ML20245B385

ATWS Alternate Rod Insertion & Recirculation Pump Trip Response to NRC Rule 10CFR50.62

ML20245B385
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Site:	Fermi
Issue date:	06/13/1989
From:	Klemptner A DETROIT EDISON CO.
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ML20245B375	List: ML20245B385 NRC-89-0140, Forwards ATWS Alternate Rod Insertion & Recirculation Pump Trip,Response to NRC Rule 10CFR50.62
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REPORT ANTICIPATED TRANSIENT WITHOUT SCP.AM'(ATWS)

. ALTERNATE ROD' INSERTION (ARI)-AND RECIRCULATION PUMF TRIP (RPT)

RESPONSE TO NRC RULE 10CFR50.62

" Requirements for reduction of risk from anticipated' transients without scram (AWTS) events for light water cooled nuclear power plants".

DETROIT EDISON COMPANY ENRICO FERMI 2 POWER PLANT-June 13, 1989 n

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P Prepared-by:

/d G t b f1 A. Klempther j

Sr. Engineer

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Reviewed by:

C b /7[/7 R.'J. Ballis Supervisor, I&C

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Plant Engineering, Nuclear Engineering Approved by:

O hE f-/5 4 9 J.\\G. Walker sGederal Supervisor Plant Engineering, Nuclear Engineering i

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TABLE'OF CONTENTS' PAGE I.:

INTRODUCTION.

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GENERAL DISCUSSION.

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1.0 ALTERNATE ROD-INSERTION H

1.1-INTRODUCTION.

1 1.2 DESIGN 0BJECTIVES 2

11 3 DESIGN BASIS REQUIREMENTS

~2

-.1.4. FERMI 2' DESIGN IMPLEMENTATION 2

1.5 PLANT SPECIFIC REVIEW CHECKLIST 6

2.0 RECIRCULATION PUMP TRIP i

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'2.1.' INTRODUCTION--

.9 2.2 DESI'GN[0BJECTIVES-9 o

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DESIGN BASIS REQUIREMENTS.

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l2.4 1 FERMI:2< DESIGN. IMPLEMENTATION-9.

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-2.5 COMPLIANCE WITH NRC CRITERIA 2.5.1 Plant-Specific Review Checklist 12 3 0-PREFERENCES 14 j

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.l LIST OF TABLES Table'No.

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.. 1-1 Checklist for Plant Specific Review of Alternate 6

1 Rod Injection System 1

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Checklist for Plant Specific Review of 12 l

. Recirculation Pump Trip l

LIST OF FIGURES 1

Figure'No.

Description Pay 1-1

- Fermi 2 ARI Design 5

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Fermi 2 RPT Design 11 1

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. Introduc' tion I

The following report addresses compliance of Fermi 2 Alternate Rod Insertion i

(ARI) and Recirculation Pump Trip (RPT) systems to the requirements'of the NRC ATWS Rule, 10CFR50.62. The report is based on General Electric (GE) Licensing l

Topical Report NEDE-31096-P-A, " Anticipated Transients Without Scram; Response to NRC ATWS Rule, 10CFR50.62" (Referer.ce 1).

The letter "-A" in the Topical Report identification symbol designt.,es the fact that the topical report has been accepted by the NRC for referencing by the individual utilities in their submittals to the NRC. The NRC accepted Licensing Topical Report NEDE-31096-P by a letter dated October 21, 1986.

Generel Discussion of Fermi 2 ATWS Design On July 26, 1984, the NRC published their final rule on ATWS, 10CFR50.62. This rule, in-paragraphs (C)(3) through (C)(5) requires three systems to mitigate the consequences of an ATWS event. They are: Recirculating Pump Trip (RPT),

4 Alternate Rod Insertion (ARI), and Standby Liquid Control System (SLC).

Paragraph (C)(6) requires that information sufficient to demonstrate to the NRC the adequacy of ATWS mitigating systems shall be submitted.

On October 21, 1986, the NRC published a letter, " Acceptance for Referencing of Licensing Topical Report NEDE 31096-P, " Anticipated Transient Without Scram; Response to NRC ATWS Rule, 10CFR50.62" and Safety Evaluation of the same topical report.- The NRC staff found the topical report to be acceptable for referencing in support of.the utility's subm.ittals describing ATWS modifications. This report and safety evaluation describe what is now referred to as the BWR' generic design requirements for ATWS.

