ML20067C495

Proposed Tech Specs Revising Modes 3 & 4 Curves in Figure 3.1-3 to Incorporate More Negative Boron Worths

ML20067C495
Person / Time
Site:	Summer
Issue date:	02/04/1991
From:	SOUTH CAROLINA ELECTRIC & GAS CO.
To:
Shared Package
ML20067C482	List: ML20067C480 ML20067C495
References
NUDOCS 9102120087
Download: ML20067C495 (14)

Text

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ATTACHMENT 1 1

MARKED-UP TECHNICAL SPEClflCATION PAGES

. Egg Specification Chanag Description l

3/4 1-3a figure 3.1-3, " Required Revises the Modes 3 and 4 Shutdown Margin curves in figure 3.1-3 to (Modes 3, 4 and 5)" incorporate the more negative boron worths associated with the Cycle 6 core and subseauent Cores.

63/4 2-2 Basis 3/4.2.1, " Axial Changes "PFLR" to "COLR."

Flux Difference" AmendmentNo.88(TACNO.

75049) replaced the PFLR with the COLR.

9102120087 910204 PDR ADOCK0500ggy P

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

ATTACHMENT 1 MARKED-UP TECHNICAL SPEClflCA110N PAGES Faae Specificption Chance Description 3/4 1-3a Figure 3.1-3, " Required Revises the Modes 3 and 4 Shutdown Margin curves in Figure 3.1-3 to (Modes 3, 4. and 5)" incorporate the more negative boron worths associated with the Cycle 6 core and subsequent cores.

B3/4 2-2 Basis 3/4.2.1 " Axial Changes "PFLR" to "COLR."

flux Difference" Amendment No. 88 (T AC NO.

75049) replaced the PFLR with q

the COLR.

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FIGURE 3.1-3 REQUIRED SHUTDOWN M ARGIFJ '

(MODES 3,4, AND 5) 4 79 . . _ - _ _ _ _ . _ - , - - - - - .

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-4 y I 100 300 500 700 900 1.100 1,300 1,500 1,700 1.900 2,100 2.300 2,500 g g RCS BORON CONCENTRATION (ppm) -

REQU:P.20 SHUTDOWN M ARGIN (MODES 3,4. AND 5) 7 _

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1.700 1,900 2, 00 2,300 2,500  ?

te RCS BORON CONCENTRATION (ppm)

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i' ATTACHMENT 1 POWER OLSTRIBUTION_LlHIT BASES AXIAL FLUX O!FFERENCE (Continued)

At pcwer levels below APLND , the limits on AFD are defined in the COLR consistent with the Relaxed Axial Offset Control (RAOC) operating procedure and limits. These limits were calculated in a manner such that expected j

operational transients, e.g. , load follow operations, would not result in the j AFD deviating outside of those limits. However, in the event such a deviation occurs, the short period of time allowed outside of the limits at reduced i power levels will not result in significant xenon redistribution such that the l envelope of peaking factors would change sufficiently to prevent operation in l

the vicinity of the APL"U power level. I 1

At power levels greater than APLND , two modes of operation are permissible; I (1) RA00, the AFD limit of which are defined in the COLR and (2) Load operation, which is def'ned as the maintenance of the AFD within s cifica- ) '

l tions band about a target value. The RA00 operating procedure above AP the same as that defined for operation below APLND. However, it is possible

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when following extended load following maneuvers that the AFD limits may result in restrictions in the maximum allowed power or xFD in order to guaranten operation with Fg (z) less than its limiting value. To allow operation at the maximum permissible power level the Base Load operating procedure restricts the indicated AFD to relatively small target band (as specified in the COLR) and  ;

power swing, (APL ND 1 power 1 APL OL or 100% Rated Thermal Power, whichever is lower). For Base Load operation, it is expected that the plant will operate within the target band. Operation outside of the target band for the short time period allowed will not result in significant xenon redistribution such that the envelope of peaking factors would change suf ficiently to prohibit continued ophration in the power rcgion defined above. To assure there is no residual xenon redistribution impact f rom past operation on the Base Load operation, a 24-hour waiting period at a power level above APL"O att allowed by RAOC is necessary. During this time perioo load changes and rod notion are restricted to that allowed by the Base Load procedure. Af ter the wr iting period extended Base load operation is permissible, f

