ML18031A307

Interim Deficiency Rept Re Deficiency in Isolation Sys for non-Class IE Loads.Caused by Inadequate Isolation Devices Connecting non-Class IE Sys to Class IE Sys.Vendor Advised of Design Deficiency

ML18031A307
Person / Time
Site:	Susquehanna
Issue date:	11/14/1979
From:	Curtis N PENNSYLVANIA POWER & LIGHT CO.
To:
References
840-4, NUDOCS 7911200557
Download: ML18031A307 (3)

Text

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, SUUJECl: Interim aeficiency rept re oeficiency in isolation sys for non-Class IE loaos ~ Causeo oy inaaequate isolation oevices connecting non Class Lh sys to Class IE, sys.Venaor aovised of oesiqn aeficiency.

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PPaL TWO NORTH NINTH STREET, ALLENTOWN, PA. 18101 PHONE: (215) 821-S IS I NORMAN W. CURTIS Vice Presiceni Engineenng d Construcrion 821-5381 November 14, 1979

. Mr. Boyce H. Grier Director, Region I U. S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, Pennsylvania 19406 SUSgJE2GQJNA STEAM ELECTRIC STATION REPORT OF A DEFZC1ENCY ZN THE SYSTEM FOR ISOLATING NON~SS 1E LOADS CONNECTED TO THE 250 VDC 1E SYSTEMS ERs 100450/100508 FILE 840-4 PLA-420

Dear Mr. Grier:

This provides information regarding the subject deficiency 'which has been deemed reportable under 10CFR 50.55(e) .

The deficiency results from the fact that non-Class 1E loads are connected to the 250 VDC Class lE systems through inadecpmte isolation devices which do not prevent faults in non-Class 1E systems from causing unacceptable influences on any other section of the Class 1E circuit. Further, the iso-

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lation devices, as specified in Bechtel design drawings, have been incorporated into the plant 250 VDC Class 1E electrical system.

The SSES FSAR section (3.13) which addresses Regulatory Guide 1.75 states:

"Isolation systems are defined as two separate, redundant breakers placed in series actuated. by fault current to prevent malfunctions in any section of a circuit from causing unacceptable influences in any other section of the circuit or in o'ther circuits."

The isolation devices, as presently installed at SSES, could result in the degradation of the 250 VDC Class 1E circuit such that safety related loads could not be sufficiently supplied as a result of:

1. Certain restricted faults on non-Class 1E circuits.

2. Faults in circuits connected to the 250 VDC Class 1E supply through single breaker isolation. (The single breaker isolation method is of itself recognized to be contrary to the referenced FSAR commitment. )

P o/)'8 PENNSYLVANIA POWER d LIGHT COMPANY 9ZZSD 55 7

Mr. Boyce H. Grier November 14, 1979 As a result of faults in non-Class 1E systems, the concurrent loss of Division I and Division II 250 VDC Class lE circuits could occur with the resultant loss of the HPCI and RCIC systems. Loss of these systems would preclude safe shutdown of the reactor under certain conditions.

This condition was initially detected by PPaL engineers while prescribind relay settings for devices in the 250 VDC system. In accordance with PP&L's procedures for reporting such items, the condition was then identified to PPGL NQA, evaluated and documented on PPaL Deficiency Report DR 0134 which has been transmitted to Bechtel Project Engineering. Bechtel Engineering has been requested to disposition the design deficiency problem, recommend an appropriate course of corrective action and advise PPGL whether any other DC Class 1E system may be similarly affected.

Bechtel's ultimate resolution of PPaL Deficiency Report DR 0134 and the subject deficiency is projected for 6/30/80.

PPGL will inform the Commission should there be any further significant developments.

Very truly yours, f~

N. W. Curtis Vice President-Engineering a Construction ARS:mcb ccrc Mr. Robert M. Gallo U. S. Nuclear Regulatory Commissi.on P. O. Box 52 Shickshinny, Pennsylvania 18655 Mr. G'.. McDonald Office of. Management Information S Program Control.

U. S. Nuclear Regulatory Commission Washington, D.C. 20555 Mr. Victor Stello (15)

Director Office of Inspection a Enforcement U. S. Nuclear Regulatory Commission Washington, D.C. 20555