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Westinghouse Setpoint Methodology for Protection Sys Beaver Valley Unit 1
	ML20236A966
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Site:	Beaver Valley
Issue date:	10/31/1987
From:	Moomau W; WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
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	WCAP-11420, NUDOCS 8903200238
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WESTINGHOUSE CLASS 3 WCAP-11420 WESTINGHOUSE SETPOINT METHODOLOGY FOR PROTECTION SYSTEMS BEAVER VALLEY UNIT 1 October, 1987 W. H. Moomau Westinghouse Electric Corporation l
Energy Systems P.O. Box 355 Pittsburgh, Pennsylvania 15230 f
c-L
' TABLE'0F CONTENTS L
Section' Title M
j i
~~1.0 INTRODUCTION~~
1-1 j
2.0 COMBINATION OF ERROR COMPONENTS 2-1
~2.1
' Methodology.
2-1
.2.2 Sensor Allowances 2-3
[
2.3 Rack Allowances 2-5 2.4 Process Allowances 2-6 2.5 Measurement and Test Equipment Accuracy 2-6 1
3.0 PROTECTION SYSTEMS SETPOINT METHODOLOGY 3-1 3.1 Margin Calculation 3-1 3.2 Definitions for Protection System 3-1 Setpoint Tolerances 3.3 Statistical Methodology Conclusion 3-6 4.0
' TECHNICAL SPECIFICATION USAGE 4-1 4.1 Current Use 4-1 4.2 Westinghouse Statistical Setpoint 4-2 Methodology for STS Setpoints 4.2.1 Rack Allowance 4-2
, 4.2.2 Inclusion of "As Measured" 4-3 Sensor Allowance 4.2.3 Implementation of the 4-4 Westinghouse Setpoint Methodology 4.3 Conclusion 4-8 Appendix A SAMPLE BEAVER VALLEY UNIT 1 SETPOINT TECHNICAL A-1 SPECIFICATIONS ii o337v:1o/021187
m LIST OF TABLES Table Title Page 3-1 Power Range, Neutron Flux-High and Low Setpoints' 3-7 3-2 Power Range, Neutron Flux-High Positive Rate and 3-8 High Negative Rate 3-3 Intermediate Range, Neutron Flux 3-9 3-4 Source Range, Neutron Flux 3-10 3-5 Overtemperature AT-3-11 3-6 Overpower AT 3-13 3-7 Pressurizer Pressure - Low and High, Reactor Trips 3-15 3-8 Pressurizer Water Level - High 3-16
{
3-9 Loss of Flow 3-17 3-10 Steam Generator Water Level - Low and Low-Low 3-18 3-11 Steam /Feedwater Flow Mismatch 3-19 i
3-12 Containment Pressure - High, Intermediate High-High,
)
and High-High 3-21 3-13 Pressurizer Pressure - Low, Safety Injection 3-22 3-14 Steamline Pressure - Low-3-23 3-15 Negative Steamline Pressure Rate - High 3-24 3-16 Steam Generator Water Level - High-High 3-25 3-17 Reactor Protection System / Engineered Safety Features 3-26 Actuation System Channel Error Allowances 3-18 Overtemperature AT Gain Calculations 3-27 3-19 Overpower AT Gain Calculations 3-29 3-20 Steam Generator Level Density Variations 3-30 3-21 AP Measurements Expressed in Flow Units 3-31 3-22 RWST Level - Low, Auto 0S Flow Reduction 3-33 3-23 Undervoltage ; RCP 3-34 l
3-24 Underfrequency - RCP 3-35 3-25 4.16 kV Emergency Bus Undervoltage - Trip Feed, Start Diesel, Degraded Voltage 3-36 0237 <:1o/021187 i
L
L LIST OF TABLES (Continued)
Table Title Page 3-26 480 Volt Emergency Bus Undervoltage - Degraded Voltage 3-37 3-27 Auxiliary Feedwater Turbine Driven Pump Discharge Pressure - Low 3-38 4-1 Examples of Current STS Setpoints Philosophy 4-10 4-2 Examples of Westinghouse STS Rack Allowance 4-10 4-3 Westinghouse Protection System STS Setpoint Inputs 4-13 1
i-t iv 0237v;1D/071187
LIST OF TLLUSTRATf0NS Figure Title Page 4-1 NUREG-0452 Rev. 4 Setpoint Error 4-11 Breakdown 4-12 4-2 Westinghouse STS Setpoint Error s
Breakdown 1
l v
0237v:10/021187
1 1.0' INTRODUCTION t
In-March of.-1977, the NRC requested several utilities with' Westinghouse Nuclear Steam Supply Systems to reply' to a series of questions concern-ing the methodology for determining instrument-setpoints. A statistical
. methodology was developed in response to those questions with a corres-ponding defense of the technique used in determining the overall-allowance for each setpoint.
The basic underlying assumption used is that several of-the error com-ponents and their parameter assumptions act independently, e.g., [
-)+a,c
.This allows the use of a statistical summation of the various breakdown components instead of a strictly arithmetic summation. A direct benefit of th: us's of this technique is' increased margin in the total allowance' For those parameter assumptions known to be interactive the technique uses the normal, conservative approach, arithmetic summation, to form independent quantities,e.g.,[
]+a,c An explanation of the overall approach is provided in Section 2.0.
\\
Section 3.0 provides a description, or definition, of each of the various components in the setpoint parameter breakdown, thus insuring a clear understanding of the breakdown. Also provided is a detailed example of each setpoint margin calculation demonstrating the technique and noting how each parameter value is derived.
In nearly all cases, significant margin exists between the statistical summation and the total allowance.
Section 4.0 notes what the current standardized Technical Specifications use for setpoints and an explanation of the impact of the statistical approach on them.
Detailed examples of how to determine the Technical Specification setpoint values are also provided. An Appendix is pro-vided noting a recommended set of Technical Specifications using the L
plant specific data in the statistical approach.
0237v:10/021187 1-1
p:
2.0' COMBINATION OF ERROR COMPONENTS
]
2.1 METHODOLOGY The methodology used to combine the error components for a channel is basically the appropriate statistical combination of those groups of l
components which are statistically independent, i.e., not interactive. Those.
errors which are not independent are placed arithmetical 11y into groups. The 1
groups themselves are independent effects which can then be systematically combined.
i The methodology used for this combination is not new. Basically it is the
" square root of the sum of the squares" which has been utilized in other Westinghouse reports. This technique, or other statistical approaches of a similar nature, have been used in WCAP-10395(1) and WCAP-8567(2),
' WCAP-8567 has been approved by the NRC Staff thus noting the acceptability of statistical techniques for the application requested.
In addition, ANSI, the
'American Nuclear Society, and the Instrument Society of America approve of the use of probabilistic techniques in 'etermining safety related d
i setpoints(3)(4)
Thus it can be seen that the use of statistical approaches f
in analysis t'echniques is now widespread. The methodology used for this report is essentially the same as that used for V. C. Summer which was i
approved by the NRC in NUREG-0717, Supplement No. 4(5)
(1) Grigsby, J. M.,
Spier, E. M., Tuley, C. R., " Statistical Evaluation of LOCA Heat Source Uncertainty," WCAP-10395 (Proprietary), WCAP-10396 (Non-Proprietary), November,1983.
(2) Chelemer, H., Boman, L. H., and Sharp, D. R., " Improved Thermal Design i
Procedure,"WCAP-8567(Proprietary),WCAP-8568(Non-Proprietary), July, 1975.
l (3) ANSI /ANS Standard 58.4-1979, " Criteria for Technical Specifications for i
Nuclear Power Stations."
(4) ISA Standard S67.04-1982, "Setpoints for Nuclear Safety-Related Instrumentation Used in Nuclear Power Plants."
(5) Nureg-0717, Supplement No. 4. " Safety Evaluation Report Related to the Operation of Virgil C. Summer Nuclear Station, Unit No.1," Docket No.
50-395, August, 1982.
)
i 1
I i
c237v:10/0211s7 2-1 l
r ij i
The relationship between the arror components and the total statistical er,ror-
)
. allowance for a channel is, 3
CSA=EA+[-(PMA)2+(PEA)2+(SCA+SMTE+SD)2+(STE)2+(SPE)2
+(RCA+RMTE+RCSA+RD)2+(RTE)21/2 (Eq.2-1) 3 where:
Channel Statistical Allowance CSA
=
Process Measurement Accuracy PMA
=
Primary Element Accuracy-PEA
=
Sensor Calibration Accuracy SCA
=
. Sensor Measurement and Test Equipment Accuracy SMTE
=
Sensor Drift
=
SD
=
Sensor Temperature Effects STE
=
Sensor Pressure Effects SPE
=
Rack Calibration Accuracy RCA
=
. Rack Comparator Setting Accuracy RCSA
=
Rack Measurement and Test Equipment Accuracy RMTE
=
Rack Drift RD
=
i Rack Temperature Effects RTE
=
Environmental Allowance j
EA
=
As can be seen in Equation 2.1, drift and calibration accuracy allowances are.
interactive and thus not independent.
The environmental' allowance is not l
necessarily considwed interactive with all other parameters, but as an additional degree of conservatism is added to the statistical sum.
It should be noted that for this document it was assumed that the accuracy effect on a channel due to cable degradation in an accident environment will be less than 0.1 percent of span. This impact has been considered negligible and is not I
factored into the analysis. An error due to this cause found to be in excess 1
of 0.1 percent of span must be directly added as an environmental error.
Li-0237v:1o/021187 2-2 l-
dv
\\
o 3
The Westinghouse setpoint methodology results in.a value with'a 95 percent probability with a high confidence level.
