ELV-03015, Application for Amends to Licenses NPF-68 & NPF-81,revising Tech Spec 3/4.2.5 Re RCS Flow Uncertainty to Replace Phrase Prior to Operation Above 75% Rated Thermal Power

Application for Amends to Licenses NPF-68 & NPF-81,revising Tech Spec 3/4.2.5 Re RCS Flow Uncertainty to Replace Phrase Prior to Operation Above 75% Rated Thermal Power

ML20082G060
Person / Time
Site:	Vogtle
Issue date:	08/08/1991
From:	Hairston W GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20082G062	List: ELV-03015, Application for Amends to Licenses NPF-68 & NPF-81,revising Tech Spec 3/4.2.5 Re RCS Flow Uncertainty to Replace Phrase Prior to Operation Above 75% Rated Thermal Power ML20082G063
References
ELV-03015, ELV-3015, NUDOCS 9108160185
Download: ML20082G060 (9)

Text

_ _ _ _ _ _ - _ _ - _ _ _ _ _ _

' o'  ;

E7;dN,7 e , n , ~ ' ,"' .

.. u ,s , a r.s m

, M 't ] A 1 i l I'* 's

v. s ,

'3 o  ;

Ig , ', i M 1.l '1

,, g , m m August 8, 1991 L * ', U '

ELV-03015 1077  !

Docket Nos. 50-424 }

50-425 ,

U. S. Nuclear Regulatory Commission ,

ATIN: Document Control Desk  !

Washington, D. C. 20555 Gentlemen:

i V0GTLE ELECTRIC GENERATING PLANT REVISION TO RCS FLOW UNCERTAINTY .

E CHNICAL SPECIFICA110N 3/4.2d i The Technical Specifications changes proposed 11: Georgia Power Company (GPC) letters ELV-02166 dated November 29, 1990, and ELV-02061 dated March 29, 1991, -

included a revision to the reactor coolant system (RCS) flow measurement ,

uncertainty. This uncertainty was determined using the Westinghouse Revised .

Thermal Design Procedure (RTDP). The applicstion of the RTDP to the Vogtle i Electric Generating Plant which were submitted to the(VEGP) NRC with was described letter in WCAPs ELV-02597 124606,1991.

dated March through 12463 ,

Page 8 of these WCAPs indicated that the uncertainty analysis for flow measurement was based on performing the heat balance flow measurement above 70%

of Rated Thermal Power (RTP). Westinghouse has determined that this should have been 90% RTP instead of 70% RTP. Errata sheets for these WCAPs are enclosed with this letter. '

The current flow measurement uncertainty of 3.5% appears in the footnote on ange 3/4 2-13 of the VEGP Technical Specifications. It establishes the relations 11p Letween the Limiting Condition for Operation (LCO) for RCS flow in Specification 3.2.5 and the value of RCS flow used in the safety analyses.

The application of the RTDP to determine this uncertainty is based on performing the precision heat balance RCS flow measurement above 90% RTP. Specification 4.2.5.3 requires that RCS flow be determined by precision heat balance prior to operation above 75% RTP after each fuel loading. The uncertainty associated with the precision heat balance is expected to be higher when performed at the lower power level. Therefore, GPC is proposing to amend the previous Technical Specification change request by requiring the precision heat balance to be -

performed within 7 days after exceeding 90% RTP after each fuel loading, instead of prior to operation above 75% RTP. <

The value for the uncertainty to be incorporated into the footnote on page 3/4 2-13 described in letter ELV-02661 was 2.3%. This value was based on the accumulation of uncertainties using the plant process computer for reattor l coolant system flow indication. Since it is our operating practice to use the  !

l 910e160185 910803 l

PDR P

ADOCK 05000424 PDR .N\- )

I@V

.i I;

l 100113 ._

1 ,

orgial\nu1 ab U. S. Nuclear Regulatory Commission ELV-03015 Page 2 i

main control board flow Indicators, GPC proposes to increase the uncertainty from 2.3% to 2.7% to account for the uncertainty associated with the use of I these indicators.

The proposed changes and their basis are described in Enclosure 1. Enclosure 2 provides an evaluation demonstrating that these changes do not involve any significant hazards considerations.

These changes are reflected in the typed and marked-up pages in Enclosure 3 to this letter. The pages in Enclosure 3 should be used to replace the pages with the same page numbers that were included in the VANTAGE-5 Technical Specifications change request contained in LLV-02166. These changes do not alter the conclusion of the evaluation of significant hazards considerations in j accordance with 10 CFR 50.92 that was submitted to the NRC with ELV-02166.

