ML20148D439
| ML20148D439 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 01/14/1988 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20148D402 | List: |
| References | |
| NUDOCS 8801250390 | |
| Download: ML20148D439 (6) | |
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UNITED STATES y
y,g NUCLE AR REGULATORY COMMISSION y
WASHINGTON. D. C. 20555
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SAFETY EVALUATION 8Y THE OFFICE OF NUCLEAR REACTOR REGUALTION GULF STATES UTILITIES COMPANY RIVER BEND STATION, UNIT 1 DOCKET NO. 50-458 COMPLIANCE WITH ATWS RULE 10 CFR 50.62 RELATING TO ALTERNATE R0D INJECTION (ARI) AND RECIRCULATING PUMPS TRIP (RPT) SYSTEMS
1.0 INTRODUCTION
On July 26, 1984, Title 10 of the Code of Federal Regulation (CFR) was amended to include Section 10 CFR 50.62, "Requirements for Reduction of Risk from Anticipated Transients Without Scram (ATWS) Events for Light-Water-Cooled Nuclear Power Plants" (known as the "ATWS Rule").
An ATWS is an expected opera-tional transient (such as loss of feedwater, loss of condenser vacuum, or loss of offsite power) which is accompanied by a failure of the reactor trip system (RTS) to shut down the reactor.
The ATVS Rule requires specific improvements in the design and operation of commercial nuclear power facilities to reduce the likelihood of failure to shut down the reactor following anticipated transients, and to mitigate the consequences of an AiVS event.
For each boiling water reactor, three systems are required to mitigate the consequences of an ATWS event.
1.
It must have an alternate rod injection (ARI) system that is diverse (from the reactor trip system) from sensor output to the final actuation devices. The ARI system must have redundant scram air header exhaust valves.
The ARI system must be designed to perform its function in a reliable manner and be independent (from the existing reactor trip system) from sensor output to the final actuation device.
2.
It must have a standby liquid control system (SLCS) with a minimum flow capacity and boron cortent equivalent in control capacity to 86 gallons per minute of 13 weight percent sodium pentaborate solution.
The SLCS and its injection location must be designed to perform its function in a reliable manner.
3.
It must have equipment to trip the reactor coolant recirculating pumps automatically under conditions indic6tive of an ATWS.
This equipment must be designed to perform its function in a reliable manner.
By letters dated July 31 and October 30, 1987 (Ref. 1 and 2) Gulf States Utilities Company (the licensee) provided information to comply with the ATWS Rule.
This safety evaluation report addresses the ARI system (Item 1) and the ATWS/RPT system (Item 3).
The SLCS (Item 2) was addressed in the October 26, 1987 safety evaluation supporting Amendment No.13 to the River Bend license.
8801250390 880114 DR ADOCK O 4]B
I l 2.0 REVIEW CRITERIA The systems and equipment required by 10 CFR 50.62 do not have to meet all of the stringent requirements normally applied to safety-related equipment.
However, this equipment is part of the broader class of structures, systems, and components important to safety defined in the introduction to 10 CFR Part 50, Appendix A, General Design Criteria (GDC).
G0C-1 requires that "structures, systems, and components important to safety shall be designed, fabricated, erected, and tested to quality standards commensurate with the importance of the safety functions to be performed." Generic Letter 85-06 "Quality Assurance Guidance for ATWS Equipment that is not Safety Related" details the quality assurance that must be applied to this equipment.
In general, the equipment to be installed in accordance with the ATWS Rule is required to be diverse from the existing RTS, and must be testable at power.
This equipment is intended to provide needed diversity (where only minimal diversity currently exists in the RTS) to reduce the potential for common mode failures that could result in an ATWS leading to unacceptable plant conditions.
The criteria used in evaluating the licensee's submittal include 10 CFR 50.62 "Rule Considerations Regarding Systems and Equipment Criteria" published in Federal Register Volurre 49, No.124 dated June 26, 1984 and Generic Letter 85-06 "Quality Assurance Guidance for ATVS Equipment that is not Safety Related."
3.0 EVALUATION OF ARI SYSTEM The licensee participated in the BWR Owners Group ATWS implementation alternatives program.
The BWR Owners Group submitted a licensing topical report NEDE-31096-P "Anticipated Transients Without Scram, Response to NRC ATWS Rule 10 CFR 50.62" (Ref. 3) for staff review.
