ML20199G372

Application for Amends to Licenses NPF-68 & NPF-81,proposing Changes That Would Facilitate Treatment of Trip Setpoints as Nominal Values & Correct Certain Typos

ML20199G372
Person / Time
Site:	Vogtle
Issue date:	11/20/1997
From:	Mccoy C SOUTHERN NUCLEAR OPERATING CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20199G377	List: ML20199G372 ML20199G390
References
LCV-1102, NUDOCS 9711250166
Download: ML20199G372 (10)

Text

, ,,

C.K. McCoy Southern Nuclear

-* Veo President Operating Company, lac.

- Vogtle Project 40 inverness Center Parkway-P0. Box 1295 Birmin0ham. Alabama 35201 Tel 205992.7122 Fax 2059910403 SOUTHERN h COMPANY Energy toServe nurWorld' November 20, 1997 LCV-Il02 Docket Nos. 50-424 50-425 U. S. Nuclear Regulatory Commission ATIN: Document Control Desk Washington, D. C. 20555 Ladies and Gentlemen:

VOGTLE ELECTRIC GENERATING PLANT REQUEST TO REVISE TECIINICAL SPECIFICATIONS REACTOR TRIP SYSTEM AND ENGINEERED SAFETY FEATURE ACTUATION SYSTEM INSTRUMENTATION TRIP SETPOINTS in accordance with the requirements of 10 CFR 50.90, Southern Nuclear Operating Company (SNC) proposes to revise the Vogtle Electric Generr. ting Plant (VEGP) Unit I and ,

Unit 2 Technical Specifications (TS) Limiting Condition for Operation (LCO) 3.3.1, Reactor Trip System (RTS) Instrumentation, and LCO 3.3.2, Engineered Safety Feature Actuation System (ESFAS) Instrumentation. The proposed changes would facilitate treatment of the trip setpoints as nominal values and correct certain typographical errors.

The proposed changes are as follows:

-* The inequalities as they are applied to the Trip Setpoint columns of Tables 3.3.1-1 and 3.3.2-1 would be deleted, and the column headings would be changed from

" Trip Setpoint" to " Nominal Trip Setpoint."

g7)f F

e A footnote would be added to the new " Nominal Trip Setpoint" columns of Tables 3.3.1-1 and 3.3.2-1 that would allow the trip setpoints to be set more conservative than the nominal value as necessary to respond to plant conditions.

. The Allowable Value for Table 3.3.1-1, Function 14.b, Turbine Trip - Turbine Stop Valve Closure, would be revised from " a 96.7% open" to " 2 90% open."

. Footnotes i and m of Table 33.1-1 would be revis:d to refer to the " Nominal Trip Setpoint" and delete the inequalities applied to the trip setpoints.

9711250166 971120' PDR ADOCK 05000424 P PDR {k , ,

3

• U. S. Nucle:r Regul: tory Commission LCV-1102 Page 2

• A superscript "(a)" should be deleted from the heading of the " Trip Setpoint" column on page 6 of 8 of Table 3.3.1-1.

• Notes I and 2 to Table 3.3.1 1, Overtemperature AT and Overpower AT, respectively, will be revised to refer to the " Nominal Trip Setpoint." In addition, these notes will be revised to deic $- inequalities from the values for the constants K ithrough K 6(except fo: ry 2 0 for decr. asing temperature and K 6 = 0 for T s T"),

and for T', T". and P'.

• The inequality apr.ied to the ESFAS Alk xable Value for Steam Line Pressure -

Low (Table 3.3.2 1, Function 1.e) should be changed from "s" to "2".

The deletion of the inequlities from the trip setpc nts of Tables 3.3.1-1 anJ 3.3.2-1 and the change in terminology fn m "Tr'p Setpoint" to " Nominal Trip Setpoint" is consistent with the treatment of RTS and .iSFA i trip setpoints as nominal values. The LCO 3.3.1 and 3.3.2 Bases discussion for trip se. coin s and allowable values refers to the trip setpoints as "the nominal values at which the bista bles are set." The proposed change will facilitate a "two-sided" calibration tolerance a rou id the nominal trip setpoint instead of forcing calibration in accordance with the inequaliw.

