ML19290E995

Forwards LER 80-009/01T-0

ML19290E995
Person / Time
Site:	Fort Saint Vrain
Issue date:	03/10/1980
From:	Warembourg D PUBLIC SERVICE CO. OF COLORADO
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19290E996	List: ML19290E995 ML19290E998
References
P-80044, NUDOCS 8003170426
Download: ML19290E995 (13)

Text

.

7 -

public Service Company ? Cc3 cede 16805 Weld County Road 191/2, Platteville, Colorado 80651 March 10, 19s0 Fort S t. Vrain Unit No. 1 P-80044 Mr. Karl V. Seyfrit, Director Nuclear Regulatory Cot:: mission Region IV Office of Inspection and Enforcement 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76012

Reference:

Facility Operating License No. DPR-34 Docket No: 50-267

Dear Mr. Seyfrit:

Enclosed please find a copy of Reportable Occurrence Report No. 50-267/

80-09, Pinal, sub:::itted per the requirements of Technical Specification AC 7.5.2(a)9.

Also, plesse find enclosed one copy of the Licensee Event Report for Reportable Occurrence Report No. 50-267/80-09.

Very truly yours,

$ WR.4.6 Don Warembourg

, Manager, Nuclear Production DV/c1s Enclosure ec: Director, MIPC oY so 3, (

.> 0 0317 0 g'g-

REPORT DATE: March 10,1980 REPORTABLE OCCURRENCE 80-09 ISSUE O OCCURRENCE DATE: Feb ruary 25, 1980 Page 1 of 12 FORT ST VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO 16805 WELD COUNTY ROAD 19 1/ 4 PLATTEVILLE, COLORADO 80651 REPORT NO. 50-267/ 80-09 /01-T-0 FINAL IDENTIFICATION OF OCCURRENCE:

While the plant was in a shutdown condition, a test was performed to evalu-ate the fixed low feedwater flow, fixed circulator speed high, and programmed circulator speed /feedwater flow trips. As a result, it was determined that the design of the bistable trip module when used with the module test unit for calibration of process trip (bistable) functions of the plant protective system induced a calibration off-set which could have possibly allowed the trips to occur outside Technical Specification limits.

This is reportable per Fort St. Vrain Technical Specification AC 7.5.2(a)9.

CONDITIONS PRIOR TO OCCURRENCE:

Steady State Power _ Routine Shutdown Hot Shutdown Routine Load Change X Cold Shutdown Other (specify)

Refueling Shutdown Routine Startup The major plant parameters at the time of the event were as follows:

Reactor Power Wth Electrical Power N/A We Secondary Coolant Pressure N/A psig Secondary Coolant Temperature N/A *F Secondary Coolant Flow N/A #/hr.

Primary Coolant Pressure 83 psia

REPORTABLE OCCURRENCE 80-09 ISSUE O Page 2 of 12 CONDITIONS PRIOR TO OCCURRENCE: (Cont' d)

Primary Coolant Core Inlet Temperature N/A 'F Primary Coolant Core Outlet Temperature 212 *F Primary Coolant Flow N/A f/hr.

Circulator lA N/A RPM Circulator 13 N/A RPM Circulator 1C N/A RPM Circulator ID N/A RPM DESCRIPTION OF OCCURRENCE:

Test T-137 was performed to collect data on the plant protective system (PPS),

ff,xed low feedwater flow, fixed circulator speed high, and programmed circu-lator speed /feedwater flow trips. The test was conducted while the reactor was in a shutdown condition and the circulator under test was shutdown.

Channel A, one of the three channels of Loop I, was selected for obtaining "as found" data, calibrating the instrumentation and obtaining "as lef t" data. When the data were evaluated, it was found that a calibration off-set existed in the process trip (bistable) modules, model PT-3D and model PT-3S. This was determined to be due to the signal from the module test unit (MU) not using the same input point as the measured signal.

APPARENT CAUSE OF OCCURRENCE:

I Design Unusual Service Condition, Including Environment Manufacture Component Failure Installation / Cons t. Other (specify)

Operator Procedure Test signal from module test unit (EU) not using the same input path as the measured signal to the bistable trip was the cauw.

REPORTABLE OCCURRENCE 80-09 ISSUE O Page 3 of 12 ANALYSIS OF OCCURRENCE:

The circulator speed and feedwater flow instrument channels are shown schematically on Figure 1.

