ML20090D857

AO-50-219/74-56:on 741025,during Surveillance Test,Main Steam Line Low Pressure Switches RE23A,B,C & D Tripped Below Min Required Trip Point.Caused by Switch Repeatability.Tech Spec Change Being Evaluated

ML20090D857
Person / Time
Site:	Oyster Creek
Issue date:	11/04/1974
From:	Ross D JERSEY CENTRAL POWER & LIGHT CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
References
AO-50-219-74-56, NUDOCS 8303030427
Download: ML20090D857 (4)

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MADISON AVENUE AT PUNCH BOWL ROAD

• MORRISTOWN. N.J. 07960

• 201-539-6111 NEuneR Of TVE Generat [{*, Public Utitities Corporation 5F372 w November 4, 1974 N,'tx N[ N,..- s gj'.?. '%

Mr. A. Giambusso Deputy Director for Reactor Projects

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Washington, D. C. 20545 4T .

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Subject:

Oyster Creek Station ,

Docket No. 50-219 ,

Abnormal Occurrence Report No. 50-219/74-56 The purpose of this letter is to forward to you the attached Abnormal Occurrence Re" ort in compliance with paragraph 6.6.2.a of the Technical Specifications.

Enclosed are forty copics of this submittal.

Very truly yours,

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V Donald A. Ross fianager, Generating Stations-Nuclear es Enclosures cc: Mr. J. P. O'Reilly, Director Directorate of Regulatory Operations, Region 1

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M ADISON AVENUE AT PUNCH BOWL ROAD

• MORRISTOWN, N.J.07960

• 201539-6111 me. a or rna General g'[j[*, Public Utilities Corporation SYSTu n OYSTER CREEK NUCLEAR GENERATING STATION FORKED RIVER, NEW JERSEY 08731 Abnormal Occurrence Report No. 50-219/74-56 Report Date November 4,1974 Occurrence Date ,

October 25, 1974 Identification of Occurrence Violation of the Technical Specifications, paragraph 2.3.7, main steam line low pressure switches RE23A, B, C, and D were 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 major parameters as follows:

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Power: Reactor, 1912 MWt Electric, 662 MWe Flow: Recirculation, 59.9 x 106 lb/hr Feedwater, 7.15 x 10 6 lb/hr Stack Gas: 17,259 pCi/sec Description of Occurrence On Friday, October 25, 1974, at 1320, 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 850, 855, 854 and 857 psig, respectively.

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

1- o o Abnormal Occurrence Report No. 50-219/74-56 Page 2

'The "as found" and "as left" switch settings were:

"As Found" Settings "As Left" Settings RE23A 850 psig 860 psig RE23B 855 psig 861 psig RE23C 854 psig 861 psig

' RE23D 857 psig 862 psig Apparent Cause of Occurrence The cause of this occurrence is the recognized problem of switch repeatability.

m Analysis of Occurrence Four pressure switches in the reactor protection system (RPS) are provided to isolate the reactor in the event of low main steam line pressure. Two of these switches (RE23A and RE23C) are in RPS Channel 1, and the other two switches '

(RE23B and RE23D) are in RPS Channel 2. Low pressure signals from two pressure switches, one in each RPS channel, are required to effect main steam isolation valve closure. A review of the "as found" switch settings indicates that reactor isolation would have occurred at a pressure of 854 psig had a main steam line ,

low pressure condition existed.

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 a reactor pressure approximately 6 psig below the specified minimum value of 850 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 psig or for power operation greater than 354 MWt with less than 10*. recirculation flow. Therefore, the consequences of a 6 psig lower than normal reactor isolation and scram setpoint 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 less than a l'F difference between the saturation temperature for 850 psig and 844 psig.

Corrective Action Steam line pressure variations during daily stop valve testing make it impractical to include in the switch setpoint the normal setpoint variations needed to provide a sufficient margin above the Technical Specification limit.

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Abnormal Occurrence Report No. 50-219/74-56 Page 3 i

- The plant has received from General Electric Company information supporting a Technical Specification Change Request which will encompass changing the present

! 850 psig setpoint of the Main Steam Line Low Pressure Switches to a lower set-l point.

This proposal was received on September 27, 1974, and has been evaluated by the plant staff. A Technical Specification Change Request was approved by the Plant t Operations Review Committee on October 28, 1974. This Change Request will be submitted to the General Office Review Board for review at their mid-November meeting and will be submitted to the Commission subsequent to this review.

Failure Data Previous abnormal occurrence reports involving these switches are:

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

2. Abnormal Occurrence Report No. 50-219/74-1 3

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

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

5. Abnormal 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

8. Abnormal Occurrence Report No. 50-219/74-37 i 9. Abnormal Occurrence Report No. 50-219/74 41

10. Abnomal Occurrence Report No. 50-219/74-42

11. Abnormal Occurrence Report No. 50-219/74-43 l 12. Abnormal Occurrence Report No. 50-219/74-49 lt 13. Abnormal Occurrence Report No. 50-219/74-51.

t ' 14. Abnormal Occurrence Report No. 50-219/74-52 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 ii Proof psi 1750 G