ML19332E515

Forwards Request for Addl Info Re LPCI Swing Bus Transfer Scheme on Single Failure Vulnerability.Response Requested within 45 Days

ML19332E515
Person / Time
Site:	Pilgrim
Issue date:	12/01/1989
From:	Mcdonald D Office of Nuclear Reactor Regulation
To:	Bird R BOSTON EDISON CO.
References
NUDOCS 8912070319
Download: ML19332E515 (3)

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December 1,- 1989 4

- Docket No."50-293 i

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Mr.LRalph G. Bird H

Senior Vice President.. Nuclear.

, ~ Boston' Edison Company G,

Pilgrim Nuclear Power Station-

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_ Plymouth,. Massachusetts 02360

SUBJECT:

= LOW:PRESSUR'E COOLANT-INJECTION SWING BUS TRANSFER

Single: failure concerns'have been identified at Fermi, Unit 2, on the low pressure; coolant. injection (LPCI)iswing bus. Your staff has indicated that.

the. single failure concerns at Fermi, Unit 2, are not applicable to-the Pilgrim e

LPCI-swing. bus design.n We have reviewed all available design documents and:

electrical diagrams related to the LPCI swing. bus. The enclosed request for 7

.additionaloinformation is necessary to complete our review.

Please provide the requested information~within 45 days.

!Thereportidgand/orrecordNeepingrequirementscontainedinthisletter affect. fewer than ten respondents:

therefore, 0MB. clearance is not required under P.L.~96-511'.

6 Sincerely, n

' Original signed byt Daniel G. Mcdonald, Senior Project Manager Project Directorate I.3 Division of Reactor Projects I/II 1

Enclosure:

As. stated.

i cc'w/ enclosure:

See:next page-

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s Mr.~ Ralph G. Bird -

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cC Mr. K. L. Highfill Mr. Richard N. Swanson, Manager Vice President of.0perations/

Nuclear Engineering Department and Station Boston Edison Company Pilgrim Nuclear Power Station 25 Braintree Hill Park RfD #1 Rocky Hill Road.

Braintree, Massachusetts 02184 Plymouth,- Massachusetts 02360 -

Resident-Inspector Ms. Elaine D. Robinson

. U. S., Nuclear Regulatory Commission Nuclear Information Manager Pilgrim Nuclear Power-Station-Pilgrim Nuclear Power Station.

Post Office Box 867 Plymouth ~, Massachusetts.

RFD #1, Rocky Hill Road 02360 Plymouth, Massachusetts 02360 a

Chairman,-Board of Selectmen Mr. Charles V. Barry

'll Lincoln Street Secretary of Public Safety i

Plymouth, Massachusetts 02360 Executive Office of Public Safety _

One Ashburton Place K

Office of the! Commissioner Boston, Massachusetts -02108 Massachusetts Department of; 9

Environmental Quality Engineering One Winter Street Boston; Massachusetts 02108

0ffice of_the Attorney General

'One Ashburton Place.

- 20th Floor Boston,' Massachusetts 02108 L

- Mr. Robert M. Hallisey, Director Radiation Control Program Massachusetts Department of Public Health 150 Tremont Street, 2nd Floor Boston, Massachusetts 02111 Regional Administrator, Region I g"

U. S.~ Nuclear Regulatory Comission

~ 475 Allendale Road

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King of Prussia, Pennsylvania 19406 Mr. John Dietrich' Licensing Division Manager Boston Edison-Company 25 Braintree Hill Park Braintree, Massachusetts 02184 h

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ENCLOSURE 1 m

REQUEST FOR ADDITIONAL INFORMATION ON LPCI SWING BUS TRAN5FER SCHEME REGARDING A-SINGLE FAILURE VULNERABILITY PILGRIM. UNIT 1 i

DOCKET NO. 50-293 i

i In our.telecon of July 17, 1989, you confirmed-that Pilgrim uses the LPCI swing bus to meet the ECCS criteria of 10 CFR 50.46. However, you stated that

_the single failure concerns at Fermi 2 may not be applicable to Pilgrim as your LPCI swing bus-design is different from the other BWRs. We have reviewed all'available electrical diagrams and the related design documentation provided in FSAR and SER for'the LPCI swing bus.

In order for the staff to ensure that Fermi 2 concerns are not applicable to Pilgrim. provide the following additional-information:

1)

' During-the review of 'the acceptability of swing bus design of BWRs, the following positions were imposed by the staff:

a) To confine single failures within the swing bus, only loads associated with LPCI function, i.e., LPCI valve motors may be connected to the swing bus.

b) To reduce probability of propagating electrical faults between divisions, the bus transfer scheme (circuitry) must meet the applicable portions of IEEE Standard 279, such as the single failure criterion, testability, and quality of components.

'c) -To lessen probability of propagating faults into non-LPCI portions of the electrical division, proper coordination of circuit protective devices must be provided. This requires.that the design provide both an adequate number of circuit breakers and proper breaker coordination.

Demonstrate how your existing bus transfer scheme for two LPCI related swing buses (i.e., B6 and panel C) meet the above requirements.

2) 10 CFR 50, Appendix K, with regard to single failure criterion, requires that the design of the ECCS system must withstand the worst single failure.

According to the-single failure definition in 10 CFR 50, Appendix A, no D

distinction is made between active and passive failures in the electrical l

systems.

It has always been the staff's position that no such distinctions of L

single failure for the electrical components should be made.

Identify all

'the single passive failures which you consider (i.e., bus, cable, breaker, etc.) in your LPCI swing bus transfer schemes which would prevent the automatic transfer to its alternate AC power source. Also, identify any l

sirgle failure which could disable both an emergency diesel generator and the DC swing bus leaving one core spray to perform ECCS function during an accident.

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