ML20091A882

License Amend Request 92-01 to License NPF-86,revising TSs to Eliminate RTD Bypass Sys

ML20091A882
Person / Time
Site:	Seabrook
Issue date:	03/20/1992
From:	Feigenbaum T PUBLIC SERVICE CO. OF NEW HAMPSHIRE
To:
Shared Package
ML20034D387	List: ML20091A880 ML20091A882 ML20091A889 ML20091A895 ML20091A900
References
NUDOCS 9203300244
Download: ML20091A882 (7)

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_ vg- e SEABROOK STATION UNIT 1

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New Hampshire i

Yankee Facility Operating Licenso NPF-86 Docket No. 50-443 License Amendment Request No. 92 01 RTD Bypass System Elimination This License Amendment Request is submitted by New Hampshire Yankee pursuant to 10 CFR50.90. The following information is enclosed in support of this License Amendment Request:

.Section I -

Introduction and Description of Proposed Changes

. Section ll -

Markup of Proposed Changes

. Section ill -

Retype of Proposed Changes

.Section IV -

Safety Evaluation of Proposed Changes

.Section V -

Determination of Significant Hazards for Proposed Changes

.Section VI -

Proposed Scliedule for License Amendment issuance and Effectiveness

. Section Vil -

Environmental Impact Assessment

. Section Vill -

Other Supporting Information Em 882

$8 Sworn and Subscribed yy to before me this 89f/ day of 77N7VI 3 ,1992 Nf

@4 s I4/M (( b/dd&/(M '

Ted C. Fe)denbaum g v Notary Public President and Chief Executive Officer

@@ o., inA;v A. er nn e rec py c u u.;;a _-fo U;;L r., W S

' t I. Introduction and Description of Proposed Channen A. Introduction The purpose of License Amendment Request 92-01 is to propose changes to the Seabrook Station Technical Specifications associated with a plant design change (DCR 90-03) that vill eliminate the Resistance-Temperature-Detector (RTD) Bypass System which is currently used for the measuro.aent of narrow range Reactor Coolant System (RCS) hot leg and cold leg temperatures. The design change will remove the RTD Bypass System piping and install new thermowell mounted fast response RTDs in the hot leg and cold leg piping. The replacement RTD/thermowell combination meets the functional and qualification requirements of the existing RTDs mounted in the bypass piping. Additional instrumentation is added to process and average the new hot leg temperature inputs. The cold leg and average hot leg temperatece signals are input to-the existing reactor protection and reactor control systems. Changes in the Westinghouse methodology for treating hot and aid leg streaming, technical differences in the instrumentation, and allowance for operation with .,ne . hot leg RTD inoperable have resulted in a change in instrumentatica uncertainties. The proposed Technical Specification changes reflect these differences in the instrumentation uncerttinties associated with the new temperature measurement system and delete requirements for verification of RTD bypass loop flow.

Additionally, the proposed Technical Specification changes modify the requirements for the performance of a precision heat balance which is used to determine RCS flew rate and to normalize the RCS flow instrumentation.

The current Technical %cification requirements specify that the precision heat balance must be performed prior to operation above 752 of rated -

thermal power af ter each fuel loading. Westinghouse has recommended that the precision heat balance be performed above 90% of rated thermal power to mJnimize measurement uncertainties that are exacerbated at lower power levels. New Hampshire Yankee is, therefore, proposing-a change to its Technical Specifications to require that the precision heat balance for determination of RCS flow rate be performed prior _ to exceeding 952 of rated thermal power. New Hampshire Yankee has also proposed additional changes to the Reactor Coolant System f. low rate requirement by - specifying the thermal design flow analysis value instead of the currently stated flow value which includes measurement uncertainty. This proposed change will provide consistency in the Technical Specification on Departure From Nucleate Bolling (DNB) related parameters. The DNB Technical Specification currently specifies the analysis value for Reactor Coolant System average temperature and pressurizer pressure however it specifies an as-measured value_for RCS flow rate. Additionally, this proposed change will enhance operator flexibility in the selection of ' the instrumentation used for measurement of RCS flow. The instrumentation uncertainty _is a function )

of the number and type of instruments utilized for the measurement of the RCS flowrate. Inclusion of bounding instrument uncertainties in the Technical Specifications may unnecessarily impose plant operating restrictions.

