ML20052C005

LER 82-007/01T-1:on 820309,standby Liquid Control Storage Tank Level & Sodium Pentaborate Concentration Calculations Did Not Correctly Account for Specific Gravity of Sodium Pentaborate.Caused by Procedure Equation Errors

ML20052C005
Person / Time
Site:	Vermont Yankee
Issue date:	04/23/1982
From:	Murphy W VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20052C002	List: ML20052C001 ML20052C005
References
LER-82-007-01T, LER-82-7-1T, NUDOCS 8205040253
Download: ML20052C005 (2)

Text

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., VTVYS1 05000271 LER 82-7/1T Rev. 1 Event Description and Probable Consequences A review of the SLC System procedures for controlling sodium pentaborate concentration in the SLC storage tank revealed the following deficiencies:

1. The SLC storage tank concentration vs. tank level correlation did not account for the specific gravity of sodium pentaborate. This resulted in a nonconservative error of approximately 5% when determining sodium pentaborate solution volumes.

2. The specific gravity of the SLC solution was not previously considered in the SLC concentration calculation. This resulted in an additional nonconservative error of approximately 5%.

Due to these 2 calculation errors, VY may have been unknowingly below the T. S. 3.4 limit and, therefore, is reporting this event in accordance wich T. S., Section 6.7.B.1.1.

There were no consequences of this event. At all times, the SLC System had sufficcint concentration to provide its intended shutdown function.

Ilowever, it does constitute a situation in which a system required corrective action to prevent operation in a manner less conservative than assumed in the accident analysis.

Cause Description and Corrective Action The required boton concentration in the SLC storage tank was less than indicated because of errors in operating procedure equations. Plant Management took the following corrective action:

1. The affected procedures were immediately corrected.

2. The sodium pentaborate concentration in the SLC tank was increased to well above the Tech. Spec. Limits (as a result of LER 82-3).

3. A task force was established to investigate boron concentration calibration and SLC design basis. In addition to 1) and 2) above, VY has implemented the following task force recommendations:

a. An administrative margin of 1.5% has been applied to the sodium pentaborate concentration curve to account for system variances.

b. The specific gravity correction factor has been increased on SLC concentration equations to ensure conservative results.

The task force also concluded that the SLC design basis and current material purchase specs. were satisfactory.

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