ML20217A821

Nonproprietary Rev 1 to WCAP-12633, RTD Bypass Elimination Licensing Rept for Turkey Point Units 3 & 4

ML20217A821
Person / Time
Site:	Turkey Point
Issue date:	11/30/1990
From:	Deblasio J, Sterrett C WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:
Shared Package
ML17348A745	List: ML20217A813 ML20217A821
References
WCAP-12633, WCAP-12633-R01, WCAP-12633-R1, NUDOCS 9011260190
Download: ML20217A821 (60)

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HESTINGHOUSE CLASS 3 HCAP-12638 Rev. 1 RTO BYPASS ELIMINATION LICENSING REPORT FOR TURKEY POINT UNITS 3 AND 4 y

l J. J. DEBLASIO m,

i C. F. STERRETT i.-

g-l NOVEMBER.:1990 1,

< 1 L

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Approved by:/

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,& # b Approved by:; W

.S. D. Ruppreyff Manager H. R. Rice, Manager 10perating_ Plant Licensing I Chemical Haste and.

Wl, Balance of Plant System l

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.. Westinghause Electric. Corporation Nuclear'and Advanced Technology Division P.O. Box 355 P

Pittsburgh, Pennsylvania 15230-0355

- Copyright e1990

..a 0895D:10/110290 l

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ACKNOWLEDGMENT The authors wish to recognize contributions by the following individuals:

H. G. Lyman I

h C. F. Clocca L. E. Erin H. J. Scherder L-R. A. Carlson 3,.

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TABLE OF CONTENTS E>

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Section Eggg List of Tables 111 List of Figures iv 1.0 Introduction 1.1 Historical Background I

a 1.2 ' Mechanical Modifications 2

1 1.3 Electrical Modifications 4

y j:

2.0 Testing 1

1 2.1. Response Time Test 11 j

2.2 Streaming; Test-11 3

y.

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5.0 Uncertainty Considerations

'3.1 Calorimetric Flow Measurement Uncertainty 14 3.2 THot Leg Temperature Streaming Uncertainty 14

'3.3; Control ~and Protection Function Uncertainties 16

~'

y L4.0 Safety Evaluation 4.1 Response, Time-36 q

4;2 ;RTD Uncertainty 36.

4.3: Non-LOCA Evaluation 37'

'4.4 LOCA Evaluation-38 l"

-H f 4.5. Instrumentation and Control -Safety Evaluation' 39

,7 4.6 Mechanical.> Safety Evaluation 48 N'

=4.7-Technical. Specification-Evaluation 50' s

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,p Section pag 1 5.0 Control System Evaluation 51 6.0 Conclusions 52 7.0 References 54 t

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P LIST OF TABLES Table Title Eigt 2.1-1 Response Time Pa'1 meters for RCS Temperature Measurement 13 i

i' 3.1-1 Rod Control System Accuracy 18 13.1-2 Flow Calorimetric Instrumentatica Uncertainties 19 3.1-3 Flow Calorimetric Sensitivities 20 3.1-4 Calorimetric RCS Flow Measurement Uncertainties 21 3.1-5 Cold Leg Elbow Tap Flow Uncertainty 23 i

3.1-6 Overtemperature_4T Reactor Trip 24 l

i 3.1-7 Overtemperature AT Gain Calculations 27 3.1-8 Overpower AT 28 3.1-9.

Overpower AT Gain Calculations 30 n

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-Loss of Flow

31' 3 ~.1 Pressurizer.Wate'r= Level - High-132' l

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-3.1 t i- ! Technical Specification Nodification 34' l!

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LIST OF FIGURES f121Ut litit Elg.t 1.2-1 Hot Leg RTD Scoop Modification for Fast-Response 8

RTD Installation 1.2-2 Hot and Cold Leg RTD Boss Installation for Fast-Response

• 9 RTD Installation 1.2-3 Cold Leg Pipe Nozzle _ Modification %st-Response 10 RTD Installation 4.5.2-1 Thermal Overtemperature and Overpower Digital Flow Diagram 43 4.5.2 Functional Logic Diagram (Tcold) 4#

-4.5.2-3 Functional Logic Diagram (Thot) 45

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1.0 INTRODUCTION

Hestinghouse Electric Corporation has been contracted by Florida Power and Light to remove the existing Resistance Temperature Detector (RTO) Bypass System and replace this hot leg and cold leg temperature m surement method with fast response thermowell mounted RTDs installed in the reactor coolant loop piping.

This r e rt is submitted for the purpose of supporting operation of Turkey Point Units 3 and 4 utilizing the new thermowell mounted RTDs as processed with the Eagle 21 process protecticii system.

1.1 HISTORICAL BACKGROUND Prior to 1968, PHR designs had been based un the assumption that the hot leg teinperature was uniform across the pipe. Therefore, placement of the temperature instruments was not considered to be a factor affecting the accuracy of the measurement.. The hot leg temperature was measured with direct immersion RTDs extending a short distance into the pipe at one location.

By the late 1960s, as a result of accumulated operating experience at several plants, the following problems associated with direct immerr on RTDs e

identified:

o Temperature streaming conditions; the incomplete mixing of the coolant leaving regions of the reactor core at different temperatures produces significant temperature gradients'within the pipe.

o The reactor coolant loops required cooling and draining before the RTDs could be replaced.

.The RTD~ bypass system was designed to resolve th'ese problems; however, operating plant experience has now shown that operation with the RTD bypass 1 oops has created it's own obstacles-such as:

o Plant shutdowns caused by excessive primary leakage through valves, flanges, etc., or by interruptions of bypass flow due to valve stem failure.

l l

. l 04200:10/102590' 1

o Increased radiation exposure due to maintenance on the bypass line and to crud traps which increase radiation exposure throughout the loop 4

compartments.

The proposed temperature measurement modification has been developed in response to both sets of problems encountered in the past.

Specifically; o

Removal of the bypass lines eliminates the components which have been a major source of plant outages as well as Occupational Radiation Exposure (ORE).

i o

Three thermowell mounted hot leg RTDs provide an average measurement (equivalent to the temperature measured by the bypass system) to account for temperature streaming, i

o Use of thermowells permits RTD replacement without draining the reactor coolant loops.

l Following is a detailed description of the effort required to p>>rform this modi fication.

-1.2 MECHANICAL H0DIFICATIONS

-The individual' loop temperature. signals required for input 'to the Reactor b

Control and Protection System will be.obtained using RTDs installed in each L

reactor coolant loop.

'l.2.1 Hot Lea

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a)- The hot leg temperature. measurement on each loop will be accomplished with-

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three-fast response, narrow range, dual element RTDs mounted in a

thermowells.

To accomplish the sampling function of the RTD bypass l'

' manifold system and minimize the need for additional hot. leg piping a

penetrations, the thermowells will be located within.he' existing 04200:10/102590 2

p e.

-~

RTD bypass manifolo

wherever possible. A hole will be made through the end of.'each scooD

) that water will flow in through the existing holes in the leadi...

e of the scoop, past the RTD, and out through the

.s new hole (Figure 1,2-1).

If plant interferences preclude the placement of a thermowell in a scoop, then the scoop will be capped and a new penetra-tion made to accommodate the thermowell (Figure 1.2-2).

These three RTDs will measure the hot leg temperature which is used to calculate the reactor coolant loop differential temperature (Delta T) and average temperature (T,yg).

b) This modification will not affect the dual element wide range RTD currently installed near t'he entrance of each steam generator.

