ML20084M095

AO 4-73-7:on 730618,following Reactor & turbine-generator Trip,Auxiliary Feedwater Pumps Failed to Automatically Start.Caused by Lack of 125-volt Dc Power Supply Fuses for Pump Auto Start Logic Circuit.Fuses Installed

ML20084M095
Person / Time
Site:	Turkey Point
Issue date:	06/28/1973
From:	Schmidt A FLORIDA POWER & LIGHT CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
References
AO-4-73-7, NUDOCS 8306010265
Download: ML20084M095 (4)

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FLORIDA POWER & UGHT CCMPANY u . 9

% e*f.Tf7Ur Mr. John F. O' Leary, Director - ~_'

Directorate of Reactor Licensing U.S. Atomic Energy Commission Washington, D. C. 20545

'RE: TURKEY POINT UNIT"NO. 4 DOCKET NUMBER 50-251 ABNORMAL OCCURRENCE NO. 4-73-7 FAILURE OF AUXILIARY FEEDWATER PUMPS TO AUTO START

Dear Mr. O' Leary:

I. INTRODUCTION This report is submitted in accordance with Technical Specification 6.6.2.a for Turkey Point Unit No. 4, Operating License No. DPR-41. This Abnormal Occurrence Report 4-73-7 describes an abnormal occurrence which was identified on June 18, 1973. The Directorate of Regulatory Operations, Region II was. notified on June 19, 1973.

II. DESCRIPTION OF THE OCCURRENCE On June 18, 1973, Turkey Point Unit No. 4 was undergoing startup and low power physics testing in accordance with approved operating procedures, testing procedures, and the Technical Specifications. About 5:16 p.m., while increasing speed on Unit No. 4 turbine-generator in preparation for initial synchronization with the transmission system, the turbine control valves opened rapidly and excessively. As the res'ulti of' high steam flow ~foF ~thi's~ ' mode ~cf~oferitiion and

, decreasing average reactor coolant temperature, the Safety t Injection System actuated when the average coolant temperature was less than 543 F. Unit No. 4 reactor and turbine-generator tripped upon actuation of the Safety Injection System. All of the Engineered Safeguard Systems were verified to be operating normally except that automatic start of the

- auxiliary feedwater_ pump _s_did_no_t occur. The Nuclear Control Center Operator promptly started Ehe three auxiliary feedwater pumps manually in accordance with approved operating procedures.

All three auxiliary feedwater pumps started and operated normally. Unit No. 4 reactor was placed in the hot shutdown condition pending review, analysis, and evaluation of the cause of the failure of the auxiliary feedwater pumps to start automatically upon actuation of the Safety Injection System.

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Mr. John F. O' Leary, June 28, 1973 Director III. ANALYSIS OF THE OCCURENCE An investigation by plant personnel to determine the cause of the failure of the auxiliary feedwater purups to auto-matically start upon' actuation of the Safety Injection

-System revealed that the 125 VDC,.. power supply fuses for

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thelauxiliary_feedwatTritWauto start logic circuit were not installed.

IV. CORRECTIVE ACTION TO PREVENT RECURRENCE The initial corrective action was to replace the 125 VDC fuses.in the auxiliary feedwater pump auto start logic circuit and check for proper operation. The auto start logic circuit was demonstrated to be operable.

The 125 VDC fuses in the auxiliary feedwater pump auto s.3: c.-a ,.n .., y.sc. .qtart... logic.. circuit. az;e ynder . admin.istrative.. c.ontrol .as.. . . . . . . .cs. 2 specified in Administrative Procedure No. 0103.4, In-Plant Equipment Clearance Orders. Before these fuses can be removed an In-Plant Equipment Clearance Order must be issued. Strict adherence to In-Plant Equipment Clearance Procedures will prevent recurrence of this and similar incidents.

