ML20059K918

Nonproprietary Resistance Temp Detector Bypass Elimination Licensing Rept for Turkey Point Units 3 & 4.

ML20059K918
Person / Time
Site:	Turkey Point
Issue date:	06/30/1990
From:	Deblasio J WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:
Shared Package
ML17348A562	List: ML17348A561 ML17348A563 ML17348A564 ML20059K918
References
WCAP-12633, NUDOCS 9009250087
Download: ML20059K918 (60)

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WESTINGHOUSE CLASS 3-

,s NCAP-12633;

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RTD BYPASS ELIMINATION LICENSING. REPORT- [

FOR

. TURKEY: POINT UNITS 3 AND 4 ,

s .

1 J. J. DEBLASIO ,-

3:

R. M. HATERS. ~[

t JUNE, 1990 l )0 .'] .

Approved ~by: -' ~ Approved by: \W d'$~. D. RuppfectJt 4ahager ~H. R. Rice, Manager:

Operating Plant Licensing I Chemical. Haste:and.

' Balance 1of Plant System 3

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Hestinghouse Electric Corporation  :

Nuclear and Advanced Technology Division c P.O. Box 355 Pittsburgh, Pennsylvania 15230-0355 Copyright c1990 l

4 f

4 4

ACKNOHLEDGEMENT.

t ' 5

- The authors wish to recognize contributions by the following individuals: ,

l i

H. G. Lyman C. F. Ciocca  !

L. E. Erin H.-J. Scherder R. A. Carlson r

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I' 0420D:10/060590 P - _ _ _ - _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ . _ - . _ _ _ _ _ _ _ _ _ _ _ - - - _ _ _ _ _ . _ _ _ _ . . _ _ . - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

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TABLE OF CONTENTS l 1

Section~ . EA.gjt ..,

, List of Tables. f11  ;

List ~of Figures iv 1.0. Introduction  :

.r 1.1 Historical Background 1' 4

.1.2 Hechanical Modifications 2  :

i 1.3 Electrical Modifications -4 R

2.0 Testing ,

2.1: Response' Time Test -11 l 2.2 Streaming Test 11- , ,

3.0 Uncertainty Considerations -

3.1 Calorimetric Flow Measurement Uncertainty 14

}

3~.2 Hot' Leg Temperature Streaming Uncertainty 14 3.3 Control and Proter. tion Function Uncertainties 16-  ;

4.0. Safety Evaluation .

]

-4 1 Response Time - 36, 4.2 - RTO Uncertainty '36 ,

37 i 4.3 Non-LOCA Evaluation

'4.4'.LOCA Evaluation 38 4.5 Instrumentation and Control-Safety Evaluation -39 4.6 Hechanical Safety Evaluati.m 48 ,

-4.7 -Technical Specification Evaluation 50 -j i

1

-04203:1D/060590 i e - y - - , , e- + 3 l

- 3

-TABLE OF CONTENTS (Cont)

Section Eggg

-5.0, Control System Evaluation 51 ' . -

6.0- Conclusions- 52 i

7.0 References 54 't n;

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i 04200

10/060590 ii v

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41 LIST OF TABLES Table Title PAgt 2.1-1 Response Time Parameters for RCS Temperature Measurement 13 I

3.1-1 Rod Control System Accuracy 18  :

I 3.1-2 Flow Calorimetric Instrumentation Uncertainties 19.

3.1 Flow Calorimetric Sensitivities 20.

3.1-4 Calorimetric RCS Flow Heasurement Uncertainties 21 j-1 L 3.1-5 Cold Leg Elbow Tap Flow Uncertainty 23 L

3.1-6 Overtemperature AT Reactor Trip 24-l l

3.1-7 Overtemperature AT Gain Calculations 27 3.1-8 Overpower AT 28; 30 I 3.1-9 Overpower AT Gain Calculations i

k 3.1-10 Loss of Flow' 31 l

i 3.1 Pressurizer Hater Level - High 32 ,

3.1-12 33 T,yg Low-Low Trip Accuracy Technical Specification Modification' 3.1-13 34 o

t 1  ;

1 04200:1D/060590 iii t

ll LIST OF FIGURES Fiaure Iltle EAgt

?1.2-1 Hot Leg RTD Scoop Modification for Fast-Response- 8 RTD Insts11ation 1.2-2 Hot and Cold Leg R1D Boss Installation for Fast-Response 9 RTD Installation 1.2-3 Cold Leg Pipe Nozzle Hodification Fast-Response 10 RTO Installation i.

4.5.2-1 -Thermai '"ertemperature and Overpower Digital Flow Diagram 43 4.5.2-2 Functional Logic Diagram (Tcold} 44 4.5.2-3 Functional Logic Diagram (Thot) 45 04200:10/060590 iv t

.a- ,

4 1.0, INTRODUCTION I 5

Westinghouse Electric Corporation has been contracted by Florida Power'and Light to remove the existing Resistance Temperature Detector (RTD) Bypass.  !

System and replace this hot leg and cold leg temperature measurement method with fast response thermowell mounted RTDs installed in the reactor coolant j loop piping. This report is submitted for the purpose of supporting operation l of Turkey Point Units 3 and 4 utilizing the new thermowell mounted RTDs as processed'with the Eagle 21 process protection system.

