ML20199B271

Forwards Response to Request for Addl Info Re MSSV Setpoint Tolerance Change

ML20199B271
Person / Time
Site:	Callaway
Issue date:	01/20/1998
From:	Randolph G UNION ELECTRIC CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
TAC-M99419, ULNRC-03717, ULNRC-3717, NUDOCS 9801280218
Download: ML20199B271 (8)

Text

__--___--__._____ --_-_-___________ - _ _ _ _ _

U21es Ehetric One Ameren Plaza 1901 Chouteau Avenue P0 Box 66149 St. louis, MO 63166-6149 msnmt January 20,1998 U. S. Nuclear Regulatory Commission A'1TN: Document Control Desk Mail Station P1-137 Washington, D. C. 20555-0001 ULNRC-03717 Gentlemen: TAC No. M99419 DOCKET NUMBER 50-483 I i

CALLAWAY PLANT l jf58fSS UNION ELECTRIC COMPANY

{ MSSV SETPOINT TOIFRANCE REVISION

References:

1) ULNR&3627 dated 8/8/97

2) ULNRL 36% dated 12/16/97

3) B. C. Westreich letter to G. L. Randolph dated 12/9/97

4) SLNRC-84-50 dated 3/23/84 References 1 and 2 transmitted information to support a change to the MSSV t

setpoint tolerance value contained in the Callaway Technical Specification Table -

3.7-2. - Rgerences 3 transmitted a request for additional information relating to o. '

amendment request. Although Reference 3 requested our response. by January 8,1998, we informed our Licensing Project Manager that additional time was needed and our response would be provided by January 31,1998 or sooner.

Attached aie responses to the request for information. Reference 4 provided proprietary and non-proprietary information concerning the Callaway Setpoint Methodology which is referenced in the attached responses.

Please contact us if you have additional questions.

Very truly yours, P

E$ $$$e3 maux Garry L. Randolph PDR Vice President and Chief Nuclear Officer ]h j Attachment .

l DES /pir ,

i. ;iI q ,

e uthsntiary et Amoren Carperetton

STATE OF MISSOURI )

) SS CITY OF ST. LOUIS )

Garry L. Randolph, of lawful age, being first daly sworn upon oath says that he Vice President and Chief Nuclear Officer and an officer of 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 knowledge, information and belief.

By Garry L. Randolph Vice President and Chief Nuclear Officer SUBSCRIBED and sworn to before me this #

day of Ww/aN , 1998.

/

.....".!$""" stih W k, ,aeskJl ARY g cwe TA ny 0Y5

,**.u...

PATRICIA L REYNOLDS IWWIY PUBUC-4WE OF AA000UN St Louis couwry MV000metBION EXPS1B 05.38,ING

cc: M. H. Fletcher Professional Nuclear Consulting, Inc.

19041 Raines Drive Derwood, MD 20855-2432 Pegional Administrator U.S._ Nuclear Regulatory Commission Region.]RT 611 Ryan Plaza Drive Suite 400 Arlington, TX 76011-8064 Senior Resident Inspector E Callaway Resident Office l: U.S. Nuclear Regulatory Commission l

8201 NRC Road Steedman, MO 65077 Barry C. Westreich (2)

Office of Nuclear Reactor Regulation l U.S. Nuclear _ Regulatory Commission 1 White Flint,= North, Mail Stop 13E16 11555 Rockville-Pike Rockville, MD 20852-2738 Manager, Electric Department Missouri Public Service Commission P.O. Box 360 Jefferson City, MG 65102 Ron 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

bcc: J. Brandt/A160.761

/QA Record (CA-758)

E210.01 J. V. Laux G. L. Randolph R. J. Irwin LP. M. Barrett J. D. Blosser A.-C.-Passwater D. E. Shafer W. E. Kahl S. Wideman (WCNOC)

A. J. DiPerna, (Bechtel)

H. D. Bono NSRB (Patty Reynolds) l Alvo.olO'Gih) 3rit3 /PM i-i f

ULNRC-3717 l Anachment 1

,, ,. UNION ELECTRIC RESPONSE TO TIIE REQUEST FOR ADDITIONAL INFORMATION REGARDING MSSV SETPOINT TOLERANCE CHAMGE

1) Ouestion: Provide the following trip function error and drift factors associated with .

