ML20207J842

Provides Addl Info Re Interchannel Comparison Criteria of Plant Spds,Per 880810 Conference Call & License Condition 2.C.(7).b

ML20207J842
Person / Time
Site:	Vogtle
Issue date:	09/20/1988
From:	Hairston W GEORGIA POWER CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
VL-83, NUDOCS 8809280142
Download: ML20207J842 (2)

Text

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Georg a Fbwer Cwpaw 333 Piedmort Aanve Atlanta, Geor;+a 30308

. . Wechone 404 526 6526 l

Ma t>rs A$ dress-Tbst Office Boa 4545 Avanta Gaorya 30302 l

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YL-83 0048e File No.: X7GJ17-V720 September 20, 1988 l

U. S. Nuclear Regulatory Commission t

^

ATTN: Document Control Desk i

Washington, D. C. 20555 i

PLANT V0GTLE - UNIT 1 NRC DOCKET 50-424 i OPERATING LICENSE NPF-68 i LICENSE CONDITION 2.C.(7).b SAFETY PARAMETER DISPLAY SYSTEM  ;

, Gentlemen: i l This letter documents information provided by Georgia Power Company  !

(GPC) to the NRC in a conference call on August 10, 1988. The subject of l the conference call was GPC's February 29, 1988 letter concerning the Yogtle Safety Paraseter Display System (SPDS), which was submitted l purt9 ant to License Condition 2.C.(7).b. NRC staf f members requested additional information with respect to interchannel comparison criteria I

, and GPC provided the following resoonse -

1 l Open Item (SSER 6, Section 18.2)  :

l  !

l "Establish and implement realistic rather than arbitrary criteria for l interchannel comparison of redundant inputs. These values must be l appropriate both for adverse and normal operating conditions, and must be I based on instrument loop accuracies."

Responsel .

CPC has established and implemented interchannel comparison criteria  :

based on expected individual instrument loop accuracies. I These accuracies are based on design performance under a nornal operating l L

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880928o142 880920 l $DR ADOCK 0500o424 ,

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( cogia Poner V. S. Nuclear Regulatory Co? mission 1 September 20, 1988 Page Two envi rorynent. While adverse operating conditions (containment pressure or radiation) can affect the expected accuracy of instruments, the same instrument comparison criteria are used. If two or more channels begin to indicate widely different values of the same pa rame te r, the interchannel comparison is intended to detect and flag this as questionab'le data (indicated by a purple color). Emergency operating procedures address the increased uncertainty in parameter values by using more conservative values for process control and decision points during adverse conditions. The SPOS displays support these procedures by display of parameter values, even if the values are coded as questionable by the interchannel comparison. The operator is thereby alerted to the uncertainty in the data and can review diverse instruments to evaluate plant conditions.

Please contact this office if you require any further information.

Sincerely, tJ.A.li i '5; L*, G. Hairston, !!!

JH/llh c: Georgia Power Company Mr. P. D. Rice Mr. G. Bockhold, Jr.

GO-NORMS U. S. Nuclear Regulatory Comission Dr. J. N. Grace, Regional Administrator Mr.1. B. Hopkins, Licensing Project Manager, NRR (2 copies)

Mr. J. F. Rogge, Senior Resident Inspector - Operations, Yogtle 1

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