ML17306B145

Proposed Tech Specs Revising TS 3.2.1 Lhr, & TS 3.2.4, DNBR Margin, Increasing Action from 1 H to 4 H for COLSS Allowed Out of Svc Time Before Requirements Based on More Restrictive Core Protection Calculator Limits Apply

ML17306B145
Person / Time
Site:	Palo Verde
Issue date:	11/20/1992
From:	ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:
Shared Package
ML17306B144	List: ML17306B145
References
NUDOCS 9212010279
Download: ML17306B145 (30)

Text

(STROLLED DOCUiMEN 3)/4. 2 POWER DISTRIBUTION LIMITS 3/4 2. 1 LINEAR HEAT RATE LIMITING CONDITION FOR OPERATION 3.2.1 The linear heat rate limit of 13.5 kW/ft shall be maintained by one of the following methods as applicable:,

a. Maintaining COLSS calculated core power less than or equal to the COLSS calculated power operating limit based on linear heat rate (when COLSS is in service); or

b. Maintaining peak linear heat rate within its limit using any operable CPC channel (when COLSS is out of service).

APPLICABILITY: MODE 1 above 20Ã of RATED THERMAL POWER.

ACT IDN:

te SURVEILLANCE RE UIREMENTS 4.2.1.1 The provisions of Specification 4.0.4 are not applicable.

4.2. 1.2 The linear heat rate shall be determined to be within its limit when THERMAL POWER is above 20Ã of RATED THERMAL POWER by continuously monitoring the core power distribution with the Core Operating Limit Supervisory System (COLSS) or, with the COLSS out of service, by verifying at least once per 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> that the linear heat rate, as indicated on any OPERABLE Local Power Density channel, is within its limit.

4. 2. 1. 3 At least once per 31 days, the COLSS Margin Alarm shall be verified to actuate at a THERMAL POWER level less than or equal to the core power operating .

limit based on linear heat rate.

PALO VERDE - UNIT 1 ~ 3/4 2-1 AMENDMENT NO. 24 m<ZOSoa79 9VS<ao PDR ADDCK 05000528

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iNTRQI L"0 DGCUA'-3'""i 3/4. 2 POWER DISTRIBUTION LIMITS 3/4 2.1 LINEAR HEAT RATE LIMITING CONDITION FOR OPERATION 3.2.1 The linear heat rate limit of 13.5 kW/ft shall be maintained by one of the following methods as applicable:

ao Maintaining COLSS calculated core power less than or equal to the COLSS calculated power operating limit based on linear heat rate (when COI SS is in service); or Maintaining peak linear heat rate within its limit using any operable CPC channel (when COLSS is out of service).

APPLICABILITY: MODE 1 above 20K of RATED THERMAL POWER.

ACTION:

SURVEILLANCE RE UIREMENTS 4.2.1.1 The provisions of Specification 4.0.4 are not applicable.

4.2.1.2 The linear heat rate shall be determined to be within its limit when THERMAL POWER is above 20K of RATED THERMAL POWER by. continuously monitoring the core power distribution with the Core Operating Limit Supervisory System (COLSS) or, with the COLSS out of service, by verifying at least once per.

2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> that the linear heat rate, as indicated on any OPERABLE Local Power 0'ensity channel, is within its limit.

4. 2. 1. 3 At least once per 31 days, the COLSS Margin Alarm shall be verified to actuate at a THERMAL POWER level less than or equal to the core power operati.ng limit based on linear heat rate.

PALO VERDE - UNIT 2 3/4 2-1 AMENDMENT NO. 19

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3/4. 2 POWER DIS'TION LIHITS 3/4 2.1 LINEAR HEAT RATE LIHITING CONDITION FOR OPERATION 3.2.1 The linear-heat rate limit of 13.5 kM/ft shall be maintained by one of the following methods as applicable:

a. Haintaining COI SS calculated core power less than or equal to the COLSS calculated power operating limit based on linear heat rate (when COLSS is in service); or

b. Haintaining peak linear heat rate within its limit using any operable CPC channel (when COLSS is out of service).

