ML19343C352

AO 50-219/74-28:on 740423,suction Valve V-20-4 to B Core Spray Pump Stuck in Closed Position for 15 Minutes,Causing Loss of Core Spray Redundancy in Sys 2.Cause Undetermined. Valve Manually Closed & Circuit Breaker Tagged Open

ML19343C352
Person / Time
Site:	Oyster Creek
Issue date:	05/01/1974
From:	JERSEY CENTRAL POWER & LIGHT CO.
To:	US ATOMIC ENERGY COMMISSION (AEC)
References
AO-50-219-74-28, NUDOCS 8103120356
Download: ML19343C352 (2)

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OYSTER CREEK NUCLEAR GENERATING STATION j

FORKED RIVER, NEW JERSEY 08731 Abnormal Occurrence-j

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Report No. S0-219/74/28

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Report Date

$ May 1, 1974 T

• Occurrence Date p

P April 23, 1974 P

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p Identification of Occurrence

[3, Violation of the Technical Specifications, paragraph 2.3.4, Electromatic ReliG Valve Pressure Switches,1A83B and 1AS3D, were found to trip at pressures in excess of the maximum allowable value of 1070 psig. This event is considered l 1,

be an abnormal occurrence as defined in the Technical Specifications, paragrag ti 1.15A.

p, Conditions Prior to Occurrence

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The plant was shut down for refueling.

The reactor mode switch was in the REFUEL position with reactor coolant tempet p

approximately 100*F.

at Description of Occurrence On Tuesday, April 23, 1974, while performing surveillance on the five Electrd Relief Valve Pressure Switches, it was found that 1A83B and 1A83D tripped at Di Psig and 1096 psig, respectively. 'Ihese values are in excess of the maximum em allowable trip points of 1084 psig and 1082 psig, respectively, which are dets Te by adding appropriate head correction factors to the Technical Specification of f 1070 psig. Switches 1A83B and 1A83D are associated with valves NR108B anf in NR108D, respectively.

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

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Associated " Desired" "As Found" "As Left" Th Setting Setting Setting Switch Valve tr NRIOSA 1079 psig 1079 psig 1079 psig 1A83A gg NR108B 1084 psig 1090 psig 1084 psig 1A83B NR108C 1077 psig 1077 psig 1077 psig 1A83C NR108D 1082 psig 1096 psig 1082 psig 1A83D NR108E 1082 psig 1082 psig 1082 psig 1A83E 8/O 3/R 6 35%

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Abnormal Occurrence No. 50-219/74/29 Page 2 Apparent Cause of Occurrence Set point repeatability has been tentatively identified as the cause of this occurrence.

Analysis of Occurrence The relief valves are provided to remove sufficient energy from the primary system to prevent the safety valves from lifting during a transient. The limiting-pressure transient is that which is produced upon a turbine trip from rated design-power with a failure of the bypass system to function. Under these conditions, the five (5) relief valves are required to operate in order to prevent the pressure excursion from reaching the lowest set point of the primary system safety valves. It should be noted that a 25 psi margin exists between.the resulting peak pressure and the lowest safety valve set point as added assurance that the safety valves will not lift during this transient. With valves NR108B and NRIOSD actuating at 6 psig and 14 psig, respectively,-above the maximum allowable trip point of 1070 psig, and assuming the most limiting pressure transient had occurred, the lowest set point safety valve or valves may have been required to actuate in order to limit the pressure transient. Since the safety valve capacity is based upon providing sufficient vessel over-pressure protection upon failure of all pressure relieving devices, in addition to a failure of the reactor to scram, over-pressur--

ization of the vessel would not have occurred.

Corrective Action The involved pressure switches, 1A83B and 1A83D, were immediately reset to trip at allowable pressure levels. Until the problem of set point repeatability is solved, the Electromatic Relief Valve Pressure Switches will be surveilled each time the reactor is shut down and the reactor coolant temperature is reduced to

<212*F.

Discussions with the Nuclear Steam Supply System vendor into the possibility of employing set points with instrument accuracy deviations taken into account for Technical Specification surveillances will continue. The successful termination of these discussions lies in the ability of the vendor to supply transient analysis information and to determine precisely the conservatisms utilized in those analyses that are relevant to the instrument set point analysis.

Failure Data This is the first abnormal occurrence report of the failure of these switches to

trip at their preset trip point.

Manufacturer data pertinent to these switches are as follows:

Manufacturer: Dresser Type: 1539VX Serial Nos.: BK3339 (1A83B)

, BK3338 (1A83D) i l

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