the Pressurizer Pressure - High channel statistical allowance:

a. Process measurement accuracy (PMA)

b. Primary element accuracy (PEA)

c. Sensor calibration measurement & test equipment accuracy (SCA)

d. Sensor pressure effects (SPE)

e. Sensor temperature effects (STE)

f. Sensor drift (SD)

g. Environmental allowance (EA)

h. Rack calibration accuracy (rack accuracy and measurement & test equipment accuracy) (RCA)

i. Comparator setting accuracy (RCSA)

j. Rack temperature effects (RTE)

k. Rack drift (RD)

Resnonse: These values are held as proprietary by Westinghouse, as noted in Reference 4. Previous setpoint changes (e.g., Amendment No. 43 dated April 14,1989 and Amendment No. 57 dated September 20,1990) required the submittal of proprietary and non-proprietary attachments.

The requested setpoint terms have not changed since Reference 4 except for the sensor drift (SD) and environmental allowance (EA) terms discussed in response to Questions 4 and 5 below.

2) Ouestion: The licensee states that the negative drift component of the Barton transmitter accounted for 4.25% of the 4.96% of the Z term. Describe the uncertainty components included in the Z term. Are sensor drift uncertainties normally included?

Resoonse: By the Westinghouse Setpoint Methodology that was used in this analysis (see Reference 4), the equation that defines Z is as follows:

Page 1 of 4

ULNRC-3717 Attachment

,, ,-, Z- /A + EA , and A = (PMA)8 + (PEA)* + (SPE)8 + (SE)8 + (RW)8 Sensor drift uncertainties are not normally included in the Z term, but were previously included for this trip function as a result of treating the Barton transmitter drift allowance as an EA bias. With the Tobar transmitters there is no sensor drift term treated as an EA bias.

3) Question: Describe the uncertainty components included in the value S.

Response: By the Westinghouse Setpoint Methodology that was used in this analysis, the equation that defines S is as follows:

S = SCA + SD.

SCA is the Sensu Calibration Accuracy (which is the algebraic sum of the calibration tclerance of the sensor and the accuracy of the Measurement & Test equipment), and SD is the Sensor Drift. See the response to questions 1, 4, and 5 for the values used in this analysis.

4) Question: -- Union Electric Company states that the drift term included in S is a

= typical value. Provide the instrument type that replaced the Barton transmitter and discuss why' a _" typical drift term" is applicable in the determination of S instead of vendor specific information.

Response: The Barton transmitters were replaced with Tobar model 32PA1 absolute .

pressure transmitters. Tobar, Inc. no longer exists, but a drift value of i0.25 % URL (Upper Range Limit)/6 months has been published by the current owner of the product line, Weed Instruments. For the calibrated range of these transmitters (170(F2500 psig), this translates into i0.78%

of calibrated span /6 months. However, this value does not necessarily_

apply to actual field performance in the 18 month calibration cycle that is applied at Callaway.

As-found and as-left data from the calibrations that have been performed on these transmitters (currently installed transmitters have been in service since Refuel 3) indicate that the combination of Sensor Drift (SD), Sensor Calibration Accuracy (SCA), and M & TE allowance is between 1.4 and 1.5% of calibrr.ted span. Since a field calibration is unable to distinguish between the three components, Sensor Drift alone cannot be determined from field calibrations. However, Sensor Drift is never used in the analysis on its own. Sensor Calibration Accuracy and M & TE allowance are always included with Sensor Drift in the combined S term. Therefore, there is no need to know what the value of Sensor Drift alone is.

Page 7 V 4

j, ULNRC-3717 Attachment L

~

Tae combination of SD, SCA, and M & TE that was assumed in the analysis results in an S term of 2.0% of calibrated span which is greater than the observed value of 1.5% of calibrated span. Therefore, the combination of SD, SCA, and M & TE allowance that has been observed at Callaway is less limiting than the S term that was submitted in the Tech Spec amendment application (Reference 1).