APPLICABILITY: MODE 1 above 20K of RATED THERMAL POWER.

ACTION:

W4h-N 5URVEI! LANCE RE UIREHENTS 4.2.1.1 The provisions of Specification 4.0.4 are not applicable.

4.2. 1.2 The 1inear heat rate shall be determined to be within its limit when THERHAL POMER is above 2(C of RATED THERHAL POMER by continuously monitoring the core power distribution with the Core Operating Limit, Supervisory System (COLSS) or, with the COLSS out of service, by verifying at least once per 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> that the linear heat rate, as indicated on any OPERABLE Local Power Density channel, is within its limit.

4.2.}..3 At, least once per 31 days, the COLSS Hargin Alarm shall he verified to actuate at a THERMAL POWER level less than or equal to the core power operating

.limit based on linear heat rate.

" 18 PALO VERDE UNIT 3 3/4 2"1 AHENDMENT NO

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a. If the DNBR cannot be maintained within the LCO limits, perform the following:

1. If COLSS is in service, within 15 minutes initiate corrective action to restore the DNBR to within the LCO limits within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, or

2. If COLSS is out of service, restore the DNBR to within the LCO limits within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

b. If DNBR cannot be restored to within the LCO limits, as required by ACTION a.,

reduce THERMALPOWER to less than or equal to 20% RATED THERMALPOWER within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.

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POWER DISTRIBUTION LIMITS 3/4.2.4 DNBR MARGIN LIMITING CONDITION FOR OPERATION 3.2.4 The DHBR margin shall be maintained by one of the following methods:

a. Maintaining COLSS calculated core power less than or equal to COLSS xalculated.core, power operating...limit. based on DNBR (when COLSS is in sdr<fce,'nd either one or .both CEACs are operable); 'or

b. Maintaining COLSS calculated core power less than or equal to COLSS calculated core power operating limit based on DHBR decreased by the allowance shown in Figure 3.2-1 (when COLSS is in service and neither CEAC is operable); or

.c. ..Operating within the region of acceptable operation of Figure 3.2-2 using any operable CPC channel (when COLSS is out of service and either one or both CEACs are operable); or

d. Operating within the region of acceptable operation of Figure 3.2-2A using any operable CPC channel (when COLSS is out of service and neither CEAC is operable).

APPLICABILITY: MODE 1 above 20K of RATED THERMAL POWER.

ACTIDM:

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SURVEILLANCE RE UIREMEHTS-4.2.4.1 The provisions of Specification 4;0.4 are not applicable.

4. 2.4.2 The DHBR shall be determined to be within its limits when THERMAL POWER is above 20K of RATED THERMAL POWER by continuously monitoring the core power distribution with the Core Operating Limit Supervisory System (COLSS) or, with the COLSS out of service, by verifying at least once per 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> that the DNBR, as indicated on any OPERABLE DHBR channel, is within the limit shown on Figure 3.2-2 or Figure 3.2-2A.

4.2.4.3 At least once per 31 days, the COLSS Margin Alarm shall be verified to actuate at a THERMAL POWER level less than or equal to the core power operating limit based on DHBR.

PALO VERDE - UNIT 1 3/4 2"5 AMENDMENT NO. 24

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POWER DISTRIBUTION L ITS 3/4. 2. 4 DNBR MARGIN LIMITING CONDITION FOR OPERATION 3.2.4 The DHBR margin shall be maintained by one of the following methods:

a. Maintaining COLSS calculated core power less than or equal to COLSS calculated core power operating limit based on DNBR (when COLSS is in service, and either one or both CEACs are operable); or

b. Maintaining COI SS calculated core power less than or equal to COLSS calculated core power operating limit based on DNBR decreased by the allowance shown in Figure 3.2-1 (when COLSS is in service and neither CEAC is operable); or

c. Operating within the region of acceptable operation of Figure 3.2-2 using any operable CPC channel (when COLSS is out of service and either one or both CEACs are operable); or

d. Operating within the region of acceptable operation of Figure 3.2-2A using any operable CPC channel (when COLSS is out of service and neither CEAC is operable).

