ML20086E388

AO 75-01:on 750108,LPCI Low Reactor Pressure Permissive Switches on Instrument 2-3-52D Actuated High.Caused by Improper Calibr Technique.Switch Reset

ML20086E388
Person / Time
Site:	Vermont Yankee
Issue date:	01/09/1975
From:	Riley B VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
AO-75-01, AO-75-1, VYV-3710, NUDOCS 8312070079
Download: ML20086E388 (4)

Text

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D O g VERMONT YANKEE NUCLE AR POWER CORPOR ATION Sc%/cNTY GCVCN -3Rovc STRccT

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RUTLA D, VE.lO!ONT. 03701 VYV-3510 [, [h ,

VERNON, VERMONT oS354 January 9, 1975 Director (g .

Directorate of Regulatory Operations, Region 1 y United States Atomic Energy Commission 631 Park Avenue King of Prussia, Pennsylvania 19406

REFERENCE:

Operating License DPR-28 Docket No. 50-271 Abnormal Occurrence No. A0-75-01 (24 llour Report) 4

Dear Sir:

As defined by Technical Specifications for the Vermont Yankee Nuclear Pcwer Station, Section 6.7, we are reporting the following Abnormal occurrence as A0-75-01 and confirming our telephone conversation with your office.

At approximately 1000 on January 8, 1975, while performing a routine surveillance test, itwasdiscoveredthatfoneoftheLowPressureCoolant Injection Systcc (LPCI) Low Reactor Fressure permissive switches on instrument 2-3-52D actuated at 382 psigt Table 3.2.1 of the Technical Specifications requires that :the trip level setting of this instrument be set at 300 1 p 1 350 psig. Failure of this suite,h to actuate within the specified tolerance resulted in fewer operable instrument channels per trip system than that required by Table 3.2.1 of the Technical Specifications. These pressure permissive switches allow the operation of the LPCI injection and recirculation discharge valves in the event of an Emergency Core Cooling System actuation.

The switch was immediately reset to a trip level setting of 340 psig which precluded the necessity of performing the action'specified'in Note 2 of Tabic 3.2.1 of the Technical Specifications. The plant was operating at full power at the time of the discovery of this occurrence.

.8312070079 750109 -

PDR ADOCK 05000271 -

S PDR , a Bradford W. Riley--

Plant Superintendent WPM /kbd -

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VCRMONT YANKCtf NUCLEAR POWCR COM*ORATICe.

Directorate of Regulatory Op rations January 9, 1975 ,

Page 2 The plant was operating at full power for the duration of this incident with an average stack release rate of approximately 325 pC1/sec.

Very truly yours, bb. ~

BradfordW.Rileyb Plant Superintendent WPM /kbd L

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ABNORMAL OCCURRENCE REPORT t' \ ~*J" h,n[

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Report Number: 50-271/75-01 2 L .,'L u,,>

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9 Report Date: January 15, 1975 l'J. G,'y t w N f m..UU;j

.n Occurrence Date: January 8, 1975 k Lbh[f V,s Vermont Yankee, Vernon, Vermont l I hD Facility:

Identificaticn of Occurrence Failure of one of the Low Pressure Coolant Injection System (LPCI)

Low Reactor Pressure permiss'ive switches to actuate within the specified tolerance of the Technical Specifications. .

Conditions Prior to Occurrence .

Steady state operation at full power.

Description of Occurrence At approximately 1000 on January 8, 1975, while performing a routine surveillance test, it was discovered that one of the Low Pressure Coolant Injection System (LPCI) Low Reactor Pressure permissive switches on instrument 2-3-52D actuated at 382 psig. Tabic 3.2.1 of the Technical 0;;ccificatienc requira= thne the trip level setting of this instrument be set at 300 5 p 1 350 psig. The switch was immediately reset to a trip level setting of 340 psig which precluded the necessity of performing the. action specified in Note 2 of Table 3.2.1 of the Technical Specifications.

Desicnation of Apparent Cause of Occurrence It has been determined that the cause of this occurrence was due to an irprcper calibration technique that was used during the calibration of the which LPCI Low Reactor Pressure permissive switch on the 2-3-52D instrument, was performed on December 5, 1974. This instrument has a locking device on the setpoint adjustment of tne switch, which can change the setpoint when secured. It is for this reason that maintenance personnel are instructed to determine that the setpoint has not deviated after making a setpoint .

adjustment and securing the locking device. At the last calibration of the pressure switch in t.he 2-3-52D instrument, the maintenance personnel involved failed to foll'ow the' proper' tech'nique by noti reche'cking the setpoint after securing the setpoint adjustment locking device.

Analysis of Occurrence ,

The LPCI Low Reactor Pressure switch on instrument 2-3-52D is one of the four reactor low pressure logic inputs to the low pressure permissive logic. This logic allows operation of the LPCI injection and~ recirculation discharge valves in the event of an Emergency Core Cooling System actuation.

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The low pressure permissive logic is made up of two parallel logic pairs.

This arrangenent provides for any type of failure in one of the two logic inputs in each of the logic pairs without preventing the initiation of the low pressure permissive. The fact that the pressure switch would trip at 382 psig, instead of the limits of 300 < p < 350 as defined in the Technical Specifications, would not have prevented satisfactory LPCI System initiation if required. Another function of the LPCl Low Reactor Pressure permissive switch, when the trip point is reached, enables the Control Room Operator a permissive to open in the same loop both injection valves RiiR-25 and RilR-27.

Even with the LPCI Low Reactor Pressure permissive switch outside the tolerance specified in the Technical Specifications, no overpressurization of the LPCI Systen piping would have occurred. This occurrence presented no adverse potential consequences from the standpoint of public health and safety.

Corrective Action The innediate corrective action to correct the abnormal occurrence was to calibrate the Low Reactor Pressure permissive switch on instrument 2-3-52D to the setpoint specified in the Technical Specifications. The applicable plant procedures that provide for the calibration of instruments that have the setpoint adjustment locking device will be revised to include verification of setpoint af ter securing the locking device and will prevent this and sinilar occurrences in the future.

Failure Data Not Applicabic

. s s Bradford W. Riley '

Plant Superintenden HE/kbd G

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