Enclosure 4 includes errata sheets for WCAP-12460, WCAP-12461 WCAP 12462, and WCAP-12463. The errata sheets change 70% RTP as the power level assumed for the uncertainty analysis to 90% RTP, Mr. W. G. Hairston, 111 states that he is a Senior 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 By: / y! /d.t M .ii--

51. f ~

W. G. Hairston, 111 Sworntoandsubscribedbeforemethis[dayof,dow s -

/~ , 1991.

I JYbttv0 No ary fu W c d NhiYUh wws:;tonumtsMtit1M2 WGH,Ill/HWM/gmb

xc: (See next page)

L

1

, o.

.. )

Get9giit l'on tT eb.

l U. S. Nuclear Regulatory Commission ELV-03015 Page 3

Enclosures:

1. Basis for Pro)osed Change

2. 10 CFR 50.92 Evaluation

3. Instructions for incorporation and Revised Pages

4. Errata Sheets c(w): hornia Power CDFSJLDY Mr. C. K. McCoy Mr. W. B. Shi) man Mr. P. D. Rusiton Mr. M. Sheibani NORMS U._S. Nuclear Reaulatory Commission Mr. S. D. Ebneter, Regional Administrator Mr. D. S. Hood, Licensing Project Manager, NRR Mr. B. R..Bonser, Senior Resident inspector, Vogtle State of Georaia Mr. J. D. Tanner, Commissioner. Department of Natural Resources

ENCLOSURE 1 V0GTLE ELECTRIC GENERATING PLANT REVISION TO RCS FLOW UNCERTAINTY TECHNICAL SPECIflCATION 3/4.2.5 EASIS FOR PROPOSED CHANGE Pro 00 sed _Changg The prop 1 sed change will replace the phrase " prior to operation above 75% RATED THERMAL POWER" with the phrase "within 7 days after exceeding 90% RATED THERMAL POWER (Unit 1) or prior to operation above 75% RATED THERMAL POWER (Unit 2)" in Specificatien 4.2.5.3.

The flow uncertainty in footnote ***" to Specification 3.2.5 will be changed from "3.5%" to "2.7% (Unit 1) or 3.5% (Unit 2)" and the associated Limiting Condition for Operation (LCO) for reactor coolant system (RCS) flow will be revised from "396,198 gpm" to "393,000 gpm (Unit 1) or 396,198 gpm (Unit 2)."

These changes will become effective with the initial use of VANTAGE-5 f uel on Unit 1 Cycle 4. With the in'tial use of VANTAGE-5 fuel on Unit 2 Cycle 3 the phrases "(Unit 1) or prior to operation above 75% RATED THERMAL POWER (Unit 2)"

and "(Unit 1) or 396,198 (Unit 2)" will be deleted.

A revision to Technical Specifications Bases section 3/4.2.5 is also included.

This revision to the Bases section describes the bases for the uncertainty used for the measurement of RCS flow. The text of the Bases change is in Enclosure 3.

Eil111 The value of the uncertainty identified in the footnote to Specification 3.2.5 is used to establish the value of the LCO for RCS flow. The value of the flow used in the safety analyses is increased by the uncertainty listed in the footnote in order to determine the LC0 value. Westinghouse has recently completed a determination of the uncertainties associl.ted with various means of determining RCS flow. The results are described in WCAP-12460 through WCAP-12463 which were transmitted to the NRC with letter ELV-02597 dated March 6, 1991. These WCAPs describe the uncertainties associated with using a precision heat balance to measure RCS flow as well as the uncertainty associated with determining the RCS flow from the procass computer output.

However, the WCAPs do not include the additional uncertainty associated with using the control roon, flow indicators. This additional uncertainty has been determined, as described in Enclosure 2, and was used to establish the value of 2.7% which is being proposed for the footnote to Specification 3.2.5. The value of flow used for the safety analyses is not affected by this change, because the proposed change to the LC0 value for RCS flow is only to account for the change in the measurement uncertainty.

The value of the measurement uncertainty is based on performing the precision heat balance flow measurement above 90% RTP. Therefore, it is necessary that the surveillance requirement for perfor.ning the heat balance be changed from prior to exceeding 75% RTP to after exceeding 90% RTP after each fuel loading.

