ML20010F457

Proposed Revisions to Tech Specs 3.3,4.3,3.11C & Table 3.11-2 Re Scram Insertion Times,Control Rod Accumulators & Min Critical Power Ratio

ML20010F457
Person / Time
Site:	Vermont Yankee
Issue date:	09/02/1981
From:	VERMONT YANKEE NUCLEAR POWER CORP.
To:
Shared Package
ML20010F453	List: ML20010F452 ML20010F457 ML20010F459
References
NUDOCS 8109100231
Download: ML20010F457 (6)

Text

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At t ach me n t 1

'@$20 Description of Proposed Changes to Technical Specifica tior..

43 kw OO 00 Reason for Change OM S7ction/ Location Ch ange 70-g uo) gg1) Table 3.11-2, p. 180-01 Change MCPR operating limits per Per licensing analysis results using Vermont 0,o a ttached changed page. Yankee methods.

"D M O ONM m-

2) Bases 3.11.C.1, p. 180-h Replace current wording with the The current words refer to a GE licensing following: "The MCPR Opera ting Limit is topical report. The proposed wording is a a cycle dependent parameter which can be more general description of the basis for determined for a number of different determining the MCPR operating limit, and combina tions of operating modes, initial thus does not conflict with the use of VY conditions, and cycle exposures in order me thod s to determine the limit.

to provide reasonable assurance against exceeding the fuel cladding integrity safety limit (FCISL) for potential abnormal occurrences. The MCPR Operating Limits are presented in Appendix A of the current cycle's Core Performance Analysis report.

3) L.C.O. 3.3C, pp. 72, Reduce control rod scram times. To provide additional MCPR margin to limits i /2a and 73 under EOC operating condtions where the MCPR l opera ting limit is set by the limiting overpressurization transient.

4) Bases 3.3B.4, p. 76 Remove reference to NEDE-24011P-A and Consistent with change to Vernont Yankee replace with reference to Vermont Yankee methods and documentation of analysis results.

Core Performance Analysis report.

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VYNPS 5.3 LIMITING CONDITIONS FOR OPERATION 4.3 SURVEILLANCE REQUIREMENTS C. Scram Insertion Times C. Scram Insertion Times 1.1 The average scram time, based on the 1. After refueling outage at.o pMor to operation de-energization of the scram pilot above 30% power with reactor pressure above valve solenoids of all operable control 800 psig all control rods shall be subject to rods in the reactor power operation scram-time measurements f rom the full.y condition shall be no greater than: withdrawn position. The scram times for single rod scram testing shall be measured without Drop-Out of %In.serted From Avg. Scram Insertion reliance on the control rod drive pumps.

Position Fully Withdrawn Time (sec)

2. During or following a controlled shutdown of the 46 4.51 0.358 reactor, but not more frequently than 16 weeks 36 25.34 0.912 nor less frequently than 32 weeks intervals, 26 46.18 1.468 50% control rod drives in each quadrant of 06 87.84 2.686 the reactor core shall be measured for scram times specified in Specification 3.3.C. All The average of the scram insertion times control rod drives shall have experienced for the three fastest control rods of all scram-time measurements each year. Whenever '

groups of four control rods in a two by 50% of the control rod drives scram times have two array shall be no greater than: been measured, an evaluation shall be made to provide reasonable assurance that proper Drop-Out of % Inserted From Avg. Scram Insertion control rod drives performance is being Position Fully Withdrawn Time (sec) maintained. The results of measurements per-formed on the control rod drives chall be 46 4.51 0.379 submitted in the start up test report.

36 25.34 0.967 26 46.18 1.556 06 87.84 2.848 1

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VYNPS 3.3 LIMITING CONDITIONS FOR OPERATION 4.3 SURVEILLANCE REQUIREMENTS 1.2 If Specification 3.3.C.l.1 cannot be met, the average scram time, based on the de-energization of the scram pilot valve solenoids of all operable control rods in the reactor power operation condition shall be no greater than:

Drop-Out of % Inserted From Avg. Scram Insertion Position Fully Withdrawn Time (sec) 46 4.51 .358 36 25.34 1.096 26 46.18 1.860 06 87.84 3.419 The average of the scram insertion times for the three fastest control rods of all groups of four control rods in a two by

two array shall be no greater than

Drop-Out of % Inserted From Avg. Scram Insertion

! Position Fully Withdrawn Time (sec)

• 46 4.51 .379 36 25.34 1.164 l

26 46.18 1.971 l 06 87.84 3.624 t

j 2. The maximum scram insertion time for 90%

! insertion of any operable control rod shall I

not exceed-7.00 seconds.

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i VYNPS l '3.3 -LIMITING CONLITIONS FOR OPERATION 4.3 SURVEILLANCE REQUIREMENTS l ]3. If ' Specification ').3.C.1.2 cannot be m:t.,

i the reactor shall not be made super-l critical; if operating, the reactor

.shall be shut down immediately upon i determination that average scram time is deficient.

4. If Specification 3.3.C.2 cannot be j met, the deficient' control rod shall j be considered inoperable, fully

inserted into the core, and

electrically disarmed.

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j D. Control Rod Accumulators D. Control Rod Accumulators -

l At all reactor operating pressures, a rod Once a shift check the status of the pressure i accumulator. may be inoperable provided that no and level alarms for each accumulator, j other control rod in the nine-rod square array 1

around this rod has a:

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i i '73 j.