At Fermi 2, ATWS modifications that installed the RPT, ARI and SLC systems were completed during initial construction of the plant. These systems are described in UFSAR' chapters 4 and 7 The installation of ATWS mitigating systems ~at Fermi 2 naceded the approval of the generic design by several years. Therefore, the existing design of Fermi 2 RPT aM ARI differs from the generic design reviewed and approved by the NRC. Design modifications will be implemented during the First Refueling Outage to provide additional features in the RPT and ARI systems that will put the Fermi 2 design in close agreement with the generic design.

This report demonstrates the compliance of Fermi 2 ATWS systems (ARI and RPT) with the ATWS Rule, 10CFR50.62 on the basis of these modifications to be completed during RF01.

1.0 Alternate Rod Insertion 1.1 Introduction This section describes the design criteria for the Alternate Rod Insertion (ARI) system for the Fermi 2 plant as required by the ATWS Rule 10CFR50.62. Table 1-1 (checklist) is provided to demonstrate compliance of Fermi 2 design to the ATWS Rule requirements.

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1 1.1 Design Objectives i

10C850.62, paragraph (C)(3) states:

Each boiling water reactor must have an alternate rod injection (ARI) 4 system that is diverne (from the reactor trip system) from sensor output to the final actuation device. The ARI system must have redundar.t scram ai? header exhaust valves. The ARI must be designed to perform its

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fanction in a reliable manner and be independent (from the existing reactor trip system) from sensor output to the final actuation device.

1 3 Design Basis Requirements j

1 The design basis for ARI is to initiate the control rod insertion I

following a transient and failure-to-scram.

1.4 Fermi 2 Design Implementation The Fermi 2 ARI logic design is depicted in Figure 1-1.

This logic also j

provideo the recirculation pump trip signal. The logic is based on the j

Monticello RPT logic in that it requires a two-out-of-two level or i

pressure signal to initiate the ARI actuation signal. The ARI solenoid valves are used such that either logic train can depressurize the scram air header and tasert the control rods within the required timing criteria (15-25 seconds).

Using the. performance objective of 10 seconds for rod insertion after the initiation of rod movement and assuming that rod movement begins immediately after a change in the state of the scram solenoid valves, the ARI design will complete the rod insertion motion within 10 seconds; that is, rod insertion will start within 15 seconds and be completed within 25 seconds from ARI initiation time.

The'ARI system is designed and installed as Class 1E (safety-related) which exceeds the quality assurance requirements outlined in NRC Generic Letter 85-06. The ARI system utilizes safety-related power supply, cabling, logic components, instruments, and solenoid valves.

The only non safety-related interfaces are accomplished with Class 1E relays with the plant annunciator. A contact to coil separation mechanism ensures that ARI logic components will not be affected by the failure of the annunciator. Because the ARI system is safety-related, no isolators are needed to interface with the other safety-related systems. The ARI system performs a function redundant to the back-up scram system. There are a total of three ARI valves per division installed on che scram air header.

Another ARI valve in each division controls the scram discharge volume vent and drain lines independently from the Reactor Trip System (RTS).

Either division is capable of meeting the design basis rod insertion time.

The ARI system is diverse from the existing RTS ft.nction. The Fermi 2 system that provides the RTS function is the Reactor Protectior, System (RPS). Diversity between the two systems is achieved by utilizing Page 2

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. energize-to-trip logic a valves in the ARI system instead of the deenergize-to trip logic i valves in the RPS.

In addition, ARI solenoid valves ars DC powered as sposed to AC powered RPS scram solenoid valves.

l With respect to the NRC staff's position that manufacturing diversity should be utilized for the analog trip units (ATU) to minimize the potential for a manufacturer's common mode failure, Detroit Edison endorses the BWR Owner's Group position that a sufficient level of diversity exists between ARI and RPS in the present design. That is, although the ARI and RPS both utilize ATUs made by the same manufacturer, the functional diversity obtained by the energize-to-trip vs deenergize-to-trip, and operational diversity resulting from DC power i

supply vs AC power is adequate.

The ARI and RPT are electrically independent from RPS power from the motive power selection to the final actuator. ARI and RPT circuits are divisionally powered from the station Class 1E batteries and the circuitry i

is run in the respective divisional tray / conduit system which is separate and independent from the RPS tray / conduit system. The RPS receives power from two AC motor generator sets, "A and

'B", which are powered from the divisional 480 var. distribution system.