The addition of the footnote would facilitate, for example, setting the Power Range Neutron Flux High trip setpoint lower than the nominal value of 109 % during startup following a refueling outage. Under these conditions, the high Oux trip setpoint is set consenatively low during initial startup until sufficient reactor power is achieved so that an accurate calibration of the power range channels can be accomplished, in addition, there may be other times when the TS v auld require the high Hux trip setpoints to be reduced in response to some equipment inot erability.

The change to the Allowabh: Value for Table 3.3.1-1, Function 14.b, Turbine Trip - Turbine Stop Valve Closure, is necessitated by the fact the current TS Allowable Value is the same as the Trip Setpoint (i. e., both are specined as " 2 96.7% open"). Simply deleting the inequality from the trip setpoints does not achieve the desired effect for this one function because there is no margin specified in the allowable value. Detecting turbine stop valve closure provides the reactor trip system logic with an indication that the turbine is tripping and steam load will soon be unavailable. The stop valves are not designed to modulate steam now, but rather to be fully open during normal operation and fully closed following turbine trip and/or shutdown. Therefore, any indication other than fully open will provide the reactor trip system with indication that the turbine is tripping. An allowable value of 90% is also consistent with on-line testing performed for the main steam isolation valves (MSIVs). The MSIVs are allowed to close to 90% open during on-line testing. Valve position below 90% open is considered to indicate imminent valve closure. Since the turbine stop valves operate similarly (either fully open or fully closed), an allowable value of 2 90% open is adequate to provide trip indication to the reactor trip system. Finally, reactor S:WOGTt.DVOGILE X VDTECilSPEC\SFTPOINITLCV i l 02. DOC

-- ,1 .

j

• ' UiS. Nucidr Regulitory Commission LCW1102 :

_ Page 3 :

4 trip on turbine stop valve closure is an anticipatory trip. It is not credited in the accident

. analyses.' i in addition, SNC proposes to correct two typographical errors:

<

• A superscript "(a)" should be deleted from the heading of the " Trip Setpoint"

. column on page 6 of 8 of Table 3.3.1-1. This superscript is a holdover from - -

NUREG-1431, Revision 0, and it referred to a footnote (a) that was a Reviewers

'- Note. The Reviewer's Note was deleted during the conversion of the VEGP TS to NUREG-1431, and the references to this footn. were deleted except in this one case. Therefore, the proposed deletion of tha pt (a) from the " Trip Setpoint" column of page 6 of 8 of Table 3.3.1-1 w rurely editorial.

e The inequality applied to the ESFAS Allowable Value for Steam Line Pressure -

Low (Table 3.3.2-1,= Function 1.e) is incorrectly shown as "s". The correct inequality is "2". The inequality is correctly show . l.,'our December 21,1995 submittal for the conversion to NUREG-1431. Therefore, the proposed change merely corrects a typographical error.

Enclosure i provides the basis for the proposed change. Pursuant to 10 CFR 50.92, Enclosure 2 demonstrates that the proposed change does not involve a cignificant hazard consideration, and Enclosure 3 is a mark-up _of the affected pages from the current VEGP Unit I and Unit 2 TS and the affected Bases pages.

Mr. C. K. McCoy states that he is a Vice President of Southern Nuclear Operating Company and is authorized to execute this oath on behalf of Southern Nuclear Operating Company and that, to the best of his knowledge and belief, the facts set forth in this letter are true.

SOUTHERN NUCLEAR OPERATING COMPANY -

By: .

C. K. McCoy .

Sworn to andsubscribedbefore me this A D ay of "Ik O(MLeth,1997.

~

$'& $. ba,)-)w

' Notary P5lic \

-Kfy cammission expires:

l 0

li'I'}

CKM/NJS S:WOGTLDVOGTI.E.KVETECIISPEC\SETPOINTLCVi102. DOC -

te : 9

-).$  ; U.' S. Nuclear Regulatory Commission - '

. LC%)102 :-

Page 4.'

