ML20069M627

End-Of-Cycle Recirculation Pump Trip Analysis for PBAPS Units 2 & 3

ML20069M627
Person / Time
Site:	Peach Bottom
Issue date:	06/30/1994
From:	Hoang H, Kumar G GENERAL ELECTRIC CO.
To:
Shared Package
ML20069M608	List: ML20069M605 ML20069M627
References
NED-32165, NED0-32165, NEDO-32165-R02, NEDO-32165-R2, NUDOCS 9406220065
Download: ML20069M627 (24)

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':5CunnerAvenue nn xse. CA 95125 ygpo.32;65 Class I DRF A00-05443 June 1994 l

END-OF-CYCLE 1l

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RECIRCULATION PUMP TRIP ANALYSIS FOR PEACH BOTTOM l jg ATOMIC POWER STATION

UNITS 2 AND 3 l

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. PREPARED FOR PECO ENERGY I I l

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I lCA n j j H. X. Hoang, V Plant Upgrade P jects 1

Approved.

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l G. V.'Kumar, f l

PECo Power Rerate Project Manager

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9406220065 940616

, PDR ADOCK 05000277 4

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NEDO-32165 Class !

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l IMPORTANT NOTICE REGARDING I

CONTENTS OF THIS REPORT l

I Please Read Carefully The only undertakings of GE Nuclear Energy respecting information in this document are contained in the contract between PECO Energy and GE Nuclear Energy, as identified in the purchase order for this report, and nothing contained in this document shall be constn:ed as ,

changing the contract. The use of this information by anyone other than PECO Energy for any 1 purpose, other than that for which it is intended, is not authorized; and, with respect to any unauthorized use, GE Nuclear Energy makes no representation or warranty and assumes no liability as to the completeness, accuracy, or usefulness of the information contained in this document, or that its use does not infringe the rights of third parties.

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NEDO-32165 Class 1 CONTENTS Ea&C

1.0 INTRODUCTION

1 2.0 SYSTEM DESCRIPTION 2 3.0 ANALYSES RESULTS 3

4.0 CONCLUSION

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5.0 REFERENCES

6 APPENDIX: TECHNICAL SPECIFICATIONS CHANGES 15

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NEDO-32165 Class I TABLES Table Ijilg Eage 1 RPT System Response Time 7 2 EOC-RPT Analysis Initial Conditions 8 3 EOC-RPT Transient Peak Values 9 4 EOC-RPT Delta CPR Results 10 FIGURES Figure T_ ilk Eage 1 RPT Interface with RPS and Recirculation System Diagram 11 2 Plant Responses to Load Rejection 12 with No Bypass,100P/100F, EOC-RPT 3 Plant Responses to Turbine Trip 13 with No Bypass,100P/100F, EOC-RPT 4 Plant Responses to Feedwater Controller 14

{- Failure with No Bypass,100P/105F, FWTR, TBP-OOS 5 Plant Responses to Feedwater Controller 15

[ Failure with No Bypass,100P/105F, FWTR, TBP-OOS, EOC-RPT

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NEDO-32165 Class i

1.0 INTRODUCTION

The purpose of the End-of-Cycle Recirculation Pump Trip (EOC-RPT) system is to reduce the severity of the fuel thermal-mechanical transient excursion resulting from the reactor pressurization following a turbine generator trip or a generator load rejection event. The EOC-RPT modification will improve the thermal response to plant scrams during the latter portion of a typical fuel cycle when slower negative scram reactivity insertion rates are encountered. The analysis results documented in this report can be used to determine and quantify the capability of the EOC-RPT feature to relax the minimum critical power ratio (MCPR) requirement necessary to accommodate anticipated operational occurrences (AOOs) postulated at the Peach Bottoms Atomic Power Station (PBAPS) Units 2 and 3.

(Proprietary inforrnation that is contained in NEDC-32165P, Rev. 2) The initiating trip signal used for RPT is either the turbine stop valves (TSV) closure as indicated by their position switches, or turbine control valves (TCV) fast closure as indicated by their loss of hydraulic oil pressure.