The signal from the circulato speed probe 01 1 cr a =1etea to a eveea modifier (SM) pre-amplifier 2 which is a pulse output and from the SM to a speed transmitter (ST) w ere the signal is c reed f rom a pulse a a voltage signal. The output of the a=plifier is smi ted the s eed switches low (SSL), speed switches high . H), , 5 , ,

and 7 and to the feedwater setpoint programmer 8 .as t e measured s g-nal. e measured signal is coc: pared to fixed setpoints which, depending on the function required, either provide a permissive to set the circulator br 9 , or to initiate a circul r trip on high water turbine speed or high steam turbine speed .

Circulator overspeed is an indication of speed control or other failure necessitating rapid shutdown of the circulator. The speed sensing system response and trip setting are chosen so that under the maximum overspeed situation possible (loss of restraining torque), the circulator will remain within design capabilities.

Th feedwater flow differential pressure across he flow element (FE) is sensed by the f transmitter (Fr), , and transmitted to th flow modifier (FM), . The output of t FM is tr mit ted the setpoint programmers and flow switches low (FSL) 16 and 1/

as the measured signal. e measured signal is co red to a fixed set-point to provide a fixed low feedwater flow trip, 8 , to avoid unstable steam generator flow conditions.

The SSL 07 is grost ==ea hF che feeaw ter f1ow distaste seevoint prest ==er

h. Low circulator speed indicates speed control or equipment failure necessitating a circulator shutdown. Too low a circulator speed causes a mismatch between thermal power input and heat removal (feedwater flow) in a steam generator. This may result in flooding of the superheater section of a steam generator.

The P3L 16 is programaed by the circulator speed bistable setpoint prog-rammer 8 . Low feedwater flow indicates control or equipment failures and res ts in an increase in superheater outlet temperature and/or unstable flow conditions in the steam generator. As a circulator speed controller failure can lead to higher than normal circulator speeds and a corresponding increase in superheater steam outlet temperature, a programmed low-feedvater-flow trip prevents prolonged operation in the region of speed versus flow which may cause excessive superheat steam tec:peratures.

r e { 5o 9 y8 t

a $ g w $g D 5N d

e ,

p e .

l o

o

@fo l

w T

E L

)

C d

r A B n e d A R) a E

p Q e x

T%

E0 S2 T

S @ O3 T

AF B L e i IB L0 Z n F U s Z O ' r

< C2i l

) 0 N 7lil llgllld R(l u e n

I CtC a iR n E

ORI TTC a

' h

( b, W

O" L

h L B

A T

S RE)

ON3 TI c

r o

F I

ABF f S LR0 u

9F yS UU gG  : M "

r CT2i l gE oL

? ' R IM (l

u a c

7I. N -

T INH)

TS OIT R

O T @

CAPC EIR OTRI TSTC i

p y

] ~  : PWI AG t

T(H LN (

~ - E l UI SRL CT

~ t - E RA s EMW IR l L LMO CE e y Il illlg!lI T

BAL AR H

S I P

O R

E F

n n

TGH N

E SOG IRI S

N a M BPH A h U H S R c LR S R T ATK O t CSC ONA T

AG n LIR h' LN UI CT RA E e

m u

r IR t CE L P B s H 2 A T

RE)

ON3 n

F S TI i

I ABF TH NT) ' hB LR0 UU r CT2f w

o IIS OWT P(I ' (S ' RIM (l U

l f

T ESl SRL E

H H P

R E

G CAPC EIR OTRI TSTC r

e EMW LMO BAL gT00,A0 L

G A RE) d t

a w

AR T T ON3 TGH EI SI T1 e SOG Sl A8F e tRI 8PH

~ pS r LR0 UU CT2i f

R E

I M

' (S , R IM CAPC (l

u d

n a

F I

L P

R E @ EIR OTRI TSTC d D

E DE EB P

M gT0 A0 L

B A

T RE) e e

p E

P EO PR A.

E ,

T

[

8, S ON3 TI s S R [o ,  : I ASF SP P , <

S LR0 r R

O E O H T h UU

, CT2i o

' (S T , S '

, R t A

S E

S IR (l

u a L

C U RO N

G CEPC TIR OARI l

u c

OI H

RI C h TT AA LR UT CE gT P AR T

E B

L TWTC

)

r i

C RN LU

}U A

T R 3

IE 7 S O F CP  : l T 0 4

') O

, CA A

LY2

, UR(

i

' (5 RIMl ILEu

@ CI XSR OUYI TC TASC nQg ~

REPORTABLE OCCURRENCE 80-09 ISSUE O Page 5 of 12 ANALYSIS OF OCCURRENCE: (Cont' d)

In accordance with SR 5.4.1, Reactor Protective System and Other Critical Instrumentation and Control Checks, Calibrations, and Tests, Table 5.4-3, Channel Descriptions 1 and 2, a monthly test is performed on the circulator speed-steam and water and the feedwater flow instrumentation. The test, Method b of the table, specifies an internal test signal to verify trip setting and indicators. The internal test signal is from a module test unit (MIU) module one of which is installed in each bay (channel) of the Plant Protective System (PPS) .