-- Enclosures xc: . Southern Nuclear Onerating Comnany Mr. J. B. Hensley, Jr.

Mr. M. Sheibani

. NORMS" U. S. Nuclear Regulatory Commission Mr. L. A. Reyes, Regional Administrator -

Mr. L. L. Wheeler, Senior Project Manager, NRR -

l- NRC Resident inspector, Vogtle

} State of Georgin J. D. Tanner, Commissioner, Department of Natural Resources i

N

' 55VOGTLOVOOTLE.KVE\TECllSPEOSETPOINTECVI101 DOC m ,

. ENCLOSUREI VOGTLE ELECTRIC GENERATING PLANT REQUEST TO REVISE TECilNICAL SPEC FICATIONS REACTOR TRIP SYSTEM A.ND ENGINEERED l'AFETY FEATURE ACTUATION SYSTEM INSTRUMENTATION TRIP SETPOINTS BASIS FOR PROPOSED CIIANGE PInimitd Changt in accordance with the requirements of 10 CFR 50.90, Southern Nuclear Operating Company (SNC) proposes to revise the Vogtle Electric Generating Plant (VEGP) Unit I aad Unit 2 Technical Speci6 cations (TS) Limiting Condition for Operation (LCO) 3.3.1, Reactor Trip System (RTS) Instrumentation, and LCO 3.3.2, Engineered Safety Feature Actu;. ion System (ESFAS) Instrumentation. The proposed changes would facilitate treatment of the trip setpoints as nominal values and correct certain typographical errors.

The proposed changes are as follows:

. The inequalities as they are applied to the Trip Setpoint columns of Tables 3.3.1-1 and 3.3.2-1 would be deleted, and the column headings would be changed from

" Trip Setroint" to " Nominal Trip Setpoint."

• A footnote would be added to the new " Nominal Trip Setpoint" columns of Tables 3.3.1-1 and 3.3.21 that would allow the trip setpoints to be set mort conservative than the nominal value as necessary to respond to plant conditions.

• The Allowable Value for Table 3.3.' i, Function 14.b, Turbine Trip Turbine Stop Valve Closure, would be revised from " 2 96.7% open" to " 2 90% open."

= Footnotes I and m of Table 3.3.1-1 would be revised to refer to the " Nominal Trip Setpoint" and delete the inequalities applied to the trip setpoints.

• A superscript "(a)" should be deleted from the heading of the " Trip Setpoint" column on page 6 of 8 of Table 3.3.1-1.

. Notes I and 2 to Table 3.3.1 1, Overtemperature AT and Overpower AT.

respectively, will be revised to refer to the " Nominal Trip Setpoint." In addition, these notes will be revised to delete the inequalities from the values for the constants Ki through K6 (except for K 52 0 for decreasing temperature and 6K = 0 for T s T"),

and T', T", and P'.

• The inequality applied to the ESFAS Allowable Value for Steam Line Pressure -

Low (Table 3.3.2 1, Function 1.e) should be changed from "s" to "2".

Ihuis for Proposed Change The trip setpoints specified in the VEGP Units 1 and 2 TS were calculated using the basic uncertainty equation identified as Equation 2.1 in WCAP.11269 Rev.1," Westinghouse El-1

. ENCLOSURE 1 VOGTLE ELECTRIC GENERATING PLANT REQUEST TO REVISE TECIINICAL SPECIFICATIONS REACTOR TRIP SYSTEM AND ENGINEERED SAFETY FEATURE ACTUATION SYSTEM INSTRUMENTATION TRIP SETPOINTS