With the exception of Process Measurement Accuracy, Rack Drift, and Sensor Drift, all uncertainties assumed are the extremes of the ranges.of the'various parameters, i.e., are better
'than 2a values.. Rack Drift and Sensor Drift are assumed, based on a survey s
of reported plant LERs, and with Process Measurement Accuracy are considered as conservative values.
2.2 SENSOR ALLOWANCES Four' parameters are considered to be sensor allowances, SCA, SD, STE, and SPE (see Table 3-17). Of these four parameters, two are considered to be statistically independent, STE and SPE, and two are considered interactive SD -
and SCA. STE and SPE are considered to be independent due to the manner in which the instrumentation:is checked, i.e., the instrumentation is calibrated and drift determined under conditions in which pressure and temperature are assumed constant. An example of this wouH be as follows; assume a sensor is placed in some position in the containment during a refueling outage. After placement, an instrument technician calibrates the sensor.
This calibration i
is performed at ambient pressure and temperature conditions.; Some time later with the plant shutdown, an instrument technician checks for sensor drift.
Using the same technique as for calibrating the sensor, the technician determines if the sensor has drifted or not. The conditions under which this determination is made are again at ambient pressure and temperature conditions. Thus the temperature and pressure have no impact on the drift determination and are, therefore, independent of the drift allowance.
SD and SCA are considered to be interactive for the same reason that STE and SPE are considered independent, i.e., due to the manner in which the instrumentation is checked.
Instrumentation calibration techniques use the same process as determining instrument drift, that is, the end result of the two is the same. When calibrating a sensor, the sensor output is checked to determine if it is representing accurately the input.
The same is done for a determination of the sensor drift.
Thus it is impossible to determine the differences between calibration errors and drift when a sensor is checked the il 0237v:1o/0211C7 2-3
second or any subsequent time. Based on this reasoning, SD and SCA have been added to form an independent group which is then factored into Equation 2.1.
An example of the impact of this treatment is; for Pressurizer Water Level-High(sensorparametersonly):
- +a,c using Equation 2.1 as written gives a total of;
[(SD + SMTE+SCA)2 + (STE)2 + (SPE)2) M
]+a,c= 1.66 percent
[
Assuming no interactive effects for any of the parameters gives the following-results:
[(SCA)2 + (SMTE)2 + (SD)2 + (STE)2 + (SPE)2) N (Eq. 2.2)
]+a,c = 1.32 percent
[
Thus it can be seen'that the approach represented by Equation 2.1 which accounts for interactive parameters results in a more conservative summation of the allowances.
0237v:1D/021187 2-4
2.3 RACK ALLOWANCES Four parameters, as noted by Table 3-17, are considered to be rack allowances, RCA, RCSA, RTE, and RD.
Three of these parameters are considered to be interactive (for much the same reason outlined for sensors in 2.2), RCA, RCSA, and RD. When calibrating or determining drift in the racks for a specific channel, the processes are performed at essentially constant temperature, i.e., ambient temperature. Because of this, the RTE parameter is considered to be independent of any factors for calibration or drift.
However, the same cannot be said for the other rack perameters. As noted in 2.2, when calibrating or c'atermining drift for a channel, the same end result is desired, that is, at what point does the bistable change state. After initial calibration it is not possible to distinguish the difference between a calibration error, rack drift or a comparator setting error. Based on this logic, these three factors have been added to form an independent group. This group is then factored into Equation 2.1.
The impact of this approach (formation of an independent group based on interactive components) is significant. For the same channel using the same approach outlined in Equations 2.1 and 2.2 the following results are reached:
- +a, c using Equation 2.1 the result is;
((RCA + RMTE+RCSA + RD)2 + (RTE)2) M
[
]+a,c = 1.82 percent 0237v:1D/021187 2-5
Assuming no interactive effects for any of the parameters yields the following less conservative results;
[(RCA)2 + (RMTE)2+ (RCSA)2 + (RD)2 + (RTE)2) 1/2 (Eq. 2.3)
]+a,c = 1.25 percent
[
Thus the impact of the use of Equation 2.1 is even greater in the area of rack effects than for the sensor.
Therefore, accounting for interactive effects in the statistical treatment of these allowances insures a conservative result.
2.4 PROCESS ALLOWANCES Finally, the PMA and PEA parameters are considered to be independent of both sensor and rack parameters.
PMA provides allowances for the non-instrument related effects, e.g., neutron flux, calorimetric power error assumptions, fluid density changes, and temperature stratification assumptions. PHA may consist of more than one independent error allowance. PEA accounts for errors due to metering devices, such as elbows and venturis. Thus, these parameters have been statistically factored into Equation 2.1.
2.5 MEASUREMENT AND TEST EQUIPMENT ACCURACY Westinghouse was informed by Duquesne Light Company that the equipment used for calibration and functional testing of the transmitters and racks does not meet the SAMA standard (1) requirement of test equipment accuracy being 10%
or less of the calibration accuracy (referenced in 3.2.6.a or 3.2.7.a.).
The
~
measurement and test equipment accuracies are identified in this report for each instrument channel.
(1) Scientific Apparatus Manufacturers Association, Standard PMC 20.1-1973.
" Process Measurement and Control Terminology."
f o237v;1D/021187 2-6
,e
. y s.
n sv
~
Of v
t 3.0 PR'0TECTION SYSTEM SETPOINT METHODOLOGY 3.1 MARGIN CALCULATION As noted in Section One, Westinghouse utilizes a statistical summation of the various components of the channel breakdown.
This approach is valid where no dependency is present. An arithmetic summation is required where an interaction between two parameters exists, Section Two provides a more detailed explanation of this approach. The equation used to determine the margin, and thus the acceptability of the parameter values used, is:
Margin =(TA)-[EA+ ((PMA)2+(PEA)2+(SCA+SMTE+SD)2+(SPE)2+(STE)2
+(RCA+RHTE+RCSA+RD)2+(RTE)2)1/2)
(Eq. 3.1) where:
TA 5 Total Allowance, and all other parameters are as defined for Equation 2.1.
Tables 3-1 through 3-16 and 3-22 provide individual channel breakdown and channel statistical allowance calculations for all protection functions utilizing 7100 process rack equipment. Table 3-17 provides a summary of the previous 17 tables and includes analysis and technical specification values, total allowance and margin.
The amount of margin allowed is based on a subjective engineer.ing judgement.
3.2 DEFINITIONS FOR PROTECTION SYSTEM SETPOINT TOLERANCES To insure a clear understanding of the channel breakdown used in this. report, the following definitions are noted:
1.
Trip Accuracy The tolerance band containing the highest expected value of the difference between (a) the desired trip point value of a process variable and (b) the 1
l 1
0237v:1o/021187 3-1 l
W.
actual value at which a comparator trips (and thus actuates some desired result). This is the tolerance band, in percent of span, within which the complete channel must perform its intended trip function.
It includes comparator setting accuracy, channel accuracy (including the sensor) for each input, and environmental effects on the rack-mounted electronics. It comprises all instrumentation errors; however, it does not include process measurement accuracy.
2.
Process Measurement Accuracy Includes plant variable measurement errors up to but not including the sensor. Examples are the effect of fluid stratification on temperature measurements and the effect of changing fluid density on level measurements.
3, Actuation Accuracy Synonymous with trip accuracy, but used where the word " trip" does not apply.
4.
Indication Accuracy The tolerance band containing the highest expected value of the difference between (a) the value of a process variable read on an indicator or recorder and (b) the actual value of that process variable. An indication must fall within this tolerance band.
It includes channel accuracy, accuracy of readout devices, and rack environmental effects, but not process measurement accuracy (such as fluid stratification).
It also assumes a controlled environment for the readout device. Although it is defined, indication accuracy is not used in this report.
5.
Channel Accuracy The accuracy of an analog channel which includes the accuracy of the primary element and/or transmitter and modules in the chain where 0237v:1o/021187 3-2
calibration of modules intermediate in a chain is allowed to compensate for errors in other modules of the chain. Rack environmental effects are not included here to avoid duplication due to dual inputs, however, normal environmental effects on field mounted hardware is included.
6.
Sensor Allowable Deviation The accuracy that can be expected in the field.
It includes drift, temperature effects, field calibration and for the case of d/p transmitters, an allowance for the effect of static pressure vari-ations.
The tolerances are as follows:
a.
Reference (calibration) accuracy - [
]+a,c percent unless other data indicates more inaccuracy. This accuracy is the SAMA reference accuracy as defined in SAMA standard PNC 20.1-1973(1) b.
Temperature effect -- [
]+a,c percent based on a nominal
~
temperature coefficient of [
]+a,e percent /100'F and a maximum assumed change of 50'F.
c.
Pressure effect - usually calibrated out because pressure is constant.
If not constant, nominal [
]+a,c percent is used.
Present data indicates a static pressure effect of approximately
[
]+a,c percent /1000 psi.
d.
Drift - change in input-output relationship over a period of time at reference conditions (e.g., constant temperature - [
]+a,c percent of span).
(1) Scientific Apparatus Manufacturers Association, Standard PMC 20.1-1973,
" Process Measurement and Control Terminology."
l 0237v:1D/021187 3-3 i
I,
7.
Rack Allowable Deviation The tolerances are as follows:
a.
Rack Calibration Accuracy The accuracy that can be expected during a calibration at reference conditions. This accuracy is the SAMA reference accuracy as defined in SAMA standard PMC 20.1-1973(1)This includes all modules in a rack and is a total of [
J+a,c percent of span assuming the chain of modules is tuned to this accuracy. All rack modules individually must have a reference accuracy.within [
]+a,c percent.
b.