1.1 HISTORICAL BACKGROUND Prior to 1968, PHR designs had been based on the assumption that the hot leg temperature 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 1 plants, the.following problems associated with direct immersion RTDs were identified:

I 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 these problems; however, i operating 1:! ant experience has now shown that operation with the RTD bypass loops has created it's own obstacles such as:.

L ,

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

04200:10/070390 1

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

a major source of plant outages as well as Occupational Radiation.

Exposure (ORE).

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.

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

1 Following is a detailed description of the effort required to perform this- >

modification.

1.2 MECHANICAL MODIFICATIONS The individual leop temperature signals required for input to the Reactor Control and Protscilon System will be obtained using RTDs installed in each reactor coolant 1oop.

l-q 1.2.1 Hot leg L a)- The hot leg temperature measurement on each loop will be acc6mplished with 4' I three fast response, narrow range, dual element RTDs mounted in h thermowells. To accomplish the sampling function of the RTD bypass manifold system and minimize the need for additional hot' leg piping L penetrations, the thermowells will be located within the existing e

~04200:10/070390 2

1 RTD bypass' manifold scoops wherever possible. A hole will be-made through  ;

=the end of each scoop so'that water will flow in through the existing ]

holes in the-16ading edge of the scoop, past the RTD, and out-through the j new hole (Figure 1.2-1). .If plant interferences preclude the placement of j a thermowell in a scoop, then the scoop will be capped and a' new penetra-t

?

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 'l temperature (T,yg).

b) This modification will not affect the dual element wide range RTD l currently installed near the entrance of each steam generator. This RTD 'i will continue to provide the hot leg temperature used to monitor reactor coolant temperature during startup, :hutdown, and port accident conditions. 3 1.2.2 Cold Leo a) One fast response, narrow range, dual-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 the cold leg temperature which is used to calculate reactor coolant loop  !

Delta T and T,yg. The existing cold leg RTD bypass penetration nozzle will be modified (Figure 1.2-3) to accept the.RTD thermowell wherever possible.

l L If structural inbrferences preclude placement'in the existing nozzle then the nozzle will be capped and a new penetration made to accommodate the I thermowell (Figure 1.2-2).

l

. b) This modification will not affect the dual element wide range RTD in each cold leg currently installed at the discharge of the reactor coolant pump. This RTD will continue to provide the cold leg temperature used to monitor reactor coolant temperature during startup, shutdown, and post accident conditions.

' 04200:1D/070390 3 6

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a 1.2.3 Crossover Lea J 9

, . The RTD bypass manifold return line will be capped at the nozzle on the >

crossover leg.= i

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..1.3. ELECTRICAL MODIFICATIONS 1.3.1 Control & Protection System t Q

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

This was done largely to satisfy Section 4.7 of the IEEE Standard 279-1968 which applies to control and protection system interaction. The new g thermowell mounted RTDs will be used for both control and protection. In L 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 "

median signal selector, which will select the signal which is between the-highest and lowest values of the three loop inputs. This will avoid any adverse plant response that could be caused by a single random failure. 3 Hith the elimination of the RTD bypass manifold, three (3) hot leg RTD's are q installed in thermowells mounted on the RCS pipe circumference approximately the same vertical' plane. The temperatures read at these locations are' somewhat different:because of streaming effects. Thus, the three temperatures 1 are processed to produce an average temperature (Thave) for each hot leg. -

, The cold leg temperature measurement on each loop is . accomplished with a narrow range dual-element RTD installed in a thermowell. The thermowell is. 4 mounted either'in the existing cold leg bypass nozzle 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 n .... a concern due to the mixing .

action of.the reactor coolant pump.

04200:10/070390 4 1

h

. The process system used to calculate Thave.and Tcold is designated the- j

-Temperature Averaging System (TAS). The Temperature Averaging System (TAS)-

becomes part of the Thermal Overpower and Overtemperature Protection System because the.TAS outputs (T and T have and Teold) replace the Thot cold signals previously derived from the bypass manifold RTD.

- )

t 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 icold. The three hot leg temperatures are processed to produce the average- .(

hot leg temperature.T have. T have is then combined with T cold to produce the loop average temperature (T,yg) and the loop difference temperature (Delta T). The resultant signals replace the same signals previously derived i in the analog Thermal Overpower and Overtemperature protection channels.

l

-The two cold leg temperature input signals are subjected-to range and consistency checks and then averaged to provide a group value for Tcold* II 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 MMI. The '

remaining T cold input signal will provide the loop T cold temperature. ,

DELTAC is an input parameter based on operating experience and is entered via the portable Man Machine Interface (MMI). 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 011minates 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 determines the validity of each input signal and automatically rejects a l L

defective input.

{ 1 4*

I 04200:10/070390 5

i 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 hot input signal by adding or subtracting as necessary, a temperature streaming correction factor. Then, the average of the three estimated average hot leg temperatures is computed and the individual estimates are checked to t determine if they agree within DELTAH of the average value. If all of the L signals do agree within DELTAH of the average value,-the group quality is set to GOOD. The group value T have is set to the average of the-three l- estimated average hot leg temperatures.

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

The quality of the deleted signal is set to POOR and a consistency check is ,

l performed on the remaining GOOD signals. If these signals pass the -

l consistency check, the group value will be taken as average of these remaining l- GOOD signals and the group quality will be set to POOR. However, if these signals again fail the consistency check (within i DELTAH), the group value-will be set to the average of these two signals; but the grou_p quality will be '

set to BAD. All of the individual 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 Man-Machine-Interface  ;

(MMI). One DELTAH is required for each temperature loop.