V. ANALYSIS AND' EVALUATION OF SAFETY IMPLICATION OF THE OCCURENCE Turkey Point Unit No. 4 reactor achieved initial criticality on June 11, 1973, and had been undergoing low power physics testing. The residual heat in the core was at a very low

- ,. . . , . ..... level..at th.e time of.the.inci. dent. Further , . the . aver. age - .

reactor coolant temperature was about 547 F at the beginning of the initial turbine roll and decreased to a value less than 543 F at the time of the reactor trip. When Safety Injection System actuation occured, the turbine control valves closed immediately which prevented steam withdrawal from the steam generators. Actuation of the Safety Injection System closed the main steam stop valves immediately, closed the feedwater control valves (main and bypass),

tripped the main steam generator feedwater pump and closed the steam generator feedwater pump discharge valves which isolated the feedwater-steam system. Actuation of the Safety Injection System should itave automatically started the three auxiliary feedwater pumps to supply approximately 600 gpm feedwater from each pump to the steam generators.

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t1 Q d Mr. John F. O' Leary, June 28, 1973 Director As a result of these prompt actions to isolate the main steam system, Unit No. 4 average reactor coolant pressure and temperature was not significantly reduced below the pressure and average coolant temperature expected for a reactor trip _on a reactor core with a low power operating history. The average reactor coolant temperature did not increase again following the reactor trip, due to-the low level of decay heat present in the core. Steam dump was not immediately required to control main steam pressure or average reactor coolant temperature. In the absence of' steam-dump'from the steam generators, coupled with the relatively large water inventory present in the steam generators at the time of the reactor trip, steam gener-

• ator water level was easily maintained. Because the steam generator water level was not rapidly depleted, feedwater addition by the auxiliary feedwater pumps was not immediately required.

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.g. . .g safety injection pumps started and operated normally. The boron injection tank inlet and outlet valves opened automatically to provide a flow path for highly borated water to the reactor core. Because the Safety Injection System pressure operates at a much lower pressure than the normal operating pressure of the reactor coolant sys-tem, there was no flow of borated water into Unit No. 4 reactor coolant system due to this incident.

Prompt operator action in starting the auxiliary feedwater pumps manually, ascured that the steam generator water

.o l.ev.el was , maintained within normal o.perating range.

Based on an analysis of the conditions stated above, the failure of the auxiliary feedwater pumps to automatically start did not adversely affect the safe operation of Unit No. 4. The prompt manual start of the auxiliary feedwater pumps demonstrated that the auxiliary feedwater pumps were operable and actually delivered feedwater flow to the three steam generators in less time than the time specified in the safety analysis.

VI. CONCLUSIONS

a. The failure of the auxiliary feedwater puaps was a result of the 125 VDC power supply fuses for the auxiliary feedwater pump auto start logic circuit not being installed.

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• Mr. John F. O' Leary, June 28, 1973 Director

b. Strict adherence to Administrative Procedure No. 0103.4 will prevent recurrence of this and similar incidents.

c. The prompt manual start of the auxiliary feedwater pump demonstrated that thesc pumps were operable and act-ually delivered feedwater flow to the steam generator in less time than the time specified in the safety analysis,

d. The Safety Injection System nozzles and piping were not subjected to thermal stresses since no flow occurred in this system.

e. This failure of the auxiliary feedwater pumps to start automati-Plly did not adversely affect the safe operation of Turkey Point Unit No. 4.

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' .' . . .e . : . . f r ., This __ abnormal.,.occurrencg _,did not present. any .d. anger . t_o the public health or safety.

Very truly yours, cs,b A.

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D. Schmidt Director of Power Resources ADS /JKH/VTC/HNP/paz cc: Norman C. Moseley, Director Region II, Directorate of Regulatory Operation U.S Atomic Energy Commission Suite 818, 230 Peachtree Street, N.W.

Atlanta, Georgia Mr. G. A. Olson Edison Electric Institute 90 Park Avenue

. New York, New York 10016 Dr. James Coughlin J. W. Williams, Jr.

J. R. Bensen J. B. Olmstead W. H. Rogers, Jr. S. G. Brain G. E. Liebler Plant Supervisors J. K. Hays Plant Nuclear Safet-f Committee C. E. Branning Documentary Files D. W. Jones