ML20236N602

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Responds to 980203 Memo Requesting Assistance in Responding to Operator License Appeal.Ts Branch Concurred in Interpretation
ML20236N602
Person / Time
Site: Sequoyah  Tennessee Valley Authority icon.png
Issue date: 02/25/1998
From: Hebdon F
NRC (Affiliation Not Assigned)
To: Gallo R
NRC (Affiliation Not Assigned)
Shared Package
ML20236J990 List: ... further results
References
FOIA-98-155, RTR-NUREG-1431 NUDOCS 9807150193
Download: ML20236N602 (4)
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i, i , 0-/3 H /b February 25, 1998 MEMORANDUM TO. Robert M. Gallo, Chief Operator Licensing Branch Division of Reactor Controls and Human Factors Omce of Nuclear Reactor Regulation FROM: Frederick J. Hebdon, Director Project Directorate ll-3 Division of Reactor Project - 1/II ,

Office of Nuclear Reactor Regulation l

SUBJECT:

TECHNICAL SPECIFICATION INTERPRETATION - SEQUOYAH This responds to your memorandum dated February 3,1998, requesting assistance in l responding to an operator license appeal. The questions in the attachment to your memo I regarding interpretation of a reactor coolant system boration Technical Specification (TS) at the Sequoyah Nuclear Plant are answered in the attachment to this memo.

Our interpretation of how much time is reasonable to "immediately initiate ... boration" in the event of inadequate margin is 15 minutes, based primarily on the position taken for this event in j the Westinghouse Standard Technical Specifications (NUREG-1431) but also considering the low probability of a Main Steamline Break Accident (the basis for the shutdown margin requirement) at a time when shutdown margin is below that required by the TS. The Technical Specifications Branch has concurred in this interpretation.

Docket Nos. 50-327, 50-328 l

Attachment:

As stated Distnbution-Docket File  !

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DOCUMENT NAME: G:\SQN\gallores. app To receive a copy of this document. Indicate in the box C=Oopy w/o attachment / enclosure E= Copy with attachment / enclosure N = No copy OFFIC PM:PD2- E LAPD2-3 E BC:TSB E D:PD2-3 E E

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% ,,,,, # February 25, 1998 l MEMORANDUM TO: Robert M. Gallo, Chief Operator Licensing Branch Division of Reactor Controls  !

and Human Factors Office of Nuclear Reactor Regulation 1

FROM: Frederick J. Hebdon, Director Q -

l Project Directorate ll-3 y -

l Division of Reactor Project - t/II I Office of Nuclear Reactor Regulation

SUBJECT:

TECHNICAL SPECIFICATION INTERPRETATION - SEQUOYAH j This responds to your memorandum dated February 3,1998, requesting assistance in responding to an operator license appeal. The questions in the attachment to your memo regarding interpretation of a reactor coolant system boration Technical Specification (TS) at the Sequoyah Nuclear Plant are answered in the attachment to this memo.

Our interpretation of how much tirne is reasonable to "immediately initiate ... boration" in the event of inadequate margin is 15 minutes, based primarily on the position taken for this event in the Westinghouse Standard Technical Specifications (NUREG-1431) but also considering the low probability of a Main Steamline Break Accident (the basis for the shutdown margin requirement) at a time when shutdown margin is below that required by the TS. The Technical Specifications Branch has concurred in this interpretation.

Docket Nos. 50-327,50-328

Attachment:

As stated l

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o SPECIFIC QUESTIONS

1. Doen o failu o to satisfy Sequoyah T.S. SURVEILLANCE REQUIREMENT 4.1.1.1.ti).b. require the licensee to take the action required by T.S. 3.1.1.1 ACTION STATEMENT. that action is to immediately initiate boration?

Answer: Yes, the TS would require "immediate" initiation of boration in that event.

