ML20054J012
| ML20054J012 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 06/11/1982 |
| From: | Trammell C Office of Nuclear Reactor Regulation |
| To: | Cavanaugh W ARKANSAS POWER & LIGHT CO. |
| References | |
| NUDOCS 8206250341 | |
| Download: ML20054J012 (3) | |
Text
3ts a s-og JUN 11 1982 Distribution:
(f4RL,rDRDocket Flie ]
Docket No. 50-368 Local PDR ORB #3 Rdg DEisenhut JHeltemes Mr. William Cavanaugh. III PKreutzer Senior Vice President CTrammell Energy Supply Department MConner Arkansas Power & Light Company OELD P. O. Box 551 OI&E (.1)
Little Rock, Arkansas 72203 NSIC ACRS (10)
Dear Mr. Cavanaugh:
It has come to our attention that Page 4 of Enclosure 2 was inadvertently omitted from our March 31, 1982 letter regarding the independence of the Reactor Protection System. Since this page could affect your future actions on this subject, it is enclosed with this letter.
Please accept our apology for any inconvenience this overs.i'ght has caused you.
Sincerely.
Oridnalsi;acd by i
Charles M. Trammell, Project Manager Operating Reactors Branch #3 Division of Licensing
Enclosure:
As stated cc w/enci:
See next page 8206250341 820611 PDR ADOCK 05000368 P
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l Irkansas Power & Light Company cc:
Mr. John Marshall Manager, Licensing Arkansas Power & Light Company P. O. Box 551 Little Rock, Arkansas 72203 U.S. Environmental Protection Agency Mr. James P. O'Hanlon Region VI Office General Manager ATTN:
Regional Radiation Arkansas Nuclear One Representative P. O. Box 608 1201 Elm Street Russellville, Arkansas 72801 Dallas, Texas 75270 Mr. Robert B. Borsum Babcock & Wilcox Nuclear Power Generation Division Suite 220 7910 Woodmont Avenue S. L. Smith, Operations Officer Bethesda, Maryland 20814 Arkansas Nuclear Planning &
Response Program Nicholas S. Reynolds, Esq.
P. O. Box 1749 c/o DeBevoise & Libennan Russellville, Arkansas 72801 1200 Seventeenth Street, N.W.
Washington, D. C.
20036 Arkansas Polytechnic College Russellville, Arkansas 72801 Mr. Charles B. Brinkman Manager - Washington Nuclear Operations t
C-E Power Systems 4853 Cordell Avenue, Suite A-1 Bethesda, Maryland 20014 Regional Administrator Nuclear Regulatory Commission, Region IV Office of Executive Director for Operations 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011 Mr. W. Johnson U.S. NRC P. O. Box 2090 f
Russellville, Arkansas 72801
. e) Acceptan:e criteria for perturbations which e:uld be allowed within the redundant vital bus without interfering with any protection system actions, f) Justification that the faults and surges used during the testing exceed the maximum worst-case failures which could occur within the protection systems circuits.
5.
Logic Matrix Circuitry Failure Due to a Vital Bus Single Failure Each plant must be reviewed to assure that, with a channel in bypass, a single failure of a vital bus will not prevent the protection system from performing its protective function.
As stated in item 4 above, the CE reactor protection system forms six logic matricies (AB, AC, AD, BC, BD and CD) from all possible coincidences of two combinations of the four protection channel bistables and associated contacts.
Due to the vital bus arrange-ment a single failure of a vital bus coincident with the bypass of a channel could prevent the required protective function of the RPS.
i Looking at figure 1, assume that a channel A trip parameter is bypassed.
This results in negating the AB, AC and AD logic matricies protective functions. This now leavgs the BC, BD, and CD logic matricies for protection.
However, as shown in figure 1, these remaining matricies are being supplied by a connon vital bus.
It can now be postulated that a. single failure (fault, ' surge, etc.) within the connon vital bus system might propogate through the logic matrix power supplies into the matrix circuitry. This could thereby cause a failure (welding of contacts) of the remaining logic matricies such that the required protective function cannot be per-
.,