APPLICABILITY: MODE 1 above 2QX of RATED THERMAL POWER.

ACTION:

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SURVEILLANCE RE UIREMENTS 4.2.4.1 The provisions of Specification 4.0.4 are not applicable.

4.2.4.2 The DNBR shall be determined to be within its limits when THERMAL POWER is above 20K of RATED THERMAL POWER by continuously monitoring the core power distribution with the Core Operating Limit Supervisory System (COLSS) or, with the COLSS out of service, by verifying at least once per 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> that the DNBR, as indicated on any OPERABLE DNBR channel, is within the limit shown on Figure 3.2-2 or Figure 3.2-2A.

4.2.4.3 At least once per 31 days, the COLSS Margin Alarm shall be verified to actuate at a THERMAL POWER level less than or equal to the core power operating limit based on DNBR.

PALO VERDE - UNIT 2 3/4 2-5 AMENOMEHT NO. 3.9

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POWER DISTR IBUTI IMITS 3/4. 2. 4 DHBR MARGIN LIMITIHG CONDITION FOR OPERATION 3.2.4 The DHBR margin shall be maintained by one of the following methods:

a. Maintaining COLSS calculated core power less than or equal to COLSS calculated core power operating limit based on DNBR (when COLSS is in service, and either one or both CEACs are operable); or

b. 'aintaining COLSS calculated core power less than or equal to COLSS calculated core power operating limit based on DNBR decreased by the allowance shown in Figure 3.2-1 (when COLSS is in service and neither CEAC is operable); or

c. Operating within the region of acceptable operation of Figure 3.2-2 using any operable CPC channel (when COLSS is out of service and either one or both CEACs are operable); or

d. Operating within the region of acceptable operation of Figure 3.2-2A using any operable CPC channel (when COLSS is out of service and neither CEAC is operable).

APPLICABILITY: MODE 1 above 20K of RATED THERMAL POWER.

ACTION:

SURVEILLANCE RE UIREMEHTS 4.2.4.1 The provisions of Specification 4.0.4 are not applicable.

4.2.4.2 The DHBR shall be determined to be within its limits when THERMAL POWER is above 20% of RATED THERMAL POWER by continuously monitoring the core power distribution with the Core Operating Limit Supervisory System (COLSS) or, with the COLSS out of service, by verifying at least once per 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> that the DNBR, as indicated on any OPERABLE ONBR channel, is within the limit shown on Figure 3.2-2 or Figure 3.2-2A.

4. 2. 4. 3 At least once per 31 days, the COLSS Margin Alarm shall be ver ified to actuate at a THERMAL POWER level less than or equal to the core power operating limit based on DNBR.

PALO VERDE " UNIT 3 3/4 2-S AMEHDMEHT NO, IB

The core power distribution and a corresponding POL based on LHR are more accurately determined by the COLSS using the incore detector system. The CPCs determine LHR less accurately with the excore detectors. When COLSS is not available the TS LCOs are more restrictive due to the uncertainty of the CPCs. However, when COLSS becomes inoperable the added margin associated with CPC uncertainty is not immediately required and a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> ACTION is provided for appropriate corrective action.

While operating with the COLSS out of service, the CPC calculated LHR is monitored at least every 15 minutes to identify any reduction in thermal margin. The increased monitoring of LHR during the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> ACTION period ensures that adequate safety margin is maintained for anticipated operational occurrences and no postulated accident results in consequences more severe than those described in Chapter 15 of the UFSAR.

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2 POWER DISTRIBUTION LIMITS BASES 3/4.2.1 LINEAR HEAT RATE The limitation on linear heat rate ensures that in the event of a LOCA, the peak temperature of the fuel cladding will not exceed 2200'F.

Either of the two core power distribution monitoring systems, the Core Operating Limit Supervisory System (COLSS) and the Local Power Density channels in the Core Protection Calculators (CPCs), provide adequate monitoring of the core power distribution and are capable of verifying that the linear heat rate does not exceed its limits. The COLSS performs this function by continuously monitoring the core power distribution and calculating a core power operating limit corresponding to the 'allowable peak linear heat rate. Reactor operation at or below this calculated power level assures that the limits of 13.5 kW/ft are not exceeded.