1.3.2 Oualification l

The EQ for Eagle 21 instrumentation is addressed in HCAP-12374. RTD quaiification will be verified to support FPL's compliance to 10CFR50.49.

The Hestinghouse qualification program contained a review of the HEED Instrument Company's qualification 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 exception.

5 04200:1D/070390 6

~Specifically, requirements relative to riow induced vibration'were not addressed. To demonstrate that flow induced vibration would.not result in I significant aging mechanisms that could cause common mode concerns during a seismicz event. Hestinghouse performed flow induced vibration tests followed by .i pipe vibration aging and a simulated seismic event. These tests confirmed that the HEED RTDs do comply with the above IEEE standards.

1.3.3 RTD Operability Indication l

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

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for Fast Response RTD Installation f

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There are two specific types of tests which are performed to support the 1 installation of the thermowell mounted fast-response RTDs in the reactor j coolant piping: RTD response time tests and a-hot leg temperature streaming test. The response time for the Turkey Point Units 3 and 4 application will be verifled by testing at the RTD manufacturer and by in-situ testing. Data j 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 RTD 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 d.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 installed 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 maximum to minimum of [ ]b,c.e A test program was implemented at an operating plant to confirm the temperature streaming magnitude and stability with measurements of the RTD bypass branch line temperatures on two adjacent hot leg pipes. Specifically, it was intended to determine the 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 temperature. This plant specific data is used in conjunction with data taken from other Hestinghouse  !

designed plants to dete. mime an appropriate temperature error for use in the

'04200:10/070390 11

= 't safety analysis and calorimetric flow calculations. Section 3 will discuss' the specifics of.these uncertainty considerations. -;

The test data was reducei and characterized to answer the three objectives of

, the test program. First, it is conservative to state that the streaming J 'C.

D pattern [ Steady state data taken at 100% power for a period of four months indicated that_the streaming pattern  :

[- ]b,c.e In other words, the temperature gradient [ ]b,c.e. This is inferred by [ 3b .c.e observed between branch lines. Since the (

)b,c.e into the RTD averaging circuit if a hot _ leg RTD fails and only 2 RTDs are used 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 Hestinghouse 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 cbserved in the operating data compared with the previous -

data indicate that the temperature gradients are smaller, so the measurement' uncertainties are conservative. The measurements at the operating 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

y L

04200:10/070390 12

- -t . _ ,

.- g. - (. t_ F TABl.E ?.1-1

. RESPONSE TIME PARAMETERS FOR RCS TEMPERATURE MEASUREMENT

~

RTD .

. Fast Responsei '

)

Bvoass SvtitE. Thermowell-RTD System-- .i a,c a,c.

RTD Bypass Piping and Thermal Lag (sec) = ,

, I

~RTD Response Time (sec) ,

-t Electronics Delay (sec) -

. . L . J-- . .

Total Response Time (sec) 6.0 sec 6.0'sec t

s

, i f

\

(

i i

I_

k

'\'.

b 1'

1 1

LO420D:1D/061590 13 3

,t' +

1. t w ----t, ---

- i Q ,

s 3.0 ; UNCERTAINTY CONSIDERATIONS ,

This method of hot leg temperature _ measurement has beun analyzed to determine the :nagnitude of the two uncertainties included in the Safety Analysis:

Calorimetric Flow Measurement Uncertainty and Hot Leg Temperature Streaming Uncertainty.

3.1 CALORIMETRIC FLOW HEASUREMENT UNCERTAINTY Reactor coolant flow is verified with a calorimetric measurement performed after the return to power operation following a refueling shutdown. The two-most important instrument parameters for the calorimetric measurement of RCS-flow are the' narrow range hot leg and cold leg coolant temperatures. The accuracy of the RTDs has, therefore, a major impact on the accuracy of the

-flow measurement.

With the use of three T hot RTDs (resulting from the elimination of the RTD Bypass lines) and the requirements of the latest kestinghouse RTD cross-calibration procedure (resui!;ing in low RTD calibration uncertainties at the beginning of a fuel cycle), the Turkey Point Units-3 and 4 RCS Flow 4 Calormetric uncertainty is determined to be C. 3a,c j including use of cold leg Elbow Taps (see Tables 3.1-2, 3, 4 and 5). This calculation is ' ased o on the stardard Westinghouse methodology previously. ,

approved or earlier submittals of other plants associated with RTD Bypass Eliminatioa or the use of the Hestinghorn Improved Thermal' Design Procedure.

