05000397/LER-1988-001, :on 880118,following Plant Shut Down,Automatic Reactor Protective Sys Actuation Occurred Due to Low Reactor Pressure Vessel Water Level Condition.Caused by Procedural Inadequacy.Plant Procedures Revised

:on 880118,following Plant Shut Down,Automatic Reactor Protective Sys Actuation Occurred Due to Low Reactor Pressure Vessel Water Level Condition.Caused by Procedural Inadequacy.Plant Procedures Revised

ML17279A831
Person / Time
Site:	Columbia
Issue date:	02/15/1988
From:	Davison W, Powers C WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
LER-88-001, LER-88-1, NUDOCS 8802230392
Download: ML17279A831 (7)

LER-1988-001, on 880118,following Plant Shut Down,Automatic Reactor Protective Sys Actuation Occurred Due to Low Reactor Pressure Vessel Water Level Condition.Caused by Procedural Inadequacy.Plant Procedures Revised

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(e)(2) 10 CFR 50.73(a)(2)
3971988001R00 - NRC Website

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ACCELZMTED DISTRIBUTION DEMONSTRATION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:8802230392 DOC.DATE: 88/02/15 NOTARIZED: NO DOCKET g

FACIL:50-397 WPPSS Nuclear Project, Unit 2, Washington Public Powe 05000397 AUTH.NAME AUTHOR AFFILIATION DAVISON,W.S.

Washington Public Power Supply System POWERS,C.M.

Washington Public Power Supply System RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 88-001-00:on 880118,Reactor protective systm automatic actuation during plant shutdown due to inadequate procedure.

W/8 ltr.

DISTRIBUTION CODE:

ZE22D COPIES RECEIVED:LTR i ENCL

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SIZE: ~

TITLE: 50.73 Licensee Event Report (LER), Incident Rpt, etc.

NOTES:

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NRC Form 366 (94)3)

LICENSEE EVENT REPORT (LER)

V.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 31604101 EXPIAES: 8/31/88 FACILITYNAME (Il Washington Nuclear Plant - Unit 2 TITLE (4)

Due to Inadequate Procedure DOCKET NUMBER (2)

PAGE 3

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1 OF EVENT DATE (5)

LER NUMBER (6)

REPORT DATE (7)

OTHER FACILITIES INVOLVED(8)

MONTH DAY YEAR YEAR @. SEGUENTIAL 'or%

'UMSER REVISION NUMBER MONTH DAY YEAR FACILITYNAMES DOCKET NUMBER(S) 0 5

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Abstract On January 18, 1988, at 1354 hours0.0157 days <br />0.376 hours <br />0.00224 weeks <br />5.15197e-4 months <br />, following a plant shutdown, an automatic Reactor Protective System (RPS) actuation occurred due to an actual low Reactor Pressure Vessel (RPV) water level condition.

While the plant was being maintained in the Hot Shutdown Condition with the Hain Steam Isolation Valves closed, a main steam Safety Relief Valve (SRV) was opened to preclude approaching the automatic reactor high pressure RPS actuation setpoint of 1037 psig.

While the SRV was open, RPV water level swell effect caused level to increase above the RPV high water level setpoint which resulted in the automatic shutdown of the Reactor Core Isolation Cooling (RCIC) System.

This system was being operated to supply water to the RPV and assist in controlling RPV pressure.

When the RCIC System shut down, the decision was made to depressurize to 875 psig with an SRV.

After reaching the desired

pressure, the SRV was closed, causing RPV level to drop from +40 inches to -5 inches.

The automatic low RPV level RPS actuation occurred as level decreased through the +13 inch setpoint.

During the event, a narrow range RPV level recorder pen stuck at the high end of the scale for approximately one minute.

The root cause of the event was procedural inadequacy.

Plant procedures did not contain sufficient information to adequately address the degree of difficulty involved in controlling reactor pressure with the plant in Hot Shutdown with the Hain Steam Isolation Valves (HSIV) closed.

The significant corrective actions include:

revision of Plant Procedures to include specific information concerning control of reactor pressure and level in Hot Shutdown with the HSIVs closed, inclusion of this event as a future simulator training scenario, required reading of this LER by licensed operators and comoletion of an evaluation of the need for a digital RPV level indicator at the reactor control console.

