05000251/LER-1978-015-01, /01T-0 on 781106:Boron Injection Tank(Bit)Sample Showed Low Boron Level.Exact Cause Is Unknown,But It Is Suspected the Actual Bit Concentration Was Proper & the Sample Was Diluted & Invalid

/01T-0 on 781106:Boron Injection Tank(Bit)Sample Showed Low Boron Level.Exact Cause Is Unknown,But It Is Suspected the Actual Bit Concentration Was Proper & the Sample Was Diluted & Invalid

ML17338A325
Person / Time
Site:	Turkey Point
Issue date:	11/20/1978
From:	Schoppman M FLORIDA POWER & LIGHT CO.
To:
Shared Package
ML17338A324	List: 05000251/LER-1978-015, Forwards LER 78-015/01T-0 05000251/LER-1978-015-01, /01T-0 on 781106:Boron Injection Tank(Bit)Sample Showed Low Boron Level.Exact Cause Is Unknown,But It Is Suspected the Actual Bit Concentration Was Proper & the Sample Was Diluted & Invalid
References
LER-78-015-01T, LER-78-15-1T, NUDOCS 7812040222
Download: ML17338A325 (3)

LER-1978-015, /01T-0 on 781106:Boron Injection Tank(Bit)Sample Showed Low Boron Level.Exact Cause Is Unknown,But It Is Suspected the Actual Bit Concentration Was Proper & the Sample Was Diluted & Invalid

Event date:
Report date:
2511978015R01 - NRC Website

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Reportabl e Occurrence 251-78-15 Licensee Event Report Pa e Two Additional Event Descri tion and Probable Conse uences During normal operation, a routine sample of the Boron Injection Tank (BIT) indicated a boron concentration of 17,900 ppm.

This was less than the. minimum concentration of 20,000 ppm required by T.S. 3.4.l.a.2.

Unit shutdown at a

lOX per hour rate was begun.

Recirculation of the BIT with the "C" Boric Acid Storage Tank (BAST) was also begun, and BIT sampling at 30 minute intervals was instituted.

A second sample indicated an increasing BIT bor'on concentration,

however, a third sample 30 minutes 'later indicated that the boron concentration was approximately constant at about 18,300 ppm.

This indicated potential blockage of the normal recirculation flow path.

This could not be verified because flow transmitter FT-934, which is in the recirculation flow path, was inoperable.

The temperature settings of the heat tracing circuits. on the normal recircula-tion path to the "C" BAST were increased in an attempt to dissolve any precipitated boron that may have been blocking the line.

The fourth BIT sample indicated that the boron concentration had not increased,. therefore, further action was necessary.

A redundant recirculation flow path, which is kept isolated and filled with non-borated water to preclude boron precipitation and blockage, was put into service.

The next BIT sample indicated a boron concentration of 21,700

ppm, which was within specification.

Approximately 165 minutes liad elapsed since the beginning of the occurrence, and power had been reduced to 66K.

A return to full power was begun.

Additional

Cause

Descri tion and Corrective Action It is possible that the boron concentration in the BIT itself was within specification during the occurrence, and that only the inlet line actually had a boron concentration less than 20,000 ppm.

This is possible because the sample valve is located in the inlet line to the BIT and the solution in that line can become.diluted slightly by minor leakage of Refueling Water Storage Tank (RWST) water, which has a minimum boron concentration of 1950 ppm, past the BIT inlet isolation valves In addition, the BIT inlet isolation valves are cycled open periodically, which further results in a potential dilution mechanism.

The apparent blockage in the normal recirculation flow path to the "C" BAST may be attributed to either inadequate heat tracing or an insufficient number of thermocouple monitoring points.on the piping.

The normal flow path was intended to operate continuously, thereby precluding recirculation flow path blockage and assuring proper BIT boron concentration.

However, the normal flow path has not operated continuously because of recirculation pump seal

problems, and has been relegated to a back-up status.

An investigation has been in progress for some time in an attempt to resolve the pump seal problems.

A redundant recirculation flow path is available to provide another back-up rreans of re-circulation in case the normal recirculation flow path is blocked.

Reportabl e Occurrence 251-78-15 Licensee Event Report Pace Three Additional-Cause Descri tion and Corrective Action (Continued)

Blockage of the normal recirculation flow path to the "C" BAST could not be confirmed because flow transmitter FT-934 was inoperable.

This, transmitter has been repaired several times, but it continues to fail due to boron blockage of the sensing lines.

This had been recognized as a problem and was under study at the time of the occurrence.

Resolution of the recirculation, pump seal problems should prevent recurrence of recirculation line blockage and BIT sample dilution.