This RTD

'will continue to provide the hot leg temperature used to monitor reactor coolant. temperature during startup, shutdown, and post accident conditions.

1.2.2 Cold Lea

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a) 'One fast response, narrow range, oal-element RTD will be located in each cold leg at the discharge of the reactor coolant pump (as replacements for the cold leg RTDs located in the bypass manifold).

This RTD will measure y

the' cold leg temperature which is used to calculate reactor coolant loop Delta T and T,yg., The existing ccid leg RTD bypass penetration nozzle will.be modified (Figure 1.2-3)'to accept'the RTD thermowell wherever possible.

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If structural interferences-preclude placement in the existing nozzle then-gg the nozzle will be capped and.a'new' penetration made to accommodate the t

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. b)'3This' modification will not affect the dual l element wide range RTD in each.

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This RTD will: continue.to provide the cold leg temperature used to v '

monitor reactor coolant temperature during startup, shutdown,.and post:

s N!i accident conditions.

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1.2.3 Crossover Leg 1

The RTD bypass manifold return line will ba capped at the nozzle on the crossover leg.

l 1.3 ELECTRICAL MODIFICATIONS 1.3.1 Control & Protection Sylig

-The present RCS loop temperature measurement system uses dedicated direct immersion RTDs in the bypass loop for the control and protection systems.

0 L

This was done largely to satisfy Section 4.7 of the IEEE S'.andard 179-1968 which applies to control and protection system interaction.

The new

.thermowell mounted RTDs will be used for both control and protection.

In j

. order to satisfy the requirements of Section 4.7 of IEEE 279-1971, the T,yg

.and. Delta T signals used in the control-grade logic will be input into a l,

median signal selector, which will select the signal which is between the

' highest'and' lowest values of.the three ioop inputs.

This will avoid any adverse plant response-that could be caused by a single random failure.

1

- Hith :the elimination of the RTD bypass manifold, three (3) hot leg RTD's are installed in thermowells mounted on the RCS pipe circumference approximately Lin the same vertical plane.

The temperatures read at these locations are is somewhat different. because of streaming effects.1 Thus,-the three temperatures.

are processed to produce an average temperature (Thave) for each hot leg.

EThe cold. leg temparature measurement on-each loop is accomplished with a h

. narrow range dual' element RTD installed in a thermowell..The thermcwell.is mounted either in.the. existing cold leg bypass nozzle or boss mounted in a new Lpenetration.. The cold leg sensors:are' inherently redundant in that~elther sensor can-adequately represent the cold leg temperature measurement.

Temperature. streaming in the cold leg is not a. concern due to the mix 1ig g

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action-of.the reactor. coolant: pump.

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04200:10/110190 4

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The process system used to calculate T and T is designated the l

have cold Temperature Averaging System (TAS).

The Temperature Averaging System (TAS) becomes part of the Thermal Overpower and Overtemperature Protection System I

because the TAS outputs (T and Tcold) replace the T and T have hot cold signals previously derived from the bypass manifold RTD.

L The Eagle 21 TAS system accepts RTD input signals representing two (2) cold leg and three (3) hot leg temperature measurements per loop.

The two cold leg temperatures are processed to produce an average cold leg temperature Tcold.

The three hot leg temperatures are processed to produce the average hot leg temperature T T

is then combined with T to produce have.

have cold 1

the loop average temperature (Tavg) and the loop difference temperature

-(Delta T).

ine resultant signals replace the same signals previously derived in thr, analog Thermal Overpower and Overtemperature protection channels.

The two cold Icg temperature input signals are subjected to range and consistency checks and then averaged to provide a group value,for T II cold'

.these signals agree within an acceptable interval (DELiAC), the group quality is set to GOOD.

If the signals do not agree within the acceptable tolerance

.DELTAC, the group quality is set to BAD and the individual input signal p

qualities are set to P00R.

The average of the two T input signals is cold g

used to represent the group in either case. One cold leg temperature input signal per. loop may be deleted manually by use of the portable Man Machine-Interface (MMI).

The remaining Tcold input signal will provide the. loop

.T t

cold? emperature. DELTAC is an; input parameter based on operating

.l '

-experience and is entered via the portable 69t!. One DELTAC'is required for cach temperature loop.

1 The Eagle'21 TAS employs an algorithm that automatically detects a defective.

. hot-leg RTD input signal and eliminates that input from the T

~

have calcula tion.-

This is' accomplished by incorporating a Redundant Sensor Algorithm (RSA) into the' not leg temperature signal processing.

The RSA determines;the validity of each input signal and automatically rejects a-defective input.

04200:1D/102590 5

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Each of the three hot leg temperature input signals is subjected to a range check and utilized to calculate an estimated average hot leg temperature which is then consistency checked against the other two estimates for average hot leg temperature.

An estimated average hot leg temperature is derived from each T input signal by adding or subtracting as necessary, a temperature hot streaming correction factor.

Then, the average of the three estimated average hot leg temperatures is computed and the individual estirrates are checked to determine if they agree within i DELTAH of the average value.

If all of the signals do agree within i DELTAH of the average value, the group quality is set to GOOD.

The group value T is set to the average of the three have estimated average hot leg temperatures.

If the signal values do not all agree within i DELTAH of the average, the algorithm will delete the signr.1 value which is furthest from the average.

The quality of the deleted signal is set to POOR and a consistency check is performed on the remaining GOOD signals.

If these signals pass the consistency check, the group value will be taken as average of these remaining GOOD signals and the group quality will be set to POOR.

However, if these signals again fall the consistency check (within i DELTAH), the group value will be set to the average of these two signals; but the group quality will be set to BAD. All of the individual signals will have their quality set to POOR. DELTAH f 3 an input parameter based upon temperature distribution tests within the hot leg and is entered via the portable Man-Machine-Interface (HMI). One DELTAH is required for each temperature loop.

1.3.2 Oualification The EQ for Eagle 21 instrumentation is addressed in NCAP-12374.

RTD i

qualification will be verified to support FPL's compliance to 10CFR50.49.

The Hestinghouse qualification program contained a review of the HEED Instrument Company's qealification documentation for testing performed on these.RTDs.

It was concluded that the equipment's qualification was in compliance-with-IEEE Standards 344-1975 and 323-1974 with one excepiion.

04200:10/102590 6

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i Specifically, requirements relative to flow induced vibration were not addressed.

To demonstrate that flow induced vibration would not result in significant aging mechanisms that could cause common mode concerns during a seismic event, Westinghouse performed flow induced vibration tests followed by pipe vibration aging and a simulated seismic event.

These tests confirmed that the WEED RTDs do comply with the above IEEE standards.

1.3.3 RTD Ooerability Indication Control board Delta T and T,yg indicators along with a RTD failure alarm and annunciator will provide the means of identifying RTD failures.

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2.0 IISTING There are two specific types of tests which are performed to support the installation of the thermowell mounted fast-response RTDs in the reactor coolant piping:

RTO response time tests and a hot leg temperature streaming test.

The response time for the Turkey Point Units 3 and 4 application will be verified by testing at the RTD manufacturer and by in-situ testing.

Data from thermowell/RTD performance at operating plants provide additional support for the system.

2.1 RESPONSE TIME TEST The RTD manufacturer, HEED Instruments Inc., will perform response time testing of each RTO and thermowell prior to installation at Turkey Point Units 3 and 4.

