ML20058M202

Proposed Tech Specs Revising TS 3/4.2.3, Azimuthal Power Tilt, Action Statements & Bases

ML20058M202
Person / Time
Site:	Waterford
Issue date:	12/14/1993
From:	ENTERGY OPERATIONS, INC.
To:
Shared Package
ML20058M195	List: ML20058M191 ML20058M202
References
NUDOCS 9312200194
Download: ML20058M202 (7)

Text

O NPF-38-147 ATTACHMENT A 1

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,f 9312200194 931214 PDR ADOCK 05000382 P PDR x

i POWER DISTRIBUTION LIMITS 3/4.2.3 AZIMUTHAL POWER TILT - Tq l

LIMITING CONDITION FOR OPERATION l 3.2.3 The AZIMUTHAL POWER TILT (T ) shall be less than or equal to the AZIMUTHAL q

POWER TILT Allowance used in the Core Protection Calculators (CPCs). ],

APPLICABILITY: MODE 1 above 20% of RATED THERMAL POWER.* j ACTION: ,

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a. With the measured AZIMUTHAL POWER TILT determined to exceed the J AZIMUTHAL POWER TILT Allowance used in the CPCs but less than or equal ,

to 0.10, within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> either correct the power tilt or adjust the  ;

AZIMUTHAL POWER TILT Allowance used in the CPCs to greater than or equal to the measured value.

b. With the measured AZIMUTHAL POWER TILT determined to exceed 0.10: j

1. Due to misalignment of either a part length or full length CEA, I within 30 minutes verify that the Core Operating Limit Supervisory System (COLSS) (when.COLSS is being used to monitor the core power distribution per Specifications 4.2.1.2 and 4.2.4.2) is detecting the CEA misalignment.

2. Verify that the AZIMUTHAL POWER TILT is within its ' limit within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> after exceeding the limit or reduce THERMAL POWER to less than 50% of RATED THERMAL POWER within the next 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and reduce the Linear Power Level - High trip setpoints to less than or equal to 55% of RATED THERMAL POWER within the next 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

3. Identify and correct the cause of the out of limit condition prior to increasing THERMAL POWER; subsequent POWER OPERATION above 50% of RATED THERMAL POWER may proceed provided that the AZIMUTHAL POWER TILT is verified within its limit at least once per hour for 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> or-until verified acceptable at- ,

95% or greater RATED THERMAL POWER. j i

A See Special Test Exception 3.10.2.

9 WATERFORD - UNIT 3 3/4 2-4

1 POWER DISTRIBUTION LIMITS l

BASES l .

3/4.2.2 PLANAR RADIAL PEAKING FACTORS Limiting the values of the PLANAR RADIAL PEAKING FACTORS (Fc ) used'in the l

l COLSS and CPCs to galues equal to or greater than'the measured PLANAR RADIAL-PEAKING FACTORS (Fxy) provides assurance that the limits calculated by COLSS' and the CPCs remain valid. Data from the incore detectors are used for t

4 determining the measured PLANAR RADIAL PEAKING FACTORS.- A minimum core power at 20% of RATED THERMAL' POWER is assumed in detarmining the PLANAR RADIAL-PEAKING FACTORS.

flux detector system The 20%inaccurate being RATED THERMAL below 20% POWER threshold is due to the. neutron core power. Core noise level at low power is too large to obtain usable detector readings. The periodic )

Surveillance Requirements for determining the measured' PLANAR RADIAL PEAKING FACTORS provide assurance that the PLANAR RADIAL PEAKING FACTORS used in )

COLSS and the CPCs remain valid throughout the fuel cycle.-' Determining the measured PLANAR RADIAL PEAKING FACTORS after each fuel loading prior to exceeding 70% of RATED THEJtMAL POWER provides additional assurance that the e

core was properly loaded.

3/4.2.3 . AZIMUTHAL POWER TILT - Tq The limitations on the AZIMUTHAL POWER TILT. are provided to ensure that design safety margins are maintained. An AZIMUTHAL POWER TILT greater than- I.

