ML19209C046
| ML19209C046 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 10/03/1979 |
| From: | Trimble D ARKANSAS POWER & LIGHT CO. |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| Z-109-2, NUDOCS 7910110434 | |
| Download: ML19209C046 (2) | |
Text
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J bra ARKANSAS POWER & LIGHT COMPANY POST OFFICE BOX 551 UTTLE ROCK. ARKANSAS 72203 (501) 371-40N October 3, 1979 2-109-2 Director of Nuclear Reactor Regulation ATTN:
'!". R. W. Reid, Chief Operat'ng Reactor Branch #4 U. S. Nuclear Regulatory Commission Washington, D C.
20555
Subject:
Arkansas Nuclear One-Unit 2 Docket No. 50-368 License No. NPF-6 CPC Task Force Site Audit (File:
1510)
Gentlemen:
During uhe recent site audit of CPC related activities at ANO-2, an item of concern was identified by CPC Task Force reviewer J. B. Bullock.
This item of concern involved a small discrepancy in the Local Power Density Trip Setpoint following the implementation and
This discrepancy was very small in magnitude and 7as never actually implemented in the ANO-2 CPC system.
The concern was more with the fact that such a discrepancy could escape detection in the software testing per CEN-39(A). The purpose of this letter is to provide a description of the events that produced the discrepancy.
The Certification of Revision 01 of the ANO-2 CPC System Software was completed on March 6, 1979.
This sof tware incorporated all of the MOD 01 changes that were described to the CPC Task Force during the recent audit.
One of the changes implemented was the conversion of, scaled fixed point arithmetic to floating point to increase accuracy, reduce software complexity and provide ease of maintenance. During this conversion to floating point all scaled fixed point constants were reassembled in floating point. This activity introduced an error in the Local Power' Density Trip Setpoint (LPDLM).
This error was not detected by Phase I testing because of the small magnitude of the error (.0027%).
1 1-m
- LO I13U CU/
Combustion Engineering's Quality Assurance of Design Procedures require that all CPC System Software documentation be independently reviewed.
The review of the software specification included a visual inspection of program constants to insure consistency with the data base document.
During this process a discrepaacy was noted with the Local Lower Density Trip Setpoint (LPDLM) used by the Trip Sequence Subroutine.
The data base value of 365.81% Design Average was implemented as 365.8% Design Average.
The decisio M EMDE A M COLE SOUT*4 UTILITIES SYSTEM
Fk. R. W. Re id '
L was then made to change the constant during a subsequent revision of the sof tware because the value of tr.e constant that was implemented is conserva-tive with respect to the value required.
This was documented in the Test and Certification Analysis of the Core Protection Calculator System Sof tware before the preparation and transmittal of the ANO-2 Site disks.
If you have any questions or comments please do not hesitate to call.
Very truly yours,
.!AU 0-AM David C. Trimble Manager, Licensing THC:DCT:sh W. D. Johnson U. S. Nuclear Regulatory Commission P. O. Box 2090 Russellville, AR.
72801 K. V. Seyf rit, Director Office of Inspection & Enforcement U. S. Nuclear Regulatory Commission Region #4 611 Ryan Plaza Dr.
Suite 1000 Arlington, Texas 76011 Laurence E. Phillips U. S. Nuclear Regulatory Commission 7920 Norfold Avenue, P-1030 Bethesda, Maryland i 13J 270