These RTD/thermowells must exhibit a response time bounded by the values shown in' Table 2.1-1.

The revised response time has been factored into the transient analyses discussed in Section 4.0.

In addition, response time testing of the HEED RTDs will'be performed in-situ at Turkey Point Units 3 and 4.

This testing will demonstrate that the HEED RTDs can satisfy the response time requirement when inst-' led in the plant.

2.2 STREAMING TEST Past testing at Westinghouse PHRs has established that temperature stratification exists in the hot leg pipe with a temperature gradient from o

max'imum to minimum of (

]b,c.e A test program was implemented at l

an operating plant to confirm the temperature streaming magnitude and L

stability with measurements of the RTD bypass branch line temperatures on two adjacent hot leg pipes.

Specifically, it was intended to determine the L

magnitude of the differences between branch line temperatures, confirm the short-term and long-term stability of the temperature streaming patterns and evaluate the_ impact on the indicated' temperature if only 2 of the 3 branch line temperatures are used to determine an average temperatu'.

This plant specific data is used in conjunction with data taken from o%r Westinghouse designed plants to determine an appropriate temperature error for use in the 04200:1D/102590 11

safety analysis and calorimetric flow calculations.

Section 3 will discuss the specifics of these uncertainty considerations.

The test data was reduced and characterized to answer the three objectives of the test program.

First, it is conservative to state that the streaming pattern (

)b,c.e Steady state data taken at i

1007. power for a period of four months indicated that the streaming pattern bl,c.e In other words, the temperature

[

b3,c.e This gradient [

bl,c.e

't. inferred by [

ooserved between branch lines.

Since thE [

)b,c.e into the RTD averaging circuit if a hot leg RTD fails and only 2 RTDs are usec to obtain an average hot leg temperature.

Both the test data and the operating data support previous calculations of streaming errors determined from tests at other Westinghouse plants.

The temperature gradients defined by the recent plant operating data are well within the upper bound temperature gradients that characterize the previous data.

Differences observed in the operating dats compared with the previous data indicate that the-temperature gradients are smaller, so the measurement uncertainties are conservative.

The measurements at the opcrating plants, obtained from thermowell RTDs installed inside the bypass scoops, were expected to be, and were,found to be, consistent with-the measurements obtained previously from the bypass loop RTDs.

i l'

l l

04200:10/102590 12 l

l

k d*

B o

1. @# M 9

////p

/(,4 9/4 kg% *T$;>#

IMAGE EVALUATION TEST TARGET (MT-3) 4 f

'\\

977k (4

777p l.0 5EMm y[Nlill4 s = Ma II o

L 1.25 i.4 i.6 i

=

+

150mm 4

+

6"

?%,

/

4%

A*4VQ, h////4,}q mRs%:{b o

43,

p, 4(t%

1 w

w D CJ hh),

'I c,;g,

..J-lb; fi

1 o

1 I

TABLE 2.1-1 RESPONSE TIME PARAMETERS FOR RCS TEMPERATURE MEASUREMENT i

RTD Fast Response Bvoass System Ihermowell RTD System RTD Bypass Piping and Thermal Lag (set)

~'

~

~

I RTD Response Time (sec)

Electronics Deiay (sec)

Total Response Time (sec) 6.0 sec 6.0 see d

i 1

I a

i i

04200:1D/102590 13

3.0 UNCERTAINTY CONSIDERATIONS This method of hot leg temperature measurement has been analyzed to determine-the magnitude of the two uncertainties included in the Safety Analysis:

l Calorimetric Flow Measurement Uncertainty and Hot Leg Temperature Streaming Uncertainty.

3.1 CALORIMETRIC FLOW MEASUREMENT UNCERTAINTY Reactor coolant flow is verified with a calorimetric m asurement performed after the return to power operation following a refueline :hutdown. The two most important instrument parameters for the calorimetric measurement of RCS flow are the narrow range hot leg and cc,ld leg coolant temperatures.

The accuracy of the RTDs has, therefore, a major impact on the accuracy of the flow measurement.

-Hith the use of-three T RTDs (resulting from the elimination of the RTD hot Bypass lines) and the requirements of the latest Westinghouse RTD cross-calibration procedure (resulting in low RTD calibration uncertainties at the beginning of a fuel cycle), the Turkey Point Units 3 and 4 RCS Flow aJ.c j

Calormetric uncertainty is determined to be [

including use of cold leg Elbow Taps (see Tables 3.1-2, 3, 4 and 5).

This calculation is based on the standard Hestinghouse methodology previously approved on earlier n'bmitt*' t of other plants associated with RTD Bypass Elimination or +he ust' of the destinghouse Improved Thermal Design Procedure.

Tables 3.1-1 through 3.1-13 were generated specifically for Turkey Point Units 3 and 4 and reflect plant specific measurement uncertainties and operating conditions.

L 3.2 HOT LEG TEMPERATURE STREAMING UNCERTAINTY o

The' safety-analyses incorporate an uncertainty to account for the difference

-between the actual hot leg temperature and the measured hot leg temperature caused by the incomplete mixing of coolant leaving regions of the reactor core at different temperatures. This temperature streaming uncertainty is based on an analysis of test data from other Hestinghouse plants, and on calculations 04200:10/110190 14 l

to evaluate the impact on temperature meas'. ament accuracy of numerous possible temperature distributions within the hot leg pipe.

The test data has shown that the circumferential temperature variation is no more than (

]b,c.e. and that the inferred temperature gradient within the pipe is limited to about b

[

3,c.e The calculations for numerous temperature distributions have shown that, even with margins applied to the observed 1

temperature gradients, the three-point temperature measurement (scoops or thermowell RTDs) is very effective in determining the average hot leg temperature.

Turkey Point plant specific calculations for the thermowell RTD bl c.e system have established an overall streaming uncertainty of [

for a hot leg measurement. Of this total, [

)b c.e,

The new method of measuring hot leg temperatures, with the three hot leg thermowell RTDs, is at least as effective as the existing RTD bypass system.

[

3"'C Although tne new method measures temperature at oic point at the RTD/thermowell tip, compared to the five sample points in a 5-inch span of the scoop measurement, the thermowell measurement point is opposite the center hole of the scoop and therefore measures the equivalent of the average scoop sample if a linear radial temperature gradient exists in the pipe. !ne thermowell measurement may have a small error relative to the scoop measurement if the temperature gradient over the 5-inch scoop span is nonlinear. Assuming that the maximum inferred temperature gradient of C bl c.e exists from the center to the end of the scoop, the difference between the thermowell and scoop measurement is limited to l.c.e Since three RTD measurements are averaged, and the o

[

nonlinearities at each scoop are random, the effect of this error on the hot bl,c.e On the other leg temperature measurement is limited to (

hand, imbalanced scoop flows can introduce temperature measurement uncertainties of up to [

ya.c l

In all cases, the flow imbalance uncertainty will equal or exceed the b

3,c.e sampling uncertainty for the thermowell RTDs, so the new

[

1 04200:1D/102590 15

measurement system tends to be a more accurate measurement with respect to streaming uncertainties.

Temperature streaming measurements have been obtained from tests at 2, 3 and 4-loop plants and from thermowell RTD installations at 3 and 4-loop p'.snts.

Although there have been some differences observed in the orientation of the individual loop temperature distributions from plant to plant, the magnitude of the differences have been [

b 3, c. e...