)) ASIS FOR PROPOSED CIIANGE Setpoint Methodology for Prote; tion Systems - Vogtle Station." The Ssic uncertainty equation utilized in WCAP-11269 defines a series of terms combined in a square root of the sum of the squares approach (SRSS). One of the basic assumptions of an SRSS calculation is that the input values are random and in the specific instance of Westinghouse calculations, two-sided. For the Rack Calibration Accuracy (RCA) and the Rack Comparator Setting Accuracy (RCSA) terms, this two-sided allowance is exrlicitly noted in the definitions section (page 3-4) items 7.a ,7.d(a) and 7.d(b) of WCAP-11269 Rev.1. Thus, from an uncertainty calculation point of view, the inequalities associated with the trip setpoints provided in Tables 3.3.1-1 and 3.3.2-1 of the VEGP Units 1 and 2 TS simply provide a direction of conservatism with respect to the Safety Analysis Limit (i.e., the value assumed in the safety analysis for a given protection or actuation function).

At VEGP, plant procedures specify calibration tolerances, and these tolerances have been appropriately reflected in the protection or actuation function specific uncertainty calculation. Each instrument channel will be calibrated as closely as possible to the nominal value at the start of each process rack's surveillance interval. It should be noted that it is not necessary for the instrument technician to recalibrate a device or channel if the as left condition is not exactly at the nominal condition, but is within the plus or minus of nominal as left procedural tolerance. As noted above, the uncertainty calculations assume that the as left tolerance (conservative and non-conservative direction) is satis 0ed on a reasonable, statistical basis, not that the nominal condition is satisGed exactly, it is acceptable for the as left condition, immediately after calibration of process rack modules or the bistable, to be in the non-consen ative direction, as long as the magnitude is within the plant procedure speciGed calibration tolerance (which has been appropriately reflected in the protection or actuation function specine uncertainty calculation). Therefore it can be concluded that the trip setpoint inequalities provided in the above noted tables do not define absolute limits for the as lef condition of the process rack modules. The limits are defined by the plant calibration procedures and reflected in the uncertainty calculations. In addition,for the purposes of channel calibration, the values specified in Notes I and 2 to Table 3.3.1-1 for K i, K , K ,3 K.i, K ,3Kc, T', T" and P' are utilized in the safety analyses without explicit tolerances, but should be considered as nominal values for instrument settings. That is, while an exact setting is not expected, a setting as close as reasonably possible is desired.

For example, where the scaling for the channel results in a distribution of the gains and references across multiple channel modules, i.e., there is no single setting point for an individual gain or reference, a direction of conservatism cannot be applied explicitly. At which point it is more appropriate to ensure that the overall calibration of the channel is not only within the calibration tolerance for the affected paranwtcr (AT, Tavg, Pressurizer Pressure and Al), but is as close as reasonably possible to th< '.4 ired overall value.

Function 14.b of Table 3.3.1 1, Turbine Trip - Turbine Stop Valve Closure, is a special case with respect to the above arguments. This trip function is implemented by valve-mounted i

El-2

o ENCLOSUREI VOGTLE ELECTRIC GENERATING PLANT REQUEST TO REVISE TECHNICAL SPECIFICATIONS REACTOR TRIP SYSTEM AND ENGINEERED SAFETY FEATURE ACTUATION SYSTEM INSTRUMENTATION TRIP SETPOINTS HASIS FOR PROPOSED CIIANGE limit switches. These trip circuits do not have analog channels, and therefore, standard analog calibration tolerances do 1.:' aoply. Calculation X5CP6267 determined that with the limit switches proprly mounted in accordance with drawings CX5DP5003 1 and CX5DP5003-2, each switch will indicate " tripped" with its associaLd stop v o ,:c at 96.7 %

(or greater) open.

