ML20235H035

Safety Evaluation Re Alternate Rod Injection & Recirculating Pump Trip Sys

ML20235H035
Person / Time
Site:	Cooper
Issue date:	09/23/1987
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20235H016	List: ML20235H014 ML20235H035
References
GL-85-06, GL-85-6, NUDOCS 8709300341
Download: ML20235H035 (9)

Text

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    $ .  "'/ j_                           W ASHINGTON, D. C. 20555 jl SAFETY EVALUATION ON COOPER NUCLEAR STATION COMPLIANCE WITH ATWS RULE 10CFR50.62 RELATING TO ALTERNATE R00 INJECTION (ARI) AND RECIRCULATING PUMPS TRIP (RPT) SYSTEMS DOCKET NO. 50-298

1.0 INTRODUCTION

On July 26, 1984, the Code of Federal Regulations (CFR) was amended to include Section 10CFR50.62, " Requirements for Reduction of Risk from AnticipatedTransientsWithoutScram(ATWS)EventsforLight-Water-Cooled Nuclear Power Plants" (known as the "ATWS Rule"). An ATWS is an expected operational 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 shutdown the reactor. The ATWS Rule requires specific improvements in the design and operation of commercial nuclear power facilities to reduce the likelihood of failure to shutdown the reactor following anticipated transients, and to mitigate the consequences of an ATWS 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. l 8709300341 870923 PDR ADDCK0500,g8 I

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2. It must have a standby liquid control system (SLCS) with a minimum flow capacity and boron content equivalent in control capacity to 86 gallons per. minute of 13 weight percent sodium pentaborate solution.

The SCLS 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 indicative of an ATWS. This

                                . equipment must be designed to perform its function in a reliable manner.

By letters dated October 14,1985 (Ref.1) and April 8, August 4,1987 (Ref. 2 & 3), Nebraska Public Power District '(the Licensee) provided information to comply with the ATWS Rule. This safety evaluation report addressestheARIsystem(Item 1)andtheATWS/RPTsystem(Item 3). The SLCS (Item 2) will be addressed in a separate document. 2.0 REVIEW CRITERIA i The systems and equipment required by 10CFR50.62 do not have to meet all of the stringent requirements nonnally 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 10CFR50, Appendix A General Design Criteria (GDC). GDC-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 perfonned." 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 1 i t w____--__ ._

o-at power. This equipment is intended to provide needed diversity (where only minimal diversity currently exists in the RTS) to reduce the potential for comon mode failures that could result in an ATWS leading to unacceptable plant conditions. The criteria used in evaluating the licensee's submittal include 10CFR50.62 " Rule Considerations Regarding Systems and Equipment Criteria" published in Federal Register Volume 49, No.124 dated June 26, 1984 and Generic Letter 85-06 " Quality Assurance Guidance for ATWS Equipment that is not Safety Related." 3.0 EVALUATION OF ARI SYSTEM The licensee is participating 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 10CFR50.62" (Ref. 4) for staff review. The staff accepted the licensing topical report NEDE-31096-P in Reference 5. Reference 2 summarizes the licensee's compliance with the ATWS Rule. The staff's evaluation is addressed in the following section. 3.1 ARI SYSTEM FUNCTION TIME The licensee stated that the size of the ARI solenoid valves has been selected, based on actual plant configuration, to allow the insertion of all control rods to begin within 15 seconds of initiation of the ATWS 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.

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3.2 SAFETY-RELATED REQUIREMEN E

                             ~The ATWS Rule does not require the ARI system to be safety grade, but the
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implementation must be such that the existing protection system continues to meet all applicable safety related criteria.

                           ' The licensee stated that the Cooper ARI will utilize the existing sensors from the Recirculation Pump Trip (RPT) system which are independent from the existing reactor protection system. The ARI will maintain the present separation criteria' that exists between safety-related systems and the RPT
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system.- The ARI logic will not violate the existing separation criteria of the Reactor Protection System (RPS)*. Since the ARI does not interface with any safety-related system, isolation devices will not be used. The staff finds this acceptable. (*RPSinlicensee'ste'rminologyissameas RTS in ATWS Rule) 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 and the RPS. The staff finds this acceptable. 3.4 DIVERSITY FROM THE EXISTING RTS The licensee stated that the ARI system controls, instrumentation, and solenoid valves are de powered with the solenoid valves energized to open. The ARI solenoid valves are separated from the backup scram valves. All instrument channel components including the sensors will be diverse from the existing RTS components. The staff finds this acceptable. 3.5 - ELECTRICAL INDEPENDENCE FROM THE EXISTING RTS The licensee stated that electrical independence from the RPS will be provided from sensor output to final actuation devices (ARI solenoid

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e valves). The ARI actuation logic is separated from the RTS logic. The staff finds this acceptable. 3.6 PHYSICAL SEPARATION FROM THE EXISTING RTS,_ The licensee stated that the ARI system is physically separated from the RPS by the following means:

1. ARI initiation signals are transmitted from different sensing instrumentation than that of RPS.

2. - ARI wiring and cables will be routed in separate conduits from either RPS Division I or Division 11 wiring.

