ML18227A441
| ML18227A441 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 12/22/1975 |
| From: | Schmidt A Florida Power & Light Co |
| To: | Moseley N NRC/RGN-II |
| References | |
| PRN-LI-75-19 | |
| Download: ML18227A441 (8) | |
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,S NRC DlSTPiBUTlON FOR PART EO DOCKET M/ERIAL (TEMPORAR Y FORM)
CONTROL NO: '8 FILE. INCIDEFZ REPORT
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DATE OF DOC DATE R EC'D LTR TWX RPT OTHE R TO:
H.C., Mosele 2-P2-5 ORIG 1 Signed 1-6-76 CC OTHER 0
XXX SENT AEC PDR XXX SENT LOCAL PDR
'- --- CLASS UNCLASS XXX PROP INFO tiNPUT No CYS REC'D DOCKET NO:
60-251 DESC R IPT tON:
Abnormal Occurrence 8 75-12, on12-12-.75 Concerning
.E6w Boron Concentration in if '4 Boron. Injection 'ank.h..j...: "
(1 Copy Received) -'"-"
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ENCLOSURES:
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Mr. Norman C. Moseley, Director, R
Office of Xnspection and Enforcement U.
S. Nuclear Regulatory Commission 230 Peachtree
- Street, N. W., Suite 818 Atlanta, Georgia 30303 8EgiPQ v,
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Dear Mr. Moseley:
ABNORMAL OCCURRENCE 251-75-12" TURKEY POINT UNIT 4 DATE OF OCCURRENCE:
DECEMBER 1'2, 1975 BOX 3100 MIAMI,FLORIDA 33101
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ecember 22, 1975 RN-LI-75-19 LOW BORON CONCENTRATXON IN UNIT 4 BORON INJECTXON TANK A.
CONDITIONS PRIOR TO OCCURRENCE The Unit 4 reactor was in steady state power operation at about 100% rated power.
The Unit 3 reactor was shutdown with preparations being made for a return to criticality following a seven week refueling outage.
B.
DESCRIPTION OF OCCURRENCE At about 1:00 PM on December 12, 1975, it was verified that the boron concentration in the Unit 4 Boron Injection Tank (BXT) was below the lower limit defined in Technical Specification 3.4.l.a.2.
The measured concentration of 19,600 ppm was 2% below the lower limit of 20,000 ppm.
C.
DESIGNATION OF APPARENT CAUSE OF OCCURRENCE The apparent cause of the occurrence was dilution of the Unit, 3 BIT with water from the Safety Injection System "C"
Accumulator followed by dilution of the "B" Boric Acid Storage Tank (BAST).
Apparently, the Unit 4 BIT was subsequently diluted by recirculation with the "B" BAST.
The dilution is suspected to have occurred during an accumulator backleakage test which was conducted on December 12.
During such a test, there are two normally-closed valves separating each accumulator from each BIT.
The test showed that valve 851C, associated with the "C"
accumulator, was leaking.
Then, following the occurrence described in this report, the second valve isolating the Unit 3 BIT from the "C" Accumulator was found to be about one turn open.
Maintenance had been performed HELPING BUILD FLORIDA
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Mr. Norman C. Moseley, Director, Region II Page Two December 22, 1975
.on this.<valve a few days previously and it had apparently not been returned to the completely closed position.
There-
- fore, a flow path had been established between the "C"
Accumulator, which contains borated water at a concentration of 1950 ppm or greater, and the Unit 3 BIT.
D.
ANALYSIS OF OCCURRENCE The role of the boron injection tank is to provide a source of negative reactivity to alleviate the consequences of the postulated steam break accident described in the FSAR.
The safety analysis is conservative in that credit is taken only for the amount of boron in the boron injection tank itself and no credit is taken for the amount of boron in the safety injection system piping.
In addition, the actual rate of boron injection, in the unlikely event of a steam break, would be greater than that utilized in the FSAR because actual safety injection flow rates would be higher than those analyzed in the FSAR.
These factors coupled with the small amount of dilution that occurred indicate that the consequences of a steam line break'ould have been within the limits pre-sented in the FSAR.
Therefore, neither reactor safety nor the health and safety of the public were jeopardized by this occurrence.
E.
CORRECTIVE ACTION Unit,4 load reduction, was initiated in accordance with the shutdown rate guidelines of Administrative Procedure 0103.8.
Recirculation of the Unit 4 BIT through the "C" BAST was also initiated.
By., about 3:20 PM on December 12, the Unit 4
BIT boron concentration was raised above 20,000 ppm and Unit 4 was returned to full power operation.
To minimize accumulator backleakage, consideration is being given to expanding the locked valve list to include the manual isolation valve which was found partially open after the occurrence.
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Mr. Norman C. Moseley, Director, Region II Page Three December 22, 1975 F.
FAILURE DATA Dilution of a Boron Injection Tank boron concentration has occurred on other occasions.
They were reported as Abnormal Occurrences 4-73-11, 250-74-5, 251-74-1, 251-74-6, and 251-75-2.
Very truly yours, A. D. Schmidt.
Vice President Power Resources MAS/pm CC'ack R.
Newman, Esquire Director, Office of Inspection and Enforcement:(40).'irector, Office of Management Information and Program Control (3)
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