The staff accepted the licensing topical report NEDE-31096-P in Reference 4.
Reference 1 summarizes the licensee's compliance with the ATWS Rule.
The staff's evaluation is addressed in the following sections.
3.1 ARI SYSTEM FUNCTION TIME The licensee stated that all ARI valves must be acutated to meet the system performance requirenents.
Rod injection motion will begin within 15 seconds of the ARI initiation signal.
All control rods will reach their full-in position within 25 seconds of the ARI initiation signal.
This will be verified by tests following installation of the ARI system. The staff finds this acceptable.
3.2 SAFETY-RELATED REQUIREMENTS The ATWS Rule does not require the ARI system to be safety grade, but the implementation must be such that the existing protection system continues to meet all applicable safety related criteria.
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The licensee stated that the ARI system is independent from the existing reactor protection system (RPS)* up to the scram air heacier.
The initiation signals and logic along with the power supplies and ARI valves are independent from the RPS.
The ARI logic will not violate the existing separation criteria of the RPS.
Since the ARI does not interface with any safety-related system, isolation devices will not be used.
The staff finds this acceptable.
3.3 REDUNDANCY The licensee stated that the ARI system has redundant valves at the scram air header.
The ARI system performs a function redundant to the backup scram system of the RPS.
The staff finds this acceptable.
3.4 DIVERSITY FROM THE EXISTING RTS The licensee stated that the API system is "energize to function" and uses dc po.ered solenoid valves.
The ARI solenoid valves are separated from the backup scram valves.
All instrument channel c.omponents are diverse from the existing RPS components.
The staff finds this acceptable.
3.5 ELECTRICAL INDEPENDENCE FROM THE EXISTING RTS The licensee stated that the ARI system is independent from the existing RPS.
The ARI actuation logic is separated from the RPS logic.
The staff finds this acceptable.
3.6 PHYSICAL SEPARATION FROM THE EXISTING RTS The applicant has stated that electrical equipment and wiring for the RPS and the ARI system are physically separate and electrically independent.
They are located so that no single credible event is capable of disabling redundant equipment in a way that would prevent reactor shutdown or removal of decay heat from the core, or that would prevent isolation of the containment in the event of an accident.
Separation requirements were applied to the control power, and instrumentation for all systems concerned.
All safety related systems are designed to comply with the independence and separation criteria in accordance with Section 4.6 (Channel Independence) of IEEE 279-1971.
The instrument cabinets and main control boards conform to the separation critieria defined in Sections 5.6 (Control Switchborads) and 5.7 (Instrumentation Cabinets) of IEEE 384-1974.
Where physical seoaration by enclosures is not possible becasue of the plant design, either a barrier or a 6-inch minimum separation distance is provided between redundant Class IE circuits and between Caiss 1E and non-Class 1E circuits.
In those instances where a barrier or 6-inch separation has not been provided, the design has been analyzed to ensure compliance with RG 1.75, R vision 2, and IEEE 384.
This is acceptable to the staff.
(*RPS in licensee's terminology is same as RTS in ATVS Rule).
- 3.7 ENVIRONMENTAL QUAllF1 CATION The licensee stated that all hardware required for the ARI system to function will be environmentally qualified to conditions that occur during an anticipatec operational occurrence up to the time the ARI function is completed. The staff finds this acceptable.
3.8 QUALITY ASSURANCE The licensee has committed to comply with Generic Letter 85-06, "Quality Assurance Guidance for ATWS Equipment that is not Safety Related." The staff finds this acceptable.
3.9 SAFETY-RELATED POWER SUPPLY The licensee stated that the ARI system will use non-class IE 125V de power that is indeperdent from RPS power. The noninterruptible power source will be provided to allow the ARI system to perform its intended functicn curing any loss of offsite power event. Th; staff finds this acceptable.
3.10 TESTABILITY AT POWER The licensee stateo that the ARI system is designed to permit on-line testing.
The functional test of the Low Reactor Water Level and High Reactor Pressure instrumentation will not cause inadvertent trip because the logic requires two level, pressure or manual initiatien signals to initiate ARI.