Rack Environmental Effects Includes effects of temperature, humidity, voltage and frequency changes of which temperature is the most significant. An accuracy of
[
J+a,c percent is used which considers a nominal ambient temperature of 70*F with extremes to 40*F and 120*F for short periods of time.
Rack Drift (instrument channel drift) - change in input-output c.
relationship over a period of time at reference conditions (e.g.,
constant temperature) - +1 percent of span, d.
Comparator 3etting Accuracy Assuming an exset electronic input, (note that the " channel accuracy" takas care of deviations frorr this ideal), the tolerance on the precision with which a comparator trip value I
(1) Scientific Apparatus Manufacturers Association, Standard PMC 20.1-1973, " Process Measurement and Control Technology".
0237v:1o/021187 3-4
can be set, within such practical constraints as time and-effort expended in making the setting.
The tolerances are as follows:
(a)Fixedsetpointwithasingleinput-(
]+a c percent accuracy. This assumes that comparator nonlinearities are compensated by the setpoint.
(b) Dual input - an additional (
]+a,c percent must be added for comparator nonlinearities between two inputs.
Total (
]+a,c percent accuracy.
Note:
The following four definitions are currently used in the Standardized Technical Specifications (STS).
8.
Nominal Safety System Setting The desired setpoint for the variable.
Initial calibration and subsequent recalibrations should be made at the nominal safety system setting (" Trip Setpoint" in STS).
9.
Limiting Safety System Setting A setting chosen to prevent exceeding a Safety Analysis Limit (" Allowable Values" in STS)'. Violation of this setting represents an STS violation.
~~10. Allowance for Instrument Channel Drift The difference between (8) and (9) taken in the conservative direction.~~
~~11. Safety Analysis Limit The setpoint value assumed in safety analyses.~~
0237v:1o/021187 3-5
3.3 STATISTICAL METHODOLOGY CONCLUSION The Westinghouse setpoint methodology results in a value with a 95 per-cent probability with a high confidence level.
With the exception of Process Measurement Accuracy, Rack Drift and Sensor Drift, all uncer-tainties assumed are the extremes of the ranges of the various parameters, i.e., are better than 2a values. Rack Drift and Sensor Drift are assumed, based on a survey of reported plant LERs, and with Process Measurement Accuracy are considered as conservative values.
0237v:10/021187 3-6

~~v ',. f vis i'~~
et 4.
e v TABLE 3-1
. POWER RANGE, NEUTRON FLUX - HIGH AND LOW SETPOINTS-Parameter Allowance
~~Prscess Measurement Accuracy~~
+a c
<a,c J
Primary Element Accuracy Sensor Calibration
[-
')+a,c Measurement and Test Equipment Accuracy Sensor Pressure Effects Se sor Temperature Effects
)+a,c Sensor Drift
+
c
[.
) a,c Environmental Allowance Rock Calibration Rack Accuracy Measurement and Test Equipment Accuracy Comparator One input Rock Temperature Effects Rack Drift
~~In percent span (120 percent Rated Thermal Power)~~
Channel Statistical Allowance =
fa,e o237v:10/021187 3-7
TABLE 3-2 POWER RANGE, NEUTRON FLUX - HIGH POSITIVE RATE AND HIGH NEGATIVE RATE Parameter Allowance
~~Process Measurement Accuracy w ha, c~~
- +a, e Primary Element Accuracy Sensor Calibration fa,c
~
" Measurement and Test Equipment Accuracy Sensor Pressure Effects Sensor Temperature Effects
+a,c Sensor Drift fa,e Environmental Allowance Rack Calibration Rack Accuracy Measurement and Test Equipment Accuracy Comparator One input Rack Temperature Effects Rack Drift
~~In percent span (120 percent Rated Thermal Power)~~
Channel Statistical Allowance =
+a, c 0237v:10/021187 3-8
s, TABLE,3-3 INTERMEDIATE RANGE, NEUTRON FLUX Parameter Allowance
~~Prq, cess Measurement Accuracy~~
+
_ a,c
- +a,e Primary Element Accuracy Sansor Calibration
+a,c
[.
3 Measurement and Test Equipment Accuracy Sensor Pressure Effects Sensor Temperature Effects
+a,c
[
]
Sensor Drift
+a,c
[
]
Environmental Allowarce Rack Calibration Rack Accuracy Measurement and Test Equipment Accuracy Comparator One input Rack Temperature Effects Rack Drift 5 percent of Rated Thermal Power In percent span (conservatively assumed to be 120 percent Rated Thermal Power)
Channel Statistical Allowance =
~
- +a,c l
0237v:1D/021187 3-9
TABLE 3-4 SOURCE RANGE, NEUTRON FLUX Parameter Allowance
~~Process Measurement Accuracy f a,c~~
+
_ a,c Primary Element Accuracy Sensor Calibration
+a,e
[
]
Measurement and Test Equipment Accuracy Sensor Pressure Effects Sensor Temperature Effects
+a,c
[
]
Sensor Drift
+a,c
[
1 Environmental Allowance Rack Calibration Rack Accuracy Measurement and Test Equipment Accuracy Comparator One input Rack Temperature Effects RackDrif) cps 3 x 10 6
In percent span (1 x 10 counts per second) l Channel Statistical Allowance =
- +a,c 0237v:10/021187 3-10
TABLE 3-5 OVERTEMPERATURE AT Parameter Allowance **
\\
Process Measurement Accuracy
_ a,c
.:+a,c
+
Primary Element Accuracy Sensor Calibration 3+a,c l
.I Measurement & Test Equipment
+
[
] a.t Sensor Pressure Effects Sensor Temperature Effects
+
[
] a,c Sensor Drift
_+a,c Environmental Allowance Rock Calibration
+a,c Me3surement and Test Equipment
+a,c i
(
0237v:10/021187 3-11
TABLE 3-5 (Continued)
OVERTEMPERATURE AT Allowance
~~Parameter Tota 1 Rack Calibration Accuracy~~
+
_ a,c
+
. a,c Comparator AT T,yg Rack Temperature Effects Rack Drift AT Tavg o* In % AT span, AT - 101.1*F, T
- 100*F, Pressure 800 psi, Power -
avg 150% RTP, al - +30% AI See table 3-18 Tor gain calculations o
+ Number of Hot Leg RTDs used
++ Number of Cold Leg RTDs used Channel Statistical Allowance =
+a, a
m e
c237v:10/o21187 3-12
c n'
~
..~
TABLE 3-6 OVERPOWER AT Parameter Allowance
~~Pro ess Measurement Accuracy~~
~
~
)+a,c Primary Element Accuracy Sensor Calibration I
)+a,c Sensor Pressure Effects Sensor Temperature Effects Sensor Drift
[
3+a,c
\\ '
Environmental Allowance t.
Rac_k Calibration
- +a, c
\\-, ' \\, \\
~
Hea_surementandTestEquipmqpg,
\\
x,-
t Total Rack Calibration Accuracy
- y ; '-
- a,c
\\s 'L,
, \\ ) '..*
s.
=
'i Comparator
. N s
AT T
~~\\' ' ' \\~~
avg
' ( a..
\\
s,-
(
s, 1
(.
7 l
[ ' '., _
N.,
0337v;1D/021187 3-13
..p W
g
TABLE 3-6 (Continued)
DVERPOWER AT Parameter Allowance *+a,c Channel Temperature Effects Rack Drift AT T,yg
~
In % AT span, AT = 101.1 'F, T
- 100*F, Power - 150% RTP g
o 0*Seetable3-19forgaincalculilions
+ Number of Hot Leg RTDs used
++ Number of Cold Leg RTDs used Channel Statistical Allowance =
+a,c W
e 4
0237v:1D/021187 3-14
--_n_a-m
TABLE 3-7 PRESSURIZER PRESSURE - LOW AND HIGH, REACTOR TRIPS Parameter Allowance *
+a,e Process Measurement Accuracy Primary Element Accuracy
. Sensor Calibration Measurement and Test Equipment Accuracy l
Sensor Pressure Effects Sensor Temperature Effects Sensor Drift I
)+a,c Environmental Allowance Rack Calibration Rack Accuracy Measurement and Test Equipment Accuracy Comparator One input Rack Temperature Effects Rack Drift In percent span (800 psi)
Chanael Statistical Allowance =
Pressurizer Pressure - Low
_+a,c Pressurizer Pressure - High
+a,c 1
0237e:1D/021187 3-15
3 TABLE 3 PRESSURIZER WATER LEVEL - HIGH Parameter Allowance
1
+a l
~,e ProessMeayggentAccuracy
{
Primary Element Accuracy
'{
Sensor Calibration Measurement and Test Equipment Accuracy Sensor Pressure Effects Sensor Temperature Effects Sensor Drift Environmental Allowance Rack Calibration Rack Accuracy Measurement and Test Equipment Accuracy Comparator l
One input l
Rack Temperature Effects Rack Drift l
l In percent span (100 percent span)
Channel Statistical Allowance =
+
_ a,c f
0237v:1D/021187 3-16
TABLE 3-9 1
l LOSS OF FLOW
]
Parameter Allowance
3
_+a,e Process Measurement Accuracy [-
,,, e Primary Element Accuracy
)+a,c Sen or Calibration
]+,,e Sensor Pressure Effects l
[
]#3,c Sen or Temperature Effects
)+a,c Sensor Drift [
J+a,e Environmental. Allowance Rack Calibration Rack Accuracy [
)+a,c Measurement and Test Equipment Allowance [
]a,c Comparator One input [
J+a,e Rack Temperature effects [
)+a,c Rack Drift 1.0 percent AP Span -
In percent flow span (120 percent Thermal Design Flow)
~~See Table 3-21 for explanation Channel Statistical Allowance =~~
~
+a,c 4
0237v:1o/021187 3-17
7 ii. />
y
. TABLE 3-10'*
b
/
STEAM. GENERATOR' WATER LEVEL - LOW AND LOW-LOW i
t
-Parameter-Allowance *-
1
&a,c.