0.10 is not expected and if it should occur, operation is restricted to only those conditions required to identify the cause of ~ the tilt. The tilt is normally calculated by COLSS. A minimum core power of 20% of RATED THERMAL 4

POWER is assumed by the CPCs in its input to COLSS for calculation of AZIMUTHAL POWER TILT.

The 20% RATED THERMAL POWER threshold is due to the

neutron flux detector system being inaccurate below 20% core power. Core noise level at low power is too large to obtain usable detector readings. The Surveillance Requirements specified when COLSS is out of service provide an- )

acceptable means of detecting the presence of a steady-state tilt. It is necessary to explicitly account for power asymmetries because the radial peaking factors used in the core power distribution calculations are based on an untilted power distribution.

AZIMUTHAL POWER TILT is measured by assuming that the ratio of the power  !

at any core location in the presence of a tilt to the untilted power at the-location is of the form:

P /P +T q g cos (0 - 0,)

tilt untilt where:

T q is the peak fractional tilt amplitude at the core periphery gistheradialnormaliiingfactor e is the azimuthal core location 0, is the azimuthal core location of maximum tilt '

I WATERFORD - tlNIT 3 8 3/4 2-2 ,

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ATTACHMENT B ,

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POWER DISTRIBUTION LIMITS 3/4.2.3 AZIMUTHAL POWER TILT -T q LIMITING CONDITION FOR OPERATION 3.2.3 The AZIMUTHAL POWER TILT (Tq ) shall be less than or equal to the FOLLOWING LIMITS:

l a, AZIMUTHAL POWER TILT Allowance used in the Core Protection i Calculators (CPCs), and ,

l l b. 0.03 (3%). l l ,

APPLICABILITY: MODE 1 above 20% of RATED THERMAL POWER.*

ACTION:

a. With the measured AZIMUTHAL POWER TILT determined to exceed the j i

AZIMUTHAL POWER TILT Allowance used in the CPCs but lez than or equal to 0.10. within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> either correct the power tilt or  ;

adjust the AZIMUTHAL POWER TILT Allowance used in the CPCs to  !

greater than or equal to the measured value.

b. With the measured AZIMUTHAL POWER TILT determined to exceed 0.03: l i

1. Due to misalignment of either a part length or full length CEA. within 30 minutes verify that the Core Operating Limit i Supervisory System (COLSS) (when COLSS is being used to monitor the core power distribution per Specifications 4.2.1.2 and 4.2.4.2) is detecting the CEA misalignment.

2. Verify that the AZIMUTHAL POWER TILT is within its limit within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> (24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> for a CEA misalignment event) after exceed 4ng the Sw4t or reduce THERMAL POWER to less than 50% of RATED THERMAL POWER within the next 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and reduce the Linear Power Level - high trip setpoints to less than or equal to 55% of RATED THERMAL POWER within the next 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

3. Identify and correct the cause of the out of limit condition prior to increasing THERMAL POWER: subsequent POWER OPERATION above 50% of RATED THERMAL POWER may proceed provided that the AZIMUTHAL POWER TILT is verified within i its limit at least once per hour for 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> or until verified acceptable at 95% or greater RATED THERMAL POWER.

• See Special Test Exception 3.10.2.

WATERFORD - UNIT 3 3/4 2-4

POWER DISTRIBUTION LIMITS

, BASES 1

l 3/4.2.2 PLANAR RADIAL PEAKING FACTORS l Limiting the values of the PLANAR RADIAL PEAKING FACTORS (fcxy) used in the COLSS and CPCs to values equal to or greater than the measured PLANAR RADIAL PEAKING FACTORS (Fm y) provides assurance that the limits calculated by COLSS and the CPCs remain valid. Data from the incore detectors are used for determining the measured PLANAR RADIAL PEAKING FACTORS A minimum core power at 20% of RATED THERMAL POWER is assumed in determining the PLANAR RADIAL i PEAKING FACTORS. The 20% RATED THERMAL POWER threshold is due to the neutron flux detector l system being inaccurate below 20% core power. Core noise level at low power is too large to obtain usable detector readings. The periodic Surveillance Requirements for detemining the measured PLANAR RADIAL PEAKING FACTORS provide assurance that the PLANAR RADIAL PEAKING FACTORS used in COLSS and the CPCs remain valid throughout the fuel cycle. Determining the measured PLANAR RADIAL PEAKING FACTORS af ter each fuel loading prior to exceeding 70% of RATED THERMAL POWER provides additional assurance that the core was properly loaded.