Testing is accomplished by injecting a signal at a point in the analog portion of the measurement channel prior to the bistable and noting the trip point against the input value as displayed on the meter indicator for the channel.

When the data from the circulator speed /feedwater flow calibration test, T-137, were analyzed, it was found that a calibration off-set existed in the process trip (bistable) modules. The off-set was determined to be due to the test signal from the MTU not using the sa=e input point as the measured signal. Refer to Figure 2.

MIU Input 0 to IV Test ks S1

% > Output Process aput Op erate R1 O to 10V YQ ~p FIGURE 2 During normal operation, the r. ode switch, S1, on the process trip (bistable) is in the OPERATE position and a O to 10 volt signal proportional to the measured process is transmitted through a 10 to 1 voltage divider network, R1, to an operational amplifier, A1, and also through a variable resistor,

REPORTABLE OCCURRENCE 80-09 ISSUE O Page 6 of 12 ANALYSIS OF 0CCURRENCE: (Cont ' d)

R2, to the module meter indicator, M. When the input reaches a predetermined s etp oint, the bistable trips, the output of Al changes state, and the required protective or permissive action is initiated to a 2 of 3 logic circuit.

During testing, S1 is placed in the TEST position and a 0 to 1 volt signal which allows simulating variations in the measured process is transmitted from the MTU to Al, R2, and M to verify or to set the bistable trip point.

Using the MrU causes a calibration off-set of the bistable due to R1, R2, and M. The off-set is variable depending on the position (resistance value) of R2, and is greater at some points than the allowable tclerances derived from the instrument error analysis used for establishing setpoints which are conservative based on the Technical Specification limits of LCO 4.4.1 for circulator speed and feedvater flow calibration.

As a result of the calibration off-set discovered in T-137, scheduled and special surveillance testing was performed on all bistable trip modules, and the results were evaluated to determine the scope of the problem.

Evaluation determined that of the forty-three (43)model PT-3D bistable trips in the plant protective system, thirteen (13)are not affected by the off-set, and of the thirty-nine (39) model PT-35 bistable trips in the plant protective system, twenty-one (21) were not affected by the off-set. Since the tesc sigm'1 from the MTU does not go directly to the bistable but to an amplifier module in the plant protective system, both the measured signal and the test signal to the bistables use the same in-put point, and no off-set is encountered.

The PT-3D bistables which were not affected are for the primary coolant pressure scram. The PT-3S bistables which were not affected are for the high reheat steam temperature scram, reactor building high teuperature scram, and low superheat header temperature which is a loop shutdown para-meter.

Table 1 listo the thirty (30) PT-3D bistables which were affected and the function of each. -

NOTE: The D on the rodel number defines a double, i.e. two b1 stables, so that SSH-21XXX and SSH-21XXX-1 are in one module and SSL-21XXX-1 and SSL-21XXX-2 are in one module .1nd FSL-22XX-1 and FSL-22XX-2 are in one module.

REPORTABLE OCCURRENCE 80-09 ISSUE O Page 7 of 12 ANALYSIS OF OCCURRENCE: (Cont' d)

Table 2 lists the eighteen PT-3S bistables which were affected and the function of each.

TABLE 1 PT-3D BISTABLES Instrument No. Function SSH-21161 Circulator 1A Steam Turbine Overspeed (Channel A)

SSH-21161-1 Circulator 1A Water Turbine Overspeed (Channel A)

SSL-21161-1 Circulator 1A Program Speed Low (Channel A)

SSL-21161-2 Circulator 1A Fixed Speed Low (Channel A)

SSH-21162 Circulator 1C Steam Turbine Overspeed (Channel A)

SSH-2H6 2-1 Cir tor 1C Water Turbine Overspeed (Channel A)

SSL-21162-1 Cir.. :or 1C Program Speed Low (Channel A)