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

t, 3.2 HOT LEG TEMPERATULE STREAMING UNCERTAINTY 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 resctor core L at different temperatures. This temperature streaming uncertainty is based on an analysis of test data from other Hestinghouse plants, and on calculations 4'

04200:lD/070390 14

- - y..--a ,y+---- a y

~' '

j 1

1 to evaluate the impact on temperature measurement' 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 [

3b,c.e,-and g

Lthat the, inferred temperature gradient within the pipe is limited to about L

[- 3b ,c.e The calculations for numerous temperature distributions have shown that, even with margins applied to the observed r temperature gradients, the three-point temperature measurement (scoops or  ;

thermowell RTDs) is'very effective in determining the average hot leg j temperature. Turkey. Point' plant specific calculations for the therm,well RTD 1 system have established an overall streaming uncertainty of.[ 3b ,c.e .

for a hot _ leg measurement. Of this total, [

)b,c.e ,

r 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,  ;

[

lC . Although the new method measures temperature at one point L at the RTD/thermowell tip conrpared to the five sample points in a 5-inch span of the scoop measurement, the thermowell measurement point is opposite the l 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. The thermowell measurement may have a small error relative to the scoop measurement if the temperature gradient over the 5-inch scoop spanlis nonlinear. Assuming that the maximum inferred temperature gradient of [

3D .C,e exists from the center to the end of the scoop, the~

difference between the thermowell and scoop measurement is limited to

[ l b,c.e . Since three RTD measurements are averaged, and the nonlinearities at each scoop are random, the effect of this error on the hot leg temperature measurement is limited to [ l b,c.e On the other hand, imbalanced scoop flows can introduce temperature measurement uncertainties of up to.[

3a .c ,

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

[ Jb.c.e sampling uncertainty for the thermowell RTDs, so the new L

1 04200:1D/070340 15

_ _ _ _ . _-- _ _ - _.- - ~ _ - . _

y

/ i i

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 plants.

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 [ f j ,b 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 r* the timperature differentials. [

3b ,c.e ,

Provisions were made in the.RTD electronic: fOr oper: tion with only two hot [

1eg RTDs in service. The two-RTD measurement will be biased to correct for the difference compared with the three-RTD average.

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 L the conclusion that sufficient margin exists for the uncertainties. Table 3.1-8 documents the breakdown for Overpower AT. Comparing the Channel i

. 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.

04200:1D/070390 16 4

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 H 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 exist for the uncertainties. Table-3.1-12 provides the uncertainty breakdown for T,yg - Low - Low. A comparison of the Channel Statistical Allowance with the Total Allowance noted on Table 3.1-12 results in the conclusion that sufficient margin exist 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.

I i

l .-

0420D:10/061590 17

N l

a. .

i

TABLE 3.1 l

..i ROD. CONTROL SYSTEM ACCURACY

-Tavg' ERI EA0 ANALOG TURBINE MSS .

SENSOR / TRANSMITTER j!

't

+5,C pMA .- 1 '

SCA .  ! .

SMTE =

i

'STE. -

SD = ,

BIAS =

PROCESS RACKS 9

+&,C '[

RCA --

KMTE =

RTE =

RD -

CA .= .

~

1. RTDs USED - TH = 2 TC = 1 .

i

+4,C j

~ ~

ELECTRONICS CSA =

1 p '

ELECTRONICS SIGMA -

CONTROLLER SIGMA -

CONTROLLER BIAS -

' CONTROLLER CSA .-

h: r 04200:1D/061290 18

a

- TABLE 3.1-2 .

i FLON CALORIMETRIC INSTRUMENTATION UNCERTAINTIES

- (%- SPAN)' ' FH TEMP FH PRES FH DP STM PRESS TH TC- PRZ' PRESS

+n,c Scg ,

SMTE = 1 4SPE' -

STE =

SD =

RCA =  ;

RMTE -

i- RTE --

RD - '

RDOT =

BIAS -

CSA -

- i

1. OF INST USED- 1- 3 l' 3-DEG F PSIA %DP PSIA DEG.F DEG F PSIA

' INST SPAN - 194. 1500.= 100. 1200. 100. 100. 800.  :

.t INST-UNC. -

.+a,c q (RANDOM) =

L l~ INST UNC.

E (BIAS) =

NOMINAL - ,

4

! t t .

l;  ;

0420D

1D/061590 19 1

,----.a a.--e, , , , , - , - - ,

I i l

l y ,

G

i.  ;

TABLE 3.1 I

)

FLOM CALORIMETRIC SENSITIVITIES

, s i FEEDHATER FLOH FA -

e TEMPERATLRE . +a.c y MATERIAL = 1 l

DENSITY i TEMPERATURE =

PRESSURE- = .1 DELTA P- -  ;

FEEDHATER ENTHALPY-TEMPERATURE' = 5 PRESSURE -

h5 -

1199.8 BTU /LBM hF - 415.5 BTU /LBM .;

Dh(SG) = 784.3 BTU /LBM STEAM ENTHALPY -

\

a PRESSURE - +a.c- .

MOISTURE -

HOT! LEG ENTHALPY TEMPERATURE -

PRE;SURE =

hH = 616.5 BTU /LBM hC . 542.5 BTU /LBM

, Dh(VESS).' = 74.1 BTU /LBM , .,

Cp(TH) = 0.1438E+01 BTU /LBM-DEGF  ;

U COLD LEG ENTHALPY TEMPERATURE . +a,c

' PRESSURE -

~Cp(TC) = O.1234E+01 BTU /LBM-DEGF-  !'

COLD LEG SPECIFIC VOLUME

~ TEMPERATURE . +a,c PRESSURE = .

0420D:1D/061590 20 ,

- __ ..n._, --

, . , . . . ,,.er-- y

U l l

l TABLE 3.1-4 CALORIMETRIC RCS FLOW MEASUREMENT UNCERTAINTIES

. '/ l

_ C0l;PONENT . INSTRUMENT ERROR FLOW UNCERTAINTY j i

+8,C

- ~'

FEEDNATER FUM  !