5) Question: . Provide the Allowable Value (AV) calculation and the revised uncertainty allowances for the channel statistical allowance. Explain how a revision to the sensor drift term impacted the AV.

Response: The Allowable Value (AV) is equal to the Nominal Trip Setpoint (NTS) value plus (for a lQh setpoint) or minus (for a low setpoint) a " Rack Trigger Value" (designated as T in the Westinghouse setpoint methodology). The value of T is the smaller of two values, Ti and T2 .

AV, T ,i and T are 2 defmed by the following equations:

AV = N'lO i minimum (T or T 2),

Ti = RCA + RCSA + RD , and 2

T = TA hA +S + EA) .

2 TA is the " Total Allowance" which is the difference between the Safety Analysis Limit (SAL) and the Nominal Trip Setpoint. The value of A is defined in the response to Question 2. The value of S is defined in the response to Question 3. See the response to Question 1 for the other

- terms.

In the original analysis, which was performed for Barton transmitters, the Sensor Drift for the Pressurizer High Pressure Trip was treated as a bias of -4.25% of calibrated span, rather than a random value of 1.0% of calibrated span, to account for excessive' observed negative drift of Barton transmitters. Therefore, it was included in the EA term of T2 as a bias of-4.25% of calibrated span. This caused the Z term (which includes the absolute value of the EA term) to have a very high value of 4.%% of calibrated span. By changing the Sensor Drift term from zero to a random component of 1.0%, sensor drift is removed from the Z term and the EA portion of T2. The random component of 1.0% is also added to the S term since S includes the random component of Sensor Drift.

Page 3 of 4

ult.,tc.3717 Atudment

• , ,, T iwas the limiting *Rt9.k Trigger Valve" in the original analysis. De

~

Increase in the S term made T decrease. In addition, the SAL was also lowered resulting in a decrease in TA which made T: limiting.- T'Js -

resulted in a change to the AV.

6) Quandon: - Provide a margin calculation confirming that the channel uncertainty is bounded by the " total allowance."

Response: The Channel Statistical Allowance (CSA) as defined in the Westinghouse Setpoint Methodology la a statistical combination of all of the terms that are discussed in Question ! wherein the square root of the sum of the squares (SRSS) of 1%t terms is added to algebraic biases. The setpoint margin is the difference between the Total Allowance (TA) and the CSA For the Pressurizer High Pressure Trip , the CSA ws:

calculated to be 2.81% while the TA was calculated to be 3.125 %. The margin, or difference between these two values, is TA-CSA = 0.315 %.

This is documented in approved Uniot Electric calculations.

7) Ouestion: Dircuss the setpoint methodology used in this application. If the setpoint methodology is based upon a vendor methodology, discuss what changes to that vendor report are tuquired by this modification. Discuss changes in margin in the setpoint cal.:alation, and why a change in margin is acceptable.

Responne: The setpoint methadology used for this analysis was the West inghouse Setpoint Methodology (Reference 4). De changes in the valas that are used in the approved UE calculation will require no changes in the methodology. Therefore, no changes to any vendor reports are required.

The original setpoint margin in the Pressurizer High Pressure Trip was 1.03%. The responsc to question 6 states that the new margin is 0.315%. nis reductica in margin was due to the reduction in the Safety Analysis Limit rather than the change to the Sensor Drift values.

- However, a significant margin still exists which provides assurance that the Safety Analysis Limit will not be exceeded. The Westinghouse setpoint methodology requires that the difference between the Safety Analysis Limit and the Nominal Trip Setpoint, defined u the Total Allowance (TA), equst the Channel Statistical Allowance (CSA) which accounts for the entire channel setpoint uncertainty, When the TA exceeds the CSA, that margin is available for future licensee use. This is not margin in the context of 10CFR50.59(a)(2)(iii). De SAL ens' ires

' that the margin of safety as defined therein is maintained. Derefore, the reduction in setpoint margin is acceptable, ,

Page 4 of 4 ,

l

- I