El-1

ENCLOSURE 1 (Continued)

V0GTLE ELECTRIC GENERATING PLANT REVISION TO RCS FL'W UNCERTAINTY TECHNICAL SPECIFICATION 3/4.2.5 BASIS FOR PROPOSilLCHANGl This change provides an appropriate uncertainty which has been developed using the Westinghouse Revised Thermal Design Procedure. Enclosure 2 provides an evaluation demonstrating that these proposed changes do not involve any significant hazard considerations.

El-2 l- . _ .... .

ENCLOSURE 2 V0GTLE ELECTRIC GENERATING PLANT REVISION TO RCS FLOW UNCERTAINTY TECHNICAL SPECIFICATION 3/4.2.5 19 CFR 50.92 EVALVATION Pursuant to 10 CFR 50.92, each application for amendment to an operating license must be reviewed to determine if the proposed change involves a significant hazards consideration. The amendment, as described below, provides a change to the flow neasurement uncertainty to be applied to the RCS flow surveillance, the associated change in the LCO value for RCS flow, and an increase in the power level at which the flow is determined by precision heat balance. Th changes have been reviewed and deemed not to involve significant hazards cc,siderations.

The basis for this determination follows.

flackaround The uncertainty included in the LC0 for RCS flow in Technical Specification (TS) 3.2.5.c had originally been 3.5%. As part of the VANTAGE-5 fuel program, the Westinghouse Revised Thermal Design Procedure (RTDP) was employed in order to develop an appropriate uncertainty for VEGP which also acc.ounted for RTD bypass loop elimination. The results of this uncertainty determination are presented in WCAPs-12460 through 12463.

The RTDP methodology had determined the flow uncertainty for VEGP to be 2.2%

based upon a once per cycle precision heat balance as well as periodically verifying RCS flow from the plant process computer output. This value was then increased to 2.3% to account for feedwater venturi fouling. However, the periodic flow verification at VEGP, performed in accordance with TS 4.2.5.1, uses flow indication from control room flow indicators which have a larger uncertainty than the process computer nutput. This additional uncertainty has been determined and used to calculate a larger RCS flow uncertainty to replace the 2.3% value from footnote "**" of TS 3.2.5.c that was originally submitted with the VANTAGE-5 program changes. The larger uncertainty, added on to the t'aign flow value, results in a larger LCO value for the RCS flow given in TS

, . 2 . :i . c .

In addition, the RTDP WCAPs had erroneously identified the once per cycle precision calorimetric described in TS 4.2.5.3 to be performed above 70% Rated Thermal Power (RTP). The value of the measurement uncertainty is based on performing the precision heat balance flow measurement above 90% RTP. In order to provide consistency between the TS and the methodology basis, TS 4.2.5.3 is being revised.to require the precision heat balance to be performed above 90%

RTP after each fuel loading. Errata sheets for the RTDP WCAPs (12460 through l 12463) are included in Enclosure 4.

Analysis To incorporate these changes, recalculation of the RCS flow measurement uncertainty using the RTDP methodology was necessary. An appropriate

! uncertainty was developed for the control room flow indicators based upon l

E2-1 l

'. j ENCLOSURE 2(CONTINUED) i REVISION TO RCS FLOW UNCERTAINTY TECHNICAL SPECIFICATION 3/4.2.5 10 CFR 50.92 EVALUATION accuracy of calibration and readability. This value then replaced the value in the RTDP calculations for the uncertainty associated with the process computer  :

output. A final revised RCS flow uncertainty was calculated to be 2.6%. No other changes in the RTDP methodology 3 resented in the WCAPs were made. For revising the footnote to TS 3.2.5.c, tle uncertainty value has been increased to 2.7% to account for feedwater venturi fouling. Therefore, with a design flow value of 382,800 gpm and an uncertainty of 2.7%, the revised RCS flow LCO value ,

for TS 3.2.5.c must be changed to 393,000 gpm. The design flow value assumed in >

the accident analyses _has remained unchanged.

The value of the flow measurement uncertainty is based on performing the l precision heat balance above 90% RTP. At lower power levels, additional uncertainties must be accounted for that have not been included in the RTDP assumptions - Therefore, in order to )rovide consistency between the analytical 1 basis and the TS, the discussion of tio precision heat balance included in 15-4.2.5.3 has been revised to assure performing the surveillance above 90% RTP after each fuel loading. The performance of the precision heat balance within 7 days after exceeding 90% RTP after each fuel loading does not result in a significant change to the surveillance requirement. The intent of this

-surveillance requirement is to provide a precise measurement of RCS flow as soon as practicable after each. fuel loading. During the time between achieving 75%

RTP-and performing the precision heat balance, the RCS flow will continue to be monitored once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> in accordance with the surveillance requirement of TS 4.2.5.1.