The computer determines the one minute average of each of the OPERABLE excore detector outputs and provides an alarm message immediately if the AFD for at least 2 of 4 or 2 of 3 OPERABLE excore channels are: (1) outside the allowed delta-1 power operating space (for RAOC operation), or (2) outside the 4 allowed delta-1 target band (for Base Load operation). These alarms are active when power is greater than: (1) 50% of RATED THERMAL POWER (for RA00 .

operation), or (2) APLNO (for Base Load operation). Penalty deviation minutes for Base Load operation are not accumulated based on the short period of time during which operation outside of the target band is allowed.

i SUMMER - UNIT 1 B 3/4 2-2 Amendment No. H . 88

• M r ATTACllMENT 2 SAFETY EVALUATION

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l .n-7 Attachment 2 to Document Control Desk Letter:

TSP 900003-t Page 1 of 2 SAFETY EVALUATION FOR THE VIRGIL C. SIM4ER NUCLEAR STATION T DESCRIPTION OF AMENDMENT REQUEST

~ Technical. Specification-Figure 3.1-3, 9 quired Shutdown Margin-(Modes 3, 4, and 5)," specifies the shutdown margin the.t must be maintained for varying

. Reactor Coolant System (RCS) concentrations of boron in order to-(l) control, within acceptable limits, the reactivity transients associated with '

postulated accident conditions. and.(2) maintain the reactor sufficiently-4 subcritical.to prevent: inadvertent criticality.

Current Shutdown Margin _ requirements in excess of 1.77% for Modes 3 and 4 and in excess-of 1% for Mode 5 are based upon the boron dilution occident evaluation submitted in support of Amendment No. 75 to the Virgil C. SJmmer NuclearStationOperatingLicense(TAC-NO.68644-VANTAGE 5IMPROVEDFUEL

'0ES10N).iTheseevaluationswere-per.ormedusing-anacceptedWestinghouse

. methodology that takes-credit for the high flux at shutoown alarm set at t u e background to alert theLoperator.that a dilution event is in-progress.

With initial RCS boron concentrations-at or above the current Technical l

< . Specification shutdown margin requirements, the analyses demonstrate that the operator has-at least 13.4 minutes.from.the high flux at shutdown alarm to

recognize and terminate an uncontrolled reactivity ' insertion before shutdown margir is: lost and.the reactor becom6s critical, b _W hile-performing the Reload Safety. Evaluation:(RSE) frr Cycle 6 in accordance with the-methodology of.WCAP-9272, " Westinghouse Reload Safety Evaluation Methodology,"-SCE&G discovered that the calcultitud boron worths for Moder 3

and 4'are more nanative than theLyalues assumed in the. current VCSNS Boron

.Oilution Accident analyses. The more' negative ooron worth reduces the required change in boron concentration to achieve criticality.during a i

dilution _ event and results in a-reduction in operator action time of approximately 2; minutes.

, , 'To resolve-this discrepancy, SCE&G-proposes to revice the Required Shutdown -

iMartin curve to ensure that the operator action time to. detect and terminate an inadvetent boron: dilution event is not reduced. . The nroposed Figure

, :3.~1-3'is providedlin Attachment 1. The boron worth for Mode 5 continues to-. m P :be. bounded-by.previously: analyzed values, and, as such,' the Mode 5 curve in Attachment l'is identical to the one currently in the Technical Specifications.;_ ,

0ne additional' proposed change in this request. involves page B3/4 2-2 in the-

VCSNS Technical Specifications which references the Peaking Factor Limit

' Report (PFLR). This report was eliminated when approval was granted,-in' k Amendment No.^o8, to utilize the COLR. This reference was overlooked in'the B . Technical Specifications-Change Request for Amendment No. 88, dated December-i

! 11; 1989.

m, ;in nature. The-proposH revision to change "PFLR" to "COLR" is administrative

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_ . _ . _ _ _ . _ .- ___m._ _ - . . - _ _ - - . . _ _ _ .

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Attachment 2 to Document Control Desk Letter I

' TSP 900003-2 l Page'2 of-2 i

SAFETY EVALUATION:

The proposed shutdown margin requirements for Modes 3 and 4 are based on additional Boron Dilution analyses utilizing the same analytical methods used in creating the current Technical Specification, which was approved by the NRC in granting Amendment Number 75 to the VCSNS Operating License (TAC NO.