VENTURI THERMAL EXPANSION COEFFICIENT TEMPERATURE KATERIAL i DENSITY ,

TEMPERATURE PRESSURE ,

DELTA P.  !

FEEDWATER ENTHALPY -

TEMPERATURE  :

PRESSURE-i STEAM ENTHALPY PRESSURE MOISTURE }

NET PUMP HEAT ADDITION HOT LEG ENTHALPY TEMPERATURE STREAMING,-RANDOM STREAMING, SYSTEMATIC PRESSURE i

COLD LEG ENTHALPY TEMPERATURE PRESSURE COLD LEG SPECIFIC VOLUME L, TEMPERATURE ,

PRESSURE .

04200:10/061590 21

n 4 i l

l  !

I TABLE 3.1-4 (continued)

CALORIMETRIC RCS FLOW MEASUREMENT UNCERTAINTIES  :

1 BIAS VALUES +a c )

FEEDWATER PRESSURE DENSITY ENTHALPY STEAM PRESSURE ENTHALPY  !

PRESSURIZER PRESSURE ENTHALPY - HOT LEG J ENTHALPY - COLD LEG j SPECIFIC VOLUME - COLD LEG j FLOW BIAS TOTAL VALUE - -

1

• ** +,++ INDICATE SETS OF DEPENDENT PARAMETERS

, , j

~

1 LOOP UNC  ;

N LOOP UNC , ,

?

I i

i 9

t D4200:10/061590 22

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

,, ., +4 C PMA =

PEA =

SCA .=

SMTE =

SPE =

STE =

SD =

BIAS =

'RCA =

RMTE =

RTE =

RD =

A/D =

ROUT =

+&,C

' ~

1 LOOP ELB0H TAP =  % FLOH N LOOP ELB0H TAP =  % FLOH N LOOP RCS FLOW TAP = ,% FLOW 04200:10/061290 23 1

^

n-i t

TABLE 3.1-6 l i

OVERTEMPERATURE AT i PARAMETER ALLOWANCE i i

Process Measurement Accuracy l

• a' '- - *"'" '

AT -

AI -

al -

~ "

Primary Clement Accuracy (

Sensor Calibration l, AT -

Pressure - ,

Measurement & test Equipment Accuracy {

Pressure - ( ).. +a.c 1

Sensor Temperature Effects  ;

Pressure - [ ]

Sensor Drift '

+a,c AT' - ,

Pressure -

4

. . i Bias Environmental Allowance

+a,c Rack Calibration DT span AI -

Pressure -

04200:1D/061590' 24 i

L l 1

l TABLE 3.1-6 (continued)

J r

i OVERTEMPERATURE AT i

t PARAMETER ALLONANCE i

Measurement & Test Equipment Accuracy  !

. .+a,c -

AT .. j AI. -  ;

i Tavg -

Pressure -

Rack Temperature Effects

+a,c AT- - [ ]

AI -

, Pressure Rack drift AT - .

t AI -

Pressure -

• In % span (Tavg - 100*f, pressure - 800 psi, power - 120% RTP, ,

AT -.75*F AI i 60% AI) .. !

• • ~See Table 3,1-7 for gain'and conversion calculations ese ( )+a C a

?

f

' 04200:1D/061290 25

TABLE 3.1-6' (continued)

OVERTEMPERATURE AT Channel Statistical Allowance - 5.6% AT SPAN

. . +a,c Total Allowance -

Margin ,,

4 04200:10/061290 26

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

AT [(l'+ sgS)/(1 + x2 S}3 E(I)#I + T 3S)3 I AT,[K) - K2 III + T4 8)#II + '5S ))[T[(1)/(1 + 56 5)) - T') + K3 (P-P') - f)(AI))

K = 1.0950 Technical Specification value K ii max)

((nominal) = [ 1+a,c K2

= 0.017/'F K3

= 0.000453/ psi vessel AT = 56.1 'F LI gain = 1.5 FP A!/%AI

. +a.C Pressure Gain -

Pressure SCA = -

Pressure SMTE =

Pressure STE =

Pressure SD =

~ -

~ ~

+4,C AI conversion =

=

AI PMA)

AI PMA2

• Total Allowance (TA) =

[- ).+a.c t

04200:10/070390 27

TABLE 3.1-8 OVERPOWER AT Parameter Allowance

• Process Measurement Accura;y . _+a.c AT - [ ]+a,c Primary Element Accuracy Sensor Calibration AT - [ ]+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 Ay-( ) +a.c Rack Drift AT -( 3+a.c 1

04200:10/061590 28

/

TABLE 3.1-8 (continued)

OVERPOWER AT In % span (Tavg - 100 *F, AT - 75 'F = 120 % RTP)

.. g 3+a,c Channel Statistical Allowance = [ ] *"'C MARGIN = [ 3+R.C TOTAL ALLONMCF. = [ 3+a.c

, 04200:1D/061590 29

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

4 AT ((1 + t)S)/(1 +2 t b)] ((I)/(

• T3 b} I AT,(K 4 - K5 EII'7b }#CI * '7b }lI(I)III + '6 )))T 5

- K (T[(1)/(1 6 +t65)) - T") - f2 (AI)3 K4 (nominal)

= 1.091) Technical Specification value K4 (max) =[ )*I' K

5

- 0.02 K

6

0.00068 vessel AT = 56.1*F Total Allowance

g )+a.c 04200:1D/070390 30

= .

