ML20244C935

Submits Evaluation Re Operability of Ac Vital Instrument Bus When Powered from non-Class IE Power Source in Lieu of Inverter

ML20244C935
Person / Time
Site:	Davis Besse, 05000000
Issue date:	05/15/1984
From:	Rubenstein L Office of Nuclear Reactor Regulation
To:	Lainas G Office of Nuclear Reactor Regulation
Shared Package
ML16342B348	List: IA-87-121, Discusses Inservice Test Programs Re Full Stroke Exercising of Normally Closed Swing or Tilting Disk Check Valves Per 10CFR50.55a & Section XI of ASME Code ML20235B266 ML20235B268 ML20235B295 ML20235B304 ML20235B322 ML20235B406 ML20235B470 ML20235B514 ML20235B581 ML20235B613 ML20235B673 ML20235B768 ML20235B785 ML20235B799 ML20235B859 ML20235B877 ML20235B922 ML20235C007 ML20235C967 ML20235C970 ML20235D014 ML20235D041 ML20235D091 ML20235D157 ML20235D188 ML20235D233 ML20235D400 ML20235D433 ML20235D484 ML20235D532 ML20244B491 ML20244B568 ML20244B571 ML20244B913 ML20244B937 ML20244B941 ML20244B943 ML20244C126 ML20244C271 ML20244C361 ML20244C777 ML20244C785 ML20244C833 ML20244C935 ML20244C940 ML20244C986 ML20244D413 ML20244D552 ML20244D582 ... further results
References
FOIA-87-121 TAC-54262, NUDOCS 8405310333
Download: ML20244C935 (2)

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UNITED STATES

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NAY I 51934 _

MEMORANDUM FOR: Gus C. Laines, Assistant Director

- for Operating Reactors, DL ,

FROM:

L. S. Rubenstein, Assistant Director for Core and Plant Systems, DSI SUBJECT : DAVIS-SESSE - THE OPERABILITY OF AN AC VITAL INSTRUMENT BUS WHEN POWERED FROM A NON-CLASS 1E P0lER SOURCE IN LIEU OF AN INVERTER (TAC NO. 54262 TIA 64-15) ., ...

Per TAL No. 54262 (TIA B4-15), the Power Systems Branth has reviewed the operability requirements for ac vital instrument buses of the Davis-Besse pl ant . Our evaluation is as follows:

/O We recognize that the technical specification requirement to the current . tandard technical specifications) are somewhat vague in

(") that the 120V ac vital buses can be energized from a non-Class 1E power supply for repairs.

for en extended period of time when an inverter is out of these plants do not limit the time that these vital buses may beEnergizing energized from a source other than battery / inverter com The generic would be interrupted in the event of loss of offsite power.

safety concern srises fromInthe si.tuation where power some designs with two vital is lost due to an assumed single failure. In other designs, buses deenergized, spurious safety act a tions will occur.

the loss of power on two buses can prevent automatic there is a potential for plants with these types of designs to be operating for extended periods of time outside their origint! licensing basis, i.e.,

in violation of the single failure criterion.

Cecause of the above concern the standard technical specifications revised to require the licensee to 1E de bus through an associated inverter within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or proceed to j shutdown the plant, While a few plants have this LCO requirement, a majority of the operatj plants do not have such requirements.

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) Gus C. Lainas 1 to other operating plants, this issue is currently being studied by the NRR statf under Generic Issue 48, " Operational Restrictions for Class 1E 120V AC Vital Instrument Buses,* in accordance with HRR Office Letter Number 39.

As part of the proposed resolution of this issue we anticipate recommending vital bus may be energized from a source other than a Cla an inverter. For regulatory consistency, subject to approval of the proposed requirement by CRGR, it will be a backfit on all operating plants (including Davis-Besse).

Our current projection for completion of this generic task is early 1986. This completes our action on TAC No. 54262 and TIA 84-15.

odlua (C ubenstein, Assistant Director L. Si for Core and Plant Systems Division of Systems Integration

/N cc: R. Mattson M. Srinivasan J. Stolz A. DeAgazio J. Knight A. Ungaro

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