ML20091P720
| ML20091P720 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 06/07/1984 |
| From: | Hukill H GENERAL PUBLIC UTILITIES CORP. |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| 5211-84-2140, GL-83-28, NUDOCS 8406130155 | |
| Download: ML20091P720 (2) | |
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GPU Nuclear Corporation NUCIMr Post Office Box 480 Route 441 South Middletown, Pennsylvania 17057-0191 717 944 7621 TELEX 84 2386 Writer's Direct Dial Number:
June 7, 1984 5211-84-2140 Office of Nu' lear Reactor Regulation Attn:
D. G. Eisenhut Division of Licensing U. S. Nuclear Regulatory Camtission Washington, D.C. 20555
Dear Mr. Eisenhut:
Three Mile Island Nuclear Station, Unit I, (TMI-1)
Operating License No. DPR-50 Docket No. 50-289 (brrection to Salen ATWS Response (GL 83-28)
Sent May 9, 1984 (5211-84-2107)
On May 9,1984 we subnitted our GPU Nuclear letter 5211-84-2107, which included a response (page 2) to the shunt trip circuit classification and separation concerns for this issue.
Attached is a corrected mgy of page 2, as indicated by a margin bar. The infonnation renoved fran this sentence was incitxled in error and should be deleted. This corrected page should replace any copies of the original page 2 which have been included in your records.
Sincerely, H. D.
- ukill, Director, TMI-l HDI/JG3/mle Attachment cc:. R. (bnte J. Van Vliet i..
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GPU Nuclear Corporation is a' subsidiary of the General Public Utilities Corpora *lon 8406130155 840607 PDR ADOCK 05000289 P
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- 4. Identify the classification (safety related or not) and separation (train l
or channel identification) for the reactor trip shunt and UV trip circuits, power s4 plies, and any interface isolation devices.
Response
The U/V trip circuits, because they are part of the Reactor Protection System (RPS), are classified Nuclear Safety Related.
Channel separation inherent in the existing RPS is maintained in aciordance with the TMI-l plant criteria for Class lE circuit routing except as analyzed in the.
following case.
Each of the 4 RPS trip circuits is run in an individual channelized conduit.
In an isolated case, these channelized conduits are not separated by 1 inch of free air space. Since either shorting or opening of the circuits in that area results in the trip of the associated circuit breakers; and because the only circuits in those conduits are the trip circuits, the worst case event resulting from a multi-channel circuit failure would be a reaciar SCRAM. Considering that the failure mode is such that the required safety function is preserved, it is unnecessary to revise the routing of these circuits.
The power supplies for the U/V and shunt' trip devices are channelized !
safety related circuits.
Channel separation will be maintained in cable routing in accordance with the TMI-l plant criteria for Class lE circuit routing except as analyzed in the following case.
The "A" channel (red) and the "B" channel (green) DC circuits feeding the shunt trip coils in the AC reactor trip breakers are routed in individual
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conduits.
These conduits are less than once inch apart over a six foot span in one isolated area..Using the analysis performed in GpuN engineering studies on raceway separation for raceway originating fires, and considering that the DC shunt trip circuits are the only circuits in the conduits, there would be insufficient heat generated from a failure of
.one circuit to effect the circuit in-the' adjacent conduit. Therefore, it i.s~ unnecessary to revise the routing of these' circuits.
The shunt trip circuit in the original TMI-1. design is used in_' the primary (AC) CRDM circuit. breakers.
It was not designated as safety related because 'it interf aces with thc non-safety.:rel_ated source interrupt: device.
The~ source interrupt trips the AC. breakers on supplyLbus undervoltage or loss of off-site power. :This function'is toL protect the holding coils forf 3;
the control rod drives-and'is:not considered safety related.
Per this ' modification,.fisolation between the' upgraded safety related shunt-trip circuit, and--the non.
safety-source interrupt;circuitLwill-'be provided1vialfuses properly coordinated with the main circuitifeeder' fuse.
Furthermore,.;the interface _
isolation ofcthe' shunt-trip circuit with_the'sourcelinterrupt circuitiwilli be7 accomplished.by theicontact.to-coil isolation:of:a qualified relayh Thelinterf ace' between,the I.] power supplyf and tihelloss Loff DC, cont"rol' power /
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alar'm is?secomplishedathrough the coi1 to? contact (is'olationTof'a;q'ualifiedl '
irelay.
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