3/4.2.3 AZIMUTHAL POWER TILT - T ThelimitationsontheAZIMhHALPOWERTILTareprovidedtoensurethatdesignsafety margins are maintained. The LC0 places a 3t limit on the maximum azimuthal tilt during normal steady state power operation. With An AZIMUTHAL POWER TILT greater than 3% 0-10-i+

nct 0:pected and " it should occur operation is restricted to only those conditions required to identify the cause of the tilt. However. Action item b.2 allows 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to restore the tilt to less than 3% following a CEA misalignment event (i.e., CEA drop). A CEA misalignment event causes an asymetric core power generation and an increase in xenon concentration in the vicinity of the dropped rod. This event may cause the azimuthal tilt to exceed 3%. The 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> action time to reduce core power is not sufficient to recover from the xenon transient. The 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period allows for correction of the misaligned CEA and allows time for the xenon redistribution effects to dampen out due to radioactive decay and absorption. The reduction in xenon concentration (which is aided by operation at full power) will in turn reduce the tilt below the 3t limit.

The 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period is applicable only to a CEA misalignment where the cause of the tilt has been identified. It is based on the time required for the expected xenon transient to dampen out. All other conditions (not due to a CEA misalignment) where the azimuthal tilt exceeds 3% require action within the specified 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.

The tilt is normally calculated by COLSS. A minimum core power of 20% of RATED THERMAL POWER is assumed by the CPCs in its input to COLSS for calculation of AZIMUTHAL POWER TILT.

The 20% RATED THERMAL POWER threshold is due to the neutron flux detector system being inaccurate below 20% core power. Core noise level at low power is too large to obtain usable detector readings. The Surveillance Requirements specified when COLSS is out of - service provide an acceptable means of detecting the presence of a steady-state tilt. It is necessary to explicitly account for power asymmetries in the COLSS and CPCs because the l radial peaking factors used in the core power distribution calculations are based on an untilted power distribution.

WATERFORD - UNIT 3 B 3/4 2-2

POWER DISTRIBUTION LIMITS ,

I BASES AZIMUTHAL POWER TILT - Tq (Continued)

AZIHLfTHAL POWER TILT is measured by assuming that the ratio of the power at any core location in the presence of a tilt to the untilted power at the location is of the form: i I

Pg /PuM -1+T q g cos (0 - O )

g where:

Tq is the peak fractional tilt amplitude at the core periphery 9 is the radial normalizing factor e is the azimuthal cor; ioc3 tion l

Gois the azimuthal core location of maximum tilt Ptilt untilt 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. l 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 analysis assumptions and which J have been analytically demonstrated adequate to maintain an acceptable minimum DNBR ,

throughout all anticipated operational occurrences. Operation of the core with a DNBR at or '

above this limit provides assurance that an acceptable minimum DNBR will be maintained. l Either of the two core power distribution monitoring systems. the Core _0perating Limit l' Supervisory System (COLSS) and the DNBR channels in the Core Protection Calculators (CPCs).

provides adequate monitoring of the core power distribution and is 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  ;

the minimum DNBR limit includes appropriate penalty factors which provide a 95/95 i probability / confidence level that the core power calculated by COLSS. based on the minimum j DNBR limit. is conservative with respect to the actual core power limit. These penalty '

factors are determined from the uncer- tainties associated with planar radial peaking measurements. 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 Figure 3.2.2 or Figure 3.2-3 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 plus those associated with startup test acceptance criteria are also included in the CPCs which assume a minimum core power of 20% of RATED THERMAL POWER. The 20% RATED THERMAL POWER threshold is due to the neutron flux detector system being inaccurate below 20% core power. Core noise level at low power is too large to obtain usable detector readings.

WATERFORD - UNIT 3 B 3/4 2-2 AHENDHENT 12

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