The ARI/RPT systems are installed divisionally from the sensors through the final trip devices (including the ARI solenoids but not including the RPT breakers), so that the physical separation is maintained between the redundant circuits in the opposite divisions. The ARI and RPT systems are physically independent from the RPS since RPS wiring is routed through its own totally enclosed raceway system. Therefore, Fermi 2 ATWS design complies with the ATWS Rule guidance, which cates that the implementation of ARI/RPT must not compromise the separation criteria applied to existing RPS. The implementation of the ATWS modifications will not compromise RPS divisional separation.

ARI components are qualified to IEEE 323-1974 to a degree that meets or exceeds the requirement. That is, the ARI sensors and solenoids are qualified to withstand the environment associated with an ATWS event. The ARI components are qualified seismically to IEEE 344-1975 although the rule does not require it.

All of the hardware included in the ARI design from sensors to final actuators (solenoid valves) bave been purchased and installed as QA1 (Detroit Edison's designation for compliance with 10CFR50, App B). The design is in compliance with generic letter 85-06, " Quality Assurance Guidance for ATWS Equioment that is not Safety-Related", dated April 16, 1985.

Motive-and logic power for the ARI and RPT systems is obtained from the l

Class IE Divisional batteries. These batteries are properly sized to provide power for all required design functions, including loss of offsite power. The RPS is an AC powered system which is independent from the Class IE divisional batteries.

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~ The already installed ARI and RPT logic utili2:e a redundant two-out-of-two arrangement in order to provide testing, calibration, or repair capability L

at' power without employing bypasses. However, the present design

' configuration does not permit exercising one relay in each division at l

power without lift'ng a lead to bypass the trip. Because of this, and the risk of a spurious crip, present surveillance procedures do not exercise all of the logic at power (all logic is exercised at shutdown).

Therefore, to ensure the compliance with-ATWS Rule requirement for the

-testability at power, a circuit modification based on the Monticello design will be implemented at the First Refueling Outage to permit maintenance. repair, _ test or calibration of all circuit devices up to,.but not including the final trip devices (ARI solenoids and RPT breakers).

The automatic signal to initiate the ARI function will come from high reactor pressure vessel (RPV) pressure or low RPV water level. The RPV high'pcessure setpoint (1133 psig) is set above the scram high RPV

. pressure setpoint (1068 psig). The RPV low water level setpoint (110.8 in.):is set lower than scram low RPV water level setpoint-(173 4 in.). To-minimize,the possibility of an inadvertent ARI/RPT actuation, the modified design will use the "two-out-of-two" sensor logic arrangement. That is,

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the trip of the level or pressure channels (A and C for Division I, or B e

and D for Divis hn II) will initiate one division of ARI. The Fermi 2

!'l design was implemented in 1984, prior to the-final ATWS Rule formulation.

The present design does not have manual initiation capability. Detroit Edison'will add four pushouttons to control center panel H11P603 (two in Division I and two-in Division II) for ARI manual initiation during the First Refueling Outage. Tne operation of two pushbuttons in one division will be required to initiate the manual ARI/RPT.

Presently, ARI system operational information available in the main control room consists of an alarm on the main annunciator for ARI

initiation and ARI valve position indicating lights (open/close). A design modification will be implemented during the First Refueling Outage to provide the operator with ARI/RPT initiation alarm on a divisional

_ basis. The_ alarm will come in after the level or pressure channels trip

_(A or-C for Division I and B or D for Division II) or if ARI/RPT is manually initiated. An additional alarm will be provided for the armed position of the ARI manual initiation switches.

The:ARI sy em is sealed in upon initiation to allow rod insertion to be completed and will remain in operation until it is rese' manually.

However, to enforce administrative procedures, that provent the operator from, resetting the initiation prior to protective acti. completion, a hardware design change will be implemented prior to the end of first i

I refueling. This design change will add a time delay to each division's

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legic that prevents manual resetting until a predetermined time after either automatic or manual initiation.

i The plant specific ARI design checklist is provided in this report to

-facilitate the review of Fermi 2 ARI design.