Over the testing and operating periods, there were only minor variations of less than [

]b,c.e in the temperature differentials between scoops, and smaller variations in the average value of the temperature differentials.

(

b3,c.e,

Provisions were made in the RTD electronics for operation with only two hot leg RTDs in service.

The two-RTD measurement will be biased to correct for the difference compared with the three-RTD avera.ge.

3.3 CONTROL AND PROTECTION FUNCTION UNCERTAINTIES Calculations were performed to determine or verify the instrument uncertainties for the control and protection functions affected by the RTD Bypass Elimination.

Table 3.1-1, Rod Control System Accuracy, note that an acceptable value for control is calculated. Table 3.1-6 provides the uncertainty breakdown for Overtemperature AT. A comparison of the Channel Statistical Allowance with the Total Allowance noted on Table 3.1-7 results in the conclusion that sufficient margin exists for the uncertainties. Table 3.1-8 documents the breakdown for Overpower AT. Comparing the Channel Statistical Allowance for this function with the Total Allowance noted on Table 3.1-9 will conclude that this function is acceptable.

Table 3.1-10 provides the Loss of Flow breakdown.

l l

l l

1 04200:10/102590 16 L

o Table 3.1-11 provides the uncertainty breakdown for Pressurizer Hater Level-High.

This channel is included by the substitution of the existing Hagan racks with the 8 digital Eagle 21 hardware. A comparison of the Channel Statistical-Allowance with the Total Allowance noted on Table 3.1-11 results in the conclusion that sufficient margin exists for the uncertainties.

Table 3.1-12 provides the uncertainty breakdown for T

- L w - Low.

A avg comparison of the Channel Statistical Allowance with the Total Allowance noted on Table 3.1-12 results in the conclusion that sufficient margin exists for the uncertainties.

Table 3.1-13 lists the affected protection function Technical Specification values, some modifications are necessary, as noted.

However, based on the calculations performed, the changes in uncertainties are acceptable with minimal modifications to the plant Technical Specifications, primarily Allowable Values.

04200:10/102590 17

,a

.e TABLE 3.1-1 ROD CONTROL SYSTEM ACCURACY 1

T&vg ERI EA0 ANALOG TURBINE HSS SENSOR / TRANSMITTER

+&,C PHA

=

SCA

=

SMTE -

STE..

SD BIAS.

P PROCESS RACKS

+4,C

~

I RCA RMTE -

RTE

=

RD.

CA

=

1. RTDs USED - TH = 2 TC - 1

+&,C ELECTRONICS CSA ELECTRONICS SIGMA -

CONTROLLER SIGMA CONTROLLER BIAS

=

CONTROLLER CSA

=

l 04200:10/102590 18

TABLE 3.1-2 FLOH CALORIMETRIC INSTRUMENTATION UNCERTAINTIES

(% SPAN)

FH TEMP FH PRES FH DP STM PRESS TH TC PRZ PRESS

+a.C SCA SMTE -

SPE STE SD

=

j RCA

=

RMTE =

RTE RD i

RDOT =

BIAS -

CSA

=

1. OF INST USED 1

3 1

3 DEG F PSIA

%DP PSIA DEG F DEG F PSIA INST SPAN =

194.0 1500.0 100.0 1200.0 100.0 100.0 800.0 INST UNC.

+a.c (RANDOM) -

INST UNC.

(BIAS)

NOMINAL

=

i i

l' 04200:1D/102590 19

i TABLE 3.1-3 FLOH CALORIMETRIC SENSITIVITIES FEEDWATER FLOH FA TEMPERATURE

+a,c MATEFIA'.

DENSITY TEMPERA 1URE

=

PRESSURE

=

DELTA P

=

FEEDHATER ENTHALPY TEMPERATURE

=

PRESSURE

=

h5 1199.8 BTU /LBM hF 415.5 BTU /LBM

=

Dh(SG) 784.3 BTU /LBM

=

STEAM ENTHALPY

+a,c PRESSURE MOISTURE

=

1 HOT LEG ENTHALPY t ~

TEMPERATURE

=

l PRESSURE

=

l:

hH

=

616.5 BTU /LBM 542.5 BTU /LBM hC

=

74.1 BTU /LBM Dh(VESS)

=

i 0.143BE+01 BTU /LBM *F Cp(TH)

=

COLD LEG ENTHALPY

+a,c TEMPERATURE l

PRESSURE

=

l.

Cp(TC).

0.1234E+01 BTU /LBM *F COLD LEG SPECIFIC VOLUME

+a.c TEMPERATURE

=

PRESSURE i

04200:10/102590 20

F '

TABLE 3,1-4 l -

CALORIMETRIC RCS FLOH MEASUREMENT UNCERTAINTIES l

COMPONENT INSTRUMENT ERROR FLOH UNCERTAIN"Y-

+&,C i

FEE') HATER FLOW VENTURI THERMAL EXPANSION COEFFICIENT TEMPERATURE MATERIAL DENSITY TEMPERATURE PRESSURE DELTA P FEEDWATER ENTHALPY TEMPERATURE PRESSURE-STEAM ENTHALPY PRESSURE MOISTURE NET PUMP HEAT ADDITIOh HOT LEG ENTHALPY TEMPERATURE STREAMING, RANDOM STREAMING, SYSTEMATIC PRESSURE COLD LEG ENTHALPY TEMPERATURE j

PRESSURE COLD LEG SPECIFIC VOLUME TEMPERATURE PRESSURE.

i 04.'00:10/102590-21 v-

l TABLE 3.1-4 (continued)

CALORIMETRIC RCS FLON MEASUREMENT UNCERTAINTIES BIAS VALUES FEEDWATER PRESSURE DENSITY

_ +a,c ENTHALPY STEAM PRESSURE ENTHALPY PRESSURIZER PRESSURE ENTHALPY - HOT LEG ENTHALPY - COLD LEG SPECIFIC VOLUME - COLD LEG FLOH BIAS TOTAL VALUE

• ** +,++ INDICATE SETS OF DEPENDENT PARAMETERS 1 LOOP UNC N LOOP UNC L

l 04200:10/102590 22 m

TABLE 3.1-5 COLD LEG ELB0H TAP FLOW UNCERTAINTY INSTRUMENT UNCERTAINTIES ACCURACY OF INDICATED RCS FLOW FROM PROCESS COMPUTER

+4, C

PMA 3

=

ALL VALUES IN % FLOW PEA SCA SMTE SPE STE SD BIAS RCA RHTE RTE RD A/D ROUT I

+A.C

'l LOOP ELB0H TAP

~

N LOOP ELB0H TAP

=

N LOOP.RCS FLOH TAP i

04200:1D/102590 23

TABLE 3.1-6 i

OVEtTEMPERATURE AT PARAMETER ALLOWANCI Process Heasurement Accuracy

+a,C

.,+1.C AT AI AI Primary Element Accuracy Sensor Calibration

+3.C AT (i

Pressure 1C Measurement & Test Equipment Accuracy

+a,c Pressure - [

)..

Sensor Temperature Effects Pressure - [

]

Sensor Drift

_ +a,c AT.