The COLSS calculated core power and the COLSS calculated core power operating limits based on linear heat rate are continuously monitored and displayed.to the operator. A COLSS alarm is annunciated in the event that the core power exceeds the core power operating .limit. This provides adequate margin to the linear heat rate operating limit for normal steady-state opera-Normal reactor power transients or equipment faiTures which do not 'ion.

require a reactor trip may result in this core power operating limit In the event this occurs, COLSS alarms will be annunciated. If the being'xceeded.

event which causes the COLSS 1imit to be exceeded results in conditions which approach the core safety limits, a 'reactor trip will be initiated by the Reactor Protective Instrumentation. The COLSS calculation of the linear heat rate includes appropriate penalty factors which provide, with a 95/95 probability/

confidence level, that the maximum linear heat rate calculated by COLSS is conservative with respect to the actual maximum linear heat rate existing in the core. These penalty factors are determined from the uncertainties associated with planar radial peaking measurement, engineering heat flux uncertainty, axial densification, software algorithm modelling, computer processing, rod bow, and core power measurement.

Parameters required to maintain the operating limit power level based on linear heat rate, margin to DNB, and total core power are also monitored by the CPCs. Therefore, in the event that the CDLSS is not being used, operation within the linear heat rate limit can be maintained by utilizing any operable CPC channel. The above listed uncertainty and penalty .factors plus those asso-ciated with the CPC startup test acceptance criteria are also included in the CPCs.

PALO YERDE " UNIT 1 B 3/4 2-1 AMENDMENT No. 24

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t og pot I D DQGUiiA "j 3/4. 2 POWER DISTRIB OH LIMITS BASES 3/4. 2.1 LIHEAR HEAT RATE The 1'imitation on linear heat rate ensures that in the event of a LOCA, the peak temperature of the fuel cladding will not exceed 2200'F.

Either of the two core power distribution monitoring systems, the Core Operating Limit Supervisory System (COLSS) and the Local Power Density channels in the Core Protection Calculators (CPCs), provide adequate monitoring-of the core power distribution and are capable of verifying that the linear heat rate does not exceed its limits. The COLSS performs this function by continuously monitoring the core power distribution and calculating a core power operating limit corresponding to the allowable peak linear heat rate. Reactor operation at or below this calculated power level assures that the limits of 13.5 kW/ft are not exceeded.

The COLSS calculated core power and the COLSS calculated core power operating limits based on 'linear heat rate are continuously monitored and displayed to the operator. A COLSS alarm is annunciated in the event that the core power exceeds the core power operating limit. . This provides adequate margin to the linear heat rate operating limit for normal steady-state opera-tion. Normal reactor power transients or equipment failures which do not

'equire a reactor trip may result in this core po~er operating limit being exceeded. In the event this occurs, COLSS alarms will be annunciated. If the event which causes the COLSS limit to be exceeded results; in conditions which approach the core safety .limits, a reactor trip will be initiated by the Instrumentation. The COLSS calculation of the linear heat rate Reactor'rotective includes appropriate penalty factors which provide, with a SS/95 probability/

confidence level, that the maximum linear heat rate calculated by COLSS is conservative with respect to the actual maximum linear heat rate existing in.

the core. These penalty factors are determined from the uncertainties associated with planar radial peaking measurement, engineering heat flux uncertainty,, axial densification, software, algorithm modelling, computer processing, rod bow, and core power measurement.

Parameters required ta maintain the operating limit power level based on linear heat rate, margin to ONB, and total core power are also monitored by the CPCs. Therefore', in the event that the COLSS is not being used, operation within the linear-heat rate limit can be maintained by utilizing any operable CPC channel. The above listed uncertainty and penalty factors plus those asso-ciated with 'the CPC startup test acceptance criteria are also included in the CPCs.

PALO VERDE " UNIT 2 8 3/4 2-1 AMEHOMEHT HO.