The change to the Allowable Value for Table 3.3.1-1, Function 14.b, Turbine Trip - Turbine Stop Valve Closure, is necessitated by the fact the current TS Allowable Value is the same as the Trip Setpoint (i. e., both are specified as " 2 96.7% open"). Simply deleting the inequality from the trip setpoints does not achieve the desired effect for this one function bec:.use there is no margin specified in the allowable value. Detecting turbine stop valve closure provides the reactor trip system logic with an indication that the turbine is tripping and steam load will soon be unavailable. The stop valves are not designed to modulate steam Dow, but rather to be fully open during normal operation and fully closed following turbine trip and/or shutdown. Therefore, any indication other than fully open will provide the reactor trip system with indication that the turbine is tripping. An allowable value of 90% is also consistent with on-line testing performed for the main steam isolation valves (MSIVs). The MSivs are allowed to close to 90% open during on-line testing. Valve position below 00% open is considered to indicate imminent valve closure. Since the turbine stop valves operate similarly (either fully open or fully closed), an allowable value of 2 90% c sen is adequate to provide trip indication to the reactor trip system. Finally, reactor trip on turbine stop valve closure is an anticipatory trip. It is not credited in the accident analyses.

The addition of the footnote allowing trip setpoints to be set more conservative than the nominal value is consistent with existing TS provisions with the inequalities in place and will be conservative with respect to the safety analysis. The footnote would facilitate, for example, setting the Power Range Neutron Flux liigh trip setpoint lower than the nominal value of 109 % during startup following a refueling outage. Under these conditions, the high flux trip setpoint is set conservatively low during initial startup until sufficient reactor power is achieved so that an accurate calibration of the power range channels can be accomplished, in addition, there may be other times when the TS would require the high flux trip setpoints to be reduced in response to some equipment inoperability.

Finally, the basis for correcting the two typographical errors is as follows:

• The superscript "(a)" as it is applied to the heading of the " Trip Setpoint" column on page 6 of 8 of Table 3.3.1-1 is a holdover from NUREG-1431, Revision 0. It referred to a footnote (a) that was a Reviewers Note. The Reviewer's Note was deleted during the conversion of the VEGP TS to NUREG-1431, and the references to this footnote were deleted except in this one case. Therefore, the proposed El-3

o ENCLOSURE 1 VOGTLE ELECTRIC GENERATING PLANT REQUEST TO REVISE TECIINICAL SPECIFICATIONS REACTOR TRIP SYSTEM AND ENGINEERED SAFETY FEATURE ACTUATION SYSTEM INSTRUMENTATION TRIP SETPOINTS HASIS FOR PROPOSED CllANGE deletion of the superscript (a) from the " Trip Setpoint" column of page 6 of 8 of Table 3.3.1 1 is purely editorial.

• The inequality appl:ed to the ESFAS Allowable Value for Steam Line Pressure -

Low (Table 3.3.2-1, Function 1.e) is incorrectly shown as "s". The correct inequality is "2". The inequality is correctly shown in our December 21,1995 submittal for the conversion to NUREG-1431. Therefore, the proposed change merely corrects a typographical error.

Conduaian In summary, a process rack channel is considered to be " calibrated" when the two-sided as left calibration procedural tolerance is satisfied, in this condition, the channel is capable of performing its safety function within the envelope of the safety analysis as explained above.

Therefore, the inequalities may be deleted from Tables 3.3.1-1 and 3.3.2-1 as discussed above, and the terminology changed to " Nominal Trip Setpoint." The addition of the footnote allowing trip setpoints to be set more conservative than the nominal value is simply a clariGeation. Setting the setpoints more conservative than the nominal value will be conservative with respect to the safety analysis, and it is consistent with the current TS requirements. Revising the allowable value for the turbine stop valve closure function resolves the con 0ict created by treating the trip setpoint as a nominal value, without affecting the safety analyses. The correction of the typographical errors has no safety significance, and is s:mply proposed as part this license amendment request as a matter of expediency.

