ML20085D624

Proposed Tech Spec Table 2.2-1 Re Reactor Trip Sys Instrumentation Trip Setpoints - Notation

ML20085D624
Person / Time
Site:	Beaver Valley
Issue date:	10/09/1991
From:	DUQUESNE LIGHT CO.
To:
Shared Package
ML20085D617	List: ML20085D613 ML20085D620 ML20085D624
References
NUDOCS 9110170019
Download: ML20085D624 (8)

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. ATTAcill41:14T A

lleaver Valley I'ower Station, Unit lio, 2 Proposed Technical Specification Change 11o. 56 i llevine the Technical Specification as follown

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TABLE 2.2-1 (Continued)

E kx REACTOR TRIP SYSTEM INSTRUMENTATION TRIP SETPOINTS -

NOTATION N

r-y NOTE 1: OVERTEMPERATURE AT

• 1+135) 1 K K (I * *4$) 1

( 3) $

^I ((1 +5 '2 ) +'3 3 2 (1 + t 5) s t (I * '63) - T'] + K3 (P - P') - fg (al))

Where: AT = Heasu ed AT; I+t S 1 = lead-lag compensator on measured AT; 2 1+T52

-P m

4o 11 ,12 = Time constants utilized in lead-lag compensator for AT, t g =8s, 12 = 3 8A

, -, M b I+T 1 = Lag compensator on measured AT; 3

f 1 3

= Time constants utilized in the lag compensator for AT, 3r = 0 s;

= Indicated AT at RATED THERMAL POWER; AT, K

y

= 1.28; K

2

= 0.027/*F;i b.0183/'F.

O 2

1+t 5 4 = The function generated by the lead-lag compensator for T dynamic compensation; '

I+t 5

=

14, 15 Time constants utilized in lead-lag compensator for T, ,?

4

= 30 s, tg = 4 s;

l ATTACllMENT D Beaver Valley Power Station, Unit No. 2 I Proposed Technical Specification Change No. 56 REVISION OF TABLE 2.2-1 FOR TECilNICAL SPECIFICAT)ON 2.2.1 A. DESCRIPTION OF AMENDMENT RrQUEST The proposed amendment would revine Note No. 1 of Table 2.2-1 which specifica the equation used in the determination of the overtemperature delta T trip setpoint.

The specific revision to Note 1 would be to change the value of Kg from 0.017/'F to 0.0183/*P.

B. BACKGROUND The overtemperature delta temperature (OTDT) trip protects the core against a low departure from nucleate boiling ratio (DNBR) and trips the reactor on a two out of three coincidence logic.

The setpoint for thin trip is continuounty calculated by analog circuitry for each loop by solving the equation stated in Note 1 of Tabic 2.2-1. The K, factor determinen the magnitude of the OTDT setpoint reduction / Increase for each degree fahrenheit Tavg in above/below 576.2'P.

In a letter dated June 3, 1991, from the Wentinghouse Electric Corporation to the Duquesne Light Company (DLC), we were notified that the current OTDT netpoint did not protect from DNB at high pressure over a small range of temperatures. Wentinghouco provided DLC a justification for continued operation (JCO) with the current OTDT netpoint. The JCO determined that the core limits would be protected by the current ar;tpoint constranto provided that a RCS flow of 2 276,225 gpm (including a 1.8% flow measurement uncertainty) is availabic at the plant. The JCO in based on maintaining a reactor coolant cyntem flow rate of 2 276,225 gpm with a reduction in the flow measurement uncertainty. Although the Technical Specification required flow of 2 274,800 gpm has not been lowered, for the purponen of justifying continued operation, credit was taken for lowering the flow measurement uncertainty from 3.5% to 1.8%. The flow measurement uncertainty was calculated to be 1.8% as part of RTD bypacs elimination analysis and la documented in WCAP-12478.

With credit taken for a 1.8% reasurement uncertainty and the measured flow rate of 2 276,225 gpm, the current OTDT setpoint provides the required protection of the core from DNB for all conditions.

C. JUSTIFICATION The current K 2 value of 0.017/'F, used in the 01DT trip setpoint determination, does not result in a trip setpoint which i protects from DNB at high prensures, over a small range of temperaturen, unican credit is Pken for flow margin of at least i 4.0% higher than the thermal dusign flow (265,500 gpm) . To i

1 ATTACHMENT B, continued proposed Technical Specification Change No. 56 l Page 2 justify continued operation, Boavor Valley Power Station Unit No. 2 must maintain a reactor coolant system (RCS) flow rate of 1 276,225 gpm. The curront RCS flow rato measuromont performed in accordanco with Surveillanco Requjromont 4.2.5.2 dotormined the flow rato to be 27C,391 gpm.

The margin betwoon the JCO minimum required flow rato and the measured flow rato does not provido adequato margin for long term plant operation. In order to recover phppt operating margin that has boon diminished by using the present K,' value of 0.017/*F, K2 value noods to be changed to 0.0183/*P.

Thorofore, the proposed revision to K 2 will ensure that protection is provided from DND at high pressures, over the range of temperatures of concern without the need to credit tho 4.0%

flow margin.

D. SAFETY ANALYSIS The proposed value of K 2 ( 0. 018 3 /

• F) wil1 onsure that the OTDT trip will protect the core against a low departure from nucleate boiling ratio by tripping the reactor at the desired notpoint.

