ML19225A589
| ML19225A589 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 06/11/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19225A587 | List: |
| References | |
| SER-790611, NUDOCS 7907190656 | |
| Download: ML19225A589 (4) | |
Text
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NUCLEAR REGULATORY COMMISSION g
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SHORTING AMENDMENT NO.12 TO FACILITY OPERATING LICENS ALABAMA POWER COMPANY FARLEY NUCLEAR PLANT, UNIT NO. 1 DOCKET NO. 50-348 Intrciuction 11, 1979 as supplemented May 23, 1979, Alabama By letter dated May Power Company (APC) proposed changes to the Appendix A Technical The Specifications for Farley Nuclear Plant (FNP), Unit No.1.
proposals included revisions to the reactor protection systen logic to require actuation of safety injection on two out of three channels The change also eliminates the coincidence of low pressurizer pressure.
logic which required pressurizer low water level and pressurizer low pressure to initiate safety injection.
These changes were considered necessary by the NRC and by Westinghouse Electric C,orporation (the Nuclear Steam Supply System designer) as a result of the evaluation of the Three Mile Island incident on March 2E,1979.
The design changes will be accomplished during a refueling outage for Cycle 2 operation now scheduled to start in mid-June 1979.
Discussion As a result of our ongoing review of the events associated with the March 28, 1979 incident at Three M14e Island Unit 2, the NRC Office of Inspection and Enforcement issued a number of IE Bulletins describing IE Bulletin 79-06 (April 11,1979) actions to be taken by licensees.
advised licensees with Westinghouse Pressurized Water Reactors to instruct reactor operators to manually initiate safety injection when the pressure indication reaches the actuation setpoint whether or not the water level indication has dropped to the actuation setpoint.
Item 3 of IE Bulletin 79-06A (April 14,1979) further advised these licensees to trip the low pressurizer level bistables manually such that, when the pressurizer pressure reached the low setpoint for safety injection, it would auto-This action was matically initiate regardless of the pressurizer level.
unnecessary at FNP as the first refueling at FNP started on March 8,1979 and was s-ill underway when IE Sulletin 79-05A was
- sued.
417 243 7907190[pj&
Since the reactor was shut down for refueling, APC proposed to modify the reactor protection logic circuitry to preclude manual tripping of pressurizer low level bistables.
Such action would have had the effect of reducing, the safety injection actuation logic to a one out of three logic. A single instrument failure of one of the three low pressure bistable channels would then result in an unwanted safety i njection.
To prevent this, APC proposed in thcir May 11, 1079 letter, a design modification which is evaluated below.
Evaluation The proposed modificaticn to the safety injection actuation system would remove the pressurizer level signal from eich of the pressurizer level, pressurizer pressure coincidence channels ind convert the system to a two-out-of-three pressurizer low pressure : rip.
The instrumentation logic receives pressurizer pressure signals from three pressure transmitters and initiates a safety injection actuation when two of the three signals reach the low pressure setpoint of 1850 psig.
These modifications will satisfy the requirements of IEEE 279-1971, and other applicable standards.
We have reviewed the instrumentation channels for pressurizer pressure measurements and their power supplies. Separate and independent pressure transmitters are provided for each channel of the protection function and for the pressurizer pressure control system.
The power sources for the protection channels are derived from three of four separate inverters.
The normal s]urce of power to the four inverters is through rectifiers frca two 600 volt emergency power buses.
On a loss of a 600 volt bus, an automatic transfer is made to one of the two 125 volt batteries by an auctioneering circuit within the inverter. A backup supply to each vital bus is provided from one of two regulated instrument buses.
Transfe r to this backup power source is by manual means.
The power source for the pressure transmitters which operate the controls for pressurizer spray and heater operation is derived from the inverter power source notA second associated with the protection system transmitters noted above.
pressure transmitter, used for control of one of the power operated relief valves (PORV) on the pressurizer, derives its power from one of the inverter power sources used by the protection system transmitters.
The effect of the postulated loss of this inverter power source would result in a trip of the protection system channel and a loss of the control action derived f rom the pressure trarsmitter.
Thus, cnly the one PORV with control power frca this inverter would not respord to an increase in However, a postulated failure which would cause pressurizer pressura.
both pressure transnitters to indicate higher thar, actual oressure would be of concern.
This could result in a control action to c:en the F]R7 and to reduce pressurizer p 1ssure.
At this time only one of the three pressure protection channels would fail to initiate ccrrec:ive action 417 244 due to the actual low pressure and the postulated high pressure i ndicati on.
The other two pressure protection channels would function properly.
The effect of a postulated abnomal output voltage at the inverter would not result in an erroneous high reading frorc.
the pressure transmitters which share this one power source.
- Thus, there are no unsafe effects due to control and protection system interaction due to the sharing of one inverter power source with the PORV control transmitter and one of the three protection pressure t ra nsmitte rs.
The indeperdance of control and protection is further assured due to the physical separation of field cables for the control l
and protection systems.
Adequate measures exist to satisfy the inde-pendence requirements of IEEE 279-1971 for cortrol and protection system interaction.
There is adequate assurarce for a reliable automatic initiation o' safety injection with the proposed modifications for I
a two-out-of three logic on low pressurizer pressure.
I ine proposed Technical Specifications revise Tables 3.3-3, 3.3-4, 3.3-5, and 4.3-2 to specify automatic safety injection actuation on a two-cut-of-three pressu -izer low pressure of 1850 psig.
These changes are consistent with the proaosed change in the actuation of safety injection on two-out-of-I three low pressure signals and are acceptable, f
Based on our review of APC's submittals, we conclude that the nodifications to the safet;' injection actuation system logic meet the requirements of IEEE 279-197 and are acceptable.
We also conclude that the proposed change will be in accordance with the above standards and guides.
None of the transient and accident analyses are adversely affected by the change. The only effect may be a safety injection actuation sooner than previously reviewed.
This is more conser-vative and ii acceptable.
Environmental Consideration We have detemined that the amendment does not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact.
Having made this detemination, we have further concluded that the amendment involves an action whir.h is insignificant from the standpoint of environmental impact and, p irsuant to 10 CFR 951.5(d)(4), that an environmental impact staten !nt or negative declaration and environnental impact appraisal need not be prepared in connection with the issuance of this amendnent.
417 245 Conclusion We have concluded, based on the consideration discussed above, that:
(1) because the abendment does not involve a significant increase in the probability or consequences of accidents previously considered dnd does not involve a significant decrea.ie in a safety margin, the ame.1dnent does not involve a signficiant hazards consideration, (2) there is reasonable assurance
- hat the health and safety of the public will not be endangered by ope 2 ion in the proposed manrer, and (3) such activities will be conducted in compliance with the Conrission's regulations and the issuante of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Date: June 11, 1979 i
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