ML19343C224

AO 50-219/74/37:on 740712,main Steam Line Low Pressure Switches RE23A,B,C & D Tripped at Pressures Less than Min Required Value of 860 Psig.Caused by Switch Repeatability. Setpoint Accuracy & Tolerance Under Investigation

ML19343C224
Person / Time
Site:	Oyster Creek
Issue date:	07/19/1974
From:	JERSEY CENTRAL POWER & LIGHT CO.
To:
References
AO-50-219-74-37, NUDOCS 8103040477
Download: ML19343C224 (3)

Text

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Jersey Central Power & Light Company (,

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MADISON AVENUE AT PUNCH BOWL ROAD

• MORRISTOWN.N.J.07960

• 201-539-6111 i

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OYSTER CREEK NUCLEAR GENERATING STATION FORKED RIVER, NEW JERSEY 08731 Abnormal Occurrence Report No. 50-219/74/37 Report Date July 19,1974 Occurrence Date_

July 12, 1974 Identification of Occurrence Violation of the~ Technical Specifications, paragraph 2.3.7, main steam line low pressure . switches RE23A. B, C, and D, found to trip at pressures less than the minimum required value of 860 psig. This event is considered to be an abnormal occurrence as defined in the Technical Specifications, paragraph 1.15A.

Conditions Prior to Occurrence The plant was at steady state power with the major parameters as follows:

Power: Reactor,1893 FMt Electric, 640 SMe Flow: Recirculation, 16.0 x 10'+ gpm Feedwater, 7.07 x 10 6 lb/hr Reactor Pressure: 1020 psig Stack Gas: 15,000 pCi/sec Description of Occurrence On Friday, July 12,1974, at 1000, while performing a routine surveillance test on the four main steam line low pressure switches, it was discovered that switches RE23A, B, C, and D tripped at 842, 848, 846, and 850 psig, respectively.

These values are below the minimum required trip point of 860 psig which is derived by adding a 10 psig head correction factor to the Technical Specification limit of 850 psig.

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Page 2 Abnormal Occurrence No. 50-219/74/37 The "as found"' and "as left" switch settings were:

"As Found" Settings "As Left" Settings-RE23A 842 psig 864 psig RE23B 848 psig 860 psig RE23C 846 psig 860 psig RE23D 850 psig 860 psig Apparent Cause of Occurrence The recognized problem of switch repeatr ?ility is the cause of this occurrence.

Design is considered to be the major contributing factor to this event.

Analysis of Occurrence As indicated in the bases of the Technical Specifications, "The low pressure isolation of the Main Steam Lines at 850 psig was provided to give protection against fast reactor depressurization and the resultant rapid cooldown of the vessel. Advantage was taken of the scram feature which occurs when the Main Steam 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."

The adverse consequences of reactor isolation occurring at reactor pressure approximately 18 psig below the speedfied minimum value of 860 psig is limited to those effects attendant to a greater than normal reactor cooldown rate. The fuel cladding integrity safety limit only comes into effect for power operation at reactor pressures less than 600 pf,ig or for power operation greater than 354 >Mt with less than 10% recirculation flow. Therefore, the consequences of an 18 psig lower than normal reactor isolation and scram set point has no threatening effect whatsoever on the fuel cladding integrity.

The effects of a too rapid cooldown due to the lower isolation pressure are inconsequential since there is approximately a 2*F difference between the saturation temperature for 850 psig and 832 psig.

Corrective Action Set point accuracy and tolerance in not only these instruments but in others as well are under investigation by Jersey Central Power 6 Light Company, GPU Service Corporation, and General Electric Company personnel as described in Abnormal Occurrence No. 50-219/74/35.

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Abnormal Occurrence No. 50-219/74/37 Page 3 1

Failure data Manufacturer data pertinent to these switches are as follows:

Meletron Corporation (subsidiary of Barksdale)

Los Angeles, California Pressure Actuated Switch Model No. 372 Catalog No. 372-6SS49A-293 Range 20-1400 psig Proof psi 1750 G Previous abnormal occurrence reports involving' these switches- are:

1.

Letter to Mr. A. Giambusso from Mr. D. A. Ross, dated December 24, 1973.

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Abnormal Occurrence Report No. 50-219/74/1

, 3. Abnormal Occurrence Report No. 50-219/74/9

4. Abnormal Occurrence Report No. 50-219/74/10

5. Abnomal Occurrence Report No. 50-219/74/12

6. Abnormal Occurrence Report No. 50-219/74/22

7. Abnormal Occurrence Report No. 50-219/74/35 i

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