=

TABLE 3.1-10 LOSS OF FLOW ,

RCS LOH FLOW TRIP ACCURACY

~

• PMA - ALL VALUES IN % FLOW SPAN PEA =

SCA =

SMTE =

SPE =

STE =

SD =

BIAS = .

RCA =

RMTE =

RCSA =

RTE =

RD =

FLONSPkh -

SAL =

ALLV =

NOM =, ,

, _+R.C ,+4.C ,

+& C MAR = S = _

Z =

TA =

CSA =

T =

i 04200:10/061590 31

TABLE 3.1-11 PRESSURIZER WATER LEVEL HIGH Parameter Allowance

• Process Heasurement Accuracy - - +a.c

.[ 3+a,c Primary Element Accuracy Sensor Calibration M&TE Sensor Pressure Effects Sensor 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 - ,

i

]+a.c

, +a C ., ,

+a,C , ,

+a,C

- T -

Z - S CSA - MAR -

TA = , , a . , .

04200:10/061290 32

i e

TABLE 3.1-12 Tavg - Low. low Trip Accuracy-

'~

pg4 , ,+&,C SCA =

SD =

RCA =

RMTE =

RTE =

RD =

BIAS =

SAL = . ,

ALLV = 542.49 Tavg SPAN = 7b.G DEG. F

. ,,+ R . C . +1.C . .+&,C

= Z

MAR S CSA = T =

TA =

04200:1D/061290 33

TABLE 3.1-13 TECHNICAL SPECIFICATION MODIFICATIONS Functional Unit /Page no. Modification Justification Pressurizer Water Addition of Allowable Application of W Level High, page 2-4 Value, 92.2%. setpoint methodology.

Overtemperature AT, RTD Response time Elimination of RTD page 2-7 constants changed to bypass lines.

I 4.0 seconds.

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

Overpower AT, Removed Deltal Gain and W Safety Evaluation page 2-10 added allowable value SECL No. 89-1164, and of 0.0%. W setpoint methodology.

Overpower AT, Removed Deltal Gain Safety Evaluation page B 2-5 from bases. W SECL No.. 89-1164.

T,yg - Low, Revised trip setpoint Application of H pages 3/4 3-23, 25, & 27 to 543'F and added setpoint methodology.

an allowable value of 542.5'F. Moved to Table 3.3-3b.

g.

04200:10/070390 34

TABLE 3.1-13 (Continued)

TECHNICAL SPECIFICATION MODIFICATIONS Functional Unit /Page no. Modification Justification Overtemperature AT Remove Note 12 Elimination of RTD Table 4.3-1, Pages 3/4 Bypass Lines 3-8 and 3/4 3-12 Reactor Coolant Flow Added an allowable Application of W Low Page 2-4 value of 88.7%. Setpoint Methodology ee tpoint Tables 2.2-1 Added bases for using Application of W and 3.3-3 and Bases the 5 column setpoint Setpoint Methodology 2-2.1,3/4-3.13/4-3.2 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 Tables 4.3-1 and 4.3-2 Change analog channel WCAP 10271 and subse-

.pages 3/4 3-8, 3/4 3-29, operational test quent W 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 NCAP 10271 and subse-pages 3/4 3-2, 3/4 3-7, testing quent W evaluation 3/4 3-15, 3/4 3-18, 3/4 3-22. for digital process control equipment 04200:10/070390 35

l 4.0 SAFETY EVALUATION The primary impacts of the RTD Bypass Elimination on the FSAR Chapter 14 (Reference 1) safety analyses are the differences in response time characteristics and instrumentation uncertainties associated with the fast response thermowell RTO system. The effects of these differences are discussed in the following sections.

4.1 RESPONSE TIME 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 C 3"'C (as presented in Section 2.1 and as given in Table 2.1-1).

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 transport, thermal lag and direct immersion RTD. This allows the total RCS 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 (OTOT) and Overpower AT (OPDT) trip performance. Those transients that rely on the above mentioned trips must be addressed for the -

modified response characteristics. Section 4.3 includes a discussion of this evaluation.

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

( ]"'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. ,.

04200:1D/070390 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 (OTDT), Overpower AT (OPDT), and Low RCS Flow reactor trip functions, RCS loop T,yg measurements used for input to the rod cca trol system, and the calculated 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.

Orly 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 thermcwell 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 elinination 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.

04200:1D/070390 37

I In conclusion, the non-LOCA safety analyses applicaDie 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 i and 2 results and conclusions are unchanged and all app 1' able non-LOCA safety analysis acceptance criteria continue to be met.

4.4 LOCA Evaluation The elimination of the RTD bypass system impacts the uncertainties associated with RCS temperature measurement. The magnitude of the uncertainties are such that RCS inlet and outlet temperatures, thermal design flow rate and the steam generator performance data used in the LOCA analyses will not be affected.

Past sensitivity studies 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 in without consideration of small uncertainties. The RCS flow rate and steam generator secondary side temperature and pressure are also determined using the loop average temperature (T,yg) output. These nominal va'ues used as inputs to the analyses are not affectsd due to the RTO 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 'iurkey 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.