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DIVISIGN 2 DIVISICN 1

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LC# LEVEL HI PRESS MANUAL INITIATICN A

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A 93 UNITS 92 UNITS RPS LCGIC RPS LCGIC A/ B A/ B FERMI 2 ARI DESIGN FIGURE 1-1

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a lij 1.5 'gANT SPECIFIC REVIEW CHECKLIST

The'following checklist (Table-1-1), prepared by the NRC Staff (SER, Appendix A), is'provided for assessing the acceptability of the Fermi 2 ARI1 design.

TABLE 1-1 CHECKLIST FOR PLANT SPECIFIC REVIEW OF ALTERNATE ROD INJECTION SYSTEM CONFORMANCE WITH ARI SER e

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YES REMARKS 1.

ARI SYSTEM FUNCTION TIME Rod. injection motion will begin within 15 seconds X

and be completed within 25 seconds from ARI initiation.

)

2.

~ SAFETY REQUIREMENTS

'(A) Class 1E isolators are used to interface N/A See page 2 with safety-related systems.

3 (3) Class 1E isolators are powered from a N/A See page 2 Class'1E source.

3 (C) -Isolator qualificat'lon documents are N/A See page 2 l

available for NRC Staff audit.

l 3

REDUNDA'WCY i

The ARI system performs a function redundant to X

the backup scram system.

4.

DIVERSITY FROM EXISTING RTS

'(A) ARI Systen is energize-to-function X

(B) ARI System uses de powered valves X

-(C) Instrument channel components (excluding X

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sensors but including all signal conditioning

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and isolation devices) are diverse from the the existing RTS components.

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NRC-89-01180 TABLE 1-1 (Continue'd)

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ELECTRICAL INDEPENDENCE FROM THE EXISTING RTS (A) ARI actuation logic separate from RTS logic X

(B) ARI circuits are. isolated from safety-N/A See page 2

.related' circuits.

6.

PHYSICAL SEPARATION FROM THE EXISTING RTS A)

ARI System is physically separated from RTS X

See page 3 L

17 ENVIRONMENTAL-QUALIFICATION i

ARI equipments are qualified to. conditions during X

an ATWS event up to the time the ARI function is completed.

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QUAL'ITY ASSURANCE A)

Comply with Generic Letter 85-C5

_X-9.

SAFETY-CELATED POWER SUPPLY (A).ARI System power independent from RTS X

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(B)~ ARI System can perform its function during X_

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any loss-of-offsite power event.

10. TESTABILITY AT PONER X

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(A) ARI testable at power X

(B) ~ Bypass fratures conform to bypass criteria used in RTS 11.

INADVERTENT ACTUATION (A) ARI actuation setpoints will not challenge X

scram (B) Coincident logic is utilized in ARI design X

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12. MANUAL IMITIATION (A) Manual initiation capsbility is provided X_ _ _ See page Il e

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13..INFORMATION' READOUT

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control room.

14. COMPLETION OF PROTECTIVE ACTION ONCE IT IS X

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INITIATED-

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'2.0 Recirculation Pump Trip (RPT) 31 stem

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2.1 Introduction This section describes the design criteria for the recirculation pump trip (RPT) system for the Fermi 2 Power Plant as required by the ATWS Rule 10CFR50.62.

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2.2 Design Objectives.

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10CFR50.62, paragraph (C)(5) states, "Each boiling water reactor must have i

equipment to trip the reactor coolant recirculating pumps automatically under conditions indicative of an ATWS. This equipment must be designed to.

perform its function in a reliable manner."

a 23 Design Basis Requirements The dasign basis for RPT is to trip reactor recirculation pumps (RRP) following a transient and failure-to-scram.

-1 2.4 Fermi 2 Design Implementation The Fermi 2 RPT design was implemented in 1984, prior to the ATWS Rule formulation. The RPT de. sign was based on the Monticello design in that it.

employs two trip coils in each recirculation system motor generator set

. generator: field breaker. This design provides for redundant trips of both motor generator sets following the transient and f. allure-to-scram. To minimize the possibility of field breakers being tripped inadvertently, the automatic' trip signals are arranged in two-out-of-two logic.

+

The automatic signal to initiate the RPT function will come~ iron high RPV pressure or. low RPV water. level. The'RPV high pressure setpuint'(1133 psig).is set above the scram high RPV pressure setpoint (1068 psig). The

'RPTl low. water level setpoint (110.8 in.) is set lower than scram low RPV water level setpoint (1'(3 4 in.).