Prteess Measurement Accuracy
_ +a,e Primary Element Accuracy 1
Sensor Calibration i
Measurement and Test Equipment Accuracy
,.Sens'or Pressure Effects Sensor Temperature-Effects l
I Sensor Drift Environmental Allowance
,,,c Rack Calibration Rack Accuracy Measurement and Test Equipment Accuracy Comparator j
One input Rack Temperature Effects l
Rack Drift
~
In percent span (100 percent span)
C* See Table 3-20-for explanation Channel Statistical Allowance (Low-Low Level) =
_ a,c
+
i Channel Statistical Allowance (Low Level) =
_+a,c 0237v:1D/021187 3-18
o
, m, y:
TABLE 3-11 1,
j STEAM /FEEDWATER FLOW MISMATCH L
Parameter Allowance *
. I 1
Process Measurement Accuracy
+a,c
+a c 1
~PrimaryElementAccurac{+a,e Sensor Calibration
. a,c
+
He,asurement and Test Equipment
+a,c
\\
Seapor. Pressure Effects l
- +a,c Sesor Temperature Effects'
+
. a,c a
Sen_sor Drift
.+a,c Environmental Allowance ~
\\
Rack Calibration Rack Accuracy Steam Flow Feed Flow Steam Pressure [
]+a,e Measurement and Test Equipment Steam Flow Feed Flow Steam Pressure [
]+a,c 0
In percent flow span (120.0 percent steam flow); percent AP span converted to flow span via 3-21.8.
0237e:1o/021187 3-19
{
j
i TABLE 3-11(Continued) l
. i I
STEAM / FEE 0 WATER FLOW MISMATCH
- Parameter' Allowance
l
+a,c Comparator Two Inputs' i
Rack Temperature Effects Rack Drift i
Steam Flow
. i i
Feed Flow Steam Pressure [-
]+a,c
~
~
Channel Statistical Allowance =
, +a,c i l
I l
M l
1 j
i 0237v:10/021187 3-20
TABLE 3-12 CONTAINMENT PRESSURE - HIGH, INTERMEDIATE HIGH-HIGH, HIGH-HIGH Parameter Allowance *
-Process Measurement Accuracy '
Primary Element Accuracy Sensor Calibration Measurement and Test Equipment Accuracy Sensor Pressure Effects Sensor Temperature Effects 9
Sensor Drift Environmental Allowance Rack Calibration Rack Accuracy Measurement and Test Equipment Accuracy Comparator One input Rack Temperature Effects Rack Drift In percent span (65 psig)
Channel Statistical Allowance =
+a c 0237v:1D/021187 3-21
TABLE.3-13 PRESSURIZER PRESSURE LOW, SAFETY INJECTION' j
Parameter Allowance *
- +a, c Process Measurement Accuracy Primary Element Accuracy Sensor Calibration Measurement and Test Equipment Accuracy l
Sensor Pressure Effects Sensor Temperature Effects Sensor Drift
' i' Environmental Allowance i
Rack Calibration Rack Accuracy s
Measurement and Test Equipment Accuracy j
1 Comparator One input Rack Temperature Effects Rack Drift i
l In percent span (800 psi) i Channel Statistical Allowance =
_ +a,c 4
L
\\
=
i I
0237v:10/021187 3-22
___ __ _ A
TABLE 3-14 STEAMLINE PRESSURE - LOW Parameter Allowance
~~1 W~~
l
-Fa,c 1
l
- Process Measurement Accuracy Primary Element Accuracy
. Sensor Calibration Measurement and Test Equipment Accuracy Sensor Pressure Effects Sensor Temperature Effects Sensor Drift i
Environmental Allowance Rack Calibration
-Rack Accuracy Measurement and Test Equipment Accuracy Comparator-One input Rack Temperature Effects Rack Drift In percent span (1400 psig)
Channel Statistical Allowance =
+a c M
l l
0237tn10/021187 3-23
)
t TABLE 3-15' l
NEGATIVE STEAMLINE PRESSURE RATE - HIGH
'l Parameter' Allowance *
- +a, c.
Process Measurement Accuracy
' Primary Elehent Accuracy i
_ a,c q
Sen_sor Calibration
+
Sensor Pressure Effects
' Sensor Temperature Effects
_ +a,c Sensor Drift
+a,c Environmental Allowance Rack:Calibra' tion Rack Accuracy Measurement and Test Equipment Allowance Comparator One input Rack Temperature Effects Rack Drift In percent span (1400 psig)
Channel Statistical Allowance =
.+a,c i
I, i
i i
0237v:1D/021187 3-24 i
l l
.4 TABLE 3-16
~ STEAM GENERATOR WATER LEVEL - HIGH-HIGH Parameter-Allowance *
- Pro _ cess Measurement Accuracy i+a,c
+a,c Primary Element Accuracy
' Sensor Calibration Measurement and Test Equipment Allowances Sensor Pressure Effects Sensor Temperature Effects Sensor Drift-Environmental Allowance Rack Calibration Rack Accuracy Measurement and Test Equipment Allowances Comparator.
One input Rack Temperature Effects j
Rack Drift In percent span (100 percent span)
~~See Table 3-20 for explanation Channel Statistical Allowance =~~
+a,c 1
I 0337v:1D/021187 3-25 1
D -
NOTES F W
~~1. ALL f Ai.UES IN PERCENT SP AN.~~
10. INCLUDES ALL0 DANCE FOR ME ASUREMENT 1ES' EGJIPMENI UNCERT AINilES 3****
~~2. AS *:CTED IN T ABLE 140-3 Or F$ait 33 4 i.~~
~~3. AS NOTED IN T AB.ES 2 2-1 AND 3.3-4 0F 124 PL ANT TF.CHNIC AL SPEC 1FIC Af lCNS.~~
134 3****
4
I4 4.
3****
S - 401 USED IN S AFETY ANALYS;S 154
6. AS N0f f 0 IN FlCURE 140-1 CF FS A*
16. INCOPE/EXCO*E f (AD COMP ARIEON AS NOTED IN T. AS NOTED IN 1 ASLE 2.2-1 NOTE i IABLE 4 3-1 0F PLANT TECHNICAL SPECIFICA110NS Or PL AMI TECHNIC AL SPECIFICAfl0NS 174 3****
~~8. AS NOTED lb 1 ABLE 2 2*l N0f f 2 08 P6 ANT TECHNIC AL $*ECIFIC ATIONS~~
9. NOT NOTED IN T APLE 140-3 or FS A*
But USED IN SAFEff ANALfSIS REACTOR PR01EC110N SG ACTUAll0N STSfGC BEAfG l
SE' ISO 9 t
2 3
8 R
l P*c E ss PP i MA *,
C At le# 4f l0m Pers9URE fr etR4furf Onl I
PR0ffCf &oll CManufL P( A$ddleMt 4f (L f Muf ACCURACT EFFfCf5 EFFECTS M
ACCJP AC T ACCUR CT 16)
Ell ill 41)
III l
POW (9 R AgCf. WEUf ROW FLUt MICH Sf f 7014f I
2 POWER 444Cf. #f Jf R08 F U2 - LOW Sf fP01mf 6
3 J0df 4 #48Cf. afUT*04 FLUV - MICM P01t f itt Raf f 4
P0df R 949CE. 4fUf R04 F6UV - MICM #f 6 Allvt #4ff 9
lef f D*Ffl Af f #4#Cf. 4Fdf #0E FLWI 4 M't 944Cf #EUf RON FLVI F p ff fft4fuPf of of CH4muf t t#0SfM0Juf t g
T Av6 CM4dW(L
(#$$f*GJNil 9
I' 10 PWE55uel tf 4 **t SSJef CH41mf L 11 f ielf CH 44NE L 13 Of f n*0df 8 of o f CM A##f L (701FMOUNf t 13 14 1 Avf CNAN8n L tRO$f DGUN T )
y 18 P#f 990Ri tf# P#ffluel
~~LOW. Rf4Cf09 f#tP #94af 0t. vMif f tei le ref stualffe P#f $$U#F = MleM (949704 EMi f f f s, e~~
IF
'#F91on'H# waf f e tivfL - MICM ts4pf 04 vM f f ret le LOSS OF FL 0d IFISC*efR P0pf te rMi f f f R$
lt
$f f AM SENfR4f 04 W4'f 4 LFvfL - LOW-L 0d (94*f0N YMif f f#1 20 ff f AM Cf 4f R4f 04 v4f f R Lf vf L - LOW (94#f 0s rMif f fR) il 6f f 44 FLod - Ff f 0 FLOW MISMAf cM Sf f AM FL0d (94af ou rMit tf 9$
22 l Sf f AM P*f 5$JPE (9 4# f 0N VMl f f f R1 23 I Fff0 Flow (Fite*4R Porf te VMf f ff 41 24 Uupf ev0Llact - RCP ti.f.f. 4FM #fL Af-905 14. Cf C8v124 #fL 47-9US 10. let 35 t umo'#F4f outuCT - eCP #M4f MAvar ef L AY sre-19-141 4
24 l PRf ttuRiffe P#f t1URf LOW = $f (84Rf04 XMi f f f #1 2
3F l 9f f A4 lef P#f $$u'F-LOW (9 A# f 0N Emit f f ti 20 C04f 41NMF4f P#f 51U#' MISM
~~544704 WMi f f f el 29 C0wf Al#4M PAf SSV8f MICM-MicM fe4RfC4 uMlffth>~~
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~~MICM (9 4# f 0sl EMlfffet f~~
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.'i
TABLE 3-18 OVERTEMPERATURE AT GAIN CALCULATIONS
~~.The equation for Overtemperature AT is:~~
Overtemperature AT l
1+t S
" AT, { K - K (1 + ti ) (T - T'] + K3(P-P')-f3 (AI))
i 3
2 5
2
[
]+a,c K-(max)
=
K-(nominal)'
1.18 (Technical Specification Trip Setpoint)
=
0.01655/'F-K
=
2 0.000801/ psi K
=
.V$sselT 609.9'F
=
H 542. 5'F--
Vessel T
=
C 1.91% FP 41/% AI Positive AI gain
=
+a,c AT. span =
l Process Measurement Accura ~cy AT
+a,c PMA =
3
=
Al
+a,c PMA1 =
3 S
PMA1 =
3 3
=
mm l
0237tt:10/021187 3-27 l
l
l TABLE 3-18 (Continu d)
OVERTEMPERATURE AT GAIN CALCULATIONS Pressure Channel Uncertainties
~
+a,c Pressure Gain =
3 3
+a, c SCA
=
s m
M&TE =
a
+a,c STE
=
a
~
~
+a,e
. 1 SD
=
a
's Total Allowance
- +a,e TA =
s a
j i
l 4
E l
1 0237v:1D/021187 3-28 l
i l
4 TABLE 3-19
'0VERPOWER AT GAIN CALCULATIONS The equation for Overpower AT is:
Overpower AT 1
'38
-K(1+ty)T-'K6 (T - T")-f2(AI))
AT,( K4 5
(
]+a,c K4(max)
=
1.07 (Technical Specification Trip Setp'oint)
K4(nominal)
=
K 0.02/*F
=
5
)
