ML19340B245

LER 80-084/01T-0:on 801002,Westinghouse Notified Util That High Steam Line Flow Setpoints Specified in PLS Document Are Less Conservative than Tech Specs Require.Caused by Calculation Assumptions Not Reflecting Installation

ML19340B245
Person / Time
Site:	North Anna
Issue date:	10/16/1980
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19340B236	List: ML19340B235 ML19340B245
References
LER-80-084-01T, LER-80-84-1T, NUDOCS 8010210694
Download: ML19340B245 (3)

Text

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~U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT CO: %0L BLOCK / / / / / / / (1) (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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/V/A/N/A/S/1/ (2)- /0/0/-/0/0/0/0/0/-/0/0/ (3) /4/1/1/1/1 (4) / / / (5)

LICENSEE CODE LICENSE NUMBER LICENSE TYPE CAT

/0/1/ /X/ (6) /0/5/0/0/0/3/3/8/ (7) /1/0/0/2/8/0/ (8) /1/o/1/6/8/0/ (9)

DOCKET NUMBER EVENT DATE REPORT DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES (10) l /0/2/ / On October 2, 1980, Westinghouse notified Vepco that high steam line flow set- /

l . /0/3/ / points specified in the PLS Document were in error. The setpoints were less /

, /0/4/ ./ conservative than those established by the Technical Specifications. This event /

/0/5/ / is reportable pursuant to T.S. 6.9.1.8 b. The error was common to both Unit /

/0/6/ / 1 and 2. The public health and safety were not affected. /

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/0/8/ / /

SYSTEM CAUSE CAUSE COMP. VALVE CODE CODE SUBCODE COMPONENT CODE SUBCODE SUBCODE

/0/9/ /I/B/ (11) g[ (12) [Z/_ (13) /I/N/S/T/R/U/ (14) [Q/ (15) /Z/ (16)

SEQUENTIAL OCCURRENCE REPORT REVISION LER/R0 EVENT YEAR REPORT NO. CODE TYPE NO.

l (17) REPORT l

NUMBER /8/0/ /-f_ /0/8/4/ /\/ /0/1/ g[ /-/ [0/

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ACTION FUTURE EFFECT SHUTDOWN ATTACHMENT NPRD-4 PRIME COMP. COMPONENT TAKEN ACTION ON PLANT METHOD HOURS SUBMITTED FORM SUB. SUPPLIER MANUFACTURER

[EL (18) /Z/ (19) [Z[(20) /Z/ (21) /0/0/0/0/ (22) g/ (23) /N/ (24) /N/ (25) /W/1/2/0/ (26)

CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (27) l

/1/0/ / Calculational assumptions used in determining the PLS flow venturi differential /

/1/1/ / pressure values corresponding to the flow setpoints specified in the T.S. do /

/1/2/ / not accurately represent instrumentation installed in North Anna Units 1 and 2./

'/1/3/ / The setpoints were recalculated and adjusted to their correct values. No /

/1/4/ / further-actions are required. /

FACILITY METHOD OF STATUS  % POWER OTHER STATUS DISCOVERY DISCOVERY DESCRIPTION (32)

/1/5/ /E/ (28) /1/0/0/ (29) / NA / (30) /D/ (31) /NSSS NOTIFICATIGN /

ACTIVITY CONTENT RELEASED 0F RELEASE AMOUNT OF ACTIVITY (35) LOCATION OF RELEASE (36)

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PERSONNEL EXPOSURES i ' NUMBER . TYPE . DESCRIPTION (39)

/1/7/ ./0/0/0/ (37) [Z[ (38) / NA /

l PERSONNEL INJURIES NUMBER . DESCRIPTION (41).

/1/8/ -/0/0/0/ (40) / NA /

LOSS OF OR TYPE- DAMAGE TO DESCRIPTION FACILITY-(43)

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PUBLICITY ISSUED DESCRIPTION (45) NRC USE ONLY r

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NAME OF PREPARER W. R. CARTWRIGHT PHONE (703) 894-5151

- 801021ogY.

