ML17261B087

LER 89-016-02:on 891117,discovered Potential Problem W/ Safety Injection Block/Unblock Switch.On 891220,determined That Single Failure of Switch Could Render Both Trains of Safety Injection Inoperable.Also Reported Per Part 21

ML17261B087
Person / Time
Site:	Ginna
Issue date:	06/28/1990
From:	Backus W ROCHESTER GAS & ELECTRIC CORP.
To:
Shared Package
ML17261B086	List: ML17261B085 ML17261B087
References
REF-PT21-90 LER-89-016, LER-89-16, NUDOCS 9007090052
Download: ML17261B087 (9)

Text

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On November 17, 1989, an initial Engineering evaluation was completed, which identified a potential problem with the Safety Injection (SI) Block/Unblock Switch.

On December 20, 1989, at 1630 EST, with the reactor't approxi-mately 994 full powert the Plant Operating and Review made a final Committee (PORC) reviewed the Engineering evaluation, determination that a single failure of the SI features Block/Unblock of both Switch could render some automatic actuation trains of SI inoperable.

The PORC, after reviewing the situation thoroughly, concluded that sufficient justification existed for continued safe plant operation.

The underlying cause of the event was a design error which occurred during the original construction of the. R.E. Ginna Nuclear Power Plant.

Immediate cor'rective action was taken to verify that the plunger position of the SI Block/Unblock Switch contacts were in the proper position.

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FACILITY HAMS III Llll HIPNtll III SCQVCHTIAL AAVISION HUM 1 QCA R.E. Ginna Nuclear Paver Plant ,o s o o'o 24 4 89 016 0 2 02 OF 0 9 TIXT IH mew eWCe H teeunCF. vM ahNeWr HlK'ern ~ CI Illl I. PRE-EVENT PLANT CONDITIONS The plant was at approximately 99% steady state full power with no major activities in progress.

II. DESCRIPTION OF EVENT A. DATES AND APPROXIMATE TIMES FOR MAJOR OCCURRENCES:

o Initial plant operation in 1969: Event date.

o November 17, 1989: Discovery date.

o December 20, 1989, 1630 EST: Reporfability date and time.

o December 20, 1989, 1630 EST: Plant Operating Review Committee (PORC) determines that safe operation of plant may continue.

B. EVENT:

On November 17, 1989, an initial Engineering evaluation was completed, which identif ied a potential problem with the SI Block/Unblock Switch. Subsequently, PORC review of the Engineering evaluation, on December 20, 1989, with the reactor at approximately 99% full power, determined that a single failure of the Safety Injection (SI) Block/Unblock Switch could render some automatic actuation features of both trains of SI Inoperable.

This determination followed an evaluation of the following correspondences:

o Letter from S.P. Swigart of the Westinghouse Electric Corporation (NS-OPLS-OPL-I-89-517) to Mr.

R. Eliasz, Rochester Gas and Electric Corporation (RG&E), dated October 12, 1989,

Subject:

Control Room Safety Injection Block Switches.

IIAC SetM BASSA O.S. IIUCLCAII ASOIILATOIIYCOMMI55IOII 10451 LICENSEE EVENT REPORT ILERI TEXT CONTINUATION ASSAOVCO OMI gO 515C~IOS 5IISIII55 SI5145 SACILITY IIAMS 111 Ltll IIUMIllllll 5 ~ 0 V 'I H T I A L AS Y IS lO H HQU A H M ~A R.E. Ginna Nuclear Power Plant 2 4 4 8 9 0 6 0 3 OF 0 9 TEXT Ill~ PCS e ~. vM eeeOOneI ISIIC Some ~'llIITI o s o o o o Interoffice Correspondence from Richard Baker to P. Wilkens and G. Wrobel, dated November 17, 1989,

Subject:

Control Room Safety Inj ection Block Switches.

The Westinghouse Correspondence (NS-OPLS-OPL-I-89-517) identified a potential single failure mechanism which could result in blocking of some automatic actuation features of both trains of SI, (i.e. SI automatic actuation from low pressurizer pressure and low steam line pressure). Specifically, a single manual switch on the Main Control Board (MCB) is used to control this SI Block/Unblock function for both SI trains. An Engineering Evaluation of the existing Ginna Station SI Block/Unblock wiring configurations has concluded tha" the Westinghouse described potential single failure mechanism is applicable to Ginna Station. The Engineer-ing Evaluation also concurred with the Westinghouse position that due to the low probability of a switch failure sufficient justification exists for continued plant operation until separate A train and B train SI Block/Unblock Switches can be installed.

The PORC after reviewing the above correspondence concluded that sufficient justification exists for continued safe operation of the plant.

C. INOPERABLE STRUCTURES, COMPONENTS, OR SYSTEMS THAT CONTRIBUTED TO THE EVENT:

None.

D. OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED:

None.

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The event was made apparent due to Engineering's review of the following correspondence:

o Letter from S.P. Swigart of the Westinghouse Electric Corporation (NS-OPLS-OPL-I-89-517), to Mr. R. Eliasz, BG&E, dated October 12, 1989,

Subject:

Control Room Safety Injection Block Switches.

o This was documented in Interoffice Correspondence from Richard Baker to P. Wilkens and G. Wrobel, dated November 17, 1989,

Subject:

Control Room Safety Injection Block Switches.

o . The event was,determined to be reportable following PORC review of the previous correspondence.

F. OPERATOR ACTION:

As this was a design deficiency, with only the potential for component failure, no immediate operator action was necessary.