SSL-21162-2 Ciretaator 1C Fixed Speed Low (Channel A)

SSH-21163 Circulator 1A Steam Turbine Overspeed (Channel B)

SSH-2H63-1 Circulgtor 1A Water Turbine Overspeed (Channel B)

SSL-21163-1 Circulator 1A Program Speed Low (Channel B)

SSL-21163-2 Circulator lA Fixed Speed Low (Channel B)

SSH-21164 Circulator 1C Steam Turbine Overspeed (Channel B)

SSH-2n64-1 Circulator 1C Water Turbine Overspeed (Channel B)

SSL-21164-1 Circulator 1C Program Speed Low (Channel B)

SSL-2n64-2 Circulator 1C Fixed Speed Low (Channel B)

SSH-21165 Circulator lA Steam Turbine Overspeed (Channel C)

SSH-21165-1 Circulator 1A Water Turbine Overspeed (Channel C)

SSL-21165-1 Circulator 1A Program Speed Low (Channel C)

SSL-2n65-2 Circulator 1A Fixed Speed Low (Channel C)

SSH-21166 Circulator 1C Steam Turbine Overspeed (Channel C)

SSH-21166-1 Circulator 1C Water Turbine Overspeed (Channel C)

SSL-21166-1 Circulator 1C Program Speed Low (Channel C)

SSL-21166-2 Circulator 1C Fixed Speed Low (Channel C)

SSH-2H67 Circulator 1B Steam Turbine Overspeed (Channel A)

SSH-2H67-1 Circulator 13 Water Turbine Overspeed (Channel A)

SSL-2H6 7-1 Circulator 1B Program Speed Low (Channel A)

SSL-21167-2 Circulator 13 Fixed Speed Low (Channel A)

SSH-21168 Circulator ID Steam Turbine Overspeed (Channel A)

SSH-21168-1 Circulator ID Water Turbine Overspeed (Channel A)

SSL-2n68-1 Circulator ID Program Speed Low (Channel A)

SSL-21168-2 Circulator ID Fixed Speed Low (Channel A)

SSH-2H69 Circulator 1B Steam Turbine Overspeed (Channel B)

SSH-21169-1 Circulator 1B Water Turbine Overspeed (Channel B)

SSL-21169-1 Circulator 1B Program Speed Low (Channel B)

REPORTABLE OCCURRENCE 80-09 ISSUE O Page 8 of 12 ANALYSIS OF 0CCURRENCE: (Con t' d)

TABLE 1 (Cont'd)

PT-3D BISTABLES Instrument No. Function SsL-21169-2 Circulator 1B Fixed Speed Low (Channel B)

SSH-21170 circulator 1D Steam Turbine Overspeed (Channel B)

SSH-21170-1 Circulator ID Water Turbine Overspeed (Channel B)

SSL-21170-1 Circulator ID Program Speed Low (Channel B)

SSL-21170-2 Circulator ID Fixed Speed Low (Channel B)

SSH-21171 Circulator 1B Steam Turbine Overspeed (Channel C)

SSH-21171-1 Circulator 1B Water Turbinc Overspeed (Channel C)

SSL-21171-1 Circulator 13 Program Speed Low (Channel C)

SSL-21171-2 Circulator 1B Fixed Speed Low (Channel C)

SSE-21172 Circulator ID Steam Turbine Overspeed (Channel C)

SSH-2112-1 Circulator 1D Water Turbine Overspeed (Channel C)

SSL-21172-1 Circulator ID Program Speed Low (Channel C)

SSL-21172-2 Circulator ID Fixed Speed Low (Channel C)

FSL-2209-1 Loop I Feedwater Flow . Fixed Low (Channel A)

FS L-2209-2 Program Low Feedwater Trig (Channel A)

FSL-2210-1 Loop II Feedwater Flow Fixed Low (Channe* 1)

E L-2210-2 Program Low Feedwater Trip (Channel A)

FSL-2211-1 Loop I Feedwater Flow Fixed Low (Channel B)

FSL-2211-2 Program Low Feedwater Trip (Channel B)

FS L-2212-1 Loop II Feedwater Flow Fixed Low (Channel B)

FSL-2212-2 Program low Feedwater Trip (Channel B)

FSL-2213-1 Loop I Feedvater Flow Fixed Low (Channel C)

FS L-2213-2 Program Low Feedwater Trip (Channel C)

FSL-2214-1 Loop II Feedwater Flow Fixed Low (Channel C)