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BASES 3/4.2.1 LINEAR HEAT RATE The limitation on linear heat rate ensures that in the event of a LOCA, the peak temperature of the fuel cladding will not exceed 2200 F.

Either of the two core power distribution monitoring systems, the Core Operating Limit Supervisory System (COLSS) and the Local Power Oensity channels in the Core Protection Calculators (CPCs), provide adequate monitoring of the core power distribution and are capable of verifying that the linear heat rate does not exceed its limits. The COLSS performs this function by continuously monitoring the core power distribution and calculating a core power operating limit corresponding to the allowable peak linear heat rate. Reactor operation at or below this calculated power level assures that the limits of 13.5 kW/ft are not exceeded.

The COLSS calculated core power and 'the COLSS calculated core power operating limits based on linear heat rate are continuously monitored and displayed to the operator. A COLSS alarm is annunciated in the event that the, core power exceeds the core power operating limit. This provides adequate margin to the linear heat rate operating limit for normal steady-state opera-tion. Normal reactor power transients or equipment failures which do not require a reactor trip may result in this core power operating limit being exceeded. In the event this occurs, COLSS alarms will be annunciated. If the event which causes the COLSS limit to be exceeded results in conditions which approach the core safety limits, a reactor trip will be initiated by the Reactor Protective Instrumentation. The COLSS calculation of the linear heat rate includes appropriate penalty factors which provide, with a 95/95 probability/

confidence level, that the maximum linear heat rate calculated by COLSS is conservative with respect to the actual maximum linear heat rate existing in the core. These penalty factors are determined from the uncertainties associated with planar radial peaking measurement, engineering heat flux uncertainty, axial densification, software algorithm modelling, computer

'rocessing, rod bow, and core power measurement.

Parameters required to maintain the operating limit power level based on linear heat rate, margin to OHB, and total core power are also monitored by the CPCs. Therefore, in the event that the COLSS is not being used, operation within the linear heat. tate limit can be maintained by utilizing any operable CPC channel. The-above listed uncertainty and penalty factors plus those associated with the 'CPC startup test acceptance criteria are also included in the CPCs.

~%5 C PALO YEROE - UNIT 3 B 3/4 2-l AMEHOMEHT HO.

The core power distribution and a corresponding POL based on DNBR are more accurately determined by the COLSS using the incore detector system. The CPCs determine DNBR less accurately with the excore detectors. When COLSS is not available the TS LCOs are more restrictive due to the uncertainty of the CPCs. However, when COLSS becomes inoperable the added margin associated with CPC uncertainty is not immediately required and a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> ACTION is provided for appropriate corrective action.

While operating with the COLSS out of service, the CPC calculated DNBR is monitored at least every 15 minutes to identify any reduction in thermal margin. The increased monitoring of DNBR during the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> ACTION period ensures that adequate safety margin is maintained for anticipated. operational occurrences and no postulated accident results in consequences more severe than those described in Chapter 15 of the UFSAR.

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/TROLLED DOCUMENT'O POQER DISTRIBUTION LIMITS BASES AZIMUTHAL'POWER TILT - T (Continued) q tilt untilt is the ratio of the power at core location a

of tilt to the power at that location with no tilt.

a in 'the presence The AZIMUTHAL POWER TILT allowance used in the CPCs is defined as the value of CPC addressable constant TR-1.0.

3/4. 2.4 DNBR MARGIN The limitation on DNBR as a function of AXIAL SHAPE INDEX represents a conservative envelope of operating conditions consistent with the safety analy-sis assumptions and which have been analytically demonstrated adequate to main-tain an acceptable minimum DNBR throughout all anticipated operational occur-rences. Operation of the core with a DNBR at or above this limit provides assurance that an acceptable minimum DNBR will be maintained in the event of a loss of flow transient.

