ML053490178

Safety Evaluation for Proposed Change of Technical Specification to Eliminate the Reactor Coolant Pump Breaker Position Reactor Trip Function.

ML053490178
Person / Time
Site:	Farley
Issue date:	12/09/2005
From:	Lois L NRC/NRR/ADES/DSS/SBWB
To:	Marinos E NRC/NRR/ADRO/DORL/LPLC
References
TAC MC6332, TAC MC6333
Download: ML053490178 (4)

Text

December 9, 2005 MEMORANDUM TO: Evengelos Marinos, Chief Plant Licensing Branch C Division of Operating Reactor Licensing FROM: Lambros Lois, Acting Chief /RA/

BWR Systems Branch Division of Safety Systems

SUBJECT:

JOSEPH M. FARLEY NUCLEAR PLANT, UNITS 1 AND 2 - SAFETY EVALUATION FOR PROPOSED CHANGE OF TECHNICAL SPECIFICATION TO ELIMINATE THE REACTOR COOLANT PUMP BREAKER POSITION REACTOR TRIP FUNCTION (TAC NOS. MC6332 AND MC6333)

By letters dated March 8, 2005 and August 16, 2005, Southern Nuclear Operating Company (SNC), the licensee for the operation of Joseph M. Farley Nuclear Plant Units 1 and 2 (FNP),

proposed changes of Technical Specification (TS) 3.3.1 to eliminate the Reactor Coolant Pump (RCP) Breaker Position Reactor Trip Function at FNP. The change will allow the elimination of a trip circuitry that is susceptible to single failure vulnerabilities that can result in unwarranted reactor trips. In the current safety analysis of design basis accident (DBA) documented in the FSAR at FNP, the RCS Low Flow reactor trip is the primary reactor trip function following a loss of RCS flow transient. The RCP breaker position reactor trip function serves as one of the backup reactor trip function in a loss of RCS flow transient.

The staff has reviewed the licensees submittals and concluded that its proposed changes are acceptable as discussed in the enclosed safety evaluation.

Docket Nos.: 50-348 and 50-364

Enclosure:

As stated CONTACT: C. LIANG, SBWB/DSS, 415-2878 DISTRIBUTION J. Wermiel J. Nakoski L. Lois R. Martin H. Garg OFFICE SBWB/DSS SBWB/DSS NAME CLIANG LLOIS DATE 12/ 08 /05 12/ 9 /05 DOCUMENT NAME: G:\DSS\FARLEY-RPS.SER.WPD

SAFETY EVALUATION BY OFFICE OF NUCLEAR REACTOR REGULATION CONCERNING CHANGE OF TECHNICAL SPECIFICATION TO ELIMINATE THE REACTOR COOLANT PUMP BREAKER POSITION REACTOR TRIP FUNCTION SOUTHERN NUCLEAR OPERATING COMPANY JOSEPH M. FARLEY NUCLEAR PLANT UNIT 1 AND 2 DOCKET NUMBERS 50-348 AND 50-364 1.0 Introduction By letters dated March 8, 2005 (Ref. 1) and August 16, 2005(Ref. 2), Southern Nuclear Operating Company (SNC), the licensee for the operation of Joseph M. Farley Nuclear Plant Units 1 and 2 (FNP), proposed changes of Technical Specification (TS) 3.3.1 to eliminate the Reactor Coolant Pump (RCP) Breaker Position Reactor Trip Function (Function 11) at FNP.

The change will allow the elimination of a trip circuitry that is susceptible to single failure vulnerabilities that can result in unwarranted reactor trips. In the current safety analysis of design basis accident (DBA) documented in the FSAR at FNP, the RCS Low Flow reactor trip is the primary reactor trip function following a loss of RCS flow transient. The RCP breaker position reactor trip function serves as one of the backup reactor trip function in a loss of RCS flow transient. There are quite a few Westinghouse designed PWRs currently operating without the Reactor Coolant Pump (RCP) Breaker Position Reactor Trip Function in their reactor protection system (RPS).