Pressure Bias Environmental Allowance

+a,c

-Rack Calibration _AT span l

AT j

AI-Pressure 04200:1D/102590 24

.=

I j

TABLE 3.1-6 (continued)

OVERTEMPERATURE AT L

PARAMETER ALLOHANCE Measurement & Test Equipment Accuracy

+a.C l

AI Tavg Pressure Rack Ten rature Effects

[

]

+a.c AT AI L

Pressure Rack drift AT AI Pressure L

Ir,% rpan (Tavg - 100*F, pressure - 800 psi, power - 120% RTP, of - 75'F AI - 160% AI).

fee Table 3.1_7 for gain and' conversion calculations g

+a c i

l-1 l

l' l'

04200:1D/110190 25

4 TABLE 3.1-6 (continued) t.

OVERTEMPERATURE AT D

Channel Statistical Allowance - 5.6% AT SPAN Total Allowance.

~

~

Margin w

E k

M L

M-h 04200:10/110190 26 F

TABLE 3.1-7 OVERTEMPERATURE AT GAIN CALCULATIONS The equation for Overtemperature AT is:

AT [(1 + t)S)/(1 + t S}3 III)/(I + '3 }3 I S

2 4 }III + '5 )][T((1)/(1 + t 5)] - T'] + K (P-P') - f)(AI)]

AT [K) - K E(I + T S

S 6

3 g

2 1.0950 Technical Specification value K1 (nominal)

=

[

3+a.c K1 (max)

=

0.0107/*F l

K2 0.000453/ psi K3 ATo: vessel AT 56.1'F AI gain 1.5 FP AI/%AI

=

+a,C Pressure Gain -

Pressure SCA

=

Pressure SMTE -

Pressure STE Pressure SD

+a,C AI conversion AI PMA)

Al PMA2

=

otal Allowance (TA) =

.) +a c-

.i 04200:1D/110190 27

TABLE 3.1-8 OVERPOWER AT Parameter Allowance

• Process Measurement Accuracy

+a,c AT - [

]+a c Primary Element Accuracy Sensor Calibration AT.- [

3+a.c Sensor Pressure Effects Sensor Drift AT - [

3+a.c Environmental Allowance Rack Calibration AT - [

]

Tavg Measurement & Test Equipment Accuracy AT-Tavg Rack Accuracy

+a.C Tavg Rack Temperature Effects A-T - [

3-+a,c Rack Drift AT

-[

3+a,c 04200:1D/110190 28

i l

TABLE 3.1-8 (continued)

OVERP0HER AT In % span (Tavg - 100*F, 4T - 75'F, POWER - 120% RTP)

• • [

)+a C Channel Statistical Allowance = [

] +a,c HARGIN

[

3+a,c TOTAL ALLONANCE - (

)+a c

- I 04200:10/102590 29

TABLE 3.1-9 OVERPOWER AT GAIN CALCULATIONS The equation _for Overpower AT-is:

r-AT ((1 + tj s)/(1 + x2 )3 III)/(I + T 3)3 I 6

3 AT [K4 - K EE(*7 )#(I + '7 )3III)#II + '6 )))T - K (T[(1)/(1

+t 6

3 S

6 )) - T"] - f2 S

COI)3 5

o 6

K4 (nominal) 1.09 Technical Specification value

=

K4 (max)

= ['

1+a c K

0.02/F 5

K 0.00068/F

=

6

.aT o - vessel AT - 56 l'F Total Allowance =

[ _

3 + a,'c l

l l.

L 04200:10/102590 30 i

%ee

?

TABLE 3.1-10 LOSS OF FLOH RCS LOH FLOW TRIP ACCURACY

+a c PMA

=

ALL VALUES IN % FLOW SPAN PEA

=

SCA SMTE SPE STE.

50 BIAS RCA RMTE n

RCSA-

- RTE

=

RD

- FLOH SPAN.

. SAL

~ ALLV

=

NOM

+a c

. +a c

+a.c MAR S

z TA CSA T

=

=

=

0420D:10/102590 31 u

TABLE 3.1-11 PRESSURIZER WATER LEVEL - HIGH Parameter.

Allowance

• Process Miasurement Accuracy

+a,c

[

J+a c c

j

. Primary Element Accuracy Sensor Calibration s

M&TE Sensor Pressure Effects Str.e;r Temperature Effects Sensor Drift Environmental Allowance Rack Calibration Rack Accuracy M&TE Rack Temperature Effects Rack Drift

• In percent span (100 percent span)

Channel Statistical Allowance - 7.9% span

+a,c

^

+a.c

+a c

- +a c T

S Z

MAR

.CSA' TA K

04200:10/102590 32 m

i TABLE 3.1-12 Tavg - Low-Low Trip Accuracy 3

PHA

+a.c SCA

=

SD RCA

=

RMTE

=

RTE

=

RD

=

BIAS

=

543.00 NOH SAL

=

ALLV Tavg SPAN =

. a.c

. a.c

+.p.c

+

+

1 Z

S MAR

=

g TA T

CSA

=

~

k 04200:10/102590 33

L 1

i TABLE 3.1-13 TECHNICAL SPECIFICATION MODIFICATIONS Functional Unit /Page no.

Modification Justification Pressurizer Water Addition of Allowable Application of 8 l

Level High, page 2-4 Value, 92.2%.

setpoint methodology.

Overtemperature AT, RTD Response time Elimination of RTD 1

page 2-7 constants changed, t,ypass lines.

Overtemperature AT, Reduced Deltal Gain 8 Safety Evaluation page 2-8 to 1.5, added allowable SECL No. 89-1164, and value of 1.5%.

H setpoint methodology.

Overpower AT, Removed Deltal Gain and 8 Safety Evaluation page 2-10 added allowable value SECL No. 89-1164, and of 1.4%.

H setpoint methodology.

Overpower AT, Removed Deltal Gain Safety Evaluation

.page B 2-5 from bases.

8 SECL No. 89-1164.

T

- Low, Revised trip setpoint Application of H avg pages 3/4 3-23, 25, & 27 to 543'F and added setpoint methodology.

l an allowable value of 542.5'F.

04200:iD/102590 34

TABLE 3.1-13 (Continued)

I TECHNICAL SP L.FICATION MODIFICATIONS Functional Unit /Page no.

Modification Justification i

Overtemperature AT Remove Note '12 Elimination of RTD Table 4.3-1, Pages 3/4 Bypass Lines I

3-8 and 3/4 3-12 I

' dded an allowable Application of H Reactor Coolant Flow i

Low Page 2-4 value of 88.7%.

Setpoint Methodology Setpoint Tables 2.2-1 Added bases for using Application of H and 3.3-3 and Bases the 5 column setpoint Setpoint Methodology 2-2.1, 3/4-3.1 3/4-3.2 format and provided Pages 2-3. 2-4, B2-3

. values for functions 3/4 3-13, 3/4 3-23. 3/4 implemented in the 3-25 3/4 3-27, B3/4 3-1 digital process system, and B 3/4 3-2, 2-7, 2-8, 2-9 and 2-10 I

Tables 4.3-1 and 4.3-2 Change analog channel MCAP 10271 and subse-pages 3/4.3-8, 3/4 3-29, operational test quent H. evaluation 3/4 3-32, 3/4 3-34.

-surveillance. test for digital process interval to quarterly control equipment Tables 3.3-1 and 3.3-2, Channel surveillance HCAP 10271 and subse-pages 3/4 3-2, 3/4 3-7, testing quent B evaluation-

-3/4 3-15, 3/4 3-18,~3/4 3-22.

for. digital process 4

control equipment 04200:1D/102590 35 l

4.0 SAFETY EVALUATION The primary impacts of the RTD Bypass Elimination on the FSAR Chapter 14 i

(Reference 1) safety analyses are the differences in response time characteristics and instrumentation uncertainties associated with the fast response thermowell RTD system.

