ML20070A984

Application for Amends to Licenses NPF-68 & NPF-81,revising Values of Z & for Pressurizer Pressure Reactor Trip Instrumentation Trip Setpoints to Allow Use of Alternate Types of Pressure Transmitters

ML20070A984
Person / Time
Site:	Vogtle
Issue date:	06/24/1994
From:	Mccoy C GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20070A986	List: ML20070A984 ML20070A998
References
LCV-0396, LCV-396, NUDOCS 9406290226
Download: ML20070A984 (7)

Text

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c. K Mccoy GCOlgia Power

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, r , .e LCV-0396 Docket Nos. 50-424 50-425 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555 Gentlemen:

VOGTLE ELECTRIC GENERATING PLANT REVISION TO "Z" AND "S" FOR PRESSURIZER PRESSURE REACTOR TRIP INSTRUN1ENTATION TRIP SETPOINTS In accordance with the provisions of 10 CFR 50.90 and 10 CFR 50.92, Georgia Power Company (GPC) hereby proposes to amend the Vogtle Electric Generating Plant (VEGP)

Unit I and Unit 2 Technical Specifications, Appendix A to Operating Licenses NPF-68 and NPF-81.

This amendment revises the values ofZ and S for the Pressurizer Pressure-Low and -High reactor trip setpoints (Table 2.2-1, Functional Units 9 and 10 respectively) to allow the use of ahernate types of pressure transmitters. The values of 7 and S for the Pressurizer Pressure-Low Engineered Safety Features Actuation System (ESFAS) Safety injection (SI) actuation setpoint (Table 3.3-3, Functional Unit Id) bound the proposed choices of transmitters and therefore are unaffected. The proposed changes do not afTect the instrumentation setpoints and safety analysis limits.

Unit 1 pressurizer pressure transmitter IPT-457 has had a chronic history of drifling predominantly in an upward direction. Attempts to correct the excessive drift have included ieplacing the transmitter several times as well as several transmitter recalibrations As discussed in the bases for Specifications 2.2.1 and 11.2, the excessive drift has been more than occasional and warrants further i,vestigation. It is believed that the source of the drift is the transmitter and not the instrumentation downstream of the transmitter. To aid in further investigative cfForts, GPC plans to substitute the current transmitter IPT-457(Tobar Model 32 pal) with a Rosemount Model 1154 Series H pressure transmitter. The Rosemount transmitter has an improved calibration accuracy and is less susceptible to drift as compared to the Tobar transmitter. The pressurizer pressure transmitters used at VEGP are a cembination of Tobar Model 32 pal and Veritrak Model 76Pil2 transmitters. The change to the Technical Specifications will also allow any or all of the pressure transmitters to be Tobar, Veritrak, or Rosemount transmitters.

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U. S. Nuclear Regulatory Commission Page 2 The values of Z and S in Table 2.2-1 for the pressurizer pressure instrument channels must be revised to allow for the use of Rosemount pressure transmitters. Even though the value l

! of Z increases and the value of S decreases, the overall instrument loop uncertainty remains within the current total allowance, theiefore, the existing totd allowance and trip setpoints remain unchanged This ensures that the conclusions of the safety analyses remain valid. The values of Z, S, total allowance, and setpoint in Table 3.3-3 remain unchanged.

Georgia Power Company plans to replace the IPT-457 Tobar transmitter with a Rosemount transmitter during the Unit I refueling outage scheduled to begin in September 1994. The refueling outage is a desirable time to replace the transmitter since it reduces the risk of a plant trip. On-line maintenance on this transmitter has resulted in two reactor trips and one safety injection at VEGP f

These Technical Specification changes are requested to be approved by August 31,1994, in order to facilitate the replacement of the Tobar pressurizer pressure transmitter during the upcoming refueling outage.

The proposed changes and bases for the changes are described in Enclosure I to this letter. Enclosure 2 provides an evaluation pursuant to 10 CFR 50.92 showing that the proposed changes do not involve significant hazards considerations. Instructions for incorporation of the proposed changes into the Technical Specifications and a markup of the alTected pages are provided in Enclosure 3.

In accordance with 10 CFR 50 91, the designated state o!Ticial will be sent a copy of this letter and all enclosures.

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Mr. C. K. McCoy states that he is a vice president of Georgia Power Company and is authorized to execute this oath on behalf of Georgia Power Company and that, to the best of his knowledge and belief, the facts set forth in this letter and enclosures are true.

GEORGIA POWER COMPANY lly: .