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! , J The elimination of the RTD Bypass System has been implemented by numerous licensees with Westinghouse Nuclear-Steam Supply _ Systems. New Hampshire-Yatikee is aware of the following licensees which have eliminated the RTD Bypass System .,

Duke Power Company (Catawba 1/2, McGuire 1/2)

-Duquesne Light Company (Beaver Valley 1/2)

Florida _ Power & Light Company (Turkey Point 3/4)

Houston Lighting &-Power Company (South Texas Project 1/2)

New York Power Authority (Indian Point 3)

Tennessee Valley Authority (Sequoyah 1/2)-

Wolf Creek Nuclear Operating Corporation (Wolf Creek)

Northeast Utilities (Millstone 3)

Carolina Power & Light (H.B. Robinson)

South Carolina Electric & Gas (V.C.~ Summer)-

Alabama Power Company (Farley 1. Farley 2 scheduled for Spring 92)

Georgia Power Company (Vogtle 1. Vogtle 2 scheduled for Spring 92)

Vestinghouse has prepared a licensing report for NHY in support of_the elimination of the RTD Bypass System at Seabrook Station. The Westinghouse -

licensing report WCAP-13181, "RTD Bypass Elimination Licensing Report for Seabrook Nuclear Station" (Proprietary) is enclosed in Section VIII.

Yankee Atomic Electric Company (YAEC) has also evaluated the RTD Bypass System Elimination relative to containment response, Steam Generator Tube Rupture and Boron Dilution events. The YAEC evaluation conclusions and documentation are discussed in Section V.

B. Description of Proposed Channes License Amendment Request 92-01 propas changes to the following Technical Specifications:

1. Table 2.2-1, " REACTOR TRIP SYSTEN INSTRUMENTATION TRIP SETPOINTS,"

Pages 2-4 -5, 7, 8, and 10-Technical Specification Ta>' 2.2 terms- associated- with_ ~!

instrumentation uncertainty (TA.- 2 S,- allowable value, and associated notes) have been revised due to technical differences in the RTD instrumentation, differences in the Westinghouse methodology for treating hot leg and cold leg streaming = and . allowance for operat_ ion with one hot leg RTD inoperable. All values have been rounded to the nearest 0.1% 'in accordance with 'the latest Westinghouse format.

The value for the Ks term in_ the ovttpower - AT trip setpoint calculation was increased (conservative direction) . ~K 6 is a penalty.-

term that reduces the overpower AT trip- setpoint when Tavg -is above the nominal Tavg. The setpoint_ when operating at or ' below the nominal Tavg is determined by a-constant, K, 4 in the overpower AT trip setpoint. calculation.

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I t The_ value of the K6 term in the overpower AT trip setpoint

-calculation was increased as stated above. The overpower AT trip is intended to limit transient overpower during Condition I and II overpower transients / operator errors to 1182 power. As discussed in UFSAR section 4,3.2.2f and 4.4.2.11f, limiting . overpower to 118Z ensures that peak fuel rod linear heat generation rates during such -

an occurrence will not exceed the linear power for prevention of fuel centerline melting. The K6 term of the overpoweri AT trip is a penalty term that reduces the trip setpoint when T ,, is above the nominal T,yg. An increase in K 6 , is therefore a chaage in the conservative direction. The need to modify K6 is explained below.

The overpower AT trip setpoint when operating at or below the nominal' T,,, is determined by the K 4 constant of the overpower AT trip setpoint equation. The increase in the instrumentation uncertainties

. . associated with _ removal of the RTD Bypass System results in an increase in the safety analysis limit value for_K . 4 This increase le reflected by the increase in the Technical Specification TA value for overpower oT (the safety analysis limit value for K4 corresponds to the nominal-K. value plus the fractional full power AT equivalent of the Technical Specification TA value) . Accommoda tion of -- the-increased instrumentation uncertainty by increasing the ! safety analysis limit value for K/ allows the Technical Specification value for the nominal K4 setpoint to remain unaffected by_',he removal of the RTD Bypass System.

The increase in the safety analysis limit for K4 was accommodated in the analysis by reducing margin available in the fit of the overpower At trip setpoint equation to the 118Z power loop AT data at average temperatures less than or equal to the nominal T.,,, The increase in the safety analysis limit for K4 however necessitated an increase in the K6 penalty term in order to maintain the trip setpoint at or below 1182 - for a range of average temperatures greater than the The proposed increase in the-Technical Specification nominal value forT.,f. i 6 ensures that the 1182 power limit will be protected at all average _ temperatures.