The effects of these differences are q

discussed in the following-sections, j

4.1 RESPONSE TIME d

The current response time parameters of the Turkey Point Units 3 and 4 RTD bypass system assumed in the safety analyses are shown in Table 2.1-1.

For the fast response thermowell RTD system, the overall response time will consist of-[

3,c (as presented in Section 2.1 and as given in Table 2.1-1).

a l

The new thermowell mounted RTDs have a response time equal to or better than the maximum allowed (assumed) time for the combined old bypass piping j

transport, thermal lag and direct immersion RTD.

This allows the total RCS l

temperature measurement response time to remain unchanged at 6.0 seconds (Reference Table 2.1-1).

This channel response time is factored into-the Overtemperature AT (OTAT) and Overpower AT (OPAT) trip performance.

Those transients that rely on the above mentioned trips must be addressed for 1

the-mooified response characteristics. Section 4.3 includes a discus,lon of j

this evaluation.

{

4.2 -RTD UNCERTAINTY The proposed fast response thermowell-RTD system will make use of RTDs, manufactured by Heed Instruments Inc...with a total uncertainty of a

'3,c assumed for the analyses.

[

The FSAR analyses make explicit allowances for instrumentation errors for some of the reactor protection system setpoints.

In addition, uncertainty allowances-are made for the average reactor coolant system (RCS) temperature, pressure and power.

These allowances are explicitly applied in the initial conditions for the transients.

0420DilD/102590 36

The following protection and control system parameters were evaluated and determined to be unaffected (with respect to current accident analysis and evaluation assumptions in References 1 and 2) by the change from one' hot leg RTD to three hot leg RTDs are:

the Overtemperature AT (OTAT), Overpower AT (OPAT), and Low RCS Flow reactor trip functions, RCS loop T avg measurements used for input to the rod control system, and the calculded value of the RCS flow uncertainty. The results of system uncertainty calculations, noted in Section 3.3, indicate that sufficient margin exists to account for known instrument uncertainties.

4.3 NON-LOCA EVALUATION The RTD response time discussed in Section 2.1 and the instrument uncertainties discussed in Section 3.3 have been considered for the Turkey Point Units 3 and 4 non-LOCA safety analysis design basis. These effects are discussed separately in the following paragraphs.

Only those transients which assume OTAT/0 PAT protection are potentially affected by changes in RTD response time. As noted in Section 4.1, the new thermowell mounted RTDs have a response time equal to or better than the old bypass transport, thermal lag and direct immersion RTD. On the basis of the information documented in Table 2.1-1, it is concluded that the safety analysis assumption for the total OTAT/0 PAT channel response time of 6.0 seconds remains valid. Additionally, evaluation of the effects of the RTD bypass elimination on the uncertainties associated with these setpoints supports the continued validity of the current non-LOCA safety analyses.

RTD instrumentation uncertainties can affect the non-LOCA transient initial condition assumptions and those transients which assume protection from the low primary coolant flow reactor trip. As determined in Section 3.0 the RTD bypass elimination does not increase any uncertainty that will affect any initial condition assumed in any non-LOCA transient or the low primary coolant flow reactor trip.

04200:10/102590 37

1 In conclusion, the non-LOCA safety analyses applicable to Turkey Point Units 3 and 4 have been evaluated with respect to the replacement of the existing RTD Bypass System with the fast response thermowell installed in the reactor coolant loop piping.

It was determined that all safety analysis assumptions currently assumed in the non-LOCA analyses remain valid.

The Reference 1 and 2 results and conclusions are unchanged and all applicable non-LOCA safety analysis acceptance criteria continue to be met.

4.4 LVI. EVALUATION The elimination of the RTD bypass system impacts the uncertainties associated with RCS temperature measurement.

The magnitude of the uncertainties are such that PCS inlet and outlet temperatures, thermal design flow rate and the steam generator performance data used in the LOCA analyres will not be affected.

Past sensitivity stuoies have shown that the variation of the core inlet temperature (Tin) used in the LOCA analyses affects the predicted core flow during the blowdown period of the transient. The amount of flow into the core is influenced by the two-phase vessel-side break flow, and the core cooling is affected by the quality of the fluid. These sensitivity studies concluded that the. inlet temperature effect on peak clad temperature is dependent on break size. As a result of these studies, the LOCA analyses are performed at a' nominal value of T without consideration of small uncertainties.

The in RCS flow rate and steam generator secondary side temperature and pressure are also determined using the loop average temperature (Tayg) output.

These nominal values used as inputs to the analyses are not affected due to the RTD bypass elimination.

It is concluded that the elimination of the RTD bypass piping will not affect the LOCA analyses input and hence, the results of the analyses for Turkey Point Units 3 and 4 remain unaffected. Therefore, the plant design changes due to the RTD bypass elimination are acceptable from a LOCA analysis standpoint without requiring any reanalysis.

04200:10/102590 38

4.5 INSTRUMENTATION AND CONTROL SAFETY EVALUATION The RTD BYPASS ELIMINATION functional upgrade modificatim affects the measurement of the RCS hot leg temperature.

Prior tc the modification, the RCS hot leg coolant was sampled by scoops in the inain piping and an average hot leg temperature was obtained from a single RTD mounted in the hot leg bypass manifold.

The RCS cold leg measurement was obtained from a single RTD mounted in the cold leg bypass manifold. With the elimination of the RTD bypass manifold, three (3) hot leg RTD's are installed in tharmowells mounted in what was previously the bypass manifold scoops wherever possible.

The temperatures read at these locations are somewhat different because of streaming effects.

Thus, the three temperatures are to be processed to produce an average temperature ;Thave) for each hot leg.

The cold leg temperature measurement on er h loop is accomplished with a dual element narrow range RTD installed in a thermowell.

The thermowe'l is mounted either in the existing cold 'eg bypass connection or boss mounted in a new penetration.

The cold leg sensors are inherently redundant in that either sensor can adequately represent the cold leg temperature measurement.

Temperature streaming in the cold leg is not a concern due to the mixing action of the reactor coolant pump.

The process system used to calcFlate T and T is designated as the have cold Eagle 21 Temperature Averaging System (TAS). The TAS becomes part of the Thermal Overpower and Overtemperature Protection System because the TAS outputs (T and Tcold) replace the Thot and Tcold tignals previously have derived from the bypass manifold RTDs.

A generic topic 01 report providing details on Eagle 21 design philosophy, system architectur1, hardware, sof tware, qualification, verification, validation, and com)liance with criteria has been documented as HCAP-12374.

04200:10/102590 39

4.5.2 DESIGN AND IMPLEMENTATION The Eagle 21 TAS system accepts RTD input signals representing two (2) cold leg and three (3) hot leg temperature measurements per loop (Figure 4.5.2-1).

The two cold leg temperatures are p Ncessed to produce an average cold leg temperature T The three hot leg temperatures are processed to produce COLD.

the average hot leg temperature T T

is then combined with have.

have TCOLD to produce the loop average temperature (Tavg) and the loop difference temperature (Delta T).

The resultant signals replace the same signals previously derived in the analog Thermal Overpower and Overtemperature protection channels.