0.00128 l
K
=
6 Vessel T.
609.9'F l
=
g 542.5'F l
Vessel.T
=
C l
AT span'=
+a,e 1
Process Measurement Accuracy AT
. +a,c PMA =
s L
Total Allowance
~
+a,c a
=
==
j 0237mio/ozus7 3-29
i 4
TABLE 3-20 STEAM GENERATOR LEVEL DENSITY VARIATIONS i
Because of density variations with load due to changes in recirculation, it is impossible without some form of compensation to have the same accuracy under all load conditions.
In the past the recommended calibra-tion has been at 50 percent power conditions.
Approximate errors at 0 percent and 100 percent water level readings and also for nominal trip points of 10 percent and 70 percent level are listed below for a typical 50 percent power candition calibration. These errors are only from
. density changes and do not reflect channel accuracies, trip accuracies or indicated accuracies which has been defined as a AP measurement only.II)
INDICATED LEVEL (50 Percent Power Calibration)
I 0
10 70 100 percent percent percent percent
+a,c Actual Level i
0 Percent Power Actual Level 100 Percent Power 2
(1) Miller, R.
B., " Accuracy Analysis for Protection / Safeguards and Selected Control Channels", WCAP-8108 (Proprietary), March 1973.
l 0237v;10/021187 3-30 i
TABLE 3-21 AP MEASUREMENTS EXPRESSED IN FLOW VNITS The AP accuracy expressed as percent of span of the transmitter applies throughout the measured span, i.e., i 1.5 percent of 100 inches AP = 11.5 l
inches anywhere in the span. Because F2 = f(AP) the same cannot be said for flow accuracies.
When it is more convenient to express the accuracy of a transmitter in flow terms, the following method is used:
(F[ = AP where N = nominal flow N
2F aFN = a(AP )
N N
l '
thus 8F a(aP )
N Eq. 3-21.1 N=G Error at a point (not in percent) is:
a[N ) = ahP )
86P )
N N
)
Eq. 3-21.2 i
=-
and AP (F
N N
(F,,x $ where max = maximum flow Eq. 3-21.3
=
APmax and the transmitter AP error is:
86P )
N x 100 = percent error (full scale AP)
Eq. 3-21.4 APmax gN) [3pmax)( percent error (FS AP) )
2
,(percenterror(FSAP))({p 100 max)
{,
2 2x100 gpmax )(p N
)
max Eq. 3-21.5 j
0237v:1o/021187 3-31
I Error in flow units is:
1 2
af )=(F ) (percent or (FS AP) )
(
)
Eq. 3-21.6'
'i N
N Error in percent nominal flow is:
2 (percent error (FS AU )
(
)'
Eq. 3-21.7 x 100
=
Error in percent full span is:
)
(F )(percent error (FS AP))
(F,,x)2 N
N 100
=
Qx F,,x x 2 x 100
{
, ( percent error (FS AP) ) (
)
.Eq. 3-21.8 Equation 3-21.8 is used to express errors in percent full span in this document.
b i
j I
0237v:1D/021187 3-32
TABLE 3-22 RWST LEVEL.- LOW, AUTO QS FLOW REDUCTION 1
Parameter.
Allowance *
- +a, e Proces's Measurement Accuracy Primary Element Accuracy
. Sensor. Calibration Measurement and Test Equipment Accuracy Sensor Pressure Effects Sensor Temperature Effects Sensor Drift Environmental Allowance Rack Calibration Rack Accuracy Measurement and Test Equipment Accuracy Comparator i
One Input Rack Temperature Effects Rack Drift
~~In percent span (100 percent span)~~
Channel Statistical Allowance =
_+a,c e
0237v:1D/021187 3-33
. TABLE 3-23 UNDERVOLTAGE - RCP 1
' Parameter Allowance *
-Fa,c Process Measurement Accuracy Primary Element Accuracy (transformer accuracy)
Sensor Calibration Measurement and Test Equipment Accuracy Sensor Pressure Effects Sensor Temperature Effects Sensor Drift Environmental Allowance Rack Calibration Rack Accuracy Measurement and Test Equipment Accuracy j
Comparat'or One input Rack Temperature Effects Rack Drift In percent span (1050 volts) 4 l
Channel Statistical Allowance =
j
+a,c l
IJ 0237v:1o/021187 3-34 I
. TABLE 3-24 r.
UNDERFREQUENCY - RCP 1
Allowance
~~l Parameter~~
~
~&a,c Process Measurement Accuracy Primary Element Accuracy Sensor. Calibration Measurement and Test Equipment Accuracy Sensor Pressure Effects Sensor Temperature Effects 4
Sensor Drift Environmental Allowance Rack Calibration Rack Accuracy
.l Measurement and Test Equipment Accuracy Comparator One_ input Rack Temperature Effects
~
Rack Drift In percent span (8' Hertz)
Channel Statistical Allowance =
+
_ a,c M
M o237v:1o/021187 3-35
(
TABLE 3-25 4.16 kV EMERGENCY BUS UNDERVOLTAGE - TRIP FEED, START DIESEL, DEGRADED VOLTAGE Parameter' Allowance *
.-&a,c Process Measurement Accuracy PrimaryElementAccuracy(transformeraccuracy)
Sensor Calibration Measurement and Test Equipment Accuracy Sensor Pressure Effects Sensor-Temperature Effects Sensor Drift Environmental Allowance Rack Calibration Rack Accuracy Measurement and Test Equipment Accuracy Comparator One input Rack Temperature Effects Rack Drift.
Inpercentspan(1050 volts)
Channel Statistical Allowance =
+a,c 0237v:;o/021187 3-36 I
1 1
TABLE 3-26 480 VOLT EMERGENCY BUS UNDERVOLTAGE - DEGRADED VOLTAGE L
Parameter Allowance *
- +a. c Process Measurement Accuracy Primary Element Accuracy (transformer accuracy)
Sensor Calibration Measurement and Test Equipment Accuracy Sensor Pressure Effects Sensor Temperature Effects Sensor Drift Environmental Allowance Rack Calibration Rack Accuracy Measurement and Test Equipment Accuracy Comparator One input Rack Temperature Effects Rack Drift l
l In percent span (120 volts) l Channel Statistical Allowance =
l
+
_ a,c l
l 0237v:1D/021187 3-37 l
L_________--__-----_----_--_-__----__--
m
\\
i l
TABLE 3-27 1
^
AUXILIARY FEEDWATER TURBINE DRIVEN' PUMP. DISCHARGE' PRESSURE - LOW
(.
L Parameter Allowance *-
4
-&a,c l
Process Measurement Accuracy e
PrimaryElementAccuracy(transformeraccuracy)
Sensor Calibration Measurement and Test Equipment Accuracy Sensor Pressure Effects i
Sensor Temperature Effects Sensor Drift Environmental Allowance Rack Calibration Rack Accuracy Measurement and' Test Equipment Accuracy I
Comparator One input Rack Temperature Effects
' Rack Drift In percent span (200 psig)
Channel Statistical Allowance =
- +a, c c237v;1o/o211s7 3-38
{
4.0 TECHN! CAL SPECEFfCATION USAGE 4.1 CURRENT USE The Standardized Technical Specifications (STS) as used for Westinghouse type plant designs (see NUREG-0452, Revision 4) utilizes a two column format for the RPS and ESF system. This format recognizes that the setpoint channel breakdown, as presented in Figure 4-1, allows for a certain amount of rack drift. The intent of this format is to reduce the number of Licensee Event Reports (LERs) in the area of instruments-tion setpoint drift.
