ML20247K556

Safety Evaluation Supporting Amends 155,151 & 126 to Licenses DPR-33,DPR-52 & DPR-68,respectively

ML20247K556
Person / Time
Site:	Browns Ferry
Issue date:	09/23/1988
From:	NRC OFFICE OF SPECIAL PROJECTS
To:
Shared Package
ML20247K486	List: ML20247K482 ML20247K517 ML20247K556
References
TAC-00101, TAC-00102, TAC-00103, TAC-101, TAC-102, TAC-103, NUDOCS 8909210195
Download: ML20247K556 (3)

Text

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.i NUCLEAR REGULATORY COMMISSION WASHINGTON. D. C. 20555 s j i

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SAFETY EVALUATION BY TH.E.0FFICE OF SPECIAL PROJECTS SUPPORTING AMENDMENT NO.155 TO FACILITY OPERATING LICENSE N0. DPR-33 AMENDMENT NO. 151 TO FACILITY OPERATING LICENSE NO. DPR-52 AMENDMENT NO. 126 TO FACILITY OPERATING LICENSE NO. DPR-6P.

TENNESSEE VA'LLEY AUTHORITY BROWNS FERRY PUCLEAR PLANT, UNITS 1, 2 AND 3 DOCKETS NOS. 50-259, 50-260 AND 50-296

1.0 INTRODUCTION

By letter dated June 13, 1988, the Tennessee Valley Authority (TVA or the licensee) requested an amendment to Appendix A of the Browns Ferry Nuclear Plant (BFN), Units 1, 2 and 3 Technical Specifications (TS). The proposed amendment would revise TS Table 3.2.B. Instrumentation that Initiates or Controls the Core and Containment Cooling Systems, and Table 4.2.B,

' Surveillance Requirements for Instrumentation that Initiates or Controls the j Core Standby Cooling Systems. The four additional instruments to be listed are to trip and isolate the High Pressure Coolant Injection (HPCI) System or Reactor Core Isolation Cooling (RCIC) System nn low s'eam supply pressure and high turbine exhaust pressure. The TS are also modified to add turbine exhaust diaphragm high pressure to the lists of conditions that cause Group 4 and 5 (HPCI and RCIC) isolation in the notes for Table 3.7.A.

2.0 EVALUATION The current TS Tables 3.2.B and 4.2.B list setpoints and surveillance requirements for instrumentation that initiates or controls the Core Standby Cooling System. TVA has proposed the following additions to those tables:

HPCI Steam Supply Low Pressure Instrument Channel HPCI Turbine Exhaust Diaphragm Pressure Instrument Channel RCIC Steam Supply Low Pressure Instrument Channel RCIC Turbine Exhaust Diaphragn Pressure Instrument Channel The above instrumentation is already installed and in operation at BFN, Units I, 2 and 3. The proposed change tn the TS is meant to clarify and complete the TS requirements for trips and isolation sierals to the HPCI and RCIC systems.

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2.1 HPCI System TheHPCIsystemisaturbinedrivenSystemusingsteamtoinjecteither condensate storage tank water or suppression pool water into the reactor vessel in the event of an intermediate or small line break. Specific trip features have been installed on the HPCI System to provide isolation capabilities and added protection to the subject system. Since these trip features have been installed, they need to be incorporated into the BFN TS.

The HPCI Steam Supply Low Pressure Instrument Channels will automatically close the HPCI steam supply line isolation valves when the steam pressure has decreased to such a low value that the HPCI turbine is inoperable, thus preventing steam and. radioactive gases from escaping through the HPCI turbine shaft seals into the Reactor Building. General Electric Company has recommended an allowable limiting trip setting of 2100 psig. Use of this setpoint will ensure that the instrumentation will generate a HPCI isolation signal when the steam supply falls below 100 psig. This value is sufficiently below the lower end of the HPCI operating range (150 psig) to avoid affecting HPCI System operational requirements yet high enough to generate an isolation signal before the reactor vessel has fully depressurized while still ensuring that no radioactive gases will escape through the HPCI turbine shaft seals. .

The HPCI turbine exheast diaphragm pressure instruments provide an exhaust rupture disc high pressure signal to the HPCI steam-supply isolation valve control circuitry for HPCI isolation. The HPCI turbine exhaust line contains a branch line with two rupture discs in series which open into the HPCI

• urbine room. In the event that a high pressure event occurs in the turbine exhaust line and the HPCI turbine is not tripped by the existing sensors, tha rupture discs are designed to fail at a pressure below the HPCI turbine casing failure pressure.

The.HPCI Turbine Exhaust Diaphragm Signal is used to detect ruptures in either the inner rupture disc or both rupture discs which protect the HPCI turbine casing from overpressurization. The maximum calculated limit setting l- is 6 52 psig. Using 20 psig as an allowable limit setting will assure isolation L

prior to 52 psig, and therefore prevent HPCI turbine casing failure.

2.2 RCIC System RCIC Steam Supply Low Pressure Instrument Channels provide RCIC steam line '

isolation in the event low pressure is detected. General Electric recommends an ' allowable setpoint for these instruments of 2. 50 psig. RCIC isoaltinn will result when the steam supply pressure falls below 50 psig. This value is sufficiently below the lower end of the RCIC System operating range (150 psig) to avoid affecting RCIC System operational requirements. However, this setpoint is high ennuch to generate an isolation signal before the reactor vessel becomes depressurized while still ensuring that no radioactive cases will escape through the RCIC turbine shaft seals.

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I The RCIC Turbine Exhaust Diaphragm Pressure Instrument detects pressure between the turbine exhaust rupture discs. A high pressure signal will initiate RCIC l

steam line isolation. As with the HP.CLTurbine Exhaust Diaphragm, the allowable trip value is 620 psig. The actual calculated maximum setting is 6 50 psig.

Using a 6 20 psig as an allowable limit will assure isolation prior to 50 psig.

2.3 Conclusion

'The above changes simply add TS requirements to instruments and functions that already exist at the plant. The FSAR discusses these systems and specifies the trip signals added by these changes in sections 4.7.5, 6.4.1, and 7.3.4.7.

Since TVA is only adding requirements to the TS and no change will be made J

to plant operation, the staff has concluded that the proposed changes to the '

TS will not adversly affect plant safety and are acceptable.

3.0 ENVIRONMENTAL CONSIDERATION

The amendments involve a change to a requirement with respect to installation or use of a facility component located within the restricted area as defined in-10 CFR Part 20 and/or changes to the surveillance requirements. The staff.

has determined that the- amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Conmission has previously issued a proposed finding that these amendments involve no significant hazards consideration and there has. been no public comment on such finding.

Accordingly, the amendments meet the eligibility criteria for categorical Pursuant to 10 CFR 51.22(b), no exclusion set forth in 10 CFR 51.22(c)(9).

environmental impact statement nor environmental assessnent need be prepared in connection with the issuance of these amendments.

4.0 CONCLUSION

The Commission made a proposed determination that the amendment involves no significant hazards consideration which was published in the Federal Register (53 FR 26533) on July 13, 1988 and consulted with the State of Alabama. No public comments were received and the State of Alabama did not have any comments.

The staff 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 nperation in the proposed manner, and (2) such activities will be conducted in compliance with the Commission's regulations, and the issuance of the amendments will rot be inimical to the common defense and security nor to the health and safety of the public.

I Prircipal Contributor: J. Velly Cated: September 23, 1988

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