2.0 Regulatory Evaluation The licensee proposed changes involve the elimination of the RCP Breaker Position Reactor Trip Function and delete Function 11 from the current TS 3.1.1 at FNP. The RCP breaker position reactor trip function is one of the backup reactor trip function for mitigating a loss of RCS flow transient. The regulatory requirements governing these proposed change include; 1)

GDC-21, regarding RPS reliability, 2)GDC-22, regarding RPS functional diversity, and 3) 10 CFR 50.36, regarding the need for establishing of limited conditions for operation (LCO) in TS based on the four Criteria specified in 10 CFR 50.36 (c)(2)(ii)(A)-(D). The NRC staffs review focused on the effects of the licensee proposed change to the compliance of the above stated regulatory requirements.

3.0 Technical Evaluation In response to the staff request for additional information, the licensee, in its letter dated August 16, 2005, indicated that the results of its evaluation confirmed that the current design of RPS will satisfy all the regulatory requirements stated in Section 2.0 after elimination of the RCP breaker position reactor trip function. The effects of the proposed change to each of the relevant regulatory requirements are addressed below:

3.1 GDC- 21 & 22 - Protection System Reliability, Diversity and Independence In the current safety analysis, the reactor coolant system (RCS) low flow reactor trip is the primary reactor trip for a complete loss of flow event and a partial loss of flow event. The RCP breaker position reactor trip function, RCP under voltage reactor trip and RCP under frequency ENCLOSURE

2 reactor trip were served as anticipatory trip to backup the primary trip function. Determistically, After elimination of the RCP breaker position reactor trip function, the RPS still maintain sufficient redundancy to assure high reliability of the system. Also, functional diversity for the loss of flow events are provided through reactor trips associated with OT delta T, OP delta T and high pressurizer pressure trips considering common mode failure which could affect multiple channels. Thus, the FNP RPS still meet the relevant regulatory requirements of GDC-21 and 22 without RCP breaker position reactor trip function.

3.2 10 CFR 50.36 (c)(2)(ii)(A)-(D) - TS LCO Requirements Criterion 1 - This Criterion is not applicable to the RCP breaker position reactor trip function since this backup trip function is not used for detection and indication in the control room of any degradation of the reactor coolant boundary.

Criterion 2 - This Criterion is not applicable to the RCP breaker position reactor trip function since this backup trip function is not an initial condition of a DBA or transient analysis.

Criterion 3 - The RCP breaker position reactor trip function is not a part of the primary success path related to the integrity of a fission product boundary. It is merely served as an anticipatory reactor trip function to backup the primary trip, the low RCS flow reactor trip function.

Criterion 4 - The RCP breaker position reactor trip function is not relied upon as a signal to initiate a reactor trip for any events modeled in the scope of the PRA model. The PRA model relies upon the high pressurizer pressure reactor trip signal for a variety of initiating events which include a complete or partial loss of flow events.

Based on the above assessment, the current RPS at FNP will continue to meet all relevant regulatory requirements without the RCP breaker position reactor trip function.

4.0 Conclusions The staff has reviewed the licensee proposed TS changes regarding the elimination of the RCP breaker position reactor trip function (TS 3.3.1, Function 11) from its RPS to support operations of the FNP units 1 and 2. The results of the licensees evaluation has adequately confirmed that the current RPS at FNP will continue to meet all relevant regulatory requirements without the RCP breaker position reactor trip function. Therefore, The staff concludes that the proposed TS changes are acceptable for FNP.

The commission has concluded, based on the considerations discussed above, that (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commissions regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or the health and safety of the public.

3 5.0 References

1. Letter from L. M. Stinson, Southern Nuclear Operation Company to NRC Request to Revise Technical Specifications to Delete Reactor Trip System, Function 11, Reactor Coolant Pump Breaker Position, dated March 8, 2005.

2. Letter from L. M. Stinson, Southern Nuclear Operation Company to NRC Response to Request for Additional Information Related to Request to Revise Technical Specifications to Delete Reactor Trip System, Function 11, Reactor Coolant Pump Breaker Position, dated August 16, 2005.