ULNRC-03748, Forwards Responses to Request for Info Re Amend Request to Change Several Setpoint Values Contained in Plant TS Tables 2.2-1 & 3.3-4
| ML20203L790 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 02/27/1998 |
| From: | Passwater A UNION ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| TAC-MA0177, TAC-MA177, ULNRC-03748, ULNRC-3748, NUDOCS 9803060228 | |
| Download: ML20203L790 (12) | |
Text
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- U. don Ehciric One Ameren Plaza 1901 Choutes venue Po Box 6614w St. louis, MO 631f66149 31 M 11222 February 27, 1998 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Station Pl-137 Washington DC 20555-0001 Gentlemen:
$Yb DOCKET NUMBER 50-483 CALLAWAY PLANT UE union EtECTRiC CouPANY CIIANGES TO RTS AND ESFAS DELTA-T FUNCTIONAL UNITS
References:
- 1) ULNRC-3673 dated 10/31/97
- 2) B. C. Westreich letter to G. L. Randolph dated 1/29/98 Reference 1 transmitted a license amendment request to change seveml setpoint values cot.tained in Callaway Technical Specification Tables 2.2-1 and 3.34.
Reference 2 transmitted a request for additional information related o our amendment request.
Attached are responses to the request for information. Please contact us if you have additional questions.
Very truly yours, l/
Alan C. Passwater Manager-Licensing & Fuels GGY/jdg
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STATE OF MISSOURI )
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. Alan C. Passwater, of lawful age, being first duly sworn upon oath says that he is Manager, Licensing and Fuels (Nuclear) for Union Electric Company; that he has read the foregoing document and knows the content thereof; that he has executed the same for and on behalf of said company with full power and authority to do so; and that the facts therein stated are true and correct to the best of his knon\\ edge, information and belief.
By Alan C.
Passwater Manager, Licensing and Fuels Nuclear SUBSCRI. BED and sworn to before me this 8
day of htfWh*M 1998.
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Fletcher Professional Nuclear Consulting, Inc.
19041 Raines Drive Derwood,1MD 20855-2432 Regional Administrator U.S. Nuclear Requiatory Commission Region IV 611 Ryan Plaza Drive Suite 400 Arlington, TX 76011-8064 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman, MO 65077 Barry C. Westreich (2)
Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission 1 White Flint, h' orth, Mail Stop 13E16 11555 Rockville Pike Rockville, MD 20852-2738 Manager, Electric Department Missouri Public Service Commission P.O. Box 360 Jefferson City, MO 65102 Roa Kucera Department of Natural Resources P.O. Box 176 Jefferson City, MO 65102 Denny Buschbaum TU Electric P.O. Box 1002 Glen Rose, TX 76043 Pat Nugent Pacific Gas & Electric Regulatory Services P.O. Box 56 Avila Beach, CA 93424 9'
Page 1 of 7 1.
_Ouestion:
Provide a copy of the setpoint calculation showing Total Allowance (TA),
Channel Statistical Allowance (CSA) each for Functional Units OT Detta T (Kl), OT Delta P[ sic) (K4), and SG water Low-Low Vessel Delta T (Power-1 and Power-2) for reactor trips and for AFW start ESFAS functions.
Response
A telecon was held on Febmary 23,1998 with NRC Staff to discuss our concerns with providing information held as proprietary to Westinghouse. As a result of that telecon, please find the r,ttached Table 1 relating current vs.
proposed values for the following parameters for the fcur affected trip functions:
a) Safety Analysis Limit (SAL, unchanged);
b) Nominal Trip Setpoint (NOM);
c) Total Allowance (TA);
d) Unannel Statistical Allowance (CSA);
e) Allowable Value (AV); and P
f)
Margin (MAR).
Note when reviewing Table 1 that values presented there are in % RTP and that 100% AT span = 150% RTP.
In addition, a discussion of setpoint methodology was desired beyond the reference provided in SLNRC 84-50 dated 3/23/84. Tne setpoint methodology used is consistent with that repr sented by Equation 6.2 ofISA-RP67.04, Part II, Recommended Practice, " Methodologies for the Determination of Setpoints for Nuclear Safety-Related Instrumentation," September 1994.
