ML20084C505

AO 50-219/74-51:on 741007,main Steam Line Low Pressure Switches RE23B & C Found to Trip at Pressure Less than Min of 860 Psig.Caused by Switch Repeatability.Ge Supplied Info Re Reduction of Setpoint.Info Being Evaluated

ML20084C505
Person / Time
Site:	Oyster Creek
Issue date:	10/11/1974
From:	Ross D JERSEY CENTRAL POWER & LIGHT CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
References
AO-50-219-74-51, NUDOCS 8304080076
Download: ML20084C505 (4)

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.ersey Centra Power & Lig7t Company /k!< n@@ I MADISON AVENUE AT PUNCH BOWL ROAD

• MORRISTdWN, N.J. 0h060

• 201-539-6111 neinstM OF Tree l ,

Generat [y*j]*, Public Utilities Corporatio'n_ _

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October 11, 1974 ,

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Mr. A. Giambusso c~ '.7 .,' --

Deputy Director for Reactor Projects ' , j [ ""'d Directorate of Licensing United States Atomic energy Commission

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Washington, D. C. 20545 ,. j

Dear Mr. Giambusso:

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Subject:

Oyster Creek Station Docket No. 50-219 '; -

Abnormal Occurrence Report No. 50-219/74-51 I

.a The purpose of this letter is to forward to you the attached Abnormal Occurrence Report in compliance with paragraph'J.6.2.a of the, Technical Specifications. ,

Enclosed are forty copics of this submittal. '.

Very truly yours,s,,

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. W Donald A. Ross / ,

Manager, Nuclear Generating Stations ,

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l cc: Mr. J. P. O'Reilly, Director Directorate of Regulatory Operations, Region 1 /

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.ersey Centra Power & Lig7t Company r

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• 201-539-6111

.. . . o, r u General ac f>,,,.,...,, Public Utihties Corporation o

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i < OYSTER CREEK NUCLEAR GENERATING STATION

'4 . FORKED RIVER, NEW JERSEY 08731 v' ,

Abnormal Occurrence

- ' Report No. 50-219/74-51 1

Report Date

. / October 11, 1974 1 s

- Occurrence Date

- October 7, 197I

' Identification of Occurrence Violation of the Technical Specifications, paragraph 2.3.7, main steam linc

, low pressurd switches RE238 and C were found to trip at a Iressure less than

,.the minimum' required value of 860 psig. This event is considered to be an abnormal oikurrence as defined in the Technical Specifications, paragraph 1.15A.

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

Power: U Reactor, 1970 MWt Electric 650 MWe Flow: - Recirculation, 14.4 x 104 gpm

j. Feedwater, 8.25 x 106 lb/hr 1020 psig 4

Reac_ tor Pressure:

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, Stack Gas: 15,619 pCi/sec

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,DesEription of Occurrence

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, . On, Monday, October 7, 1974, at 1106, while performing a routine surveillance

' , , test on'the four main steam line low pressure switches, it was discovered that

~~cswitclics RE23B and C cach tripped at 855 psig. This value is below the minimum required trip point of 860_ psig, which is derived by adding to the Technical Sp,ecification limit of 850 psig, a 10 psig head correction factor.

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o o Abnormal Occurrence Report No. 50-219/74-51 Page 2 The "as found" and "as left" switch settings were:

"As Found" Settings "As Left" Settings RE23A 860 psig 860 psig RE23B 855 psig 860 psig RU23C 855 psig 860 psig RE23D 860 psig 860 psig Apparent Cause of Occurrence The cause of this occurrence is the recognized problem of switch repeatability.

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 corocquences of reactor isolation occurring at reactor pressure approximately 5 psig below the specified 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 psig or for power operation greater than 354 MWt with less than 101, recitculation flow. Therefore, the consequences of a 5 psig lower than normal reactor isolation and scram setpoint has no threaten-ing 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 l'F difference between the saturation temperature for 850 psig and 845 psig.

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

The General Electric Company has furnished information on the feasibility of reducing the 850 psig setpoint to a lower value. This information is presently being evaluated by the Oyster Creek Nuclear Station s staff, and a Technical Specification Change Request may be submitted as s result of this evaluation.

O O Abnormal Occurrence Report No. 50-219/74 Page 3 Failure Data 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 D. A. Ross, dated December 24, 1973.

2. ALnormal 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. 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

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

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

11. Abnormal Occurrence Report No. 50-219/74-43

12. Abnormal Occurrence Report No. 50-219/74-49

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