C. K. McCoy Sworn to and subscribed before me thisNby of J

[Julw ,1994.

j YL% R' 0 Af N '

Notary Public LCV-0396

Georgia Power $

U. S. Nuclear Regulatory Commission Page 3

Enclosures:

1. Basis for Proposed Change ,

2.10 CFR 50.92 Evaluation

3. Marked-Up Pages cc: Georgia Power Comnany Mr. J. B. Beasley, Jr.

Mr. M. Sheibani i NORMS l I

U. S. Nuclear Reculatery Comnission  ;

Mr S. D. Ebneter, Regional Administrator Mr. D. S. Ilood, Licensing Project Manager, NRR Mr. B. R. Bonser, Senior Resident inspector, Vogtle Slate _ofGrArgia Mr. J. D. Tanner, Commissioner, Department of Natural Resources l

l LCV-0396 7007F6

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ENCLOSURE 1 REVISION TO "Z" AND "S" FOR PRESSURIZER PRESSURE REACTOR TRIP INSTRUMENTATION TRIP SETPOINTS BASIS FOR PROPOSED CHANGF, Propmed Chan2e in table 2.2-1 the Z and S values for pressurizer pressure-low and ressurizer pressure-high will be changed from "0.71" and "1.67" respectively to "0.71 (1.04)" and "1.67 #(1.17)" respectively. A footnote will be added which states, "#The instrumentation -

used shall be bounded by either pair of values for Z and S."

DMi1 Four redundant pressurizer pressure transmitters (PT-455, PT-456, PT-457, and PT-458) provide inputs to the logic for reactor trips on low and high pressurizer pressure and safety injection (SI) actuation on low pressurizer pressure. The setpoints at which the trips and SI actuation occur are specified in Technical Specification Tables 2.2-1 and ,

3.3-3, respectively.

Specific values of pressurizer pressure are assumed in the safety analyses for the initiation of reactor trips and Si actuation. In determining the values of the setpoints to ensure that the safety analysis limits are not exceeded, allowances are made for the accuracy with which the process variable, in this case pressurizer piessure, can be measured. These allowances account for instrument rack errors (R), sensor (transmitter) errors (S), and other errors (Z) associated with the measurement. The combination of these errors is referred to as the total allowance (TA). Values of TA,7, and S are specified in Technical Specification Tables 2.2-1 and 3.3-3. The Allowable Value in the tables accounts for the efTect of the rack errors, R, on the setpoints. In accordance with Specifications 2.2.1 and 3.3.2, the allowable values of the setpoints may be exceeded for a limited period of time as long as it is demonstrated that the total allowance is not exceeded. This is demonstrated using Equation 2.2-1 in Specification 2.2-1: Z + R + S < TA.

Unit I pressurizer pressure transmitter 1PT-457 has had a chronic history of drifling predominantly in an upwar j direction. Attempts to correct the excessive drift have included replacing the transmitter several times as well as several transmitter recalibrations. As discussed in the bases for Specifications 2.2.1 and 3.3.2, the excessive drin has been more than occasional and warrants further investigation. It is believed that the source of the drifl is the transmitter and not the instmmentation downstream of the El-1 i

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ENCLOSURE 1 (CONTINUED)

REVISION TO "Z" AND "S" FOR PRESSURIZER PRESSURE REACTOR TRIP INSTRUMENTATION TRIP SETPOINTS BASIS FOR PROPOSED CHANGE transmitter. To aid in further investigative efforts, GPC plans to substitute the current transmitter IPT-457(Tobar Model 32 pal) with a Rosemount Model 1154 Series H pressure transmitter. The Rosemount transmitter has an improved calibration accuracy and is less susceptible to drin as compared to the Tobar transmitter. The pressurizer pressure transmitters used at VEGP are a combination of Tobar Model 32 pal and Veritrak Model 76Pil2 transmitters. The change to the Technical Specifications will also allow any or all of the pressure transmitters to be Tobar, Veritrak, or Rosemount transmitters.

As mentioned above, transmitter IPT-457 has been replaced and recalibrated several times. Afler each replacement or recalibration, the transmitter output continued to dria.

The investigation into the root cause of the transmitter drin included: comparison of transmitter outputs, noise analyses, comparison of transmitter environments (temperature and vibration), troubleshooting and replacement of rack electronics, examination of sensing lines for leaks, laboratory testing, as well as discussions with the vendor and other utilities. To date, no apparent cause of the drin has been determined. Currently, some of the transmitters that have exhibited drin are installed in the plant on a test leg along with a Rosemount transmitter and a reference transmitter at r.ormal system pressure.