Since the overpower AT trip with the modified setpoints will continue -

to ensure that the 118Z overpower limit is protected for all ranges of operation, there is no decrease in the margin of-safety.

2. 3/4.2.5, "DNB PARAMETERS," Page 3/4 2-10 -

The current Technical Specification Surveillanca Requirement 4.2.5.3 specifies that the precision heat balance must be performed-prior =

to operation above - 75Z of rated thermal power after each fuel loading. Westinghouse has recommended that the precision heat-balance be performed above 90% of rated thermal power to minimize measurement uncertair. Lies that are exacerbated at lower power levels.

New ifampshire Yankee has therefore proposed a change to Surveillance Requirement 4.2.5.3 to require that the precision heat balance for -

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determination of RCS flow rate be performed prior to exceeding 95%

of rated thermal power.

l New Hampshire Yankee has-also proposed additional changes to the .

Reactor- Coolant System flow rate requirement of . Technical' Specification Limiting Condition for Operation 3.2.5c by specifying the thermal design flow analysis value of 382,800 gpm instead of the currently stated flow value of 391.000 gpm which includes measurement uncertainty. This proposed change will provide consistency in!the Technical Specification on Departure From Nucleate Boiling (DNB)-related parameters. This Technical Specification currently l specifies the analysis value _ for. Reactor Coolant _ System average temperature and _ pressurizer pressure however it specifies an as-measured value for RCS flow rate. Additionally, this proposed change will enhance operator ~ flexibility in the selection of tha '

instrumentation used for _ . measurement of RCS flow. The instrumentation uncertainty is a function of the number and type of instruments utilized for the measurement of the RCS flowrate. -

Inclusion of bounding instrument - uncertainties in the Technical Specifications may unnecessarily impose plant operating restrictions e New Hampshire Yankee notes that WCAP-13181 does not reflect NHY's proposed inclusion of the thermal design flow analysis value - in Technical Specification 3.2.5c._ WCAP-13181 specifies the RCS flow

, rate of 392,000 gpm which is associated with a revised RCS flow l calorimetric uncertainty of 2.3% attributable to the new RTD hot leg and cold leg measurement system.

3. Table 4 . 3 - 1,- " REACTOR - TRIP SYSTEM INSTRUMENTATION SURVEILLANCE

• REQUIREMENTS, Pages 3/4 3-9 and 13 l

l Note 12, relating to verification of RTD bypass loop flow rate, has l been deleted since the RTD Bypass System is being eliminated.

4. BASES 2.2.1, ' REACTOR TRIP SYSTEM SETPOINTS, Overtemperature AT and -

Overpower AT," Page B 2-5 New Hampshire Yankee has proposed to revise the BASES for Technical:

Specification- 2.2.1 to clarify the source of .the time delays associated with the Overtemperature AT and Overpower AT reactor trips

. The proposed BASES changes are modelled after the Methodically Engineered, Restructured : and __ Improved Technical Specifications (MERITS) program (WCAP-13029).

5. BASES 3/4.2.5, "DNB PARAMETERS," Page B 3/4 2-4 As discussed above, NHY has proposed a change to the DNB parameter limit on RCS flow rate from the current value of 391,000 gpm which includes measurement uncertainty to 382,800 gpm which' represents the RCS thermal design' flow rate" analysis value which does not include measurement uncertainty. Additionally as discussed above, NHY-has proposed that the current requirement for performing a precision heat 4

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balance prior to operation. above 752 rated thermal power be revised .

to-require that the precision heat balance be- performed prior to operation above 952 power. ..These proposed Technical Specification changes have been reflec+ed in the BASES for Technical-Specification 3/4.2.5.

New Hampshire Yankee notes that the deletion of the Technical Specification for ,

the Low RCS Tavg coincident with reactor trip feedwater isolation Functional Unit . '

(Table 3.3-4,-Functional Unit 6.b) that was. recommended in WCAP-13181 will be addressed in a future license amendment request.

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11. Markun of Proposed Chanites Sea attache + markup of proposed changes to Technical Specifications.

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