RI-05, " Preparation for Standby Operation of the RCIC System," will be revised to bypass the RCIC system high stem flow isolation switches will be bypassed during the system return to service. Before the outboard isolation valve (IE51-F008) is opened, the equalizing valves for instruments IE31-N013AA and IE31-N0138A will be opened. After the outboard isolation valve is opened, the equalizing valve will be closed, and warming of the steam lines will continue. This procedure will continue until a pennanent resolution is made. A modification request which addresses a pennanent resolution 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 conpletion of this review.

F. PREVIOUS EVENTS LER Number iltle 373/85-022-00 RCic Steam Line High Flow Isolation During Warmup 373/84-060-00 RCIC Stem Line Differential Pressure High Isolation 373/83-122/03L RCIC Steam Line Isolation During Wannup 373/89-018-00 RCIC isolation During Wanaup Due to Spurious High Steam Flow Signal 373-89-022-00 RCIC isolation During Wannup G. COMPONENT FAILURE DATA None.

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