The method discussed by that recommended practice is a combination of statistical and algebraic methods that use statistical squire root sum of squares (SRSS) methods to combine random uncertainties and then algebraically combine the nonrandom terms with the result. The fonnulas and following discussion present the basic principles of this methodology.
3
E.,.
Page 2 of 7 The basic formula fu ' our uncenainty calculations takes the form:
CS A = 1 [A +B +C )]v2 1 lFl + L-M 2
2 2
where A,B,C random and independent tennL The terms are zero-centered,
=
approximately normally distributed, and are indicated by a i sign.
F abnormally distributed uncenainties and/or biases (unknown
=
sign). The term is use4 to represent limits of error associated with uncenainties that are not normally distributed and do not have known direction. The magnitude of this term (absolute value) is assumed to contribute to the total uncertainty in a worst-case direction and is also indicated by a i sign.
L&M biases with known sign. The terms can impact an uncertainty in
=
a specific direction and, therefore, have a specific + or -
contribution to the total uncertainty.
CSA resultant uncertainty. The resultant uncertainty combines the
=
random uncertainty with the positive and negative components of the nonrandom tenus separately to give a final uncertainty.
~
The positive and neghtive nonrandom terms are not algebraically combined before combination with the random component. This calculated result is also called the Channel Statistical Allowance in our setpoint methodology.
The addition of the F, L, and M terms to the A, B, and C uncertainty terms allows the formula to account for influeaces on total uncertainty that are not random or independent. For biases with known direction, represented by L and M, the terms are combined with only the applicable portion (+ or -) of the random uncertainty. For the uncertainty represented by F, the terms are combined with both portions of the random uncertainty. Since these terms are uncertainties themselves, the positive and negative components of the terms cannot be algebraically combined into a single term. The positive terms of the nonrandom uncertainties should be summed separately, and the negative tenns of the nonrandom uncertainties should be summed sepamtely and then individually combined with the random ui. certainty to yield a final value.
Individual nonrandom uncertainties are independent probabilities and may not be present simultaneously. Therefore, the individual tenns cannot be assumed
^
to offset each other. The purpose of the setpoint calculction is to ensure that protective actions occur 95 percent of the time with a high ?egree of confidence before the analytical limits are reachad. A conservative philo? phy applies the SRSS 'echnique only to those uncertainties that are characterized as i
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Page 3 of 7 independent, random, and approximately normally distributed. All other uncenainty components are combined using the maximum possible uncertainty treatment, i.e., algebraic summation of absolute values as necessary.
If R equals the resultant uncertainty (A + B + C )ia, the maximum positive 2
2 2
uncenainty is
+CSA = +R + l Fl + L and the maximum negative uncenainty is l
-CS A = -R - l F l - M.
I SRSS combination for bias uncenainties is inappropriate since, by their nature, they do not satisfy the prerequisites for SRSS. Bias uncertainties are not random and are not characterized by a no mal probability distribution. Since the number of known biases is typically small and they may or may not be present simtdtaneously, the recommended practice ',RP67.04) conservatively endorses algebraic summation for bias unceaainties.
In the detennination of the random portion of an uncenainty, situations may arise where two or more random terms are not totally independent of each o'her I
but are inclependent of the ether random tenns. This dependent relationship can be accommodated within the SRSS methodology by algebraically summing the l.
dependent random tenns prior to perfonning the SRSS determination. The fonnula takes the following form:
CSA = i IA +B +C + (D + E)2)tc i lFl + L-M 2
2 where D and E = random dependent uncertainty terms that are independent of terms A, B, and C.
The above methods are also discussed in Sections 4.4.1 and 4.4.2 of ISA-S67.04, Part I, Standard, "Petpoints for Nuclear Safety-Related Instrumentation", September 1904. The setpoint methodology used in this license amendment request has not changed since 1984 and follows the SRSS j
approach discussed above. A graphical breakdown of this approach is attached i
in Figure 7-1 from an internal 1994 I&C SSFA.
I i
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Page 4 of 7 2.