Sensors, logic, and cabling are safety related. Final control elements, the generator field breakers and trip coils are not. The sensors and logic trains are divisional and redundant.- A single final actuation device is provided on a divisional basis.

The RPT sensors and channel ecmponents (excluding field circuit breaker trip coils)'are qualified to operate while exposed to the environmental conditions associated with an ATWS event.

}

For a description of specific RPT logic design features, see section 1.4, p

with the following exceptions, The'RP'I logic delays recirculation pump trip on low reactor vessel a.

f water level for 9 seconds. This time delay was provided to account for 1

the difference in the pump coastdown time if the field breaker is

. tripped rather than the MG set drive motor, as was assumptt in the LOCA

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analysis.

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.lb./'The' manual reset of the generator field breaker ' rip seal-in circuit.

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will be implemented'without any. time delay due to the rapid, operation _.

S time'of the circuit breaker..

.c.; The RPT.will bc. manually initiated by the same two pushbuttons (oh a

.~ divisional basis) as ARI. 'Thi difference will be that 191tiation of-ono. division: will. trip both ' field breakers.

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Fermi 2'is planning to implement the MG set drive motor trip.. This will provide diversity in-final actuation device, and improve the reliability of the system.

Implementation schedule will be

.prioritized in the Fermi 2 five year plan.

The compliance of'RPT with NRC criteria is demonstrated in Table 2-1.

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2.5.1. Plant Specific Review Checklist The following checklist (Table 2-1), prepared by General Electric in.

NEDE-31096-P-A, ic provided for assessing the acceptability of.the Fermi'2 RPT design.

~TALLE 2-1 t

.RPT EVALUATION FERMI 2.

CONFORMANCE WITH BWROG f:

GUIDANCE 1.

SAFETY-RELATED o NOT REQUIRED,.BUT IMPLEMENTATION MUST NOT

'YES PREVENT EXISTING RTS FROM MEETING ALL APPLICABLE SAFETY CRITERIA.

2.

' REDUNDANCY-

'YES o NOT REQUIRED DIVERSITY FROM RTS

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o. REASONABLE AND PRACTICABLE DIVERSITY IS YES

_ REQUIRED NOT' INCLUDING SENSORS AND FINAL CONTROL. DEVICES.

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ELECTRICAL INDEPENDENCE FROM RTS YES n

o REQUIRED FROM SENSOR OUTPUT TO THE FINAL L

ACTUATION DEVICE 5

PHYSICAL SEPARATION FROM RTS o NOT REQUIRED IF EXISTING RTS REDUNDANT YES I

DIVISIONS AND CHANNELS ARE SEPARATED.

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FERMI 2-CONFORMANCE WITH BWROG GUIDANCE E

6... ENVIRONMENTAL QUALIFICATION o REQUIRED FOR OPERATIONAL OCCURRENCES YES

-7 SEISMIC QUALIFICATION YES o NOT REQUIRED 8.

QUALITY ASSURANCE o NRC GENERIC LETTER 85-06 YES 9

SAFETY-RELATED POWER SUPPLY l

o' SAME AS ARI YES j

'O 5' STABILITY AT POWER o REQUIRED YES

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INADVERTENT ACTUATION YES o SAME AS ARI l

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References GE Licensing Topical Report, NEDE-31096-P-A, " Anticipated

1..

Transient without Scram Response to-NRC ATWS Rule, 10CFR50.62",.

. dated February, 1987.

2.

'USNRC Generic Letter 85-06, " Quality Assurance Guidance for ATWS Equipment That is Not Safety Related", dated' April 16, 1985.

3 USNRC-Report No., 50-341/88029 (DRS)

' 4.;

Fermi 2 UFSAR,.Section 3 12, " Separation Criteria for Safety

.Related Mechanical and Electrical Equipment; Sections 7.1.2.1 33, i

7.6.1.18 and 7.6.2.18, " Alternate Rod Insertion"; Sections

'[,

7.1.1.2 and 7 7.1.2 3 1, " Recirculation Pump Trip"; Section 15.8, 1

c

" Anticipated' Transient Without Scram (ATWS)".

5. -

Detroit Edison Letter, NRC-89-0053 dated March 17, 1989 6.

USNRC Safety Evaluation of Topical Report (NEDE-31096-P),

" Anticipated Transient Without Scram, Response to ATWS Rule, 10CFR50.62", dated October 21, 1986.

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