Either of the two core power distribution monitoring systems, the Core Operating Limit Supervisory System (COLSS) and the DNBR channels in the Core Protection Calculators (CPCs), provide adequate monitoring of the core power distribution and are capable of verifying that the DNBR does not violate its limits. The COLSS performs, this function by continuously monitoring the core power distribution and calculating a core operating limit corresponding to the allowable minimum DNBR. The COLSS calculation of core power operating limit based on DHBR includes appropriate penalty factors which provide, with a 95/95 probability/confidence level, that the core power limits calculated by COLSS (based on the minimum DNBR Limit) are conservative with respect to the actual core power limit. These penalty factors are determined from the uncertainties associated with planar radial peaking measurement, engineering heat flux, state parameter measurement, software algorithm modelling, computer processing, rod bow, and core power measurement.

Parameters required to maintain the margin to DNB and total core power are

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also monitored by the CPCs. Therefore, in the event that the COLSS is not being used, operation within the limits of Figures 3.2-2 and 3.2-2A can be maintained by utilizing a predetermined DNBR as a function of AXIAL SHAPE INDEX and by monitoring the CPC trip channels. The above listed uncertainty and penalty factors are also included in the CPCs which 'assume a minimum core power of 20K of RATED THERMAL POWER. The 20K RATED THERMAL POWER t'hreshold is due to the neutron flux detector system being less accurate below 20K core power.

Core noise level at low power is too large to obtain usable detector readings.

A DNBR penalty factor has been included in the CDLSS and CPC DHBR calcu-lations to accommodate the effects of rod bow. The amount of rod bow in each assembly is dependent upon the average burnup experienced by that assembly.

Fuel assemblies that incur higher average burnup will experience a greater magnitude of rod bow. Conversely, lower burnup assemblies will experience less rod bow. In design calculations, the penalty for each batch required to com-pensate for rod bow is determined from a batch's maximum average assembly burnup applied to the batch's maximum integrated planar-radial power peak. A single net penalty for COLSS and CPC is then determined from the penalties associated with each batch, accounting for the offsetting margins due to the lower radial power peaks in the higher burnup batches.

PALO VERDE " UNIT 1 B 3/4 2-3 AMENDMENT NO. 24

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GNTRQ'" D DQCUM2" POWER DISTRIBUTION LIMITS BASES AZIMUTHAL POWER TILT - T (Continued)

Pt.lt/Pnt.l is the ratio of the power at a core location in the presence of a tilt to the power at that location with no tilt.

The AZIMUTHAL POWER TILT allowance used in the CPCs is defined as the value of CPC addressable constant TR-1.0.

3/4. 2. 4 DNBR MARGIN The limitation on DNBR as a function of AXIAL SHAPE INDEX represents a

- conservative envelope of operating conditions consistent with the safety analy-sis assumptions and which have been analytically demonstrated adequate to main-tain an acceptable minimum DNBR throughout all anticipated operational occur-rences. Operation of the core with a DNBR at or above this limit provides assurance that an acceptable minimum DNBR will be maintained in the event of a loss of flow transient.

Either of the two core power distribution monitoring systems, the Core Operating Limit Supervisory System (COLSS) and the DNBR channels in the Core Protection Calculators (CPCs), provide adequate monitoring of the. core power distribution and are capable of verifying that the DNBR does not violate its limits. The COLSS performs this function by continuously monitoring the core power distribution and calculating a core operating limit corresponding to the allowable minimum DNBR. The COLSS calculation of core power operating limit based on DNBR includes appropriate penalty factors which provide, with a 95/95 probability/confidence level, that the core power limits calculated by COLSS (based on the minimum DNBR Limit) is conservative with respect to the actual core power limit. These penalty factors are determined from the uncertainties associated with planar radial peaking measurement, engineering heat flux, state parameter measurement, software algorithm modelling, computer processing, rod bow, and core power measurement.

Parameters required to maintain the margin to DNB and total core power are also monitored by the CPCs. Therefore, in the event that the COLSS is not being used, operation within the limits of Figures 3.2-2 and 3.2-2A can be maintained by utilizing a pr edetermined DNBR as a function of AXIAL SHAPE INDEX and by monitoring the CPC trip channels. The above listed uncertainty and penalty factors are also included in the CPCs which assume a minimum core power of 20M of RATED THERMAL POWER. The 20~ RATED THERMAL POWER threshold is due to the neutron flux detector system being less accurate below ZOX core po~er.