The two cold leg temperature input signals are subjected to range and consistency checks and then averaged to provide a group value for TCOLD (Figure 4.5.2-2).

If these signals agree within an acceptable interval (DELTAC), the group quality is set to GOOD.

If the signals do not agree within the acceptable tolerance DELTAC, the group quality is set to BAD and the individual input signal qualities are set to POOR. The average of the two TCOLD input signals is used to represent the group in either case. One cold leg temperature input signal per loop maybe deleted manually by use of the portable HMI. The remaining T input signal will provide the loop cold T

temperature.

DELTAC is an input parameter based on operating cold experience and is entered via the portable Man Machine Interface (HMI). One DELTAC is required for each temperature loop.

The Eagle 21 TAS employs an algorithm that automatically detects a defective hot leg RTD input signal and eliminates that input from the Thave calculation. This is accomplished by incorporating a Redundant Sensor Algorithm (RSA) into the hot leg temperature signal processing. The RSA 1

determines the validity of each input signal and automatically rejects a defective input (Figure 4.5.2-3).

i 04200:lD/10251C 40

Each of the three hot leg temperature input signals is.n:bjected to a range check.

These signals are utilized to calculate an estimated average hot leg temperature which is then consistently checked against the other two estimates for average hot leg temperature. An estimated average hot leg temperature is derived from each T input signal by adding or subtracting as necessary, a hot temperature streaming correction factor (Sj).

Then, the average of the three estimated average hot leg temperatures is computed and the individual estimates are checked to determine if they agree within i DELTAH of the average value.

If all of the signals do agree within i DELTAH of the average value, the group quality is set to GOOD.

The group value T i s set to have the average of the three estimated average hot leg temperatures.

If the signal values do not all agree within i DELTAH of the estimate of the hot leg average temperature, the RSA will delete the signal value which is furthest f om the average.

The quality of the deleted signal is then set to POOR and a consistency check is performed on the remaining GOOD signals.

If the two remaining signals pass the consistency check, the group value will be taken as average of these remaining G000 signals and the group' quality will be set to POOR. However, if these signait again fail the consistency check (within i DELTAH), the group value will be set to the average of the two signals; but the group quality will be set to BAD. All of the individuals signals will have their quality set to POOR. DELTAH is an input parameter based upon temperature distribution tests within the hot leg and is entered via the portable MMI. One DELTAH is required for each temperature loop.

The Eagle 21 system has been designed with the capability to perform automatic surveillance tests on the TAS algorithms associated with the RTD Bypass i

t' Elimination fuisctional upgrade.

l l

04200:10/102590 41

,e

4.5.3 ALARMS. ANNUNCIATORS AND STATUS LIGHTS

]

Additional control room alarms, annunciators and status lights are provided as part of the RTD 'Upass Elimination functional upgrade.

These additional indications are as follows:

1.

A " Trouble" alarm and annunciator window is added common to all 3 loops.

This light is actuated anytime the T group value for a coolant loop have is set to POOR as described in Section 4.5.2.

(This alarm and annunciator informs the operator that there are only two good narrow signals for one of the coolant loops.)

range Thot 2.

An "RTO Failure" alarm and annunciator window is added common to all 3 loops.

This alarm and annunciator is actuated anytime the Tcold or T

group value for a coolant loop is set to BAO as described in have Section 4.5.2.

This alarm and annunciator informs the operator that there is an invalid T or T group value for a loop. A cold have Technical Specification action statement will be in effect to cover this condition.

3.

A bypass alarm and annunciator window is added for each affected rack.

This alarm and annunciator is actuated anytime a protection rack is placed in bypass.

This alarm and annunciator informs the operator that a protection channel has been bypassed. This is consistent with l

IEEE-279-1971.

Bypassing of Protection functions for the Eagle 21 channels will be administratively controlled, r

The conversion to thermowell mounted RTOs will result in elimination of the control grade RTDs and their associated control board indicators.

The protection grade channels will now be used to provide inputs to the control system through isolators to prohibit faults in the control system from propagating into the protection racks.

In order to satisfy the control and protecti0n interaction requirements of IEEE 279-1971, a Median Signal Selector (HSS) will be used in the control 1

1 04200:10/102590 42 l

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SDm0R ALDORmed Cj f STATUS UPDATE fC I I Figure 4.5.2-2 Functional Logic Diagram (Teold) 04200:10/070390 44

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l 04200:10/070390 45

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channels presently utilizing a high auctioneered T,yg or Delta T signal (there will be a separate HSS for each function).

The Median Signal Selector will use as inputs the protection grade T or Delta T signals from all avg three loops, and will supply as an output the enannel signal which is the median of the three signals.

The effect will be that the various control grade systems will still use a valid RCS temperature in the case of a single signal failure. Utilization of the Median T and AT signals will have gyg no adverse effects on Control System operability.

To ensure proper action by the Median Signal Selector, the present manual switches that allow for defeating of a T or Delta T signal from a single avg loop will be elirainated.

The MSS will automatically select a valid signal in the case of a signal failure. Warnings that a failure haJ occurred will be provided by loop to median T,yg and Delta T deviation alarms.

The overtemperature, overpower, T,yg low-Low, Loss of Flow, and pressurizer level existing Model 7100 process electronics will be replaced with the Eagle 21 Process Protection System for each affected protection set. All existing 7100 modules for these channels will be removed for use as spares in other protection channels.

The two of three voting relay logic now derived from the Eagle 21 protection channels will remain the same.

For unaffected channels, the inputs to the bistables remain the same.

The Reactor Protection System for the U affected channels will remain the same, as that previously utilized.

For example, two out of three voting logic channels continues to be utilized with the model 7100 process control bistables continuing to operate on a "de-energize to actuate" principle.

The above principles of the modification have been reviewed to evaluate conformance to the requirements of IEEE-279-1971, and associated 10CFR50

. General Design Criteria (GDC), Regulatory Guides, and other applicable industry standards, for the affected channels.

IEEE 279-1971 requires documentation of a design basis.

Following is a discussion of design basis requirements in conformance to pertinent I&C criteria:

0420D:1D/102590 46

I The single failure criterion continues to be satisfied by this change a.

because the independence of redundant protection sets is maintained.

b.

The quality of the components and modbles being added is consistent with use in a Nuclear Generating Station Protection System.

For the Westinghouse Quality Assurance program, refer to 8370/7800 Rev. 11/7 A.

The changes will continue to maintain the capability of the protection c.

system to initiate a reactor trip to the same extent as the existing system.

d.

Channel independence and electrical separation is maintained because the Protection Set circuit assignments continue to be loop I circuits input to Protection Set I; Loop 2 to Protection Set II; and Loop 3 to N

Protection Set III.

Due to the elimination of the dedicated control system RTD elements, e.

temperature signals for use in the plant control systems must now be derived from the protection system RTDs.

To eliminate any degrading control and protection system interaction mechanisms introduced as a consequence of the RTD Bypass Elimination modification, a Meilan Signal Selector has been introduced into the control system.

The Median Signal Selector preserves the functional isolation of interfacing control and 3

protection systems that share common instrument channels.

The signal selector implementation is described in Section 1.3.1.

On the basis of the foregoing evaluation, it is concluded that all I&C equipment being upgraded for Turkey Point Units 3 and 4 is in compliance with IEEE 279-1971, applicable GDCs, and industry standards and regulatory guides.