It appears that this approach has been successful in achieving its goal. However, the approach utilized is fairly sim-plistic and does not recognize how setpoint calibrations and verifica-tions are performed in the plant.
In fact, this two column approach forces the plant to take a double penalty in the area of calibration error. As noted in Figure 4-1, the plant must allow for calibration error below the STS Trip Setpoint, in addition to the allowance assumed in the various accident analyses, if full utilization of the rack drift is wanted. This is due, as noted in 2.2, to the fact that calibration error cannot be distinguished from rack drift after an initial calibra-tion. Thus, the plant is left with two choices; 1) to assume a rack drift value less than that allowed for in the analyses (actual RD =
assumed RD-RCA) or, 2) penalize the operation of the plant (by increas-ing the possibility of a spurious trip) by lowering the nominal trip setpoint into the operating margin.
The use of the statistical summation technique described in Section 2 of this report allows for a natural extension of the two column approach.
This extension recognizes the calibration / verification techniques used in the plants and allows for a more flexible approach in reporting LERs. Also of significant benefit to the plant is the incorporation of sensor drift parameters on an 18 month basis (or more often if necessary).
0237v:10/021187 4-1
l 4.2 WESTINGHOUSE STATISTICAL SETPOINT METHODOLOGY FOR STS SETPOINTS 1
Recognizing that besides rack drift the plant also experiences sensor j
drift, a different approach to technical specification setpoints, that j
i is somewhat more sophisticated, is used today.
This methodology accounts for two additional factors seen in the plant during periodic
)
surveillance, 1) interactive effects for both sensors and rack and, 2)
I sensor drift effects.
l 4.2.1 RACK ALLOWANCE 1
The first item that will be covered is the interactive effects. When an instrument technician looks for rack drift he is seeing more than that.
This interaction has been noted several times and is handled in Equations 2.1 and 3.1 the arithmetic summation of rack drift, rack comparator setting accuracy, and rack calibration accuracy for rack j
effects and sensor drift and sensor calibration accuracy for sensor effects. To provide a conservative " trigger value", the difference between the STS trip setpoint and the STS allowable value is determined by two methods.
The first is simply the values used in the statistical calculation, T =(RD + RCA + RMTE + RCSA). The second extracts these 3
values from the calculations and compares the remaining numbers statistically against the total allowance as follows:
1
((A) + (S)2] M+ EA)
(Eq.4.1)
T2 = TA - (
where:
Rack trigger value T
=
2 (PMA)2 + (PEA)2 + (SPE)2 + (STE)2 + (RTE)2 A
=
(
I 0237v:1o/021167 4-2
l l
(SCA + SMTE + SD)
I S
=
e EA, TA and all.cther parameters are as defined for Equations 2.1 and o
l 3.1.
l The smaller of the trigger values should be used for comparison with the "asmeasured"'(RD+RCA+RMTE+RCSA)value. As long as the "as mea-l sured" value is smaller, the channel is well within the accuracy I
allowance.
If the "as measurod".value exceeds the " trigger value", the actual numbers'should be used in the calculation described in Secticn j
4.2.3.
I
-l 1
This means that all the instrument technician has to do during the 31 l
p r
ti i
t S
1 a e n
es not have to account for any additional effects.
The same approach is used for the sensor,.i.e., the "as measured" value is used when raquired. Tables 4-1 and 4-2 show the current STS setpoint philosophy (NUREG-0452, Revision'4).and the Westinghouse rack allowance (for use on
~
31 day surveillance only). A comparison of the two different Allowable Values will show the net gain of the Westinghouse version.
4.2.2 INCLUSION OF "AS MEASURED" SENSOR ALLOWANCE l
If the approach used by Westinghouse was a straight arithmetic sum, sensor allowances for. drift would also be straight forward, i.e., a three column setpoint methodology. However, the use of the statistical summation requires a somewhat more complicated approach.
This method-ology; as demonstrated in Section 4.2.3, Implementation, can be used i
quite readily by any operator whose plant's setpoints are based on sta-tistical summation. The methodology is based on the use of the follow-ing equation.
I 0237v:10/021187 4-3
+
1 1
(A)1/2 + R + S + EA < TA u
(Eq.4.2) where:
i i
the "as measured ~ rack value" (RD + RCA + RMTE + RCSA)
R
=
[.
L the "as measured sensor value" (SD + SCA + SMTE) l S
=
and all other parameters are as defined'in Equation 4.1.
l Equation 4.2.can be reduced further, for use in the STS to:
Z + R + S < TA (Eq.4.3) where:
J 2=A 1/2 + EA Equation 4.3 would be used in two instances, 1) when the "as measured"'
]
rack setpoint value exceeds the rack " trigger value" as defined by the i
STS Allowable Value, and, 2) when determining that the "as measured" sensor value is within acceptable values as utilized in the various Safety. Analyses and verified every 18' months.
4.2.3 IMPLEMENTATION OF THE WESTINGHOUSE SETPOINT METHODOLOGY Implementation of this methodology is reasonably straight forward, Appendix A provides a text and tables for use in the Technical Specifications. An example of how the specification would be'used for the Pressurizer Water Level -'High reactor trip is as follows.
Every 31 days, as required by Table 4.3-1 of NUREG-0452, Revision 4, a functional test would be performed on the channels of this trip fune-tion. During this test the bistable trip setpoint would be determined 0237v;1D/021187 4-4
for.cach channel.
If the *as measured" bistable trip setpoint crror was found to be less than or equal'to that required by the Allowable Value, no i
action would be necessary by the plant staff.
The Allowable Value is determined by Equation 4.1 as follows:
T = TA - (
((A) + (S)2)1/2 + EA)
I where:
1 5 percent (an assumed value)
TA
=
+a,c
-A
=
(S)2 EA
=
T
=
s i
3 l
However, since only 1.8 percent is assumed for T in the various analy-ses, that value will be used as the " trigger value". The lowest of two values is used for the " trigger value"; either the value for T assumed i
in the analyses or the value calculated by Equation 4.1.
1 I'
0237v:10/021187 4-5
('
Now assume that-one bistable has odrifted" noro than that allowed by the STS for 31 day surveillance.
According to ACTION statement "A", the plant staff must verify that Equation 2.2-1 is met. Going to Table l
2.2-1, the following values are noted: 2 = 2.18 and the Total Allowance (TA) = 5.0 for the purpose of this example. Assume that the "as measured" rack setpoint value is 2.25 percent low and the "as measured" j
sensor valu is 1.5 percent.
Equation 2.2-1 looks like:
2 + R + S s TA i
2.18 + 2.25 + 1.5 5 5.0 5.9 s 5.0 As can be seen, 5.9 percent is not less than 5.0 percent thus, the plant j
staff must follow ACTION statement "B" (declare channel inoperable and place in the " tripped" condition).
It should be noted that if the plant staff had not measured the sensor drift, but instead used the value of S l
in Table 2.2-1 then the sum of Z + R.+ S would also be greater than 5.0_
percent.
In fact, almost anytime the "as measured" value for rack drift is greater than T (the " trigger value"), use of S in Table 2.2-1 will result in the sum of I + R + S being greater than TA and requiring the l
reporting of the case to the NRC.
If the sum of R + S was about one percent less, e.g., R = 2.0 percent, S = 0.75 percent'thus, R + S = 2.75 percent, then the sum of Z + R + S would be less than'5 percent.
Under this condition, the plant staff would recalibrates the instrumentation, as good engineering practice suggests, but the incident is not reportable, even though the " trigger value" is exceeded, because Equation 2.2-1 was satisfied.
In the determination of T for a function with multiple channel inputs there is a slight disagreement between Westinghouse proposed methodology and NRC approved methodology. Westinghouse believes that T should be either:
0237v:10/021187 4-6 1
1 + RD ) + (RCA2 + RMTE + RCSA2 + RD ) (Eq.4.4)
T12 = (RCA1 + RMTE + RCSA 1
2 2
y 22 = TA -((A + (S )2,(3 ) )
+EA)
(Eq.4.5)
T 1
2 where the subscript 1 and 2 denote channels 1 and 2, and the value of T used is whichever is smaller.
The NRC in turn has approved a method of determining T for a multiple channel input function as follows, either:
T = [(RCA1 + RMTE + RCSA1 + RD )2 + (RCA2 + RMTE + RCSA2 + RD ) I 3
3 1
2 2
or (E'q.4.6)
Equation 4.5 as described above.
Again the value of T used is whichever is smaller. This method is described in NUREG-0717 Supplement 4, dated August 1982.
An example demonstrating all of the above noted equations for Overpower aT is provided below:
(Numbers arbitrarily assumed for purposes of this example)
- +a,c TA
=
A
=
(S )2 1
(S )
2 5+a,c
~
RCA + RMTE1 + RCSA1 + RD1
=
3 RCA2 + RMTE2 + RCSA2 + RD2 RCA3 = 0.007 EA
=
Bias
=
0237v:1o/021187 4-7
Using Equation 4.4; e-
+a,c T12
~~Using Equation 4.5;~~
~~.+a,c T22~~
~~Using Equation 4.6; q+a,c T~~
=
3
=
The value of T used is from Equation 4.5.
In this document Equations 4.5 and 4.6, whichever results in the smaller value is used for multiple channel input functions to remain consistent with current NRC approved methodologies. Table 4-3 notes the values of TA, A, S, T, and 2 for all protection functions and is utilized in the determination of the Allowable Values noted in Appendix A.
