BECO-93-136, Provides Response to NRC 930811 Request to Review Neutron Flux Monitoring Sys Instrumentation Against Criteria of NEDO-31558-A Re Reg Guide 1.97

Provides Response to NRC 930811 Request to Review Neutron Flux Monitoring Sys Instrumentation Against Criteria of NEDO-31558-A Re Reg Guide 1.97

ML20059A959
Person / Time
Site:	Pilgrim
Issue date:	10/21/1993
From:	Boulette E BOSTON EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
RTR-REGGD-01.097, RTR-REGGD-1.097 BECO-93-136, TAC-M77660, NUDOCS 9310270237
Download: ML20059A959 (5)

Text

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BOSTON EDISON

. Pilgren Nuclear Power Station Rocky Hill Road Plymouth, Massachusetts 02360 e

E. T. Boulene, PhD Senor Vee Presdent- Nuclear i i

BECo 93-13^

October 21, 1993 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 License DPR-35 ,

Docket 50-293 Regulatory Guide 1.97: Boiling Water Reactor Neutron Flux Monitorina (TAC No M77660)

The attachment to this letter provides Boston Edison Company's (BEco) response to an NRC request dated August 11, 1993.

The August 11, 1993 letter requested us to review our neutron flux monitoring

• system (NMS) instrumentation against the criteria of NED0-31558-A to determine whether Pilgrim Nuclear Power Station met the criteria. This response confirms that Pilgrim meets most of the criteria provided in NE00-31558-A. We have, however, provided a basis for deviating from strict compliance with the ,

criterion requiring the NMS to be powered by an uninterruptible power source and have provided additional discussion of other criteria.

t Additional engineering effort is required to determine the applicable ATWS temperature to be used in connection with the ATWS environmental criterion.

We will be working with other utilities through the BWR Owner's Group to establish a suitable basis for analysis. We will provide an update and a schedule for any remaining work in the February,1994, BEco Long Term Program .

(LTP) update letter.

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E. T. Boulette, Ph.D. #

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BOSTON EDISON COMPANY ,

U. S. Nuclear Regulatory Commission

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cc: Mr. R. Eaton, Project Manager Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation r Mail Stop: 14D1 '

O. S. Nuclear Regulatory Commission 1 White Flint North

• 11555 Rockville Pike Rockville, MD 20852  ;

U. S. Nuclear Regulatory Commission i Region I i 475 Allendale Road .

King of Prussia, PA 19406 I Senior NRC Resident Inspector .)

Pilgrim Nuclear Power Station

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Attachment to BEco Letter 93- 136 i Rea. Guide 1.97 - BWR Neutron Flux Monitorin_g l l

A. General {

Pilgrim Station meets the requirements of the following design criteria in NED0-31558-A 5.2.1 (range) -

5.2.3 (response characteristic)  !

5.2.6 (seismic qualification) .

5.2.7 (redundancy and separation)  !

5.2.9 (channel availability) ' '

5.2.10 (quality assurance)  ;

5.2.11- (display and recording) ,,

5.2.12 (equipment identification) l 5.2.13 (interfaces)  !

5.2.14 (service, test, and calibration) '

5.2.15 (human factors) ,

5.2.16 (direct measurement) j B. Justification of Specific Desian Criteria Deviation  !

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1. Criterion 5.2.2 (Accuracy) ,

NED0-31558-A states an accuracy of +/- 2% of rated power is judged to be f sufficient to allow the operator to take appropriate action. The NEDO goes on  !

to say that by proper and frequent calibration of the LPRMs, the power range  !

accuracy level can be met. PNPS has an extensive program for performing j surveillance on the Neutron Monitoring System and will continue to perform the  !

required surveillance in lieu of preparing loop accuracy calculations.  ;

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The Neutron Monitoring System at PNPS is included in normal maintenance i programs established by the plant staff. These procedures demonstrate and  :

ensure system and recorder operability. The power range accuracy is dependent }

on the calibration of the LPRM signals and heat balances to provide accurate i measurement of average core-wide power. The calibration schedule has been  ;

l established to ensure Technical Specification requirements are satisfied and  !

the instrument requirements are within the manufacturer's perforniance l l specif' ' ion.

l Since PNPS erforms many calibrations, functional checks, and heat balances, i it is reasonable to expect the Neutron Monitoring System accuracy to be sufficient to allow the operator to make appropriate action decisions, j

2. Criterion 5.2.4 (Eauipment Oualification) and Criterion 5.2.5 (Function '

Time) s Criteria 5.2.4 (Equipment Qualification) and 5.2.5 (Function Time) require a  :

plant-specific e:."'uation of ATWS environments in comparison with NMS design .!

specifications to insure NMS equipment performance. l i

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LPRM detectors consists of the following types of components located in the drywell: < '

a) Penetrations b) Field cables  :

c) Connectors Our review indicates the above components have been designed to withstand high temperature environments. Drywell temperature for an ATVS event at PNPS has  :

not been determined at this time.

l The PNPS safety valves discharge directly into the drywell and will therefore produce a higher temperature in the drywell during an ATWS event than in ,

plants with safety valves that discharge into the torus or wetwell. '

A BWROG workshop was held to discuss this topic. Additional time is needed to  !

work with other BWRs to determine the applicable ATWS temperature profile and  !

to complete analysis.  :

3. Criterion 5.2.8 (Power Sources) ,

t PNPS design does not fully meet Criterion 5.2.8 which requires uninterruptible .

and reliable power sources. Our review indicates a deviation is justified for .l PNPS.  ;

Pilgrim's Average Power Range Monitoring (APRM) is powered by two separate .

Reactor Protection System (RPS) Motor-Generator Power Supplies (A and B RPS M- f G sets, panel C511 A and B). The RPS M-G sets are high-quality and reliable -

power sources. The 480v motor-generator sets are the normal source of' power for the APRM's.  !

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There is no single power supply failure that would cause a loss of both NMS channels when they are powered by their normal suurce. During a loss-of-  ;

offsite-power (LOOP) event, normal power to the NMS would be temporarily lost.  !

However, backup power is available via a 480/120v transformer fed from an e emergency diesel generator (EDG). Either one of - , '~isions of the RPS can i be energized. Operator action is required to t.onsier normal power to back-up power via a transfer switch located in the RPS M-G set room. The M-G set room l is located convenient to the control room and is easily accessible.  !

l In addition to the above, the Rod Position Indication System (RPIS), Reactor i manual control, and the EPIC computer are available to provide the operator  !

with alternative information concerning reactor power during an ATWS. Our ,

review concludes that no single failure will prevent operators from 1 determining whether or not the reactor is shut down using APRMs, RPIS, and the l EPIC computer. Power supplies for these information systems are separate from  !

each other and are highly reliable. The power supply for each system is described below:

a e APRM- RPS M-G set backed by EDG (after operator action)

• RPIS- Uninterruptible vital M-G set (AC and DC motor combination) with ,

EDG as a backup

• EPIC- Uninterruptible with battery backup power l 5

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1 In the-event that information is not available or reactor power level cannot be determined with the above systems, operators will follow the guidance ,

provided in the Emergency Operating Procedures (E0P-02) by utilizing Alternate  !

Rod Insertion methods and injection of boron via the Standby Liquid Control  :

System. Hence, loss of NMS, concurrent with loss of the information systems, provides no decrease in plant safety.

Based on the above discussion, there would be no significant increase in plant -

safety by powering the APRM from uninterruptible power supplies and therefore  !

deviation from criterion 5.2.8 of NED0-31558-A is justified for Pilgrim.  !

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