1 El-4

. ENCLOSURE 2 VOGTLE ELECTRIC GENERATING PLANT REQUEST TO REVISE TECI'NICAL SPECIFICATIONS REACTOR TRIP SYSTEM AND ENGINEERED SAFETY FEATURE ACTUATION SYSTEM INSTRUMENTATION TRIP SETPOINTS SIGNIFICANT IIAZARDS CONSIDERATION EVALUATION l'rnamed. Change in accordance with the requirements of 10 CFR 50.90, Southern Nuclear Operating Company (SNC) proposes to revise the Vogtle Electric Generating Plant (VEGP) Unit 1 and Unit 2 Technical Specifications (TS) Limiting Condition for Operation (LCO) 3.3.1, Reactor Trip System (RTS) Instrumentation, and LCO 3.3.2, Engineered Safety Feature Actuation System (ESFAS) Instrumentation. The proposed changes would facilitate treatment of the trip setpoints as nominal values and correct certain typographical errors.

The proposed changes are as follows:

• The inequalities as they are applied to the Trip Setpoint columns of Tables 3.3.1-1 and 3.3.2-1 would be deleted, and the column headings would be changed from

" Trip Setpoint" to " Nominal Trip Setpoint."

• A footnote would be added to the new " Nominal Trip Setpoint" columns of Tables 3.3.1-1 and 3.3.2-1 that would allow the trip setpoints to be set more conservative than the nominal value as necessary to respond to plant conditions.

• The Allowable Value for Table 3.3.1-1, Function 14.b, Turbine Trip - Turbine Stop Valve Closure, would be revised from " 2 96.7% open" to " 2 90% open."

. Footnotes I and m of Table 3.3.1-1 would be revised to refer to the " Nominal Trip Setpoint" and delete the inequalities applied to the trip setpoints, e A superscript "(a)" should be deleted from the heading of the " Trip Setpoint" column on page 6 of 8 of Table 3.3.1-1.

. Notes I and 2 to Table 3.3.1-1, Overtemperature AT and Overpower AT, respectively, will be revised to refer to the " Nominal Trip Setpoint." In addition, these notes will be revised to delete the inequalities from the values for the constants K ithrough K 6(except for K 25 0 for decreasing temperature and K 6 = 0 for T s T"),

and for T', T", and P',

e The inequality applied to the ESFAS Allowable Value for Steam Line Pressure -

1/ w (Table 3.3.2 1, Function 1.e) should be changed from "s" to "2".

E2-1

I

- l

. ENCLOSURE 2 VOGTLE ELECTRIC GENERATING PLANT REQUEST TO REVISE TECilNICAL SPECIFICATIONS REACTOR TRIP SYSTEM AND ENGINEERED SAFETY FEATURE ACTUATION SYSTEM INSTRUMENTATION TRIP SETPOINTS SIGNIFICANT H AZARDS CONSIDERATION EVALUATION Es aluntion

1. Does the proposed change involve a significant increase in the probability or

- consequences of an accident previously evaluated?

No. The proposed changes affect only the presentation of the trip set points for the RTS and ESFAS in the VEGP Units I and 2 TS. The calibration of the channels whose setpoints are specified in the TS will continue to be performed in a manner consistent with the setpoint methodology described in WCAP-11269 Rev.1. There will be no adverse effect on the ability of those channels to perform their safety functions as assumed in the safety analyses. Since there will be no adverse affect on the trip setpoints or the instrumentation associated with those trip setpoints, there will be no increase in the probability of any accident previously evaluated.

Similarly, since the ability of the instrumentation to perform its safety function is not adversely affected, there will no increase in the consequences of any accident previously evaluated.

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

No. The proposed change affects only the presentation of trip setpoint requirements in the TS. Plant operation will not be changed, and the response of safety related equipment as assumed in the accident analyses will not be adversely affected.

Therefore, the proposed change does not involve a new or different kind of accident than any previously evaluated.

3. Does the proposed change involve a signifhnt reduction in a margin of safety.

No. As described -bove, the RTS r.rt ESFAS instrumentation will remain capable of performing its safety function rs amed in the accident analyses. The treatment of trip setpoints as nominal value s is consistent with the methodology used to establish those setpoints. As suel, margin is not affected by the proposed change.

Condusion Based on the aoove, the proposed changes do not involve a significant hazards consideration as defined in 10 CFR 50.92.

E2-2

__ - _ - - . _ --_ _ _ _ _ _ _ _ - _ .