2CAN088803, Clarifies & Corrects Control Element Assembly Drop Time in 880509 Application for Emergency Tech Spec Change.Info Necessary Due to Complex Analysis Review

Clarifies & Corrects Control Element Assembly Drop Time in 880509 Application for Emergency Tech Spec Change.Info Necessary Due to Complex Analysis Review

ML20151W852
Person / Time
Site:	Arkansas Nuclear
Issue date:	08/15/1988
From:	Howard D ARKANSAS POWER & LIGHT CO.
To:	Calvo J NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM), Office of Nuclear Reactor Regulation
References
2CAN088803, 2CAN88803, NUDOCS 8808250155
Download: ML20151W852 (2)

Text

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A ARKANSAS POWER & LIGHT COMPANY POST OFFICE BOX 551 UTTLE ROCK. ARKANSAS 72203 (501) 377-4000 August 15, 1988 2CAN088803 U. S. Nuclear Regulatory Commission Document Control Desk Mail Station P1-137 Washington, DC 20555 ATTN: Mr. Jose A. Calvo, Director Project Director, Region IV Division of Reactor Projects III, IV, V and Special Projects

SUBJECT:

Arkansas Nuclear One - Unit 2 Docket No. 50-368 License No. NPF-6 Clarification of CEA Drop Time Technical Specification Change Request

Dear Mr. Calvo:

Our letter dated May 9, 1988 (2CAN058802) transmitted a request for an emergency license amendment regarding TS 3.1.3.4, Control Element Assembly (CEA) drop time. Included as part of the amendment request were the results of a review of the ANO-2 SAR Design Basis Accident Analyses to determine the impact of ar, increased CEA drop time. These accident analysis review results were later independently reviewed and verified by AP&L to ensure correctness and clarity in the amendment request; we are now forwarding the findings of this independent review. These findings consist of editorial corrections and clarifications and do not alter the technical statements and conclusions of the amendment request.

The statement on page 8 of 2CAN058802 in the Seized Rotor paragraph (b.) which reads "the revised scram reactivity data . . . at the time of approach to a SAFDL is more conservative than the design data"; should read "is less conservative." This is evident by noting that the time of 3pproach to a Specified Acceptable Fuel Design Limit (SAFDL) of 1.08 seconds is actually just prior to the 1.16 second time when the revised scram reactivity data becomes more conservative (see Table 6 of 2CAN058802). The correction of this statement does not effect the conclusion maoe in the paragraph. The seized rotor analysis described by the paragraph was done at asymptotic flow conditions and is, therefore, insensitive to a small dalay in the CEA drop time. The additional (but necessary to determine the impact of an increased CEA drop time) statement is then made incorrectly that the revised reactivity data is more conservative than the design data. The fact that this latter statement is simply dditional information which does not effect the conclusion can be seen by ex. mining what is meant by the seized rotor analysis being done at asymptotic flow conditions.

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MEMBER MiOOLE SOUTH UToitiES SYSTEM

yy.e August 15, 1988 A qualitative comparison of the "actual DNBR", the calculated design DNBR, and the revised DNBR for an increased CEA drop time for the seized rotor analysis may be derived from Figures 7.2.5-1, core flow vs. time, and 7.2.5-3, core

. heat flux vs. time, from the ANO-2 Cycle 2 Reload Analysis Report (RAR). The shape of the DNBR curve results from the combination of the two dominant DNBR-components, core flow and core average heat flux, vs. time. An initially flat profile for the design and revised DNBR curves results due to the conservative 4

a:sumption that core flow is initially at the three pump flow level while an i "actual DNBR" profile reflects the flow coastdown that actually occurs.

. The conservative assumption that core flow is initially at the three pump flow condition (asymptotic ficw conditions) determines the minimum DN8R value while the core average heat flux vs. time (driven by the CEA drop time) determines the time at which the minimu'n DNBR occurs. Therefore, an increased CEA drop time results in the minimum DNBR occuring later in the transient, but does not effect the minimum DNBR value, which is the criterion of interest.

Other corrections / clarifications from the independent review of 2CAN058802 are identified below (page numbers are from the Description of Amendment Request and Determination of Significant Hazards attachment):

Page 8, Seized Rotor paragraph (b.) - The reference to Table 7.2.5-2 would more appropriately be Table 7.2.5-1 since this table contains the analysis assumptions.

Page 24 Table 9 - The column heading "Time to Closest Approach to a SAFDL" would more appropriately read "Time to Closest Approach to a safety Limit."

Other corrections / clarifications to Page 24, Table 9:

Uncontrolled CEA Withdrawal - 1% Power reference (Figures 1 & 2) should be just (Figure 1) and 100% Power should have (Figure 2) as a reference.

Loss of Condenser Vacuum - Reference time should be 2.6 seconds, not 2.3 seconds, to be consistent with comments on page 10.

Asymmetric Steam Generator Transient reference time should be 2.3 seconds, not 2.1 seconds, to be consistent with comments on page 13.

Note 3, Page 25 - Second sentence should have ~ 1.08 seconds as time to reach minimum DNBR, not ~ .95 seconds.

Note 4, Page 25 - First sentence should read "The closest approach to the peak RCS pressure safety limit...", not SAFDL.

These corrections / clarifications were necessary due to tne complex nature of the required analysis review, coupled with the limited time available to edit the text for consistency. As stated j eviously, they do not ef fect the technical statements or conslusions of the amendment request, but are being forwarded to document and assure the accuracy of our TS change submittal.

Very truly yours, s

Dan R. Howard Manager, Licensing DRH:RBT

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