The allowances described above have been reevaluated to account for the differences in the characteristics of the existing transmitters and Rosemount transmitters. The allowances in Technical Specification Tables 2.2-1 and 3.3-3 for pressurizer pressure are based on Tobar and Veritrak transmitters. For the Pressurizer Pressure-Low and -High reactor trips in Technical Specification Table 2.2-1, the value of Z increases from 0.71 to 1.04 and the value of S decreases from 1.67 to 1.17 for the Rosemount transmitter. The i overall instrument loop uncertainty did not increase, therefore, the total allowance and hence the trip setpoints in Technical Specification Table 2.2-1 remain unchanged. This ensures that the conclusions of the safety analyses remain valid. The values of 2 and S for the Rosemount transmitter will be added to Technical Specification Table 2.2-1. The values Z and S for the safety injection actuation on Pressurizer Pressure Low in Technical Specification Table 3.3-3 bound the values determined for the Rosemount transmitter, therefore, no changes to the values ofZ and S in the table are required. Also, the values of the trip setpoint and the total allowance are not affected.

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d ENCLOSURE 2 REVISION TO "Z" AND "S" FOR PRESSURIZER PRESSURE REACTOR TRIP INSTRUMENTATION TRIP SETPOINTS 10 CFR 50 92 EVALUATION Pursuant to 10 CFR 50.92, Georgia Power Company (GPC) has evaluated the proposed revision to the Technical Specifications (TS) and has determined that operation of the facility in accordance with the proposed amendment would not involve any significant hazards considerations.

The proposed change will add values of Z and S to Technical Specification Table 2.2-1 for the Pressurizer Pressure-Low and -High reactor trip setpoints (Table 2.2-1, Functional Units 9 and 10) to allow the use of the existing Tobar and Veritrak pressure transmitters  ;

or the proposed Rosemount pressure transmitters. The corresponding values of Z and S for the Pressurizer Pressure-Low setpoint for safety injection actuation (Table 3.3-3, Functional Unit Id) are bounding for these pressure transmitters. The setpoints, allowable values, and total allowances in the tables are not affected.  ;

1. Does the change involve a significant increase in the probability or consequences of an accident previously evaluated?

The proposed change revises the allowances Z and S in Technical Specification Table 2.2-1 for the Pressurizer Pressure-Low and ligh trip setpoints (Table 2.2-  ;

1, Functional Units 9 and 10) to allow the use of Tobar Veritrak, or Rosemount pressure transmitters Also, the corresponding values of Z and S for the Pressurizer Pressure-Low setpoint for safety injection actuation (Table 3.3-3, Functional Unit id) are bounding for these pressure transmitters. The allowances for Z and S are not assumed in any of the initiating events for the accident analyses. Therefore, the probability of any accident previously evaluated will not ,

be affected by the proposed changes. Furthermore, the setpoints, allowable values, and total allowances are not afrected. Since the total allowances are not affected, it is ensured that the safety aralysis limits for the trips aie not affected. Therefore, the proposed change does not involve a significant increase in the consequences of any accident previously evaluated.

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l ENCLOSURE 2 REVISION TO "Z" AND "S" FOR PRESSURIZER PRESSURE REACTOR TRIP INSTRUMENTATION TRIP SETPOINTS

.10.ER 50 923BL11KUDE

2. Does the change create the possibility of a new or different kind of accident from any accident previously evaluated?

The safety fimetion provided by the reactor trips and safety injection actuathn and the manner in which the plant is operated are not affected. The setpoints, allowable values, and total allowances are not affected. Since the total allowances are not affected, it is ensured that the safety analysis limits for the trips are not affected.

Thus, this change does not create the possibility of a new or different kind of accident f om any accident previously evaluated.

3. Does this change involve a significant reduction in a margin of safety?

For both the reactor trips and safety injection actuation, there are no changes to -

the setpoints. The total allowance for each setpoint is the difTerence between the safety analysis limit and the setpoint. Since the total allowances are not affected, there are no changes to the safety analysis limits. Therefore the proposed change will not involve a reduction in margin of safety.

Gmchisina Based of the preceding arguments, Georgia Power Company has determined that the proposed changes to the technical specifications will not significantly increase the l probability or consequences of an accident previously evaluated, create the possibility of a i new or difTerent kind of accident from any accident previously evaluated, or involve a j significant reduction in a margin of safety. Therefore, the proposed changes meet the requirements of 10 CFR 50.o2(c) and do not involve a significant hazards consideration.

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