DCL-84-092, Forwards Response to Request for Addl Info Re Class IE Electrical Raceway Supports.Design Supports Have Sufficient Margin to Assure That Loss of Single Support Will Not Cause Loss of Safety Function
| ML20081C778 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom, Diablo Canyon  |
| Issue date: | 03/07/1984 |
| From: | Schuyler J PACIFIC GAS & ELECTRIC CO. |
| To: | Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| DCL-84-092, DCL-84-92, NUDOCS 8403150013 | |
| Download: ML20081C778 (3) | |
Text
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PACIFIC GAS AND E LE C T RIC C O M PANY IP G w E j
77 DEALE STREET SAN (RANCISCO, C Allr0RNI A 94106 4415) 781 4211. TWX 910 3 72-6587 e
J.O.SCHUYLER blCS P.t Ut f %f h ALI A4 PO*t a Gt%ti Af tets
!! arch 7, 1984 PGandE Letter No.: DCL-84-092 Mr. John B. Martin, Regional Administrator U. S. Nuclear Regulatory Commission, Region V 1450 Maria Lane, Suite 210 Walnut Creek, CA 94596-5368 a
ATT)I fir," D. Kirsch tfo
@tj Re:o Docket No. 50-275, OL-DPR-76 W
' Docket No. 50-323 E Diablo Canyon Units 1 and 2
,I Class lE E1ectrical Raceway Supports - Additional Information De Mr. Martin:
4 The enclosure to this letter provides the response to a request for additional information concerning the single failure aspects of using common supports for mutually redundant Class lE circuits. This response supplements PGandE letter No. DCL-84-064, dated February 17, 1984.
Kindly acknowledge receipt of this material on the enclosed copy of this letter and return it in the enclosed addressed envelope.
Sincerely, l
./
Enclosure cc:
G. W. Knighton Service L1::t 8403156013 840307 DR ADOCK 0500027 16-d{\\
PGandE Letter No.:
DCL-84-092 ENCLOSURE
Background
In January,1984, the NRC observed that redunhnt circuits are supported by a common raceway support in two Plant areas - the Cable Spreading Room and i
Area K, elevation 100'. This creates the potential for using common supports t
for mutually redundant Class 1E circuits. As a result, this condition would be inconsistent with the FSAR, Page 8.3-28, which states, " Class 1 supports i
are not shared by mutually redundant Class 1 circuits." The NRC requested that PGandE provide an explanation for these conditions.
PGandE provided a response on February 17, 1984 (PGandE Letter No. DCL-84-064) i which addressed the seismic aspect of this issue. The NRC, on March 4, 1984, requested additional information directed to the single failure aspect of circuit separation.
Response
The current design and installation of Class lE vital circuits meets or exceeds all regulatory and IEEE requirements ar.d standards. None of these requirements or standards prohibits mutually redundant circuits from being supported from a common support.
The design basis for routing of redundant circuits at Diablo Canyon is established by:
4 1.
10 CFR 50, Appendir 4. General Design Criteria for Nuclear Power Plants--The commitmerd to meet these criteria is identified in the FSAR, Chapter 3.
2.
IEEE Standard 279-1971, Criteria for Protection Systems for Nuclear Power Generation Stations--The commitment to meet these criteria is identified in the FSAR, Chapter 8.
3.
IEEE Standard 308-1971, Class lE Electrical Systems for Nuclear Power Generating Stations--The comitment to meet these criteria is identified in the FSAR, Chapter 8.
l With respect to the item of comon support, compliance with NRC Regulatory l
Guide 1.75, Physical Independence of Eiectrical Systems, is established, since l
this Regulatory Guide adopted the above mentioned IEEE Standard 279-1971.
IEEE Standard 279-1971 Section 4.2 identifies the single failure design criteria as-follows:
l
[Any single failure within the protection system shall not prevent proper protective action at the system level when required.]
0506d/0005K --
~
The standard then continues to state:
[ NOTE: " Single failure" includes such events as the shorting or open-circuiting of interconnecting signal or power cables. It also includes single credible malfunctions or events that cause a number of consequential component, module, or channel failures. For example, the overheating of an amplifier module is a " single failure" even though several transistor failures result. Mechanical damage to a mode might become involved.gle failure" although several channels switch would be a " sin Therefore, the Standard limits credible failures to those associated with electrical failures. Separation for the failure modes described above is accomplished in congested areas, including the Cable Spreading Room and Area K, elevation 100', by the enclosure of redundant circuits in separate conduits.
The FSAR statement that Class I supports are not shared by mutually redundant circuits was a design conservatism established by PGandE; however, deviation from this design standard was found to be required to show seismic qualification of raceways to the revised seismic spectra generated during the Diablo Canyon Phase 1 Verification Program. Prior to acceptance of this design standard change, reviews were performed which showed that no regulatory requirements, including those stated eerlier, were impacted. The design of supports has sufficient margin to assure that loss of a single support will not cause loss of safety function. As stated in the previous submittal on this issue, an FSAR change will be submitted to clarify Page 8.3-28.
0506d/0005K.