ML20038A898
| ML20038A898 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 11/10/1981 |
| From: | Lentine F COMMONWEALTH EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| REF-SSINS-6820 2862N, IEB-79-14, NUDOCS 8111240413 | |
| Download: ML20038A898 (3) | |
Text
.
/- ~N Commonwealth Edison
[
) one First National Plaza. Chicago._ttlinois 7 Address Reply to. Post Office Box 767 j Chicago. Illinois 60690 November 10, 1981 Mr. James G.
Keppler, Director Directorate of Inspection and Enforcement - Region III U.S.
Nuclear Regulatory Commission 799 Roosevelt Roao Glen Ellyn, IL 60137
Subject:
Zion Station Units 1 and 2 Response to I.E.Bulletin 79-14
" Temperature Effects on Level Me a su remerit s" NRC Docket Nos. 50-295 and 50-304 References (a):
August 13, 1979, letter from J.
G.
Keppler to Byron Lee, Jr.
(b):
September 21, 1979, letter from D.
L.
Peoples to J.
G. Keppler.
Dear Mr. Keppler:
Reference (a) required Commonwealth Edison to teke certain actions with regard to I.E. Bulletin No. 79-21, " Temperature Effects on Level Measurements."
Our response was provided in Reference (b).
Item 3 of that response described how the bias induced by the heat-up of the steam generator level reference leg could delay or prevant reactor trip / auxiliary feedwater initiation on low-low steam generator water level.
Since this signal provides the primary trip function for a feedline rupture accident, the low-low steam generator level setpoint was revised upward to accomodate the maximum bias that could occur.
Westinghouse generically estimated the maximum bias to be 10% for temperatures up to 2800F.
Above 2800F, reactor trip /
auxiliary feedwater actuation would occur on a high containment pressure signal.
Westinghouse stated that a plant-specific contain-ment analysis, possibly combined with changes in the high containment pressure setpoint, could be used to justify reducing the clas that had been estimated generically.
Since the low-low steam generator level setpoint was raised from 10% to 15%, several reactor trips have occurred as a result of brief water level transients, causing unnecessary challenges to safety-related equipment and personnel.
In an effort to prevent these undesirable trips, Commonwealth Edison has performed the plant-c, 8111240413 81111'O~
gDRADOCK 05000295 NOV 2 0 1981 Sl q)
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J. G. Keppler November 10, 1981 specific evaluation suggested by Westinghouse and concluded that a reduction in the value of the maximum temperature-induced bias is justified.
For the present high containment pressure setpoint of 4.5 psig, the maximum temperature reached prior to unit trip is approximately 1500F, This results in a maximum bias of 2%, as compared to the 10% estimated by Westinghouse.
Therefore, Commonwealth Edison has concluded that the low-low steam generator level setpoint may be returned to a value of 10%, which will provide adequate margin for the existing instrument inaccuracies and the 2% maximum temperature-induced bias.
This change will be accomplished on Uni't 2 prior to startup following the current refueling outage, and on Unit 1 shortly thereaf ter.
Please address questions regarding this matter to this office.
Very truly yours, b
h F.
G.
Lentine Nuclear Licensing Administrator cc:
NRC Office of Inspection and Enforcement - Wash.,
D.C.
Zion Resident Inspector FGL/lm 2862N
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