ML17174A054
| ML17174A054 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Quad Cities, Zion  |
| Issue date: | 10/05/1979 |
| From: | Peoples D COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML17174A055 | List: |
| References | |
| TASK-07-04, TASK-7-4, TASK-RR NUDOCS 7910110269 | |
| Download: ML17174A054 (2) | |
Text
Commonwe:A Edison One First Nation~aza, Chicago. Illinois Address Reply to: Post Office Box 767 Chicago, Illinois 60690 October 5, 1979 Dr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C.
20555
Subject:
Dresden Station Units 1, 2 and 3 Quad-Cities Station Units 1 and 2 Zion Station Units 1 and 2 Response to Potential Unreviewed Safety Questions on Interaction between Non-Safety Grade Systems and Safety Grade Syst~ms{
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NRC Dpc~t Nos.
50-1~/~~7/249, 50-25'4/2'b5 and 50-295/3'04 Reference (a):
September 17, 1979 letter from H. R.
Dear Dr. Denton:
Denton to All Operating Light Water Reactors Per Reference (a), Commonwealth Edison Company was requested to determine whether the potential "for an unreviewed safety matter related to the effects of the environment on control systems resulting from high energy line breaks inside or outside containment and the results of these effects on the required safety systems" exist at its Dresden, Quad-Cities and Zion Stations.
This potential problem was further addressed in IE Information Notice No.
~9-22, "Qualification of Control Systems," dated September 14, 1979.
Cominonwealth Edison has reviewed the specific non-safety grade systems listed in IE Information Notice No. 79-22, as well
- as others, for potential interactions that could constitute a sub-stantial safety hazard.
No such interaction has been identified that would alter the basic conclusion of the Dresden( Quad-Cities or Zion Final Safety Analysis Reports (FSARs), i.e., that these events do not constitute an undue risk to the health and safety of the public.
A preliminary analysis by the Nuclear Safety Analysis Center (NSAC) has determined that there is a very low probability of severe *consequences resulting from one of these high energy line breaks.
(The NSAC study which will be submitted to the NRC by the Atomic Industrial Forum (AIF) is entitled "Probablistic Analysis of IE Information Notice No. 79-22 Scenarios.")
Furthermore, such breaks are more likely to be small cracks rather than abrupt failures so that the resulting adverse environment builds q, up over a period of time providing the potential for detection priorf',.a';
to component failure.
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Commonwealth Edison Dr. Harold R. Denton:
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October 5, 1979 Westinghouse Electric Corporation and General Electric company have provided Commonwealth Edison with generic evaluations with regard to high energy line breaks on non-safety equipment.
Additional generic evaluations coupled with detailed, plant specific evaluations as required in NUREG-0578, "TMI-2 Lessons Learned Task Force Status Report and Short-Term Recommendations,"
are proceeding.
The results of these evaluations will be reported'*
to the NRC Staff consistent with the schedules delineated in NUREG-0578.
However, based on the results to-date from generic and detailed, plant specific evaluations at its Dresden, Quad-Cities and Zion Stations, Commonwealth Edison has concluded that continued operation of its NRC licensed plants is warranted and that its NRC licenses need not be modified, suspended, or revoked. to this letter contains Commonwealth Edison's "Evaluation of Interactions Between Non-Safety Grade Systems and Safety Grade Systems for Zion Station."
While this attachment specifically addresses the four systems identified in IE Information Notice No. 79-22, these four postulated scenarios were the only potential safety qu~stions identified by Westinghouse in over a year's review of system interactions.
As previously presented to the NRC, Westinghouse used engineering judgement to derive a 7x7 matrix of those systems for* which a safety interaction might exist.
A detailed review of this matrix suggested possible safety signifi-cance in only the four scenarios which Commonwealth Edison has addressed. to this letter contains Commonwealth Edison's "Evaluation of Interactions Between Non-Safety Grade Systems and Safety Grade Systems for Dresden and Quad-Cities Stations."
This attachment specifically addresses a comprehensive review in matrix form of all potential environmental interactions at Dresden and Quad-Cities Stations.
It should be noted that the matrix assessments contained in Attachment 2 were performed by Commonwealth Edison jointly with. General Electric and other BWR Owners.
I.
Please address any questions that you might have concerning this matter to this off ice.
WFN:mae attachments (2)
SUBSCRIBED and SWORN *to c:-'TI; before me
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Ne>tary Public Very truly yours, D. Louis Peoples Di~~ctor of Nuclear Licensing
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