ML20084M082

AO 4-73-9:on 730713,safety Injection Accumulator Level Limiting Conditions for Operation Exceeded.Caused by Incorrectly Specified Level Alarm Setpoints.Setpoints Corrected

ML20084M082
Person / Time
Site:	Turkey Point
Issue date:	07/20/1973
From:	Schmidt A FLORIDA POWER & LIGHT CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
References
AO-4-73-9, NUDOCS 8306010250
Download: ML20084M082 (3)

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FLORIDA POWER & UGHT CO',1PM4Y July'20, 1973 '

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Mr. John F. O' Leary, Director Q . (;,

Directorate of Reactor Licensing g ,n $,',y,7//, ~ C. x U. S. Atomic Energy Commission " A. ,.,f a Washington, D. C. 20545 1 sl l,'g ' , ,

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TURKEY POINT UNIT NO. 4 ^ .- .

DOCKET NUMBER 50-251 ABNORMAL OCCURRENCE NO. 4-73-9 Q",5Wmg

.t. tj e nf ACCUMULATOR LEVEL LIMITING CONDITIONS FOR OPERATION EXCEEDED

Dear Mr. O' Leary:

1. 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 No. 4-73-9, describes an abnormal occurrence which was identified on July 13, 1973. The Directorate of i Regulatory Operations, Region II, was notified on July 13, 1973.

II. DESCRIPTION OF OCCURRENCE f On July 13, 1973, it was determined that- the limiting condition for operation regarding safety injection l accumulator level had been exceeded. New calculations i

revealed that the upper end of the allowable operating band permitted water volumes greater than the Technical Specification limit. The operating band germitted a water volume of 796.1 ft 3 which is 5.1 ft abgve the 1 Technical Specification upper limit of 791 ft (a

l. difference of less than 1%).

l Unit No. 4 is still undergoing power operation testing and had only achieved a maximum power of 47% during the total operating period prior to this incident. The accumulator nitrogen pressure was maintained within the allowable limits for the entire time.

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l 8306010250 730720 PDR ADOCK 05000251 f' )(\ ( .-

S PDR ,~3,0 s a I- COM 6ENf ItEGION /

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r--- ..2 N July 20, 1973 e

• Mr. John F. O/ary, Director \- (~/

N-Therefore, to assess the effect of the higher accumulator level on the loss of coolant accident, the mitigating effects of actual plant conditions of operation were considered.

The reduced power level that has existed during the operation of Turkey Point Unit 4, in combination with the higher accumulator nitrogen pressure, and actual lower resistance of the accumulator discharge piping, would have served to mitigate the consequences of the LOCA presented in the FSAR. These factors more than compensate for the higher accumulator level and would have kept the results within th.e limits presented in the FSAR.

VI. CONCLUSIONS

a. Exceeding the specified accumulator level was caused by incorrectly specified level alarm setpoints.

b. This abnormal occurrence did not adversely affect the safe operation of Turkey Point Unit No. 4

c. Correcting the alarm setpoints, strengthening the operating instructions pertaining to accumulator 1mrel

. adjustments, and installation of the new level in-

• dicating scales, should prevent recurrence of this and similar incidents.

d. This abnormal occurrence did not present any danger to the public health and safety.

Very truly yours, 1 W' Schmidt A. D.

Director of Power Resources i

ADS /JHB/HNP/VTC/ GEL:paz i cc: Norman C. Moseley, Director

! Region II, Directorate of Regulatory Operation

. U. S. Atomic Energy Commission l Suite 818, 230 Peachtree Street, N.W.

l Atlanta, Georgia l

l Mr. G. A. Olson Edison Electric Institute 90 Park Avenue New York, New York 10016 rf...,

4355#e.

Dr. James Coughlin C. E. Branning Plant Supervisors J. R. Bensen D. W. Jones Plant Nuclear W. H. Rogers, Jr. J. W. Williams, Jr. Safety Committee

'G.rE.'Liebler-(3) J. B. Olmstead ' Documentary ' Tiles J. K. Hays S. G. Brain

r. .1 f

Mr. John F. O[~'jary ,

Director vs

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N' July 20, 1973 III. ANALYSIS OF THE OCCURRENCE Excessive leakage through the Turkey Point Unit No. 3 accumulator check valves into the accumulator has required frequent level adjustment to keep the level within the narrow allowable range of 18% level (2.65 in.). This situation led to an effort to gain acceptance for an increased allowable accumulator level operating band for both Unit Nos. 3 and 4 even though Unit No. 4 was not experiencing excessive accumulator check valvo leakage.

In connection with this effort, calculations were made relating the level instrument indication in " percent level" to actual water volumes in the accumulator. The results of these calculations indicated that the specified high level alarm setpoint slightly (<1%) exceeded the Technical Specifications for maximum accumulator water volume. The low level alarm setpoint was shown to be within the allowable band with a more than normal margin to the Technical Specification limit. The Nuclear Steam Supply System (NSSS) designer verified that a discrepancy in the level alarm setpoints did exist and provided revised level alarm setpoints.

IV. CORRECTIVE ACTION TO PREVENT RECURRENCE Immediate corrective action was to issue instructions to the operating shift on July 13, 1973 to operate Unit No. 4 accumulators within the range of the revised setpoints. On July 14, 1973, Unit No. 4 accumulator alarm setpoints were changed.to the revised values.

In addition, the new accumulator operating limits were incorporated into the approved operating procedure for charging boric acid into the accumulators (OP 4 513.1) .

New scales marked off in cubic feet, were installed on Unit No. 4 accumulator level indicators located in the control room. In addition, the new scales have a green band signifying normal operation, purple lines signifying Technical Specification limits and yellow lines signifying the alarm setpoints.

V. ANALYSIS AND EVALUATION OF SAFETY IMPLICATIONS OF THE OCCURRENCE The concern associated with exceeding the specified high water 'evel in the accumulator is, that based on the analysis presented in FSAR, Section 14.3, the high water level tends to reduce the effectiveness of the accumulator performance for the large LOCA. However, the PSAR LOCA analysis is intended to model the most conservative condition and the actual plant operating conditions will always be more favorable than conditions presented in the FSAR.

M'N ,