ML19268B942
| ML19268B942 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 02/21/1978 |
| From: | Rosa F Office of Nuclear Reactor Regulation |
| To: | Butler W Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7910220588 | |
| Download: ML19268B942 (2) | |
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WEMORANDUM FOR: Walt R. Butler, Chief. Plant Systems Branch, DOR i
i FROM:
Faust Rosa Chief. Power Systems Branch. 055 i
SUBJECT:
D.C. POWER SYSTEM OF 111REE MILE ISLAND UNIT 1 3
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l' This menerandum identifies two design features in the Class 1E DC Power
,e Systaa of Three Mile Island thit 1 which do not meet present design t
E criteria. These desica features were uncovered during our OL review of
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the Three Mile Islanfunit 2 design. In our stew, they do not con-ii E
However, stace they are stNte an famediata serious safety concern.
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not being addressed in the TM12 SER (because they pertain to the TMI 1 design), they are brought to your attention for correr.tive action as
-i say be doesmed appropriata for an operating plant.
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.W.. e. Problem Areas (Reference Fig 8-4. TMI 1?FSAR); ~
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i i t. q ;y,c g,5 Theiswitchyard breakers'are prov de 2.$.',51 the control power for this circuitry is sappited from the p
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l%.U switchyard breakers and their control power sourcis 005 This
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. However, this arrangesact does not meet presenindependence criteria i
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3 The applicant has committed to installation of ndundant fuses for
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3, each of the control pesar circuits to the switchyard prior to opera-i tion of TM12 above 51 power. With this modification in the event 4
of a fault in the underground duct, failure of four sets of fuses 2
is required before both rddundant ESF divisions of TM1 ) areH i
plant design,*h implementation of,this cosmitment should be adversely affected.
' reviewed by DOR.
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' Walt R. Butler The TMI 1 DC Power System design includes an automatic transfer switch to transfer distribution panel IM from or.e redundant sub-Thi 2.
system to the other.However, both power circuits to the kwitch are fused and of RG 1.6.
both sets of fuses would have to fail in order to adversely effect both redundant DC power sources.
The above has been coordinated with D. Tor)di. Please advise if we can e
be of further assistance.
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