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NEDO-32165 Class l 2.0 SYSTEM DESCRIPTION 1

I The Recirculation Pump Trip System (RPT) is classified as non safety-related system. Its I

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function is to mitigate the consequences of the turbine / generator trip or load rejection event.

l (Proprietary information that is contained in NEDC-32165P, Rev. 2) The RPT system will be operable above the power setpoint for turbine stop valve closure and control valve fast closure scram bypass.

I (Proprietary information that is contained in NEDC-32165P, Rev. 2)

The RPT system logic will not cause the inadvertent trip of more than one pump given a single component failure in the system. The redundant sensor circuits in each channel are electrically, mechanically and physically independent so that they are unlikely to be disabled by a common cause except for an electrical power failure.

Testability is provided for one channel to enable routine maintenance to be performed.

Indicator lights monitor when the system is bypassed. Indicators are provided for input trip signals, the status of the trip coil, the mechanical position of the circuit breaker, and the ASD stop circuit, for each of the recirculation loops. An annunciator is provided for the RPT activation.

The RPT system design response time delay from start of Turbine Stop Valve Closure or Turbine Control Valve Fast Closure to complete suppression of the electric are between the fully open contacts of the circuit breaker (Proprietary information that is contained in NEDC-32165P, Rev. 2) or the complete suppression of the ASD output current is shown in Table 1.

The RPT interface with the RPS and the recirculation system is shown in Figure 1. 4 I

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NEDO-32165 Class 1 3.0 ANALYSIS AND RESULTS The EOC-RPT system is designed to protect the integrity of the fuel barrier in conjunction with the reactor scram function following a postulated AOO. This function is accomplished by tripping both recirculation pumps early in the pressurization phase of the events and introduce negative void reactivity to the core, thus reducing the neutron flux and fuel surface heat flux excursions. Upon detection of a fast closure of the TCVs or the closure of the TSVs at core power level above 30% of rated thermal power the reactor protection system will initiate a reactor scram signal and concurrently a RPT signal to keep the fuel within the design safety limit. (Proprietary information that is contained in NEDC-32165P, Rev. 2) The time required to interrupt the power supply after the initiation of the EOC-RPT signal is as shown in Table 1.

To quantify the margin ofimprovement to the fuel performance which can be realized with the implementation of the EOC-RPT system, transient analyses are performed for the following AOOs directly affected by the EOC-RPT feature: load rejection with no bypass (LRNBP),

turbine trip with no bypass (TTNBP) and feedwater controller failure (FWCF) maximum demand. Core nuclear dynamic parameters and inputs assumptions used in this analysis are consistent with the Cycle 10 reload licensing bases (Reference 1). The events are postulated to initiate at 100% power and 100% flow at EOC exposure condition. Since the FWCF failure 1

l event is sensitive to core inlet subcooling effect, this event was analyzed at 100% power /105 %

core flow with 48 F reduction in feedwater temperature. In addition, the FWCF event is analyzed with the turbine bypass system available as well as out-of-service to provide a sensitivity study of the EOC-RPT function combined with the turbine bypass system. Selected initial conditions are summarized in Table 2.

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The core-wide transients analyses results are shown in Table 3 and the corresponding operatmg MCPR limits are summarized in Table 4. Key parameters responses during the transients are shown in Figures 2 through 5. As can be seen, the EOC-RPT feature reduced the t

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ClassI severity of the thermal-mechanical excursions during these transient pressurization events by a significant amount.

Approximately 0.03 to 0.04 delta CPR reduction for the TrNBP, LRNBP and FWCF events can be realized with the implementation of the EOC-RPT system. This margin is applicable to fuel designs from GE7 to GE10 currently in the Peach Bottoms core. To provide a typical margin trend for Gell fuel, the Cycle 10 limiting event, LRNBP, was analyzed with bounding core nuclear characteristics specific to GElI consistent with Reference 1 methodology.

The results showed that for Gell, the EOC-RPT system also yield an improvement in the operating limit MCPR requirement, about 0.05 lower than without credit for EOC-RPT. Note that the analysis results shown here are cycle-specific and may require verification for future fuel reloads or for new fuel designs.