However, the TS simplistically assumes that, if control rod bank position is below ,

the rod insertion limit (RIL) curves in the COLR, shutdown margin has dropped l to less than the required 1.6% ak/k. There is margin between control rod l position dropping below the Rll curves and shutdown margin dropping below l l

1.6% ak/k. The surveillance uses rod position to determine that required l l shutdown margin is met because it is simpler than performing a calculation every i 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

I The term immediate is not defined in the Sequoyah TS. The Westinghouse l l Revised Standard TS (NUREG-1431) states that "when 'immediately' is used as l a completion time, the Required Action should be pursued without delay and in a l controlled manner." At Sequoyah, operators are mandated to use the " STAR" j philosophy, that is Stop,Ihink,6ct, and Beview. Also, the alarm response l procedure for a Low-Low Rod insertion Alarm is not required to be committed to i l memory, in fact, operators are trained to read and make sure they understand the procedure hafore taking any action. Furthermore, the corresponding TS (Shutdown Margin) in NUREG-1431 allows 15 minutes for the operator to j commence boration in this event. - I

2. Does a failure to satisfy Sequoyah T.S. SURVEILLANCE REQUIREMENT l 4.1.1.1.[1].b require the licensee to take the action required by T.S. 3.1.3.6.

ACTION STATEMENT- that action is to restore the control banks to within the limits (of the COLR) within two hours.

Answer- Yes, both TS are related to maintaining adequate shutdown margin and are therefore related to control rod bank position complying with the limits in the COLR. Failure of surveillance requirement 4.1.1.1.1.b (i.e. rod position not within the COLR limits) would require implementation of one of the TS 3.1.3.6 action statements (i.e., restore control rod position within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, reduce reactor power to below that for the existing control rod position on the RiL curve within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, or be in hot standby within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />).

3. If the licensee concludes that T.S. SURVEILLANCE REQUIREMENT 4.1.1.1.[1].b is l not met, and that boration is necessary to restore SHUTDOWN MARGIN, how does the NRC interpret the action statement to "immediately initiate" boration?

How much time is considered acceptable to "lNITIATE" the boration?

Answer: As discussed above, the staff has taken the position in NUREG-1431 that, for I this event,15 minutes is a reasonable time to initiate boration.

r ATTACHMENT l

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4. Is it a correct Technical Specification interpretation that the licensea must begin boration immediately (T.S. 3.1.1.11 and has 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> to restore the control rod banks to the COLR limits within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />?

l Answer. The only interpretation invobed here is what is a reasonable time fiume associated with the word "imenediate." Even using the definition cor.tained in NUREG-1431, the elapsed tiras between symptom and action is not ..learly .

defined but depends on the es ent, the complexity of the procedure goveming the action and the complexity of tha action itself. For example, actions takin solely by control room operators woukt be expected to bis more timely than those taken by personnel outside the control room, such as auxiliary operators, beca1se of the required communications and coordination.

l l 5. The above questions address the apparent difference between the requirements of T.S. 3.1.1.1. and 3.1.3.6. Both T.S. focus on the control bank position. T.S.

l 3.1.1.1. specifies that the control bank position outside the COLR limits requireo l Immediate action. T.S. 3.1.3.6 specifies that the control bank outside of the

COLR limit requires actions to restore control rods to within liraits within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.

Answer. Although the two TS would appear to be inconsistent, TS 3.1.1.1 is intended to cover a wider range of events, including an inadvertent boron dilution event as l well as shutdown margin reduction due to control rod insertion. The Sequoyah TS are more conservative than NUREG-1431 in two ways:

1) The Sequoyah TS surveillance for shutdown margin is every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />; the NUREG-1431 surveillance frequency is every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> ' based on the generally slow [ rate of] change in required boron concentration and the low  ;

l probability of an accident occurring without the required SDM."  !

1 l 2) The Sequoyah TS requires boration to comrnonce immediately; NUREG-1431 allows 15 minutes. I As discussed above, shutdown margin can be dete' mined by calculation at power or shut down. At power, it is more convenient to determine that shutdown margin is met by observing control rod bank position than to perform calculations. It is a fact that, if control rods are above the insertion limits, shutdown margin requirements are met. But is not necessarily true that, if rod insertion limits are not met, shutdown margin is less tha'i that required by TS.

With the plant shut down, shutdown margin must be determined by calculation, taking into consideration RCS boron concentration, control bank position, RCS temperature, fuel bumup, xenon and samarium concentration, and isothermal temperature coefficient.

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