~g'dry- Core noise leuel at low power is too large to obtain usable detector readings.

Ly A ONHR penalty factor has been included in the COLSS and CPC ORBR calcula-tions to accommodate the effects of rod bow. The amount of rod bow in each assembly is dependent upon the average burnup experienced by that assembly. .Fuel assemblies that incur higher average burnup will experience a greater magnitude of rod bow. Conversely, lower burnup assemblies will experience less rod bow. In design calculations, the penalty for each batch required to compensate for rod  !

bow is determined from a batch's maximum average assembly burnup applied to the batch's maximum integrated planar-radial power peak. A single net penalty for COLSS and CPC is then determined from the penalties associated with each batch, accounting for the offsetting margins due to the lower radial power peaks in the higher burnup batches.

PALO VERDE - UNIT 2 B 3/4 2-3 AMENDMENT NO. 19

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POWER OI STR I BUTI0 MITS BASES AZIMUTHAL POWER TILT - T (Continued)

Ptilt/Puntilt >s the ratio of the power at a core location in the presence o f a ti t 1 to .the power at that 1 ocati on wi th no ti t.

1 The AZIMUTHAL POMER TILT allowance used in the CPCs is defined as the value of CPC addressable constant TR-1.0.

3/4.2.4 DNBR MARGIN The limitation on DNBR as a function of AXIAL SHAPE INOEX represents a conservative envelope of operating conditions consistent with the safety analy-sis assumptions which have been analytically demonstrated adequate to main-tain, an acceptable minimum ONBR throughout all anticipated operational occur-rences. Operation of the core with a DNBR at or above this limit provides assurance that an acceptable minimum ONBR will be maintained in the event of a loss of flow transient.

&ther of the two more power distribution monitoring systems, the Core Operating Limit Supervisory System (COLSS) and the OHBR channels in the Core Protection Calculators (CPCs), provide adequate monitoring of the core, power distribution and are capable of verifying that the OHBR does not violate its

'limits. The COLSS performs this function by continuously monitoring the core power distribution and calculating a core operating limit corresponding to the allowable minimum OHBR. The COLSS calculation of core power operating limit based on ONBR includes appropriate penalty factors which provide, with a 95/S5 probability/confidence level, that the core power limits calculated by COLSS (based on the minimum ONBR Limit) are conservative with respect to the actual core power limit. These penalty factors are determined from the uncertainties associated with planar radial peaking measurement, engineering heat flux, state parameter measurement, software algorithm modelling, computer processing, rod bow, and core power measurement.

Parameters required to maintain the margin to DHB and total core power are also monitored by the CPCs. Therefore, in the event that the COLSS is not being used, operation within the limits of Figures 3.2-2 and 3.2.2a can be maintained by utilizing a predetermined DNBR as a function of AXIAL SHAPE INDEX and by monitoring the CPC trip channels. The above listed uncertainty and penalty factors are also included in the CPCs which assume a minimum core power of 20K of RATED THERMAL POMER. The 20K RATED THERMAL POMER threshold is due to the neutron flux detector system being less accurate below 20K core power.

Core noise level at low power is too large to obtain usable detector readings.

A NBR penalty factor'has been included in the COLSS and CPC ONBR calcula-tions to accommodate the effects of rod bow. The amount of rod bow in each assembly is dependent upon the average burnup experienced by that assembly.

Fuel assemblies that incur higher average burnup will experience a greater magnitude of rod bow. Conversely, lower burnup assemblies will experience less rod bow. In design calculations, the penalty for each batch required to com-pensate for rod bow is determined from a batch's maximum average assembly burnup applied to the batch's maximum integrated planar radial power peak. A single net penalty for COLSS and CPC is then determined from the penalties associated with each batch, accounting for the offsetting margins due to the lower radial power peaks in the higher bur nup batches.

PALO VERDE - UNIT 3 B 3/4 2-3 AMEHOMEHT HO. IB

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