A corresponding discussion of the basis for these revisions is also proposed as ,

additional text in TS Bases 3/4.2.5, and is included in Enclosure 3.

Emil11 .

Based on the information presented above, the following conclusions can be reached.with respect to 10 CFR 50.92.

1. The revised RCS flow uncertainty basis does not involve a significant I. increase in the probability or consequences of an accident previously L evaluated. The reactor coolant flow will continue to be mnnitored once per u 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> in accordance with TS 4.2.5.1. Although the revised uncertainty results in the requirement for higher flow values to be measured, .no new performance requirements are being imposed on the RCS in order to satisfy this criteria. .The revised RCS flow requirement of 393,000 gpm remains smaller than the 396,198 gpm value required with a' 3.5% uncertainty, for which previous.RCS flow surveillances were routinely satisfied. This indicates that the RCS configuration is capable of providing the required 1

L E2-2 l

].

ENCLOSURE 2 (CONTINVED)

REVISION TO RCS FLOW UNCERTAINTY TECHNICAL SPEClflCATION 3/4.2.5 10 CFR 50.92 EVALUATION flow. In addition, no new requirements .nust be considered by the safety  !

analyses which model RCS flow since the design flow value of 382,800 gpm I used as a basis for the VANTAGE-5 and RID bypass loop elimination programs remains unchanged. Reactor coolant system flow is an assumed initial condition in the safety analyses and does not act as an initiator for any transient. Therefore, the probability of occurrence of an accident is not affected.

The consequences of an accident previously evaluated are not significantly 1 increased due to the revised RCS flow uncertainty basis. Given that the i accident analyses are unaffected, no additional fuel failures or mass  !

releases will result. Therefore, no more severe conditions than those already assumed in the radiological dose consequence analysis will result, and the conclusions pertaining to the VANTAGE-5 program remain bounding.

2. The revised RCS flow uncertainty basis does not create the possibility of a new or different kind of accident from any accident previously evaluated.

The RCS flow uncertainty does not affect the design value for RCS flow used in the safety analyses. The change in the power level requirement for performing the RCS flow measurement by heat balance after each fuel loading is not significant since RCS flow will continue to be monitored once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> in accordance with TS 4.2.5.1. Reactor coolant system flow is an initial condition assumed in the safety analyses. A change in the basis for the uncertainty associated with measuring this flow does not introduce any new failure scenarios that must be considered. The types of accidents analyzed for the VANTAGE-5 and RTD bypass loop elimination programs already represent the credible scanarios that must be considered in order to demonstrate plant safety. .

3. The revised RCS flow uncertainty basis does not involve a significant reduction in a margin of safety. Although the uncertainty is being reduced from the initial 3.5% value, this is being done based on an uncertainty ieview, which includes VEGP-specific calibration procedure and equipment considerations, using the RTDP methodology. The 2.7% value for flow uncertainty to be included-in the footnote to TS 3.2.5.c provides a value which accounts for an appropriate margin of safety. Accident analyses performed at a more conservative lower flow value (without the uncertainty) than that defined by the TS (which includes the uncertainty) demonstrate acceptable results in all cases. Raising the power level at which the precision heat balance is performed reduces the uncertainty associated with l RCS flow measurement, which maintains the appropriate margin of safety for l this calculation. This change does not introduce a significant reduction ~1n the margin of safety because the RCS flow will continue to be monitored once l per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> in accordance with TS 4.2.5.1. Therefore, the revised RCS flow -

l uncertainty basis does not introduce a significant reduction in any margin '

of safety.

E2-3 l

l ENCLOSURE 2 (CONTINVED)

REVISION TO RCS FLOW UNCERTAINTY TECHNICAL SPECIFICATION 3/4.2.5 4

10 CFR 50.92 EVALUATION ConclusiqD 4 Based upon the preceding analysis, it has been determined that the proposed  ;.

changes to the Technical Specifications do not involve a significant increase in the probability or consecuences of an accident previously evaluated, create the possibility of a new or cifferent kind of accident from any accident previously evaluated, or involve a significant reduction in a margin of safety. Therefore, i it is concluded that the proposed changes meet the requirements of 10 CFR 50.92 (c) and do not involve a significant hazards consideration.

l l

E2-4 i

. . . . .- . ,- - - . _- - . . _ . ~ , . - . . - . , ,