Table 4.3-1 also requires that a calibration be performed every refuel-ing(approximately18 months). To satisfy this requirement, the plant staff would determine the bistable trip setpoint (thus, determining the "as measured" rack value at that time) and the sensor "as measured" value. Taking these two "as measured" values and using Equation 2.2-1 l
again the plant staff can determine that the tested channel is in fact within the Safety Analysis allowance.
~~4.3 CONCLUSION~~
Using the above methodology, the plant gains added operational flexibil-ity and yet remains within the allowances accounted for in the various 0237v:1D/021187 4-8
(
accident analyses.
In addition, the methodology allows for a sensor drift factor and an increased rack drift factor. These two gains should significantly reduce the problems associated with channel drift and thus, decrease the number of LERs while allowing plant operation in a safe manner.
0237v:1o/021187 4-9
TABLE 4-1 EXAMPLES OF CURRENT STS SETPOINT PHILOSOPHY Power Range Pressurizer Neutron Flux - High Pressurc - High Safety Analysis Limit 118 percent 2410 psig STS Allowable Value 110 percent 2395 psig STS Trip Setpoint 109 percent 2385 psig I
TABLE 4-2 EXAMPLES OF WESTINGHOUSE STS RACK ALLOWANCE Power Range Pressurizer Neutron Flux - High Pressure - High l
l Safety Analysis Limit 118 percent 2410 psig 1
STS Allowable Value' 111.2 percent 2396 psig l
(TriggerValue) 1 STS Trip Setpbint 109 percent 2385 psig l
l 02ny:1o/0211s7 4-10 1
Safety Analysis Limit Process Measurement Accuracy Primary Element Accuracy Sensor Temperature Effects Sensor Pressure Effects Sensor Calibration Accuracy Sensor Drift
}EnvironmentalAllowance ack Temperature Effects Rack Comparator Setting Accuracy
}RackCalibrationAccuracy STS Allowable Value Rack Drift STS Trip Setpoint Actual Calibration Setpoint Figure 4-1 NUREG-0452 Rev. 4 Setpoint Error Breakdown o237v:1o/021187 4-11
_ _ _ _ =
4-
'Sofety Analysis Limit.
'f> Process Measurement Accuracy rimary Element Accuracy
, Sensor Temperature Effects Sensor Pressure Effects
' Sensor Calibration Accuracy l l Sensor Drift Environmental Allowance
> Rack Temperature Effects STS Allowable Value h>RackComparatorSettingAccuracy p> Rack Calibration Accuracy ack Drift STS Trip Setpoint Figure 4-2 Westihekeuse STS Setpoint Error Breakdown c237v:to/o21187 4-12
l
~ n l
l, l
WESTINGHOUSE PROTECTION S1 BEAVER UNil 1 ABLE 4-3 PROTECT 10m CHANNEL TOTAL ALLOWANCE (9)
(9)
(T A)
(9)
(A)
(1 )
(S)
(2)
(T) 7.5
~_
"l" * '
O.0 1
'POWEM RANCE. NEUT RON FL S-+tlCM! SEf *0 INT 0.0 1
8.3
~~POWER R ANCE. NEUIRON FLth-LOW STT POI NT 0.0 JPOWER RANCE. NEUF RON FLtsW10tf POSI TIVE R ATE I.6 0.0 I. E.~~
POVEM R ANCE. NEUF RON FLIN-Hitit' hEG Af f yE R ATE 0.0 5
17.0 JNTERMEDI ATE R ANCE. NEU EI)N KL U Y-0.0 17.0 5007.CE RANCE. NEUIRON Fim<
1.40*0 69 B.0 OVERTEMPER ATURE af 1.40 5.4 0YER70VER af 1.62
'TRESSUR 12E R PRESSURE-LOW. RE-ACTG8 TRIP 3.1 l
0.62 6.4 PRESSUR17ER PRESSURE-HION 1 62 B.0 PRESSURIZER WATER LEVEL-telCR 0 60 2.5
. LOSS or FLOW 1.62 12.0 ME AM CENER ATOR W ATER L EVEL-LOV-LOW 1.62 25.0 STE AM CENER A10R W ATER L EVEt - LOW 1 9?*0.81+1 00 20.0 Sf E AM FLOW - FEED FLOW M!SMATCH 0.0 10.0 UNDERVOLTACE - RCP 0.0 6.2 UNDERFREQUENCY - RCP 1.62 18.1 PRESSURIZER PRESSURE LtW - 9.1.
1 62 12.6 STE f.MLINE PRES $URE - LOW 1.62 3.1 CONT AIMMENT PRESSURE HIOM 1,$2 3.1 CONTAIN>ENT PRESSURE HICH - HICH 1.62 C031 AINMENY PRESSURE INTEPMEDI ATE H1CH - HICH 3.f 0.0 3.0 JiCATIVE STEAM PRESSU*E RATE - HICH 1.62 STE AM CENER ATOR WATER LEVEt HlCH - HICH 5.0 1.62 3.7 RWS1 LEVEL - L OW 1.62 4.0 RYST LEVEL-Auf 0 OS FLOW REDUC?l0N 0.0 4,16 KV ENERCENCY BUS UNDERVOLT ACE - TRIP FEED 15.0 0.0 4.16 KV E ME RC E N C Y BUS UNDERVOLT ACE - START OlESEL 15.0 0.0 4.16 FY EME RCE N C Y BUS UWDERVDtfACE - DECRADED VOLYACE 15.0 480V EMERCENCY BUS UNDERVOL T ACE - DECR ADED VOL T ACE f3.0 0.0 0.0 AUX FEED TUR9INE ORlVEN PUMP OlSCH ARCE PRESSURE - LOW 5.0 NOTES:
+s.s
)
.e.s gg 93 (81 AS NOTED IN NOTES 1.2 AND 3 0F TABLE 2 2-1 0F Sis.
(2)
(91 ALL V ALUES IN PERCfNT SPAN (3)
]
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15:32iG5 ll-SEP-87 TEM STS SETPOINT INPUTS
,LLEY D
INSTRUMENT STS TRIP STS ALLOWABLE MAXIMUM (9)
(9)
SPAN SETPOINT VALUE VALUE (3)
(Z)
(4)
(10)
(7) 4.56 120% RTP 109% RTP 111.3% RTP 9
4.56 120% RIP 25% RTP 27.3% RTP 0.50 12Q,1 RTP 5.0% RTP 6.1% RTP 0.50 120% RTP 5.0% RIP 6.3% RTP 8.41 120% RIP 25% RTP 31.1% RTP 10.01 1.0E+06. CPS 1.0E*05 CPS l.4E*05 CPS 4.34 (5).
FUNCfl0N (8)
FUNCTION (81+3.4% af SPAN g
1,38 (6).
FUNCTION (8)
FUNCflON (8) + 3. 4% a f SPAN 0.71 800 PSIC 1945 PSIC 1934 PSIC 4.96 800 PSIC 23M ISic 2394 PSIC 2.18 100% SPAN 92% SPAN 93.9% SPAN I.77 120% OESlCN FLOW 90% FLOW 89.2% FLOW 10.18 100% SPAN 12.0% SPAN 10.7% SPAN 2.18 100% SPAN 25.0% SPAN 23.1% SPAN 2.66 120% FLOW 40.0% STE AM FLOW 43.4% STE AM FLOW 1.39 1050 VOL TS 2750 Y0Lis 2687 YOLTS 0.50 8 H2, 57.5 H2, 57.4 H2.
14.41 800 PSIC 1845 PSIC 1830 PSIC l
l l
10.71 1400 PSI 500 PSIC 488 PSIC 0.71 65 PSIC l.5 PSIC 2.4 PSIC 0.71 65 PSIC 8.0 PSIC 8.9 PSIC 0.71 65 PSIC 3.0 Psic 3.9 PSIC 0.50 1400 PSI 100 PSI 127 PSI 2.18 100% SPAN 75.0% SPAN 76.9% SPAN 0.71 12 FEET 19 FEET 2.5 INCHES 19 FEET O INCHES 0.71 12 FEET 11 FEET 10 FEET 9 INCHES 3
I.39 1050 YOLTS 75.0% Or BUS VOLTACE 73% OF BUS YOLYACE
)
1.39 1050 V0Lis 83.0% OF BUS VOLTACE 81% OF BUS VOLTACE
)
1.39 1050 YOL TS 90.0% OF BUS VOLTACE 88% OF BUS VOLTACE p
1.39 120 YOL TS 90.0% 08 BUS VOLTACE 88% OF BUS VOLTACE
)
2.00 200 PSIC 468 PSIC 464 PSIC r
SI APERTURE
. CARD Also Available On Aperture Card REV. O FOR INTERNAL PLANT USE ONLY N3 aoogM-ea 0
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_____.m_-___________.__.______.__m__
l APPENDIX A SAMPLE BEAVER VALLEY UNIT 1 SETPOINT TECHNICAL SPECIFICATIONS 0237v:1D/021187 A-1
SAFETY LIMITS AND LIMITING SAFETY SYSTEM SETTINGS 2.2 LIMITING SAFETY SYSTEM SETTINGS REACTOR TRIP SYSTEM INSTRUMENTATION SETPOINTS 2.2.1 The Reactor Trip System Instrumentation and Interlock Setpoints shall be consistent with the Trip Setpoint values shown in Table 2.2-1.
APPLICABILITY:
As shown for each channel in Table 3.3-1.
ACTION:
l a.