(Proprietary information that is contained in NEDC-32165P, Rev. 2) l

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NEDO-32165 Class 1 l

4.0 CONCLUSION

S The EOC-RPT function reduced the coolant flow delivery to the reactor core during a

( pressurization event. This flow reduction subsequently introduced negative void reactivity which would limit the transient severity of the fuel thermal-mechanical response. The analyses results documented in this report conducted for PBAPS Unit 2 Cycle 10 confirmed that the implementation of the EOC-RPT system triits would yield improvement in the range from 0.03 to 0.05 reduction in the operating limit MCPR requirements for the pressurization transient events. The same improvement trend would be expected for PBAPS Unit 3 base on the similarity in the EOC-RPT system design and the plant configuration between PBAPS Unit 2 and 3.

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NEDO-32165 Class 1 I

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5.0 REFERENCES

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1. Reload Licensing Submittal for Peach Bottoms Atomic Power Station Unit 2 Reload 9 Cycle 10,23A7188, Revision 0, September 1992 l

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NEDO-32165 Class I Table 2 EOC-RIT ANALYSIS INITIAL CONDITIONS TTNBP/LRNBP FWCF (100P/100F)_ (100P/105F)

Thermal Power (MWt/% rated) 3293/100 3293/100 Core Flow (Mib/hr/% rated) 102.5/100 107.62/105 Steam Flow (Mlb/hr) 13.37 12.62  ;

Feedwater Temperature, F 376 326 Core Coolant Inlet Enthalpy (Btu /lb) 522 517 Dome Pressure (psig) 1005 1005 Core Average Void Fraction (%) 35 32 l

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NEDO-32165 Class i Table 3 EOC-RPT TRANSIENTS PEAK VALUES Peak Peak Peak Peak Neutron Heat Steamline Vessel Transients Power / Flow Flux. % Flux. % Press. osig Press. nsig LRNBP w/o RPT 100/100 509.4 125.5 1173 1210 LRNBP w/ RPT 100/100 423.8 120.7 1173 1204 TTNBP w/o RPT 100/100 486.9 124.5 1172 1209 TTNBP w/ RPT 100/100 397.3 119.I 1172 1202 FWCF w/o RPT 100/105, 507.5 132.7 1170 1208 (w/ TBP-OOS) FWTR FWCF w/ RPT 100/105, 405.7 126.7 1170 1202 (w/ TBP-OOS) FWTR Note: FWTR = Feedwater temperature reduction

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2 EOC-RPT DELTA CPR RESULTS 3

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i 2 Transient Power / Flow Uncorr. Opt. A Opt. B i LRNBP w/o RPT 100/100' .198 .25 .21 l j LRNBP w/ RPT 100/100 .170 .22 .18  ;

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LRNBP w/o Rirr 100/100 .293 . 39 .31 i (Gell Fuel) i

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LRNBP w/ RPT 100/100 .241 .34 .26 (gel 1 Fuel) i l- TTNBP w/o RPT 100/100 .I88 .24 .20 i TTNBP w/ RPT 100/100 .159 .21 .17 i l

j FWCF w/o RPT, 100/105, .227 .27 .24 l 4 (w/ TBP-OOS) FWTR j FWCF w/ RPT 100/105, .195 .23 .21 j (w/ TBP-OOS) FWTR 4

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j NEDO-32165 1 Class I i

i APPENDIX: TECIINICAL SPECIFICATIONS CIIANGES j

The following changes to the current PBAPS technical specifications are recommended for the implementation of the EOC-RPT feature:

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1) Modify the description ofinstrumentation that initiates recirculation pump trip to include f EOC-RPT function, to be provided by signals' from Turbine Stop Valves or Turbine Control Valves Closure.

2) Modify the trip level setting for recirculation pump trip to include Turbine Stop Valve.

I position and Turbine Control Valve hydraulic oil pressure.

3) Modify the test and calibration for recirculation pump trip to include verification of the I

time delay from turbine-generator trip signal to the interruption of the power supply to l t 1 i the recirculation pump motor, i.e. the complete suppression of the electric arc between l 1

the circuit breaker contacts, or the complete suppression of the ASD output current. '

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4) Modify affected bases.

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