44200:10/070390 38

4.5 INSTRUMENTATION AND CONTROL SAFETY EVALUATION _

The RTD BYPASS ELIMINATION functional upgrade modification affects the measurement of the RCS hot leg temperature. Prior to the modification, the RCS hot. leg coolant was sampled by scoops in the main 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 ]l~~

mounted in the cold leg bypass manifold. With the elimination of the RTD bypass manifold, three (3) hot leg RTD's are installed in thermowells 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 each loop is accomplished with a dual element narrow range RTD installed in a thermowell. The thermowell is mounted either in the existing cold leg bypass connection or boss mounted in a new penetration. The cold leg sensors are inherently redundant in that either -

sensor c!' adequately represent the cold leg temperature measurement. _

Tempf streaming in the cold leg is not a concern due to the mixing actict 21 the reactor coolant pump.

The process system used to calculate T have and T cold is designated as the Eagle 21 Temperature Averaging System (TAS). The Temperature Averaging System -

(TAS) becomes part of the Thermal Overpower and Overtemperature Protection System because the TAS outputs (T and Teold) replace the Thot and have Teold signals previously derived from the bypass manifold RTDs. A generic topical report providing details on Eagle 21 design philosophy, system architecture, hardware, software, qualification, verification, validation, and compliance with criteria has been documented as WCAP-12374. -

04200:1D/070390 39 .

l 4.5.2 DES!GN AND IMPLEMENTATION The Eagle 2) 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 processed to produce an average cold leg temperature TCOLD. The three hot leg temperatures are processed to produce the average hot leg temperature Thave. T have is then combined with T to produce the loop average temperature (Tavg) and the loop difference COLD 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 de .iot agree within the acceptable tolerance DELTAC, the group quality is ;et to BAD and the individual input signal qualities are set to POOR. The verage 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 MMI. The remaining Tcold input signal will provide the loop T temperature. DELTAC is an input parameter based on operating cold experience and is entered via the portable Man Machine Interface (MMI). 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 determines the validity of each input signal and automatically rejects a defective input (Figure 4.5.2-3).

4 04200:1D/070390 40 i '4 1 - rin iiiiiiiii i i

Each of the three hot leg temperature input signals is subjected 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 hot input signal by adding or subtracting as necessary, a 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 ao agree within i DELTAH of the average value, the group quality is set to GOOD. The group value T have is set to the av' age 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 from 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 GOOD signals and the group quality will be set to POOR. However, if these signals 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 Elimination functional upgrade.

04200:10/070390 41

4.5.3 ALARMS, ANNUNCIATORS AND SIATUS LIGHTS 2

Additional control room alarms, annunciators and status lights are provided as part of the RTD Bypass 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 have group value for a coolant loop 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 range T hot signals for one of the coolant loops.)

2. An "RTD Failure" alarm and annunciator window is added common to all 3 loops. This alarm and annunciator is actuated anytime the Tcold OI T

have group value for a coolant loop is set to BAD as described in Section 4.5.2. This alarm and annunciator informs the operator that there is an invalid T cold or T have group value for a loop. A 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 I IEEE-279-1971. Bypassing of Protection functions for the Eagle 21 channels will be administrative 1y controlled and will not be used at this time.

The conversion to t5ermowell mounted RTDs 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 protection interaction requirements of IEEE 279-1971, a Median Signal Selector (HSS) will be used in the control 04200:10/070390 42

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.To REDUNDANT SENSOR AL90Rmed C1 f STATUS UPDATE Yo Figure 4.5.2-2 Functional Logic Diagram (Teold) 04200:1D/062990 44 2 .

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%1 ha T T

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04200:10/062990 45

channels presently utilizing a high auctioneered T avg or Delta ** signal _.

(there will be a separate MSS for each function). The Median Signal Selector will use as inputs the protection grade T,yg or Delta T signals from all three loops, and will supply as an output the Channel 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 avg and AT signals will have 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,yg or Delta T signal from a single _ _ _ _

loop will be eliminated. The MSS will automatically select a valid signal in (

the case of a signal failure. Warnings that a failure has occurred will be provided by loop to median T,yg and Delta T deviation alarms.

The overtemperature, overpower, 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 unaffected 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 i continuing to operate on a "de-e..segize to actuate" principle.

The above princip h: 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:

04200:10/070390 46

a. The single failure criterion continues to be satisfied by this change because the independence of redundant protection sets is maintained.

b. The quality of the components and modules 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.

c. . The changes will continue to maintain the capability of the protection 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 1 circuits input to Protection Set I; Loop 2 to Protection Set II; and Loop 3 to Protection Set III.

e. Due to the elimination of the dedicated control system RTD elements, temperature signals for use in the plant control systems must now be derived from the protection system RTDs. To eliminate any degrading control and pic4vction system interaction mechanisms introduced as a consmence of the RTD Bypass Elimination modification, a Median Signal Selector has been introduced into the control system. The Median Signal Selector preserves the functional isolation of interfacing control and 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.

04200:10/070390 47

l 4.5.4 TEST ENHANCEMENTS For those racks being upgraded with Eagle 21 process protection equipment, test enhancements discussed and approved generically in HCAP-10271-P-A

" Evaluation of Surveillance Frequencies and out of service times for the reactor protection instrumentation system" are being implemented (Reference 3).

The specific enhancements being implemented are as follows:

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

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

In the Sequoyah Safety Evaluation Repoc+ (Docket No. 50-327) dated May 16, 1990, the NRC staff concluded that these same test enhancements were consistent with the approved Topical Report HCAP-10271-P-A and therefore, are acceptable.

