ML051260264

Additional (Draft) Information on Tcold in Footnote to TS 3.2.6

ML051260264
Person / Time
Site:	Waterford
Issue date:	05/05/2005
From:	Barry Miller Entergy Operations
To:	Alexion T NRC/NRR/ADPT
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Download: ML051260264 (5)

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Thomas Alexion - Additional_(Draft) Information onTcold in Footnote to TS 3.2.6 e ----- -- I - _ .-. .... . S. -. .. 0...

Page 1 From: MILLER, D BRYAN" <dmill14@entergy.com>

To: "Thomas Alexion'" <TWA@nrc.gov>

Date: 5/5/05 2:22PM

Subject:

Additional (Draft) Information on Tcold in Footnote to TS 3.2.6

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Technical Specification 3.2.6 Footnote

• to Technical Specification 3.2.6 allows the upper limit on Tcold to increase to 559OF for up to 30 minutes following a reactor power cutback in which (1) regulating groups 5 and/or 6 are dropped or (2) regulating groups 5 and/or 6 are dropped and the remaining regulating groups are sequentially inserted. This value is considered an arbitrary value to which uncertainty need not be applied. Footnote

• to Technical Specification 3.2.6 was in the Waterford-3 Technical Specifications at the time of initial licensing. There has been no change to that footnote between initial licensing and EPU.

A reactor power cutback is a non-safety system which is in! the ey of a load rejection, such as a turbine trip or a loss of one of two main feedwat E Jx ceeds the capacity of the turbine bypass valves. The reactor power cutbac$ Bathe dropping of one or more preselected CEA groups. This rapid reduction o povm te which is greater than that provided by the normal high speed CEA ins he plant to within prescribed operating ranges. Reactor power cutback iin a RChapbr15 safety analyses.

The reactor power cutback system will also throttle the t ion valve (for a loss of a feedwater pump) to rebalance turbine and reactor wer. If tl minor mismatch and core power is greater than turbine demand, cold le rE hgcrease. With a negative MTC, the increasing temperature s .se to match the turbine demand, resulting in a stable pow he re 1fbe turbine. Since this power is substantially below full power, e is n len al margins.

Control system analyses conduc 1PU have modeled the plant response to transients involving Ixample, reactor power cutback would result in a core poweriag e (EOC) Turbine Trip. With no operator actio drive in a about a 7F rise in Tcold from a nominal 543F ut 550F.

As stated in AttacW F1VQ L0074, the 3716 MWt Extended Power Uprate License Amendment R Unglue is be ised from 5680 F to 5590 F for EPU, in conjunction with the char the T :O; the Logs being revised from a range of 541 0F to 558OF to a new range OF to 549 bie revision of this value to 5590 F maintains the existing 10F difference t maximum TX Waterford-3 ensed wi Tcold range of 541 OF to 558OF, based on a nominal temperature rat Hot Zero Power (HZP) to 553OF at Hot Full Power (HFP).

Under 10CFR50. a d-3 revised this nominal temperature program to a constant 5450F value in the early 1990's. For power uprate, a 20F ramp is being adopted, with nominal Tcold ranging from 5410F at HZP to 543OF at HFP. Thus, with the implementation of EPU, there will be a more restrictive range of 160F (559OF versus 5430F) to the footnote value compared to the pre-EPU range of 230F (568 0F versus 545OF).

The original 568OF value in Technical Specifications was arbitrarily chosen to be 100F above the upper limit of the LCO, on the basis that it is reasonable to allow some deviation for a short period of time (30 minutes) to allow recovery and subsequent plant stabilization after the reactor power cutback. This also prevents unnecessary plant entries into Technical Specification ACTION statements. The 10F offset is unchanged for 3716 MWt Power Uprate.

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Operators select the appropriate CEA group(s) to drop during a reactor power cutback. The selection ensures that the reactor power following cutback will be less than the capacity of the turbine bypass valves of about 65%. Because a reactor power cutback is a plant transient of short duration, no additional accident or transient is postulated to occur simultaneously during the 30 minute time period of the TS 3.2.6 footnote where TCOd may be above the explicitly analyzed range. Also, due to the reduced power, there is significantly less energy and latent heat in the reactor core after the cutback.

Because the 559F value for the TS 3.2.6 footnote approved via Amendment 199 is not based on a specific analysis but is intended as a reasonable allowance for operator action to restore the plant within the normal LCO band of TS 3.2.6, there is no need to address instrument uncertainty with respect to this parameter. This footnote is not i onsisteyith many other Technical Specifications for which there is not any expliciit al tWa orts the time required for ACTION statements. _

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Power Level for OPERABILITY of ADV Automatic Actuation Technical Specification 3.7.1.7 New Technical Specification 3.7.1.7 is being added due to EPU to specify OPERABILITY requirements for the Atmospheric Dump Valves. This TS is being added since the EPU Small Break LOCA Emergency Core Cooling System (ECCS) analysis credits one Atmospheric Dump Valve for the purpose of secondary pressure control; the ADV's were previously credited only for cooldown to shutdown cooling entry conditions and for their containment isolation function.

The small break LOCA analyses assume a maximum ADV setpoint of 1040 psia. This value is specified in the footnote to TS 3.7.1.7 and explicitly accounts for the instrument uncertainty offset from the nominal setpoint of 1007 psia. _ Adz The footnote to the LCO also documents that the ADV i channels are not required to be operable when the reactor has been at d 70% Rated Thermal Power for greater than 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> (following long-term oje hjrhermal PQwer of 3716 MWt). The value of 70% is specified based on r a power level below which automatic actuation of the ADS acceptability of this arbitrary value, a calculation was pE pto demonstral&lHe decay heat load associated with operation for 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> at 70% Wnal Power is such that the ADV's need not be credited to demonstrate acceptable ance. The ADV's are not credited in the Waterford 3 Cycle 13 pre-uprata )C S analyses, which leads to the conclusion that long-term oper 3of 3J Wt (92.6% of EPU -

Rated Thermal Power) is acceptable with editi the SB§CA analysis. The 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> time frame supports the Bases for ONs c s TS 3.7.1.7, which calls for exiting TS applicability within 6 hourfte edu 1Nhan or equal to 70% of Rated Thermal Power.

Margin exists in the decay h lysis betwe - ate power where ADV's are not required (e.g.2 term opno at 3441 MWt) ecay heat corresponding to operation at 70% of uprN rmal PO 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> or less. The decay heat for a reactor trip after operation for sixh t 70% o d thermal power after long-term operation at 3716 MWt is around 10% bel from Ion operation at 3441 MWt. A strict analytical approach would result in creasing Thermal Power as a function of time, that is, the reactor powe d be s crease o approximately 92.6% in order for this decay heat logic to be ained. In eration of this margin and the fact that the decay heat load associated M70% power o will decrease with longer times, it is not considered necessary t Ny any explic e to account for power measurement uncertainty to the 70%

value specifi e hn ifications.

Based upon this ntergy considers this to be an arbitrary value to which uncertainty need not be applied and therefore a Category D parameter. If explicit analysis were performed this value could be raised to a value closer to 92.6%.

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