BVY-93-133, Provides Results of Reg Guide 1.97 Re Boiling Water Reactor Neutron Flux Monitoring

Provides Results of Reg Guide 1.97 Re Boiling Water Reactor Neutron Flux Monitoring

ML20058G211
Person / Time
Site:	Vermont Yankee
Issue date:	12/01/1993
From:	Tremblay L VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
RTR-REGGD-01.097, RTR-REGGD-1.097 BVY-93-133, NUDOCS 9312090130
Download: ML20058G211 (4)

Text

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ERMONT YANKEE  !

MUCLEAR POWER CORPORATION ,

A p. Ferry Road, Brattleboro, VT 05301-7002 e

, - ENGINE hNG OFFICE I

• ' f '1 $80 M AIN ST'REET BOL TON. M A 01740

/,

{ LOBI 779-6711 December 1,1993 BVY 93 - 133 United States Nuclear Regulatory Commission A'ITN: Document Control Desk  !

Washington, DC 20555 ,

References:

a. License No. DPR-28 (Docket No. 50-271)

b. Letter, VYNPC to USNRC, BVY 93-64, dated 6/29/93

c. Letter, USNRC to VYNPC, NVY 93-36, dated 4/29/93 .

d. BWR Owners' Group Topical Report NEDO-31558-A, "Posidon on NRC ,

Regulatory Guide 1.97, Revision 3, Requirement for Post-Accident Neutmn Monitoring System", dated March,1993 l Subject- Regulatory Guide .97 - Boiling Water Reactor Neutron Flux Monitoring 1

Dear Sir:

Per Reference (c), the NRC requested Vermt.' Yankee to review our neutron flux monitoring instrumentation against the criteria of Nc00-31558 [ Reference (d)] to determine

, whether it meets these criterie. and to provide a letter to the NRC documenting the result of this

! review. In Reference (b), we not fied the NRC of our intention to perform this review work and_

i we anticipated the submittal of the results of oar review by December 1,1993. The purpose of this ,

. letteris to provide these results.

Vermont Yankee has completed the comparison of our exisdng neutra. monitoring system to i the alternate criteria of NEDO-31558. We have determined that all the NEDO-31558 criteria are satisfied by existing neutron monitoring instrumentation. As such, Vermont Yankee no longer considers this instrumentation to be required to satisfy Regulatery Guide 1.97 Category 1 criteria.

Reference (c) also requested Vermont Yankee to perform a plant-specific evaluadon to review the power supplies to neutron flux monitoring instmmentation, including recorders. A description of the power supplies to neutron monitoring instrumentation including recorders is included with this letter as Attachment I. A pordon of the power source design includes the use of an  ;

uninterruptible power supply. In addition, the incogoration of safety class equipment arid systems - i as described in Attachment I ensures reliable power sources. Based on this, Vermont Yankee concludes that the alternate criteria of NEDO-31558 for power sources are satisfied.

Vermont Yankee is presently completing our evaluat:on of the need to pursue a proposed change to the Tect nical Specifications with regard to this issue, and will submit a pmposed change -

in the near future should it be warranted. -

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United States Nuclear Regulatory Conanission )

December 1,1993 ,

Page 2 I l

i We trust that tnis information adequately responds to your requests; however, should l additional information be required, please contact this office.  !

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Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION i 4%g -

>4Ti O' s \ r.

Ixonard A. Tremblay, Jr. j kaior Licensing Engineer Attachment cc: USNRC Region I Administrator USNRC Resident Inspector- VYNPS USNRC Projcet Manager- VYNPS -

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d ATTACHMENT I j i

Power Suoplies To Neutron Flux ,

Monitoring Instrumentation  ;

I. POWER SOURCES 1.1 NEDO-31558 Alternate Requirement:

Uninterruptible and Reliable Power Sources 1.2 R. G. 1.97 Requirement:  !

Standby Power Source (RG 1.32) [

1.3 NEDO-31558 Report Stated Capability: t "A plant-specific evaluation is required to review the power distribution to the NMS including the recorders to verify that the instrument power is not lost during events by load shedding logics or similar schemes."  ;

1.4 VY Specific Capability:  !

Power to the subject portion of the Neutron Monitoring System is provided by the Reactor Protection System (RPS).  ?

Each of the RPS System buses are normally powered by a high  ;

inertia ac motor-generator (MG) set. High inertia is provided by a flywheel. The inertia is sufficient to  ;

maintain voltage and frequency within 5% of rated values for  ;

at least 1 second following a total loss of power to the  ;

drive motor. This RPS Bus arrangement is original plant-design and incorporates the " Fail-Safe" (reactor scram) -

scenario on loss of power. Alternate power is available to one RPS Bus at any one time from an electrical bus that can i receive standby electrical power. Power for the LPRMs/APRMs ,

is supplied by these two 120 volt ac Reactor Protection ,

System (RPS) Buses; one-half of the LPRMs are supplied from each bus. Since the RPS MG sets trip following a loss of  ;

offsite power, the APRMs use Vital and Instrument ac as i i

automatic transfer alternate power sources for shutdown verification. The addition of this automatic transfer was a design modification which was implemented as a system improvement in order to enhance the post-accident monitoring function. The station 120 Vac Vital Power supply is  ;

h ATTACHMENT I (cont)  ;

t described below along with the recorder power supply discussion. The station 120 Vac Instrument bus is a 120/240 i

e p-- w - - , - . - - , - .-- ,- . --

= . .. - . .. . .. . ._

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ATTACHMENT I (cont) {

i described below along with the recorder power supply  ;

discussion. The station 120 Vac Instrument bus is a 120/240 j volt ac single phase bus normally powered from a safety  ;

class MCC source which automatically transfers to an  !

alternate emergency safety class MCC source upon loss of i voltage. l Recorder power is provided from the station 120 Vac Vit al l Instrument Bus. This vital bus is a 120-240 volt single-  ;

phase uninterruptible power source used for vital '

instruments and controls. The vital distribution bus receives power from a continuous ac power supply. The '

continuous ac power supply is a three-unit, rotating motor- ,

generator (MG) set consisting of an ac generator, an ac motor, a de motor, and a flywheel. The ac & de motors are -

powered from safety class power sources.

-l; The uninterruptible ac distribution bus is normally energized by the ac generator / motor. Upon loss of power to  ;

the ac motor, the ac starter drops out and the contactor for j the de motor closes automatically, thereby using the dc ,

motor to drive the generator. The flywheel provides stable output from the generator and maintains rated output  :

frequency during the transfer between the ac and de prime  ;

movers. The bus can also be powered directly from a safety l class MCC supplied by the Emergency Diesel Generator. l

1.5 conclusion

VY installation meets the alternate criterion of l NEDO 31558 for power sources.

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