ML19347C813

Ao:On 731206,Meletron Corp Model 372,main Steam Line Low Pressure Switches RE23A Through RE23D Found to Trip at Pressure Below Min Required Setpoint of 850 Psig.Cause of Setpoint Drift Under Study.Switches Reset

ML19347C813
Person / Time
Site:	Oyster Creek
Issue date:	12/24/1973
From:	Ross D JERSEY CENTRAL POWER & LIGHT CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 8103040820
Download: ML19347C813 (2)

Text

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. i, hrc':2ry F::3 Cy, Jersey Central Power & Light Company f b/

MADISON AVENUE AT PUNCH BOWL ROAD

• MORRISTOWN,N.J.07960

• 201-539-6111 usuun av run General

(({e Pubhc Utahties Corporation gpLW

.. a December 24, 1973  ;,. 7 ,n ..

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,9 5 N5 0 h l * ^ !): ,.

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>fr. A. Giambusso LJ . y ,~

Deputy Director for Reactor Projects J ,'P- .f Directorate of Licensing L'gf a(f;/. '

United States Atomic Energy Commission / O Washington, D. C. 20545 'f,..[,fY

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Subject:

Oyster Creek Station Do::ket No. 50-219

' Instrument Set Point Drift This letter serves to report a violation of the Technical Specifi-cations, paragraph 2.3.7, low pressure main steam line pressure switches were found to trip at a pressure less than 850 psig. This event is considered to be an abnormal occurrence as defined in the Technical Specifications, paragraph 1.15A. Notification of this event as required by the Technical Specifications, paragraph 6.6.2.a, was made to hir. E. Greenman, AEC Region I, Directorate of Regulatory Operations, on Wednesday, December 12, 1973, during his site visit, and by telecopier on Thursday, December 13, 1973.

On Thursday, December 6,1973, while performing a surveillance test on the main steam line low pressure switches, RE23A, B, C, and D, all four switches were found to trip at a pressure below the minimum required set point of 850 psig. The "as found" trip values were recorded as follows:

RE23A - 835 psig RE23B - 835 psig (,

RE23C - 800 psig /'d, ..

RE23D - 820 psig Itr n

blanufacturer data pertinent to the switches is as follows: l s*/

7 bieletron Corp. (subsidiary of Barksdale)

Los Angeles, California a

g '6gf l Pressure Actuated Switch j blodel 372 gg Catalog No. 372-6SS49A-793 Range 850 G Dec. /00 o Proof Psi 1750 G At this time, the cause of this drift has not been determined. Plant personnel have contacted the manufacturer who acknowledged that problems of set point drift with lnstruments of this type have been recognized. Currently, Tib30'ID W

Mr. Giambusso December 24, 1973 the manufacturer is conducting a study with General Electric Company to investigate and resolve this drift problem. The results of this study are to be reported to the AEC by the manufacturer.

All four switches were reset to conform with the Technical Specifi-cation requirement of >850 psig.

The significance of this event is indicated in the bases of the Technical Specifications. "We low pressure isolation of the main steam lines at 850 psig was provided to give protection against fast reactor depressurization and the resulting rapid cooldown of the vessel. Advantage was taken of the scram feature which occurs when the main steam line isolation valves are closed to provide for reactor shutdown so that high power operation at low reactor pressure does not occur, thus providing protection for the fuel cladding integrity safety limit." He temperature difference for saturated steam at 850 psig and 800 psig is less than 8*F, thus the resulting vessel cooldown effect is considered negligibic.

With regards to power operation below 850 psig and the attendant effects on the fuel cladding integrity safety limit, power IcVel must be limited when pressure is less than 600 psig or flow is less than 10% to 354 MWt or approximately 18.3*6 of rated. As stated in the Technical Specifi-cations, "We value is applicable to ambient pressure and no flow conditions.

For any greater pressure or flow conditions there is increased margin." he fuel cladding integrity safety limit curve has been developed and is applicable for pressure in excess of 600 psig. B erefore, whether a reactor scram occurs at 850 psig or 800 psig has little safety significance since no severe re-strictions on critical heat flux are imposed unless the reactor pressure is less than 600 psig.

The following actions are planned to avoid recurrence of this event:

1. Evaluate vendor recommendations as soon as they are available to possibly reduce or eliminate the sensor drift problem.

2. During various normal plant operating evolutions, measurements of " hydraulic noise" in main steam line sensing lines will be

. made. Based on the amount of " hydraulic noise" present, an operating set point will be selected above 850 psig which will ,

provide some reasonable operating margin to avoid spurious '

trips and still tolerate some downward drift in instrument set point.

5 Enelched are forty copies of this reth*rt.

Verytru)yyours, 1

Donald A. Ross Manager, Nuclear Generating Stations es ,

cc: Mr. J. P. O'Reillyc Director Directorate of Pegtalatory Operations, Region I