In order to test the final actuation relay X101A, B, C, and D, a temporary ju.nper is to be used to avoid an inadvertent ARI scram during testing.
The staff has reviewed the test procedure (Ref. 5) which addresses the practice of using jurper and lifting leads during the performance of surveillance testing, based on this review, the staff concludes that the procedure includes the essential key elements of
'E Information Notice 64-37 to preclude degracing system function as a result of inappropriate practice of using jumpers and to assu e that the safety-related circuitry is restored to normal concition after testing. The staff finds the design acceptable.
3.11 INADVERTENT ACTION The licensee stated that the ARI design will utilize coincident logic. Both channels must be tripped in order to initiate the mitigative actions. The ARI actuation setpoints will not challenge scram setpoints. The staff finds this acceptable.
3.12 RANUAL INITIATION The licensee stated that the manual initiation capability will be provided.
The staff finds this acceptable.
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e 3.13 INFORMATION READOUT The licensee stated that all ARI solenoid valves will provide an open/ closed f
position indication in the Control Room.
Indication will also be provided to l
indicate when the system is in test or out of service.
Annunciators will be provided for:
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1.
ARI Initiated 2.
ARI Ready to Reset 3.
AR1 Manually Armed The staff finds this acceptable.
3.14 COMPLETION OF PROTECTIVE ACTION ONCE IT IS INITIATED The licensee stated that the ARI design will have a seal-in feature to ensure the completion of protective action once it is initiated.
After initial conditions return to normal, deliberate operator action is required to reset the safety system logic to normal.
The staff finds this acceptable.
3.15 CONCLUSION ON ARI SYSTEM As stated in Reference 4, the staff SER on GE Topical Report NEDE-31096-P, the staff does not intend to repeat its review of the design hformation described in the GE Topical Report and found acceptable when the report appears as a reference in a specific license application.
Reference 1 summarizes the licensee's compliance with the ATWS Rule.
The staff finds that the River Bend 1
ARI design is in compliance with the ATWS Rule,10 CFR 50.62 paragraph (C)(3),
and is therefore acceptable.
4.0 EVALUATION OF ATVS/RPT SYSTEM The original RPT logic consisted of two trip systems each with one-out-of-four logic flow water level or Mgh reactor pressure) which would trip both l
recircuiation pumps. This logic has been modified to a two-out of-two logic similar to the Monticello design to prevent inadvertent pump trips.
The RPT initiation signal iill open two circuit breakers in the normal power supply and one circuit breaker in the low frequency motor generator (LFMG) power supply.
The River Bend design uses two power supplies at different frequencies to 5
provide for two speed operation of the pump motors.
The primary power supply, J
used during power operation, is at 60 hertz while the secondary power supply is at 15 hertz to allow for pump operation at one quarter speed during plant j
startup.
The secondary power supply is from a low frequency motor generator i
s...
While breaker redundancy is not provided in the LFMG power supply, this I
does not significantly affect recirculation pump trip reliability in that this power supply is only used for relatively short periods of time during plant startup operation.
In addition to the automatic initiation logic. all breakers have manual operation switches in the main control rc..a.
As stated in Reference 4, the staff SER on GE Topical Report NEDE-31096-P, the Monticello design is an acceptable reference ATWS/RPT design.
The staff concludes that the River Bend ATWS/RPT design is in compliance with the ATWS Rule,10 CFR 50.62 paragraph (c)(5), and is therefore acceptable.
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5.0 REFERENCES
1.
Gulf States Utilities Company letter J. E. Booker to NRC Document Control Desk, dated July 31, 1987.
2.
Gulf States Utilities Company letter J. E. Booker to NRC Document Control Desk, dated Octcber 30, 1987.
3.
GE Topical Report NEDE-31096-P "Anticipated Transients Without Scram; Response to NRC ATWS Rule 10 CFR 50.62," dated December 1985.
4.
Staff SER on GE Topical Report NEDE-31096-P.
Letter from Gus Lainas (NRC) to Terry A. Pickens (BWR Owners' Group Chairman), dated October 21, 1986.
5.
River Bend Station Operating Procedure GMP-0042, "Circuit Testing and lifted Leads and Jumpers" dated June 10, 1987 (REv. 5).
Principal Contributor:
H. Li Dated: January 14, 1988 J
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