The OTDT setpoint constants that protect the core limits are calculated using the methodology of WCAP-8745. The OTDT constants, with the proposed value of K, woro verified by Westinghouse to provido protection for t$o core limits. The non-LOCA analynos that trip on OTDT and model the plant specific trip sotpoint aro limiting when Tavg is greator than 576.2'F.

Above a Tavg value of 576.2*F, increasing the K 2 valu9 will result in a lowering of the OTDT sotpoint. Therefore, the increano in K will provido an earlier trip for the non-LOCA analysis. Bo$ow a Tavg value of 576.2*F, increasing the K 2 value will result in a higher OTDT setpoint. Thero is a margin betwoon the DNB limits and the sotpoint in this region; thus, the protection that the OTDT trip is required to provido is not compromised. The current Technical Specification LCO requiremont 3.2.5, which requires the RCS flow to be 2 274,800 gpm, will romain valid with the proposed X 2 value.

Thorofore, this change is considered safe based on the proposed K2 valuo providing an OTDT trip setpoint which will protect the core against a low DNDR with a RCS flow of 2 274,800 gpm. The protection of the core is provided as assumed in final nafety analysis conclusions.

E. NO SIGNIFICANT HAZARDS EVALUATION The no significant hazard considerations involved with the proposed amendment have been evaluated, focusing on the three standards set forth in 10 CFR 50.92(c) as quoted below:

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• • AYTACHMENT B, continued proposed Technical Specification Chiange No. 56 pago 3 -

The Coma.ission may make a final determination, pursuant to the procedures in paragraph 50.91, that a proposed amendment to an operating licenso for a facility licensed under '

paragraph 50.21(b) or paragraph so.22 or for a testing facility involves no significant nazards considoration, it operation of the facility in accordance with the proposed amendment would nots (1) Involve a significant incroano in the probability or consequences of an accident previously evaluated; or (2) Croato the possibility of a now or differer.t kind of accident from any accident previously evaluated; or (3) Involve a significant reduction in a margin of safety.

The following ov:Tuation is provided for the no significant hazards consider ..on standards.

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

The 'oposed value for K 7 will lower the OTDT trip notpoi:nt in the range of plant operation where the OTDT trip is credited for protecting the core from a low DNDR. By providing a lower trip sotpoint, changing the K2 value does not involve a significant increano in the probability or consequences of an accident previously evaluated. ,

2. Does the change croato the possibility of a now or differe"t kind of accident from any accident previously evaluatod?

The -proposed value for K j is a correction to the OTDT sotpoint. The resulting OTDT sotpoint will provido protection for the core limits as originally assumed in safety analysis. Thoroforo, the proposed chango does not croato the possibility of a now or different kind of accident previously evaluated.

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

The proposed chango will continue to ensure that the coro is protected against a low departure from nucleate boiling ratio by tripping the reactor at the required sotpoint.

The proposed change to the K 7 value will increase the margin of safety overall by protecting the core from DNB at high pressure over the required range of temperatures without the nood to credit the 4.0% flow margin. Thereforo, the proposed chango does not involve a significant reduction in a margin of safety.

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-NfTACHMENT B,-contir.ued Proposed Technical Specification channe No. 56 Page 4 F. NO SIGNIFICANT RaZARDS CONSIDERATION DETERMINATION Dased on the considerations expressed above, it is concluded that the activities associated with this license amendment request satisfies the no significant hazards consideration standards of 10 CFR 50.92(c) and, accordingly, a no significant hazards consideration finding is justified.

G. ENVIRONMENTAL EVALUA1 ION The proposed change have been evaluated and it has been det(rmined that the changes do not involve (i) a significant hazards consideration, (ii) a significant change in the types or significant increase in the amounts of any effluents that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed changes meet the eligibility criterion for categorical exclusion set forth in 10 CFR 51. 22 (c) (9) . Therefore, pursuant to 10 CFR 51.22 (b), an environmental assessment of the proposed change is not required.

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ATTACllMEliT C l ,

Deaver Valley Power Station, Unit No. 2

! Proposed Technical Specification Change No. 56 Typed Page: 2-7 l

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TABLE 2.2-1-(Continued) ',

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E REACTOR TRIP SYSTEM INSTRUMENTATION TRIP SETPOINTS ,.

• MOTATION s

r-m NOTE 1: OVERTEMPERATURE AT 1 8

(I * '45) 3 -

I-I j AT(1 (1 ++ t1 y S)5) lI ^ +1TMI 3

o 1~ 2. (1 + Q)- 1+16 5) - 3 * "3 l

" = Measured AT;'

Whern: AT 1+t5 1 = Lead-lag compensator on measured AT; 1+T 2b

,12 = Time constants utilized in lead-lag compensator for AT, t y

=8s,

{ I T

• 3 5; y 8 2

" 5 2 3 = Lag compensator on measured AT; I+1b3

= T M constants u W iz d in W 1ag c e nsator for AT, 13 = 0 s; f' 1 3

O = Indicated AT at RATED THERMAL POWER; AT, Kg = 1.28; i

Kg = 0.0183/ F;

}

m 2

h 1+t S dynamic compensation; 4 = The function generated by the lead-lag compensator for T, 5 1.+ 15b z

P = Time constants utilized in lead-lag compensator for I, ,1 = 30 s, r5" ';

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14. IS

_ . . = . . . .

u . _ _ _

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