FS L-221.' -2 Program low Feedwater Trip (Channel C)

TABLE 2, PT-3S BISTABLES Instrument No. Function ISH-93454A Pipe Rupture North Wall XSH-93454B Pipe Rupture North Wall ISH-93454C Pipe Rupture North Wall XSE-93455A Pipe Rupture North Wall ISR-93455B Pipe Rupture North Wall ISE-93455C Pipe Rupture North Wall XSH-93456A Pipe Rupture South Wall

REPORTABLE OCCURRENCE 80-09 ISSUE O Fage 9 of 12 ANALYSIS OF OCCURRENCE: (Cont' d)

TABLE 2 (Cont'd)

PT-3S BISTABLES Instrument No. Function XSH-93456B Pipe Rupture South Wall XSH-93456C Pipe Rupture South Wall XSH-93457A Pipe Rupture South Wall XSH-934573 Pipe Rupture South Wall XSH-93457C Pipe Rupture South Wall XSH-93470A Pipe Rupture Under PCRV XSH-93470B Pipe Ruptdre Under PCRV XSH-03470C Pipe Rupture Under PCRV XSH-93471A Pipe Rupture Under PCRV XSH-934713 Pipe Rupture Under PCRV XSH-93471C Pipe Rupture Under PCRV Testing of the affected bistables listed in Table 1 disclosed that a total of nine (9) would have tripped outside the limits of LCO 4.4.1, Table 4.4-3, Items No.1, No. 6, and No. 9. Those bistables are listed below in Tables 3, 4, and 5 respectively.

TABLE 3 Item No.1 FUNCTIONAL UNIT: Circulator Speed - Low LCO TRIP SETTING: 1910 rpm Below Normal as Programmed by W flow Instrument Circulator "As Found" Trip (rpm)

SSL-21161-1 1A 1940 SSL-21162-1 1C 19 25 SSL-21163-1 1A 1940 SSL-21165-1 1A 19 25 SS L-2116 7-1 la 1940 SSL-21170-1 1D 1925 SSL-21172-1 1D 1925

REPORTABLE OCCURRENCE 80-09 ISSUE O Page 10 of 12 MIALYSIS OF OCCURRENCE : (Cont' d)

TABLE 4 Item No. 6 FTICTIONAL ETIT: Circulator Speed - High Steam LCO TRIP SETTING: < 11,000 rpm Instrument Circulator "As Found" Trip (rpm)

SSH-21170 1D 11,310 TABLE 5 Item No. 9 FUNCTIONAL UNIT: Circulator Speed - High Water LCO TRIP SETTING: < 8,800 rpm Instrument Circulator "As Found" Trio (rpm)

SSH-21170-1 1D 8,910 Although the trip settings were found to be less conservative than those established by the Technical Specifications, they did not prevent the ful -

fillment of the functional requirements of the affected systems.

Testing of the affected bistables listed in Table 2 disclosed that all trips were within LCO 4.4.1, Table 4.4-2 limits.

CORRECTIVE ACTION:

1. Surveillance testing was performed and the results evaluated to determine which bistable trips were affected.

2. As found trip points were determined and :: hose bistables listed in Tables 3, 4, and 5 which were not in tolerance were recalibrated to the proper setpoints.

3. Recalibration was accomplished by use of a modified MTU and e.cender board which will also be used for testing until permanent change is implemented. Refer back to Figure 2. The modified MrU and extender board use the Process Input line and a 0 to 10V MrU signal so that S1 remains in the OPERATE position during test. In this manner, no cali-bratien off-set exists, and compliance with test, Method b, of Table 5.4-3 of SR 5.4.1 is maintained.

REPORTABLE OCCURRENCE 80-09 ISSUE O Page 11 of 12 CORRECIIVE ACIION: (Con t' d)

4. Change Notices have been initiated to modify affected bistable modules and bay wiring to utilize the same input point for both test and process signals.

No further corrective action is anticipated or required.

FAILURE DATA /SIMILAR REFORTED OCCURRENCES:

N/A PROGRAMMATIC IMPACT:

N/A CODE IMPACT:

N/A

REPORTABLE OCCURRENCE 80-09 ISSUE O Page 12 of 12 Prepared By:

Mic ael J. Ferris ( l Tech (itical Services htgineer Reviewed By: _. .

. W Gahn

/ Technical Services Supervisor Reviewed By:

Frank M. Mathie Operations Manager Approved By: - MLu4 Don Warerbourg

[

Manager, Nuclear Production

.