1 a .,

Virginia Electric and Power Company North Anna Power Station, Unit 1

Attachment:

Page 1 of 2 Docket No. 50-338 Report No. LER 80-084/01T-0 Description of Event Steam flows for each steam generator are obtained by measuring the pressure differential between the throat of a venturi tube and a point upstream of the venturi tube. Currently full scale differential pressure indication (100%

Delta P) corresponds to 1687.4 inches of water and 5 million lb/hr (123.8%

full load flow). The Technical Specifications specify a high flow trip setpoint Delta P corresponding to 40% of full steam flow between 0 and 20% turbine load and then a Delta P increasing linearly to a Delta P corresponding to 110% of full steam flow at full turbine load. The allowable setpoint values are less than or equal to a Delta P corresponding to 44% of full steam flow between 0  ;

and 20% turbine load and then a Delta P increasing linearly to a Delta P '

corresponding te 111.5% of full steam flow at full turbine load. According to the Precautions, Limitations and Setpoint Document (PLS) provided by Westing-  ;

house Electric Corporation, 9% of full scale Delta P corresponds to 40% of l full steam flow and 84% of full scale Delta P corresponds to 110% of full l flow. 1 On October 2,1980, Westinghouse notified Vepco that the high steam flow setpoints specified in the PLS were in error and provided new setpoints in ,

their notification letter. Preliminary calculations by site personnel revealed '

that the new setpoints specified in the notification letter were also in error. The correct setpoints were determined by a subsequent engineering evaluation performed by Vepco and Westinghouse site personnel. The table below compares the PLS setpoints, the setpoints specified in the Westinghouse notification letter, the setpoints determined by preliminary calculations, and the correct setpoints determined by the, engineering evaluation.

l

% DELTA P SPAN j l

1

% RATED NOTIFICATION PRELIMINARY CORRECT STEAM FLOW PLS LETTER CALCULATION VALUE l

Setpoint Value 110.0 84.0 79.0 75.6 72.7 Allowable Value 111.5 - - -

74.8 Setpoint Value 40.0 9.0 8.4 7.4 7.4 Allowable Value 44.0 - - -

9.0 l

Since the setpoints specified in the PLS were nonconservative, this event  ;

is reportable pursuant to T.S. 6.9.1.8.b.

Probable Consequences of Occurrence l The nonconservative setpoints reduced the safety margin for a SI signal generated by.a high steam line flow coincident with low steam line pressure or_Lo-Lo Tavg. Protection against a steam line break accident was reduced.

Two other SI signals for steam line break protection were available; pressurizer low pressure and high differential pressure between steam lines. Since the safety analysis of the steam line break accident is relatively insensitive to l

l l

J

0 .o Page 2 of 2 Probable Consequences of Occurrence (cont.)-

the High Steam Line' Flow SI actuation setting and two other safety signals for SI actuation.in response to~a steam line break accident were available, the public health and safety were not affected.

Cause of Event Calculacional. assumptions used in determining the PLS flow venturi differ-ential pressure values corresponding to the flow setpointa specified in the T.S. do not accurately repres ent instrumentation installeu in North Anna Units 1 and 2.

Immediate Corrective Action The'setpoints for high steam line flow Delta P were lowered to the set-points determined by preliminary calcr.lations while a concurrent engineering evaluation was being performed. The setpoints were subsequently adjusted to

-the values determined by the engineering evaluation.

Scheduled Corrective Action No scheduled corrective actions are required.

Actions Taken to Prevent Reccurrence No actions to preJent recurrence are required.

Generic Implications The setpoint error was common to both Unit 1 and 2. A similar error was reported by Westinghouse at the Trojan Power Station. Westinghouse has reviewed all the PLS documents to determine if a similar error exists at other plants.

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