Ouestion:
Provide a copy of the calculations used for ULNRC-2808 dated June 4,1993, ULNRC-03198 dated April 17,1995, and ULNRC-2196 dated April 12, 1990.
Please note that these documents are included as References 2,3 and 4 to the October 31,1997 submittai.
Response
Those o'.her license amendments were referenced only inasmuch as they demorstrated the use of the setpoint methodology and provided c history of the A T and T,y channel setpoint changes implemented since the RTD Bypass Modification (see Reference 4 of ULNRC-3673). They are not neede'l for tne approval of ULNRC-3673 as they covered other, previously approved modifications. The infonnation provided in response to Quettion 1 is similar to that contained in the above references.
3.
Question:
In reference ta the "Significant Hazards Evaluation" more infonnation is needed as noted below.
a.
Item 2, page 3 of the Attachment 1. It is stated that out of random and systematic portions of the Process Measurement Accuracy (PM A) error (due to hot leg streaming), the systematic component will be replaced with a biis considerine
- s "burndown effect". Provide information as to how the bias-value s
. teulated or provide a copy of the calculation for this bias. Also, it is not clear how the random portion of the PMA could be eliminated from the OT Delta T setpoint calculation since this error-component will always be present (due to some streaming and due to other effects), although in some circumstances its value may be different.
Explain how elimination of tiie random PMA error component is justified by moving the axial-flux-difference (AFD) penalty function deadband by 2 percent on both sides.
Resoonse:
This question actually consists of three parts and will be addressed as such.
As discussed on pages 4 and 5 ot the 50.92 evaluatior, the treatmer of the hot leg streaming portion of the OTAT PMA term as a bias is justified by operating experience at Callaway demonstrating its unidirectional nature. It is not a random term that should be included with the square-root-sum-of-squares (SRSS) treatment of the other random, independent terms. The value of this bias was not calculated; it was detennined from Callaway's operating experience during Cycle 8. The AT bias was observed to be
Page 5 of 7 bounded by 0.6 F, but a value of 1.0 F was used in the calculation for conservatism. Likewise, the T,y, bias was observed to be bounded 1 0.3 F, but a value of 0.5 F was used in the calculation.
Not all portions of the OTAT PMA team were eliminated; only thux portions related to hot leg stmaming (which has been demonstrated by operating experience to be unidirectional and more appropriately treated as a bias) and the AI incore/excore comparison term discussed below were eliminated. The treatment of the hot leg stmaming PMA term and the scoop streaming bias discussed in the Reference 4 (ULNRC-2196,, page 10) spreadsheet for OTAT is not only more appropriately handled as a bias,,,iven its unidirectioaal nature, but it is more conservative to do so wnen considering these uncenainty terms and comparing the CSA calculated with a SRSS handling of the hot leg
algebraically added biases for both AT and T.,,.
The OTAT AFD penalty function should only take away operating margin when the penalty deadband is exceeded on either side. Moving the OTAT AFD penalty function deadband in 2% AI on 6 uth sides is the same as treating this function (hsted as the 3 % AI incore/excore con.parison PMA term C in the same Reference 4 OTAT spreadsheet mentioned above and later revised to a 2% AI PMA term in Reference 2 to ULNRC-3673) as a bias directly to the parameter of interest, rather than always taking away setpoint margin when no AFD penalty is warranted given operation within the penalty deadband.
Questio_ti:
b.
Item 3, page 3 of the Attachment 1: It is stated that RTD sensor calibration accuracy and drift can be elimina:ed from the setpoint calculation because (a) periodic re-normalization of each loop's parameters performed during quanerly surveillance will compensate for the RTD uncenainty, (b) an additional error component which has been added for power calorimetric that will compensate for the RTD sensor calibration accuracy, and (c) addition of burndown effect bias will compensate for the RTD drift.
In this situation, if OT Delta T protection is required due to a transient during the peried between the two successive surveillances (i.e., just before the loop being re-normalized), how will the loop respond without compromising safety since RTD accuracy and drift are eliminated from the setpoint calculation. Also, justify by a quantitative evaluation tnat the buindown effects bias will compensate for the RTD drift in addition tc compensating the mndom component of PMA.