3. ARI instrumentation and control in the Control Room will be physically separated from their RPS counterparts.

4. The ARI actuating solenoid valves on the scram air header are different than those used by the RPS.

The staff finds this acceptable. 3.7 ENVIRONMENTAL QUALIFICATION Th'e licensee stated that all hardware required for the ARI to function  ! properly will be environmentally qualified to conditions that occur during an anticipated operational occurrence. Qualification of new equipment will be to temperature, pressure, humidity, and radiation levels associated with an ATWS event up to the time the ARI function is complete. 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.  !

4 3.9 SAFETY-RELATED p0WER SUPPLY The licensee stated that the ARI will use'nondivisional de power that is independent from RPS power. A noninterruptible power source will be provided to allow the ARI to perform its intended function during any loss of offsite power event. The staff finds this acceptable. 3.10 TESTABILITY AT POWER The licensee stated that the ARI system will be testable up to, and including, the final actuating devices while the reactor is at power. A 3-way ARI solenoid will be installed in the scram air header supply as close as possible to the Hydraulic Control Units (HCUs) to block the air supply pressure leading to the HCU and SDV and to depressurize this portion of the air header upon ARI initiation. A separate solenoid valve will be installed downstream of the vent portion of the 3-way valve to prevent inadvertent header depressurization. A 2-way solenoid ARI valve will be installed in parallel with the 3-way solenoid valve to allow continued air supply to the header during plant operation surveillance testing of the 3-way solenoid valve. The other three ARI air header vent paths contain an inboard and outboard ARI solenoid valve in series. During surveillance testing, all inboard and outboard valve groupings will be tested I separately. The ARI system utilizes no bypass features for testing. The staff finds this acceptable. , 1 I 3.11 INADVERTENT ACTION 1 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. l l l i (' I _ __ I

j 3.12 MANUAL INITIATION The licensee stated that the manual initiation capability will be provided. The staff finds this acceptable. 3.13.INFORMATION READ 0UT The licensee stated that all ARI solenoid valves will provide an open/ closed position indication in the Control Room. Indication will a' Iso ce  ! provided to indicate when the system is in test or out of service. Two annunciators will be provided for ARI initiation. They are:

1. ARI Channel 1 or 2 Initiated

2. ARI Initiated (either manual or automatic)

The staff finds this acceptable. 3.14 COMPLETION OF PROTECTIVE ACTION ONCE IT IS INITIATED j The licensee stated that the ARI design will have a seal-in feature for  ; 30 to 35 seconds to ensure the completion of protective action once it is f initiated. After initial conditions return to nortral, deliberate operator action is required to reset the safety system logic to normal. The staff

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finds this acceptable. -{ 3.15 CONCLUSION ON ARI SYSTEM As stated in Reference 4, the staff SER on GE Topical Report NEDE-31096-P, l the staff does not' intend to repeat its review of the design information  ! described in the GE Topical Report and found acceptable when the report appears as a reference in a specific license application. Reference 2 summarizes the licensee's compliance with the ATMS Rule. The staff finds I l i

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d 8 that the Cooper Station AR1 design is in general compliance with the ATWS Rule,10CFR50.62 paragraph (C)(3). 3.16 ARI TECHNICAL SPECIFICATIONS The equipment required by the ATWS Rule to reduce the risk associated.with an ATWS event must be desigr.ed to perform its function in a reliable manner. A method acceptable to the staff for demonstrating that the equipment satisfies the reliability requirements of the ATWS Rule is to provide ARI Technical Specifications which include operability and surveillance requirements. The staff will provide guidance on a generic basis regarding Technical Specification requirements for ARI at~ a later date. 4.0 EVALUATION OF A_TWS/ PPT SYSTEM By. letter dated April 8,1987, the licensee stated that the present RPT system at Cooper will be upgraded to the "Monticello" design which is described in NEDE-31096-P. The licensee will install redundant trip coils on the field breakers of the recirculation system motor-generator sets and will use a redundant two-out-of-two initiation logic. 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 Cooper's ATWS/RPT design is in compliance with the ATWS Rule,10CFR50.62 paragraph (C)(5), and therefore is acceptable.

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4,. 5.0 REFERENCE (1) Nebraska Public Power District letter J. M. Pilant to

                                  'H. L. Thompson, Jr. , dated October 14, 1985.

(2) Nebraska Public Power District letter G. A. Trevors to NRC Docunent Control Desk, dated April 8,1987. (3)' Nebraska Public Power district telex copy from G. Smith to.NRC Project Manager W. Long, dated August 4,1987. (4) GE Topical Report NEDE-31096-P " Anticipated Transients Without Scram;-Response to NRC ATWS Rule 10CFR50.62," dated December, 1985. 1 (5) Staff SEP on GE Topical Report NEDE-31096-P. Letter from Gus Lainas (NRC) to Terry A. Pickens (BWR Owners' Group Chairman), dated October 21, 1986. 1 i j l _ _ _ _ _ _ _ _ I}}