4.6 MECHANICAL SAFETY EVALUATION The presently installed RTD bypass system is to be replaced with fast acting narrow i . ige 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 Hinter 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 accomplisn the sampling function of the RTD bypass manifold system and minimize thy need "or additional hot leg piping penetrations, the RTD thermowell assemt. lies be located within the existing RTD Bypass Manifold Scoops wherever possible. [

]"'C to provide the proper fiow path. If structural interferences preclude the placement of a thermowell il a given scoop, then 04200:1D/070390 48

f '

the scoop will be capped and a new RCS per<.; ration made to accommodate the i L relocated thermowell. The relocated RTD/thermowell will be 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 R.TD average tempereture. 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 (SMAH). The welding will be examined by pen'trant 4

test (PT) pet M ASME Code Section XI. Prior to welding, the surface of the scoop or bos, onto which welding will be performed will be examined as l

required by Section XI.

l-The colo leg RTD bypass line must also be removed. The nozzle must then be

-modified to accept the fast response RTO thermowell. If necessary, the RTD's ,

will be relocated because of interferences. The installation of the ,

thermowell into the nozzle will be performed using GTAH for the root pass and finished with either GTAH or SMAN. Held inspection by PT will be performed as a .c-required by Section XI. The thermowells will extend approximately [ 3 7 inches into the flow stream. This depth has been justified based on [ <

3c a

analysis. The root weld joining the thermowells to

- the modified nozzles will be deposited with GTAH and the remainder of the weld L may be deposited with GTAN.or SMAN. Penetrant testing will be performed in d accordance with the ASME Code Section'XI. The thermowells will be fabricated

$ 'in accordance with.the ASME Section III (Class 1). If-structural-

[ ' interferences peclude placeme'nt in the existing nozzle then the nozzle will be l capped and a.new penetration made to accommodate the thermowell. The ,

thermowell will be. installed in a boss. The installation of the thermowell I L

[ into the boss will be the same as for the nozzle installation.

1 1

-The cross-over leg bypass return piping will be severed tu ' eave 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 either GTAH or SMAH. Non-destructive examinations (PT and 04200:10/070390 49 l

radiographs) will be performed per ASME Section XI. Machining of.the bypass _;

. return nozzle, as well as any machining performed'during modification of the. .t

penetrationf. in the hot and cold legs, shall be performed such'as to minimize

' debris escapfng into the reactor coolant system.  ;

The design and analysis of the loop piping and associated branch connection-boss, weld, and pipe cap, where applicable, will meet the requirements of the

. USAS-831.1.0 Code 1967 Edition, No Addenda. ,

- In accordance with Article INA-4000 of Section X' the ASME Code. a hydrostatic test of new pressure boundary velds 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 [ J a.c inches and L the-cold leg RTO connections are [ 3a ,c inches, a system hydrostatic test

- is required after the bypass elimination modification is complete. Paragraph' l - IHB-5222 of Section XI defines this test pressure to be 1.02 times the normal L operating pressure at a temperature of 500'F or greater.

l in .'In sum 4ry, the integrity of the reactor coolant piping as a pressure boundary '

component, is maintained by adhering to the applicable ASME Code sections and Nuclear _ Regulatory Commission General Design Criteria. Further, the pressure retainina ::a-"'lity and fracture prevention characteristics of the_ piping is not compro.4ied oy these modifications.

4.7 TFrad' CAL SP7' GTION EVALUATION As a r: , se v ulations summarized in Section 3.0, several protection I

functh n wier' .,pecifications are modified. The affected functions and their aC : * .,ip Setpoint information, are noted on Table 3.1-13.

t l

04200:1D/070390 50

1 i

5.0- CQHIROL SYSTEM EVALUATION l

A prime input to the various NSSS 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, i

The effect of the new RTD temp cature measurement system is to potentially change the t W, response of the T,yg channels in the various loops. This in turn ec W 5eptti the response of [ t f't However, as previously noted, the new RTD system (thermowell mounted RTO) will have a time reponse identical to that of the current system 1 (RTD + bypass line). The additional delay resulting from the Median Signal L Selector (MSS) is small in comparison with the RTC time response ( ,

a J .c. Therefore, there will J

~

be no significant impact on the T,yg channel response and no need, as a result of implementing the new system, to revise any of the control system L setpoints. It should be recognized that control systems do not perform any l protective function in'the FSAR accident analysis. With respect to accident L analyses, control systems are assumed operative only in cases in which their action aggravates the consequences of an event, and/or as required to establish initial plant conditions for an analysis. The modeling of control ,

systems for accident analyses =is based on nominal system parameters as i presented in the Precautions Limitations, and Setpoint document.

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04200:1D/070390 51

l 6.0; CONCLUSIONS )

.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 l Lincorporation of this system into the Turkey Point Units 3 and 4 design meets all safety, licensing and control requirements necessary for safe operation of 1 these units. The analytical evaluation has been supplemented with in-plant  ;

and laboratory testing to further verify system performance. The fast response RTOs 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.

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, i 104200:1D/070390 52

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7.0. REFERENCES

- . . .l il'. '_ Turkey. Point Units 3 and 4 Updated FSAR. l L 2._ 'WOAP-10271-P-A " Evaluation of Surveil d ce Frequencies and Out of Service 1 Times for the Reactor Protection Instrumentation System."

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