ML20085M478

Application for Amend to License DPR-33,changing Tech Specs to Reverse Sensing Lines of Differential Pressure Switches PdIS-75-28 & PdIS-75-56

ML20085M478
Person / Time
Site:	Browns Ferry
Issue date:	01/18/1974
From:	Gilleland J TENNESSEE VALLEY AUTHORITY
To:	Moore V US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085M471	List: ML20085M478 ML20085M482 ML20085M507
References
NUDOCS 8311080595
Download: ML20085M478 (2)

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Mr. Voss A. Moore 46 %

[ Assistant Director for Boiling Water Reactors 9 '% <

U.S. Atomic Energy Commission f.ra Washington. DC 20545

Dear Mr. Moore:

This is to request authorization to make temporary modifications .

to certain instrumentation in unit 1 of Browns Ferry Nuclear Plant and to make a temporary change to unit 1 Technical Speci. -

fications. The proposed modification involves only reversing the sensing lines of both differential pressure switches PdIS-75-28 and PdIS-75-56 which should indicate during normal operation the pressure drop between the bottom of the core (top of core plate, outside of fuel channels) and the core spray sparger.

Reversal of the sensing lines at both of the pressure switches

! is needed to obtain a positive onseale indication during normal operation.

- - - . The differential pressure switches referred to above have not -- -

indicated as predicted because the pressures sensed are not

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as predicted. This problem has been reported in abnormal occurrence report BFAO-7345W, E. F. Thomas to John F.' O' Leary.

Reversal of the sensing lines will give a positive differential pressure indication of about 3.5 paid during normal operation. Failure of the core spray piping in the pressure vessel-shroud annulus (which this instrumentation is installed to detect) would give a negative pressure differential. Therefore, it is proposed to change page 64, Table 3.2.B, of Browns Ferry unit 1 Technical Specifications according to the enclosure to this letter. The proposed change'would respecify l the alarm setpoint of the Core Spray Sparger to Reactor Pressure i 1,

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. l Mr. Voss A. Moore January 18, 1974 f.

I Vessel d/p instruments at 2 paid i 0.4 paid rather than 5 paid i 1.5. Thus, in case of the failure mentioned, the indicated differential pressure would drop from a positive 3.5 paid to zero _

and the' switches would activate the alarm at 2 paid.

Reversal of the sensing lines would permit continuous indication of the integrity of the core spray piping. At this time this monitoring is being done intermittently.

We are studying a permanent modification to this instrumentation; .

4 results of this requested temporary modification will be of use in evaluating proposed permanent modifications. We will submit the proposed permanent modifications and proposed technical specification change for approval. In the meantime we request prompt authorization of this proposed temporary modification and approval of the. proposed temporary technical specification.... .

ery truly yours, 4 ,h l l y s

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J. E. Gilleland f ,

AssistanttotheManagerofPo/wer f

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