This event posed no threat to the safety of Plant personnel or the Public

~

)8802230392 '8802k 5 j DR:.ADOCK 05000397,(94)3)

LICENSEE EVENT REPORT {LER) TEXT CONTINUATION V.S. NUCLEAR REQVLATORYCOMMISSION APPROVEO OM8 NO. 3)50&)04 EXPIRES: 8/31/88 FACILITYNAME (11 DOCKET NUMBER (2)

LER NVMSER (6)

SEQUENTIAL g>f REVISION N U ME E R

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Washin ton Nuclear Plant - Unit 2 TEXT ///moro 4/Mco /4 I/U)rorLoff~ H/(C fomr36((4'4/ (17)

Plant Conditions

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a)

Power Level -

OX b) Plant Mode

- 3 (Hot Shutdown)

Event Descri tion Following a scheduled plant shutdown on January 18,

1988, an automatic Reactor Protective System (RPS) actuation occurred at 1354 hours0.0157 days <br />0.376 hours <br />0.00224 weeks <br />5.15197e-4 months <br /> due to an actual low Reactor Pressure Vessel (RPV) water level condition.

At the time of this RPS actuation, the reactor was shut down and the plant was being maintained in a hot condition with the Main Steam Isolation Valves (HSIVs) closed.

RPV level and pressure control were being maintained using the Reactor Core Isolation Cooling (RCIC) System and the Reactor Water Cleanup (RWCU) System.

Just prior to the event, it was noted by the Control Room Supervisor (CRS) that when RCIC was not injecting into the vessel, reactor pressure was rising at an approximate rate of 3 to 4 psig per minute.

When reactor pressure reached

'l020 psig, with reactor level at approximately 40 inches, the decision was made to lower reactor pressure to 875 psig using a Main Steam System (HS) Safety Relief Valve (SRV) to discharge to the pressure suppression pool.

This decision was based on preventing an automatic reactor high pressure RPS actuation at 1037 psig and to preclude the automatic actuation of SRVs.

Under direction of the CRS, in accordance with approved plant procedures, HS-RV-5B was opened and then reclosed.

RPV level subsequently

swelled, due-to core void increase, to greater than +60 inches by narrow range level indication

(+50 inches on upset range, no increase on wide range),

causing the RCIC turbine steam admission valve (RCIC-V-45) to close at +54.5 inches (RPV Level 8).

This resulted in shutdown of RCIC, the system which was supplying water to the reactor vessel.

In accordance with approved Abnormal Condition Procedures, approximately ten seconds

later, HS-RV-5B was reopened for about two minutes, dropping reactor pressure to 875 psig.

The basis for this action was to allow sufficient time for restart of the RCIC turbine in order to minimize SRV lifting prior to restoration of RCIC spray to control pressure.

When HS-RV-5B was closed, reactor level dropped from +40 inches to -5 inches.

As level decreased through

+13 inches, a reactor low level (RPV Level 3) automatic RPS actuation occurred.'mmediate

Corrective Action

The plant operators responded in accordance with Plant Procedures by promptly restarting the RCIC System to supply feedwater to the RPV.

Reactor level was restored to greater than

+13 inches at 1403 hours0.0162 days <br />0.39 hours <br />0.00232 weeks <br />5.338415e-4 months <br />.

Further Evaluation and Corrective Action o

This event is being reported as an automatic actuation of an Engineered Safety Feature per the requirements of 10CFR50.73(a) (2) (IV).

NRCPQRM 346A (943)

• V.S GPO 1986 0 624 538/455

NRC form 358A (SS3)

LICENSEE EVENT REPORT ILER) TEXT CONTINUATION U.S. NUCLEAR REGULATORY COMMISSION APPROV EO OMS NO, 3(50M)DE EXPIRES: 8/31/88 FACILITYNAME ()I Washin ton Nuclear Plant - Unit 2 TEXT ///more EF>>c>> S>>>>)M)er/ rr>>>> ac /I/O/I>>/HRCForm 3//Sl3/117)

DOCKET NUMSER (21 0

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SEOVENTIAL NVMEER

+~ REVISION

" NVM ER PACE (3)

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The immediate cause of this event was opening the SRV for a longer continuous period than necessary to control RPV pressure rise, thus allowing water inventory loss sufficient to cause a low RPV level RPS actuation.

The licensed senior reactor operator (CRS) did not anticipate the exact response of RPV level as a result of opening an SRV with no feed water being supplied to the RPV.

o The root cause of this event was determined to be inadequate procedures in that, approved Plant Procedures did not contain sufficient information to adequately address the degree of difficulty involved in controlling reactor pressure and level with the plant in Hot Shutdown w'ith the Main Steam Isolation Valves closed.

Control of RPV level while isolated from the condenser with significant decay heat generation and the accompanying level swell-and-shrink transient effects during SRV operation were not 'addressed in detail by the Plant Procedures.

o Several contributing factors were identified as having some impact on the response to this event:

During the course of the initial RPV water level swel'l transient, the ink pen for the narrow range reactor level recorder stuck at the high end of the scale.