68644-VANTAGE.5. IMPROVED FUEL DESIGN). Bounding values of boron worth were utilized to preclude violations during Reload Safety Evaluations for future

. cycles. These additional analyses define the-required shutdown margin as a function of RCS boron concentration for Modes 3 and 4 that will maintain at least 13.4 and 13.6 minutes, respectively, for operator action time. As illustrated in-Atta:hment 3, the proposed shutdown margins for Modes 3 and 4-are more restrictive than-the current requirements (i.e., the area of acceptable operation is reduced). -However, by requiring this increased shutdown margin, the_ proposed _ amendment preserves the previously accepted operator action time, and thus maintains the margins of safety defined in the bases for the Shutdown Margin. Technical Specification.

The_ lines defining'the regions of acceptable operatta for Modes 3 and 4 in

'the revised figure exhibit definite curvature, whereas the current Required Shutdown Margin curve consists of straight lines. The method of calculating the data points .is identical for both curves. . The data for the curve cu ently in Technical Specifications was-bounded by straight lines. To bound the data In the proposed cur: 0 would, however, result in requiring prohibitively high shutdown margins for operations at increased boron

, concentrations. Because of this, the lines defining the regions of l acceptable operation for Modes ~3 and 4 in the proposed figure reflect the

l. analyses results,'and have not been bounded by a linear line.

To summarize, thL proposed revision in Figure 3.1-3:

L i .entures that the operator has, at least,.the previously accepted.

L 13.4=and 13.6 minutes for Modes 3 and 4 respectively, to recagnize l .and terminate the uncontrolled reactivity inse tion associated with a boron dilution before shutdown margin is lost and the reactor becomes critical..

• is. based o'n methods previously reviewed and approved by the Nuclear Regulatory Commission.

. Based upon the information provided above, SCELG has determined that the proposed change will not adversely affect the health and safety of the public.

In, addition, tu proposed revision tc change "PFLR" to "COLR" in Technical

-Specification Basis 3/4.2.1, is purely administrative and has no impact on plant operations or. safety. .This change deletes'the reference to an obsolete

report-(PFLR) and replaces it with a reference to the current report (COLR).

SCE&G is. requesting this change to achit:ye consistency throughout the VCSNS

~ Technical Specificatinns.

ATTACHMENT 3 PROPOSED REQUIRED SHUTDOWN MARGlH CURVE VS.

CURRENT TECHNICAL SPECIFICATIONS REQUIRED SHUTDOWN MARGlH CURVE

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PROPOSED REQUIRED SDM CURVE VS. CURRENTTECHNICAL SP2CIFICATION REQUIREMENTS SDM CURVE 7 _

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CURRENT TECH.5FdC. REQUIREMENTS

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MODE 3 PROPOSED LIMITS F-MODE 4 PROPOSED LIMITS ----- p-100 300 500 700 900 1,100 1,300 1,500 1,700 1,900 2,100 2,300 2,500 g, i x RCS BORON CONCENTRATION (ppm) 3

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l ATTACitMENT 4 NO SIGNIFICANT llAZARDS EVALUATION l

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[ Attachment 4-to Document Control Desk Letter TSP 900003 Page 1 of S NO SIGNIFICANT HAIARDS EVALUATION FOR THE VIRGIL C. SUMER NUCLEAR STATION DESCRIPTION OF AMEN 0 MENT REQUEST:

Technical Specification Figure 3.1-3, " Required Shutdown Margin (Modes 3, 4, and 5)," specifies the shutdown margin that must be maintained for varying Reactor Coolant System-(RCS) concentrations of boron in order to (1) c. crol, within_ acceptable limits, the reactivity transients associated with postulated accident conditions, and (2) maintain the reactor sufficiently subcritical to prevent inadvertent criticality.

. Current Shutdown Margin icquirements in excess of 1.77% for Modes 3 and 4 and in excess of 1% for Mode 5 are based upon the boron dilution accident evaluation submitted in support of-Amendment No. 75 to the Virgil C. Summer Nuclear _ Station Operating License (TAC NO. 68644 - VANTAGE 5 IMPROVE 0 FUEL DESIGN). ?These evaluations were performed using an accepted Westinghouse methodology that takes credit for the high flux at shutdown alarm set at twice background to 61ert the operator that a dilution. event-is in progress.

klth initial RCS boron concentrations at ce above the current Technical Specification shutdown margin requirements, the analyses demonstrate that the operator.has-at least 13.4 minutes from the high flux at shutdown alarm to

-recognize and terminate-an uncontrolled rcactivity insertion before shutdown margin.is lost and the reactor becomes critical.