With a Reactor Trip System Instrumentation or Interlock Setpoint less conservative than the value shown in the Trip Setpoint column but more conservative than the value shown in the Allowable Value Column of Table 2.2-1, adjust the Setpoint consistent with the Trip i
Setpoint value.
b.
With the Reactor Trip System Instrumentation or Interlock Setpoint less conservative than the value shown in the Allowable Values column of Table 2.2-1, either:
1. ' Adjust the Setpoint consistent with the Trip Setpoint value of Table 2.2-1 and determine within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months that Equation 2.2-1 was satisfied for the affected channel, or 2.
Declare the channel inoperable and apply the applicalbe ACTION statement requirement of Specification 3.3.1 until the channel is restored to OPERABLE status with its setpoint adjusted consistent with the Trip Setpoint value.
EQUATION 2.2-1 Z + R + S TA 5
where:
The value for column Z of Table 2.2-1 for the affected channel, 2
=
the "as measured" value (in percent span) of rack error for the R
=
affected channel, either the "as measured" value (in percent span) of the sensor S
=
error, or the value in column S (Sensor Error) of Table 2.2-1 for the affected channel, and the value from column TA (Total Allowance in % of span) of Table TA
=
2.2-1 for the affected channel.
0237v:1D/021187 A-2
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2.2 LIMITING SAFETY SYSTEM SETTINGS s
1 BASES 2.2.1 REACTOR TRIP SYSTEM INSTRUMENTATION SETPOINTS The Reactor Trip Setpoint Limits specified in Table 2.2-1 are the nominal values at which the Reac' tor Trips are set for each functional unit..The Trip Setpoints have been selected to ensure that the reactor core and reactor coolant system are prevented from exceeding their safety limits during normal operation and design basis anticipated operational occurrences and to assist the Engineered Safety Features Actuation System in mitigating the consequences of accidents..The
-l i
setpoint for a reactor trip system or interlock function is considered to be adjusted consistent with tne nominal value when the'"as measured" setpoint is within the band allowed for calibration accuracy.
To accommodate the instrument drift assumed to occur between operational 3
tests and the accuracy to which setpoints can be measured and calibrated, Allowable Val _ues for the reactor trip-setpoints have been specified in Table 2.2-1.
Operation with setpoints less conservative than the Trip Setpoint but within the Allowable Value is acceptable q
since an allowance has been made in the safety analysis to accommodate this error. An optional provision has been included for determining the OPERABILITY of a channel when its trip setpoint is found to exceed the Allowable Value. The methodology of this option utilizes the "as measured" deviation from the specified calibration point for rack and
]
l sensor components in conjunction with a statistical combination of the other uncertainties in calibrating the instrumentation.
In Equation l
2.2-1, Z + R + S,TA the interactive effects of the errors in the 5
3 rack and the sensor, and the "as measured" values of the errors are considered.
2, as specified in Table 2.2-1, in percent span, is the statistical summation of errors assumed in the analysis excluding those associated with the sensor and rack drift and the accuracy of their 0237v:10/021187 A-10 t
l l
t 1
-l
\\
1 l
i
' measurement.
TA or Total Allowance is the difference, in percent span,
-between the trip setpoint and the value used.in the analysis for reactor trip.
R or Rack Error is the "as measured" deviation, in percent span, l
for the affected channel from the specified trip setpointi S or Sensor Drift is either the "as measured" deviation of the sensor from its calibration point or the value specified in Table 2.2-1, in percent span, from the analysis assumptions. Use of Equation 2.2-1 allows for a sensor drift factor, an increased rack drift factor, and provides a
)
threshold value for REPORTABLE OCCURRENCES.
l The methodology to derive the trip setpoints is based upon combining all of the uncertainties in the channels.
Inherent to the determination of the trip setpoints are the magnitudes of these channel uncertainties.
Sensors and other instrumentation utilized in these channels are expected to be capable of operating within the allowances of these uncertainty magnitudes.
Rack drift in excess of the Allowable Value exhibits the behavior that the rack has not met its allowance. Being that there is a small statistical chance that this will happen, an infrequent excessive drift is expected. Rack or sensor drift, in excess of the allowance that is more than occasional, may be indicative of more serious problems and should warrant further investigation.
l l
0237v:1D/021187 A-11
1 I
l 3/4.3.2 ENGINEERED SAFETY FEATURE ACTUATION SYSTEM INSTRUMENTATION j
l LIMITING CONDITION FOR OPERATION
?.3.2 The Engineered Safety Feature Actuation System (ESFAS) l instrumentation channels and interlocks shown in Table 3.3-3 shall be OPERABLE with their Trip Setpoints set consistent with the values shown in the Trip Setpoint column of Table 3.3-4 and with RESPONSE TIMES as shown in Table 3.3-5.
APPLICABILITY: As shown in Table 3.3-3.
I ACTION:
a.
With an ESFAS Instrumentation or Interlock Setpoint Trip less j
conservative than the value shown in the Trip Setpoint column but more conservative than the value shown in the Allowable Value column of Table 3.3-4 adjust the Setpoint consistent with the Trip Setpoint l
value.
b.
With an ESFAS Instrumentation or Interlock Trip Setpoint less conservative than the value shown in the Allowable Value column of Table 3.3-4, either:
1.
Adjust the Setpoint consistent with the Trip Setpoint value of Table 3.3-4 and determine within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months that Equation 2.2-1 was satisfied for the affected channel, or l
2.
Declare the channel inoperable and apply the applicable ACTION statement requirements of Table 3.3.3 until the channel is restored to OPERABLE status with its Setpoint adjusted consistent with the Trip Setpoint value.
EQUATION 2.2-1 2+R+S 5 TA 0237v:1o/021187 A-12
where:
The value for Column Z of Table 3.3-4 for the affected channel, Z
=
The "as measured" value (in percent span) of rack error for the R
=
affected channel, Either the "as measured" value (in percent span) of the sensor S
=
error, or the value from Column S (Sensor Drift) of Table 3.3-4 for the affected channel, and I
The value from Column TA (Total Allowance) of Table 3.3-4 for TA
=
the affected channel.
0237v:10/021187 A-13
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3/4.3 INSTRUMENTATION BASES 3/4.3.1'and 3/4.3.2 REACTOR TRIP AND ENGINEERED SAFETY FEATURE ACTUATION SYSTEM INSTRUMENTATION The OPERABILITY of the Reactor Protection System and Engineered Safety Feature Actuation System Instrumentation and interlocks ensure that 1) the associated action and/or reactor trip will be initiated when the parameter monitored by each channel or combination thereof reaches its setpoint, 2) the specified coincidence logic is maintained, 3) sufficient redundancy is maintained to permit a channel to be out of service for testing or maintenance, and 4) sufficient system functional capability is available from diverse parameters.
The OPERABILITY of these systems is required to provide the overall reliability, redundancy, and diversity assumed available in the facility design for the protection and mitigation of accident and transient conditions. The integrated operation of each of these systems is consistent with the assumptions used in the accident analyses. The surveillance requirements specified for these systems ensure that the overall system functional capability is maintained comparable to the original design standards. The periodic surveillance tests performed at the minimum frequencies are sufficient to demonstrate this capability.
The Engineered Safety Feature Actuation System Instrumentation Trip Setpoints specified in Table 3.3-4 are the nominal values at which the bistables are set for each functional unit. A setpoint is considered to be adjusted consistent with the nominal value when the "as measured" setpoint is within the band allowed for calibration accuracy.
To accommodate the instrument drift assumed to occur between operational tests and the accuracy to which setpoints can be measured and calibrated, Allowable Values for the setpoints have been specified in 0237v:1D/021187 A-19
2 Table 3.3-4.
Operation with'setpoints less conservative than the Trip Setpoint but within the Allowable Value is acceptable since an allowance 1
has been made in the safety analysis to accommodate this error. An optional provision has been included for. determining the OPERABILITY of a channel when its trip setpoint is'found to exceed the Allowable Value. The methodology of this option utilizes the "as measured" deviation from the specified calibration point for rack and sensor components in conjunction with a statistical combination of the other uncertainties of the instrumentation to measure the process variable and f
the uncertainties in calibrating the instrumentation.
In Equation 2.2-1, Z + R + S < TA, the interactive effects of the errors in the rack and the sensor, and the "as measured" values of the errors are considered.
Z, as specified in Table 3.3-4, in percent span, is the i
statistical summation of errors assumed in the analysis excluding those associated with the sensor and rack drift and the accuracy of their measurement. TA or Total Allowance is the difference, in percent span, between the trip setpoint and the value used in the analysis for the
~
actuation. R or Rack Error is the as measured" deviation, in percent span, for the affected channel from the specified trip setpoint. S or
,j Sensor Drift is either the "as measured" deviation of the sensor from its calibration point or the value specified in Table 3.3-4, in percent span, from the analysis assumptions.
Use of Equation 2.2-1 allows for a j
sensor drift factor, an increased rack drift factor, and provides a threshold value for REPORTABLE OCCURRENCES.
l The methodology to derive the trip setpoints is based upon combining all i
e ri se o t r t ma tu o
h c nn e
Sensor and rack instrumentation utilized in these channels are expected to be capable of operating within the allowances of these uncertainty magnitudes. Rack drift in excess of the Allowable Value exhibits the I
behavior that the rack has not met its allowance.
Being that there is a small statistical chance that this will happen, an infrequent excessive drift is expected.
Rack or sensor drift, in excess of the allowance that is more than occasional, may be indicative of more serious problems and should warrant further investigation.
0237v:10/021187 A-20
__a

ML20236A966

Text

1.0 INTRODUCTION

4.3 CONCLUSION

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