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VYNPS 3.3 (cont 'd)

B. Control Rods

1. Control rod dropout accidents as discussed in the FSAR can lead to signif cant core damage. If coupling integrity is maintained, the possiblity of a rod dropout accident is eliminated. The overtravel position feature pr vides a positive check as only uncoupled drives may reach this position. Neutron instrumentation response to rod movement provides a verification that the rod is following its drive.

2. The control rod housing support restricts the outward movement of a control rod to less than 3 inches in the extremely remote event of a housing failure. The amount of reactivity which could be added by this small amount of rod withdrawal, which is less than a normal single withdrawal increment, will not contribute to any damage of the primary coolant system. The design basis .ven in Subsection 3.5.2 of the FSAR, and the design evaluation is given in Subsection 3.5.4. This auE . is not required if the reactor coolant system is at atmospheric pressure since there would then be no driving force to rapidly eject a drivu housing.

3. In the course of performing normal startup and shutdown procedures, a pre-specified sequence for the withdrawal or insertion of control rods is followed. Control rod dropout accidents which might lead to significant core damage, ca inot occur if this sequence of rod withdrawals or insertions is followed. The Rod Worth Minimizer restric;s withdrawals and insertions to those listed in the pre-specified sequence and provides an additional check that the reactor operator is following prescribed sequence. Although beginning a rasc*or startup without having the RWM operable would entail unnecessary risk, continuing to withdra:r rods RWM fails subsequently if a second licensed operator verifies the withdrawal sequence. Continuing L... startup increases core power, reduces the rod worth and reduces tl.e consequences of dropping any rod.

Withdrawal of rods for testing is permitted with the RWM inoperable, if the reactor is subcritf. cal and all other rods are fully inserted. Above 20% power, the RWM is not needed since even with a single error an operator cannot withdraw a rod with suf ficient 'iorth, which if dec pped, would result in anything but minor cons eque nce s.

4. Refer to the Vermont Yankee Core Performance Analysis report.

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VYNPS Table 3.11-2 MCPR Operating Limits MCPR Operating Limit for

! Value of "N" in RBM Average Control Rod Cycle Fuel Type (2)

Equa t ion (1) Scram Time Exposure Range 8X8 8X8R P8X8R 42% Equal or better BOC to EOC-2 GWD/T 1.29 1.29 1.29 1 than L.C.O. EOC-2 GWD/T to EOC-1 GWD/T 1.29 1.29 1.29 3.3 C.1.1 EOC-1 GWD/T to EOC 1.29 1.29 1.29 Equal or better BOC to EOC-2 GWD/T 1.29 1.29 1.29

, th an L.C.O. EOC-2 GWD/T to 20C-1 GWD/T 1.30 1.30 1.30

3.3 C.1.2 ~

EOC-1 GWD/T to EOC 1.33 1.32 1.32 41% Equal or better BOC to EOC-2 GWD/T 1.25 1.25 1.25 than L.C.O. EOC-2 GWD/T to EOC-1 GWD/T 1.25 1.25 1.25 3.3 C.1.1 EOC-1 GWD/T to EOC 1.27 1.27 1.27

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Equal or better BOC to EOC-2 GWD/T 1.25 1.25 1.25 th an L.C.O. EOC-2 GWD/T to EOC-1 GWD/T 1.30 1.30 1.30 j . 3.3 C.I.2 EOC-1 GWD/T to EOC 1.33 1.32 1.32 .

(40% Equal or better BOC to EOC-2 GWD/T 1.24 1.24 1.24 th an L. C . O . EOC-2 GWD/T to EOC-1 GWD/T 1.24 1.23 1.23

3.3 C.1.1 EOC-1 GWD/T to EOC 1.27 1.27 1.27 .

Equal or better BOC to EOC-2 GWD/T 1.24 1.24 1.24 l than L.C.O. EOC-2 GWD/T to EOC-1 GWD/T 1.30 1.30 1.30 3.3 C.1.2 EOC-1 GWD/T to EOC 1.33 1.32 1.32 4

4 75% Special Testing at Natural Circ nlation (Note 3, 4) 1.30 1.31 1.31

! (1) The Rod Block Monitor (RBM) trip setpoints are determined by the equation shown in Table 3.2.5 of the Technical' Speci fica tions.

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! (2) The current analyses for MCPR Operating Limits do not include 7x7 fuel. On this basis further evaluation of MCPR operating limits is required before 7x7 fuel can be used in Reactor Power Operation.

-(3). For the duration of pump trip and stability testing.

(4) Kf factors are not applied during the pump trip and stability testing.

180-01 4

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. _ _ _ _ . _ _ . . . . _ . _ _ . _ _ _ _ . . __. _. .m Bases:

l 3.11C Minimum Critical Power Ratio (MCPR) j Opera ting Limit MCPR I

l'. The MCPR Operating Limit is a cycle dependent parameter which can be determined for a number of l di fferent combina tions of opera ting modes, initial e -ditions, and cycle exposures in order to i l provede reasonable assurance agains t exceeding the ruel cladding integrit'y safety limit (FCISL) for potential abnormal occurences. The MCPR operating limits' are presented in Appendix A of the current cycle's Core Performance Analysis report.

-2. In order to counteract the postulated thermal margin degradation for the worst-casa Fuel Loading-Error accident, a higher MCPR opt. rating limit is applied to the event air ejector off gas radiation exceeds levels that could be associated with a mis-load fuel assembly.

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f 180-h

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