Page 6 of 7 i
Response
The h1D sensor drift and cr.libration accuracy tenns from the Reference 4 spreadsheet aren't just eliminated, as suggested by the question. They are treated mom appropriately. When the method used to calculate the CSA in Reference 4 (i.e., PMA term for hot leg streaming, hot leg scoop strn ning bias, RTD drift sensor term, and RTD calibration accuracy sensor tenn) is co:npamd against the proposed method of calculating the CSA:
(1) including a 2% RTP (1.33 % AT span) power calorimetric PMA term to address the RTD calibration accuracy and M&TE sensor terms; (2) handling the incore/excore mismatch as a direct, functional bias in the setting of the 7300 function generator cards, outside the OTAT setpoint calculation itself, by moving the OTAT penalty deadband in by 2% cn both sides as discussed above; (3) and adding in biases of 1.0 F for AT burn /own and 0.5 F for T,y burndown to account for RTD drift and hot leg stmaming effects, the proposed method is acceptable for addressing channel uncertainties. See also attached Table 1.
4.
Ouestion:
Provide more detailed discussions and justifications for the following changes.
In addition provide a discussion of the effect of these changes on analyses and operating hmits/ assumptions. Provide a comparison of your new setpoints to the analytical limits, a.
The 2.41 percent RTP increase in the Nominal Trip Setpoints for the Vessel delta T Power-1 and Power-2 portions of the SG Water Level Low-Low RTS and ESFAS trip functions, s
Response
By virtue of the above discussions, the Vessel Delta-T Power-1 and Power-2 CSA values have decreased by 1.45 % RTP. The Nominal Trip Setpoints were allowed to increase by 2.41 % RTP span by using available setpoint margin. The Nominal Trip Setpoints of 12.41 % RTP and
(
22.41 % RTP are bounded by corresponding Safety Analysis Limits of 19% RTP and 29% RTP. There will be no effect on any safety analyses and only a minor effect on normal operations in that a trip time delay will be in effect up to 22.415 RTP to counteract inadvertent reactor trips due to SG level shrink / swell phenomena. See also attached Table 1.
e k
1
.-4 Page 7 of 7 k
Ouestion:
b.
The 2 percent reduction in the q(t) -q(b) values.
Response
This response to this question on the OTAT AFD penalty function deadband is discussed above in response to Questions 3a and 3b.
k
.,. ^
1 TABLE 1 Old New Old New Old New Old New OTDT OTDT OTDT OTDT DTP1 DTP1 DTP2 DTP2
(%RTP)
(%RTP)
(%RTP)
(%RTP)
(%RTP)
(%RTP)
(%RTP)
(%RTP)
CSA 11.96 8.75 6.81 5.02 7.29 5.84 7.29 5.84 Margin 2.04 0.75 0.69 0.75 1.71 0.75 1.71 0.75 TA 14.00 9.50 7.50 5.77 9.00 6.59 9.00 6.59 SAL 129.00 129.00 116.50 116.50 19.00 19.00 29.00 29.00 NOM i15.00 119.50 109.00 110.73 10 00 12.41 20.00 22.41 AV 118.45 121.35 112.6 112.55 13.90 13.90 23.90 23.90
lM' t
SSFA 94-01(I&C)
Page 96 of 118.
I SetDoint Uncertainty Breakdown AN AN
)k Margin Y
Y JL
- L A
y Bias A
Environmental Allowance (EA) d d ProcessMeasurement Accuracy (PMA)
Pnmary Element TA Z
p Accuraty(PEA) d SensorTemperature l
A V EITects (STE)
F k Sensor Pressure CSA g
y EfTects(SPE) y Al Rack *iemperature EfTects(RTE)
Y 3 r V
t g
Sensor Calibration Accuracy (SCA)
S V
Al STS Allowable Value y
p SensorDnft(SD)
JL A
A Rack Comparator y Setung Accuracy (RCS A)
Tcm:n(K C r* T )
N#$
A a
Rack Calibration Accuracy (RCA)
V F'
A
(
STS Trip Setpoint(NOM) V yV y
Figure 7-1 E
-