While performing-the Reload Safety Evaluation (RSE) for Cycle 6 in accordance with'the methodology.of WCAP-9272, " Westinghouse Reload Safety Evaluation Methodology " SCE&G discovered that the calculated-boron worths for Modes 3

-and 4 are more negative than the values assumed in the current VCSNS _ Boron L Dilution. Accident analyses. The more negative ~ boron worth-reduces the required change in boron concentration to achieve criticality during a dilution event and results in a reduction in operator action t;me of approximately 2 minutes.

To resol _ve this: discrepancy, SCE&G proposes to revise.the Required Shutdown Margin curve to ensure that the operator. action time to detect and terminate

an inadver+ent: boron-dilution event is' not reduced.. The proposed Figure 3.1-3 is provided in Attachment 1. The boron worth for Mode 5 continues.to

.be bounded by'previously analyzed values, and, as such, w Mode 5 curve -in

. Attachment-1 is identical to the one currently.in the %ctaical

-Specifications.

One additional proposed change in this request involves page B3/4 2-2 in the.

=VCSNS Technical Specifications which referenc.o the Peaking Factor Limit Report-(PFLR). This report was eliminated whui approval was granted, in Amendment No.-88, to utilize the COLR. This reference was. overlooked in the Technical Specifications Change Request t - Amendment No. 88, dated December 11, 1989. The proposed revision to change "PFLR" to "COLR" is administrative in nature.<

Attachment 4 to Document Control Desk Letter TSP 900003-2 Page 2 of 3 BASIS FOR PROPOSED NO SIGHlflCANT HAZARDS CONSIDERATION:

Pursuant to 10CFR50.91, SCE&G has determined that operation of the facility in accordance with the proposed license amendment request does not involve any significant hazards considerations as defined by NRC regulations in 10CFR50.92. The following discussion describes how the proposed amendment satisfies each of the three stendards of 10CFR50.92(c).

1) The proposed change does not involve a significant increate in the probability or consequences of an accident previously evaluated.

The proposed Shutdown Margin requirements reflect the use of a more negative boron worth as a bounding assumpti'n in the Bc on Dilution Analyses. In combination with the high flux at shutdown alarm set at twice background, the proposed change ensures that the operator will have at least 13.4 minutes from the alarm to recognize and terminate an uncontrolled dilution event before shutdown margin is lost. Thus, there will be no increase in the probability or consequences of the Boron Dilution Accident because current margin to criticality will be maintained.

The proposed revision to change "PFLR" to "COLR" in Technical Specification Basis 3/4.2.1 is administrative in nature and does not, therefore, involve an increase in the probability or consequences of an accident previously evaluated.

2) The proposed change does not create the possibility of a new or different kind of accident from any accident previously evaluated.

No safety-related equipment, safety function, or methods of plant operations will be altered as a result of the proposed change to Figure 3.1-3. Therefore, the higher boron concentrations (the end result of the higher shutdown margin requirements) that will be maintained during portions of the fuel cycle while in Modes 3 and 4 do not in any way

-create the possibility _of a new or different kind of recident from any accident previop*ly evaluated.

The proposed revision to change "PFLR" to 'CCLR" ir Technical Specification Basis 3/4.2.1 is administrative in rature and does not in any way create the possibility of an accident which is new or different from any accident previously evaluated. The change simply deletes a reference to an obsolete report (PFLR) and references the report which replacedit(COLR).

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Attachment'4 to Document Control Desk Letter TSP 900003 'Page 3 of 3

3. The proposed change does not involve a significant reduction in a margin of safety, The proposed change to Figure 3.1-3 revises the required shutdown margin as a function of RCS boron concentration for Modes 3 and 4 such that the operator will have at least 13.4 minutes and 13.6 minutes, respectively, from receipt of a high flux at shutdown alarm to recognize and terminate an uncontrolled dilution event before shutdown margin is lost. This will maintain the current margin to criticality, as reflected in the FSAR analysis of the Boron Dilution Event, and thus preserves the margin of safety as defined in the bases for the Stutdown Margin Technical Specification.

The proposed revision to change "PFLR" to "COLR" in Technical Specification Basis 3/4.2.1 is administrative in nature. The change simply deletes a reference to an obso'ete eport (PFLR) and references the report which replaced it (COLR). The change does not affect the margin of safety currently provided by the lechnical Specifications.

Therefore, based on the above considerations SCEtG has determined that the proposed changes do not involve any sionificant ht? teds considerations.

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