G. SAFETY SYSTEM RESPONSES:

None required.

CAUSE OF EVENT The underlying cause of the event is a design error which occurred during the original construction .of the R.E.

Ginna Nuclear Power Plant.

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The "basic component" is the SI Block/Unblock Switch, supplied by Westinghouse Electric Corporation as part of the original Ginna Station design. The potential failure of the SI Block/Unblock Switch rendering the automatic actuation of SI from low pressurizer pressure and low steamline pressure inoperable is considered a condition that alone could have prevented the immediate fulfillment of a safety function needed to mitigate the consequences of an accident.

An assessment was performed considering both the safety consequences and implications of this event with the following results and conclusions:

PORC determined there were no,immediate operational or adverse safety consequences due to the potential failure of the SI Block/Unblock Switch because:

0 Westinghouse has stated that the probability of a SI Block/Unblock Switch failure is very low (approximately 10 to 10" /yr).

Immediate action step 4 (performed from memory) of Emergency Operating Procedure E>>O, Reactor Trip or Safety In)ectionP directs the operator to check parameters for SI actuation rather than rely on automatic, actuation features. Manual actuation of SI and containment isolation is required if parameters fall below the auto SI actuation -

setpoints.

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e vm oaaeoW SIIC Ame ~ 5 I IITI o s o o o Containment pressure of 4 psig will automatically actuate SI independent of the SI Block/Unblock Switch conf igurat ion. SI on HI Containment Pressure is used as a backup to the low pressurizer pressure and low steamline pressure SI actuation.

o If the SI signal is blocked during depressurization, a bistable light will alert the operator of the blocked status.

o Initial inspection of the plunger position of the verified that the switch SI Block/Unblock Switch contacts were (and continue to be) in the proper position.

Based on the above, it can be concluded that the health and safety will be assured at all times.

public's Due to the date of occurrence, the condition is technically not 10 CFR 21 reportable. However, due to the potential significance of the failure scenario, Rochester Gas and Electric is submitting voluntary notification.

V. CORRECTIVE ACTION A. ACTION TAKEN AS A RESULT OF THE EVENT:

0 Knowledgeable personnel inspected the plunger position of the SI Block/Unblock Switch and verified that the switch contacts were in the proper position.

0 Operating Procedure 0-1.1 (Plant Heatup From Cold Shutdown to Hot Shutdown) was changed to add the following note and check-off to step 5.11.6:

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OOCKET <<UIME<< 1jl LE<< HVMCE<<101 SIOVI<<TEAL ItgV<<IOR NVM 1 U R.E. Ginna Nuclear Power Plant: o s o o o 2 4 4 8 9 0 1 6 0207 ap 09 TEXT 11' <<wee <<neeeC ~ aaeaoeV <<AC Ann ~'el l ill NOTE Prior to placing the SI Block/Unblock Switch to the normal position, station an operator inside the MCB in direct observation of the SI Block/Unblock Switch, to observe that both plunger tips are recessed inward after the switch is placed to normal position.

Block switch plunger tips position inward o An RG&E operator aid tag was placed on the MCB adjacent to the SI Block/Unblock Switch denoting the note from 0-1.1.

o An RG&E operator aid tag was also placed inside the MCB adjacent to the rear of the SI Block/Un-block Switch stating the following: This is the switch we verify that the plunger's tips are recessed inward when the switch is placed to normal (labeled LAK).

o A spare switch of similar design has been placed in the Control Room for the purpose of training the operators to recognize the differences in plunger position.

B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:

0 During the 1991 Refueling Outage, subject to

'ecpxipment availability, a design change and modification will be made to separate the Block Switches for each SI train.

review of the application of similar switches 0 A will be performed, to determine generic implications.

if there are 0 Due to the delay between "discovery. date" and

<<reportability date", improvements will be made =in the RG&E internal review process, including means for formal notification of Ginna Station of potentially reportable issues.

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~ t V toVIJ SA R.E. Ginna Nuclear Power Plant o'o 2 489 0 1 6 0 2 0- Sos 09 raXr IA <<eee Mace e ~. we eeeee>>vr +AC Sa ~ SI I ITI o 5 o o Westinghouse will be notified of this isolated occurrence, in which Ginna Station was not notified by Westinghouse.

The review of the application of similar switches was performed. The results of this review identified six manual reset switches that could result in disabling both safeguards trains if a switch failed in the reset position. These switches are as follows:

Safety Injection Reset Containment Isolation Reset Containment Spray Reset Containment Ventilation Isolation Reset Feehwater Isolation - Loop A Reset Feedwater Isolation - Loop B Reset 0 The six manual switches were verified (using plunger position) to be in the proper position and functioning properly.

0 A design change will be made either to add separate independent reset switches for each safeguards train, or to rewire/reconfigure the between existing switches to provide adequate separation SI trains.

VI. ADDI ONAL INFORMATION A. FAILED COMPONENTS:

None .identified.

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~ cUM NUM CA R.E. Ginna Nuclear Power Plant:. o 5 o o o 24 489 0 1 6 0 2 09 DFO 9 TEXT III'C<<CC NCCCC N CCCCNCd. ~ CNCCCCW HAC ACCCC ~ Cl I ITI B. PREVIOUS LERs ON SIMILAR EVENTS:

A similar LER event historical searchdocumentation was conducted of with the following results: No similar LER events with the same root cause at Ginna Station could be identified.

C. SPECIAL COMMENTS:

Information regarding this event and subsequent informa-tion was placed on Nuclear Network on June 6, 1990.

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