04200:10/102590 47 m

~

4.5.4 TEST ENilANCEMENTS Tor those racks being upgraded with Eagle 21 process protection equipment, test enhancements discussed and approved generically in WCAP-10271-P-A

" Evaluation of Surveillance Frequencies and out of service times 'or the reactor protection instrumentation system" are being implementeJ (Reference 2).

The specific enhancements being implemented are as follows:

1. Extending survelliance intervals for Reactor Trip (RT) channels from one month to quarterly.

2. Increasing the two hour time limit to four hours for a RT channel to be bypassed to allow for testing of another r,hannel in the same function.

In the Sequoyah Safety Evaluation Report (Docket No. 50-327) dated l4a.i 16, 1990, the NRC staff concluded that these same tes'; enhancements were consistent with the approved Topical Report WCAP-10271-P-A and therefore, are acceptable.

4.6 NECHANICAL SAFETY EVALUATION The presently installed RTD bypass system is to be replaced with fast acting narrow range RTD thermowells.

This change requires modifications to the hot leg scoops, the hot and cold leg piping, the crossover leg bypass return nozzle, and the cold leg bypass manifold connection. All welding and NDE will be performed per ASME Code Section XI 1980 through Winter 1981 Addenda requirements.

Each of these modifications is evaluated below.

The hot leg temperature measurement on each loop will be accomplished using three (3) fast response, narrow range dual element RTDs mounted in thermowells.

To accomplish the sampling function of the RTD bypass manifold system and minimize the need for additional hot leg piping penetratic1s, the RTD thermowell assemblies will be located within the existing RTD Bypacs Manifold Scoops wherever possible.

[

ja.c to provide the proper flow path.

If a structurai

. interferences or a skewed scoop preclude the placement of a thermowell in a 04200:10/102590 48

__ ___?--_-------------

given scoop, then the scoop will be capped and a new RCS penetration made to accommodate the relocated thermowell.

The relocated RT0/thermowell will bo located in an installation boss and be positioned such that the process measurement accuracy associated with temperature streaming (Section 3.3) will be maintained for the three RTD average temperature.

The thermowell will be fabricated in accordance with Section III (Class 1) of the ASME Code.

The installation of the thermowell into the scoop or boss will be performed using GTAH for the root pass and finished out with either Gas Tungsten Arc Held (GTAH) or Shielded Metal Arc Held (SHAH).

The welding will be examined by penetrant test (PT) per the ASME Code Section XI.

Prior to welding, the surface of the scoop or boss onto which welding will be performed will be examined as required by Section XI.

The cold leg RTD bypass line must also be removed.

The nozzle must then be modified to accept the fast response RTD thermowtl1.

If necessary, the RTD's will be relocated because of interferences.

The lnstallation of the thermowell into the nozzle will be performed ustr.g GTAH for the root pass and finished with either GTAH or SMAN. Held inspection by PT will be performed as a3c required by Section XI. The thermowells will extend approximately (

inches into the flow stream.

This depth has been justified based on [

3a.c analysis.

The root weld joining the thermowells to the modified nozzles will be deposited with GTAH and the remainder of the weld may be deposited with GTAH or SMAN. Penetrant testing will be performed in accordance with the ASME Code Section XI.

The thermowells will be fabricated in accordance with the ASME Section III (Class 1).

If structural interferences preclude placement in the existing nozzle then the rozzle will be capped and a new penetration made to accommodate the thermowel'.

The thermowell will be installed in a boss. The installation of the thernewell into the boss will be the same as for the nozzle installation.

The cross-over leg bypass return piping will bt, severed to leave a stub of pipe protruding from the nozzle and the stub will be capped.

The cap design, including materials, will meet the pressure boundary criteria of ASME Section III (Class 1).

The cap will be root welded to the pipe stub by GTAH and fill welded by eithen GTAH or SMAN.

Non-destructive eaminations (PT and 04200:1D/102590 49

radiographs) will be performed per ASME Section XI. Machining of the bypass' g

returri nozzle, as well as any machining performed during modification of the penetrations in the hot and cold legs, shall be performed such as to minimize debris escaping into the reactor coolant system.

The design and analysis of the loop piping and associated branch connection boss, weld, and pipe cap, where applicM:le, will meet the requirements of the ASA B31.1.0 Code 1955 Edition, No Addenda.

In accordance with Article IWA-4000 of Section XI of the ASME Code, a 3

hydrostatic test of new pressure boundary welds is required when the connection to the pressure boundary is larger than one inch in diameter.

Since the cap for the crossover leg bypass return pipe is [ ]"'C inches and 1 'C inches, a system hydrostatic test 8

the cold leg RTD connections are (

is required after the bypass elimination modification is complete.

Paragraph INB-5222 of Section XI defines this test pressure to be 1.02 times the normal operating pressure at a temperature of 500*r or greater.

In summary, the integrity of the reactor v:oolant piping as a pressure boendary component, is maintained by adhering to the applicable ASME Code sections and Nuclear Regulatory Commission General Design Criteria.

Further, the pressure retaining capability and fracture prevention characteristics of the piping is not compromised ey the r modifications.

W 4.7 TECHNICAL SPECIFICf, TION EVALUATION As a result of the calculations summarized in Section 3.0, several protection functions' Technical Specifications are modified.

The affected functions and their associated Trip Setpoint information, are noted on Table 3.1-13.

04200:10/102590 50

5.0 CONTROL SYSTEM EVALUATION _

A prime input to the various NSS$ control systems is the RCS average temperature, T,yg.

This is calculated electronically as the average of the measured hot and cold leg temperatures in each loop.

The effect of the new RTO temperature measurement system is to potentially change the time response of the T,y channels in the various loops.

This in turn could impact the response of (

8 3

'C However, as previously noted, the new RTO system (thermowell mounted RTO) will have a time response identical to that of the current system (RTO + bypass lino.

The additional delay resulting from the Median Signal Selector (MSS) is shall in comparison with the RTO time response [

]"'C Therefore, there w'il be no significant impact o.7 the T,yg channel response and no need, a5 a result of implementing the new system, to revise any of the contro' system setpoints.

It should be recognized that control systems do not perform any protective function in the FSAR accident analysis.

With respect to accident analyses, control systems are assumed operative only in cases in which their action aggravates the consequences of an event, and/or as reautred to establish initial plant conditions for an analysis.

The modeling of control systems for accident analyses is based on nominal system parameters as presented in the Precautions, Limit; cions, and Setpoint document.

04200:10/102590 51

l

6.0 CONCLUSION

S The method of utilizing fast-response RTDs installed in the reactor coolant loop piping as a means for RCS temperature indication has undergone extensive analyses, evaluation and testing as described in this report.

The incorporation of this system into the Turkey Point Units 3 and 4 design meets all safety, licensing and control requirements necessary for safe operation of

+Aese units.

The analytical evaluation has been supplemented with in-plant and laboratory testing to further verify system performance.

The fast response RTDs installed in the reactor coolant loop piping adequately replace the present hot and cold leg temperature measurement system and enhances ALARA efforts as well as improve plant reliability.

I 04200:10/102590 52 w

I

7.0 REFERENCES

1.

Turkey Point Units 3 and 4 Updated FSAR.

2.

WCAP-10271-P-A " Evaluation of Surveillance Frequencies and Out of Service Times for the Reactor Protection Instrumentation System."

04200:10/102590 53

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