This provided the operators with an erroneous indication of actual RPV level from this recorder.

This instrument is one of four narrow range level indicators located on the Reactor Control Console and consequently did not have a major impact on the operational response to this event.

Previous to this event, the operator training program covered Hot Shutdown scenarios during simulator training; however, this particular event (i.e.,

Hot Shutdown with NSIVs closed and no high pressure water source) has not been stressed.

Lack of specific training relating to this scenario is considered a contributing factor.

o All automatic actions which should have been initiated at RPV Level 3 (+13 inches) did occur as designed.

The only actual operation of components that occurred were logic relay actuation and repositioning of valves for the reactor scram function of the Control Rod Drive (CRD) System.

No control rods were actually repositioned since they had been previously inserted fully into the core.

Other automatic functions which occurred are:

Reactor Recirculation Pumps received a signal to automatically shift to slow speed (15 hertz) operation.

This shift did not occur because both pumps were being operated at 15 hertz at the time of the event.

Nuc'lear Steam Supply Shutoff System (NS4) Groups 5 and 6 received an isolation signal.

No valves or components changed status because they were in the isolation position at the time of the event.

An Automatic Depressurization System (ADS) Low RPV Level 3 Confirmation Signal was generated.

This is one of two control logic RPV level functions required for the ADS initiation of seven Safety Relief Valves.

NRC FORM SEEA (8831

• U.S GPO.108S 082>> 538/>>55

NRC Form 388A (9031 LICENSEE EVENT REPORT ILER) TEXT CONTINUATION U.S. NUCLEAR REQULATORY COMMISSION APPROVED OMB NO. 3150-0104 EXPIRES: 8/31/SS FACILITYNAME (I)

DOCKET NUMBER (2)

YEAR LER NUMBER (8)

SEQUENTIAL NUMSER REVISION NUMSER PACE (3)

Washington Nuclear Plant - Unit 2 TEXT//Imare g>>ce /e derr)her/. Iree I//aar>>///RC Arm3r/SA'f/ (13) o s

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o The narrow range reactor level recorder is a Model Ho. 732, manufactured by Bailey Instrument

Company, GE MPL Number C34-R608.

This instrument was inspected,

cleaned, calibrated and placed back into service.

These instruments ar e a known high maintenance item.

WNP-2 is in the process of evaluating qualified replacements for this type of recorder.

No further corrective action is planned.

o Plant procedures will be revised to include specific information concerning control of reactor pressure and level in Hot Shutdown with the MSIVs closed.

o A technical evaluation of the need for a digital RPV level indicator at the reactor control console wi 11 be performed.

o This LER will be required reading for all licensed operators at WNP-2 and will be added to the subject matter list for requalification training.

o This event scenario will be specifically covered as a part of future simulator requa1 ification training.

.Safet Si nificance The Reactor Protective System functioned correctly to cause an automatic actuation in response to an actual reactor vessel low level (Level 3) condition.

The faulty RPV narrow range level recorder reading was compensated for by valid readings on the vertical section of the reactor control console from three reactor narrow range level indicators.

With the reactor shut, down, the significant safety concern is potential uncovering of the fuel.

The top of active fuel is located at -161 inches vessel level.

Since the level transient was terminated at -5 inches, more than adequate vessel water inventory remained to assure fuel coverage.

This event posed no threat to the safety of Plant personnel or the public.

Similar Events

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EIIS Information Text Reference EI IS Reference System Component RPS RPV MSIV RCIC RWCU MS-RV-5B RCIC-V-45 Narrow Range Reactor Level Recorder JC

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WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O. Box 968

~ 3000 George Washington Way

~ Richland, Washington 99352 Docket No.

50-397 February 16, 1988 Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C.

20555

Subject:

NUCLEAR PLANT NO.

2 LICENSEE EVENT REPORT NO.88-001

Dear Sir:

Transmitted herewith is Licensee Event Report No.88-001 for the WNP-2 Plant.

This report is submitted in response to the report requirements of 10CFR50.73 and discusses the items of reportability, corrective action taken, and action taken to preclude recurrence.

Very truly yours, C.H.

Powers (H/D 927H)

WNP-2 Plant Hanager CHP:sm

Enclosure:

Licensee Event Report No.88-001 cc:

Hr. John B. Hartin, NRC Region V

Hr. C.J.

Bosted, NRC Site (H/0 901A)

INPO Records Center Atlanta, GA Hs. Dottie Sherman, ANI Hr. D.L. Williams, BPA (H/D 399) ss "

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