ML19343C230
| ML19343C230 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 06/06/1974 |
| From: | Ross D JERSEY CENTRAL POWER & LIGHT CO. |
| To: | Giabusso A US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8103040536 | |
| Download: ML19343C230 (3) | |
Text
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Jersey Central Power & Light Company %/
MADISON AVENUE AT PUNCH BOWL ROAD
- MORRtSTOWN. N.J. 07960
- 201-539-6111 a.m a r-f.1. ] Public Utilites Corporation cen ral SVETE R
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June 6, 1974
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Deputy Director for Reactor Projects
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Dear Mr. Giambusso:
Subject:
Oyster Creek Station h u...,
Docket No. 50-219
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Core Spray System II - Condition for Possible Deviation in Component Operating Sequence The purpose of this letter is to report to you, as a matter of interest, a condition that temporarily existed in the control system of Core Spray System II that would have prevented the normal sequence of component operation in the event that core spray had been called for.
On May 25, 1974, at 1530, while performing the toutine semi-annual core spray pump discherge pressure switch calibration, it was observed that pressure switches RV29B and RV29D were in the tripped condition. At the time of the event, the reactor was in the shutdown condition with the reactor vessel head and drywell dome in place.
l The switches, which trip at 100 psig and reset at 55 psig, sense core l
spray pump discharge pressure and are used in the core spray system logic to perform two functions:
1.
They act to trip the primary core spray pump (NZ01B) and start the redundant pu=p if the primary pump fails to start or develop a discharge pressure of 100 psig within 5 seconds which is indicative of improper pump operation.
2.
They are also interlocked into the starting logic sequence for the core spray booster pumps NZO3B and D in that the booster pump will start when either of the two pressure switches are tripped, core spray is called for, and there is power to the pump motor.
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l' Mr. Giambusso June 6, 1974 While investigating this event, it was observed that a pressure of 68 psig was impressed upon the switches causing them to be in their tripped condition.
It was determined that this pressure was due to the core spray system fill pump which is used to automatically fill the core spray system piping to prevent water hammer.
During normal system surveillance testing procedures, switch reset is achieved by the operation of the core spray system blocking valves, V-20-92 for System I and V-20-93 for System II, which act to depressurize the core spray piping by opening up a drain path to the torus from a point in the system between the discharge of the core spray pumps and suction of the core spray booster pumps. Operation of this valve causes the line pressure to temporarily drop well below the 55 psig reset pressure until the fill pump reestablishes the 68 psig pressure which is nomal for this system.
It is thought that the pressure switches were not reset by opening blocking valve V-20-93 after completing the core spray system pump operability test performed on May 22, 1974.
It should be pointed out that when a switch is tripped, this condition is alarmed in the station control room. However, this alam is common for several pressure switches in the core spray system, one of which is tripped when the reactor pressure is less than 285 psig (RE17B and D core spray parallel injection valve pemissive). Since the reactor was depressurized during the time of this event, the alam was on continuously, thereby masking the tripped condition of the RV29 switches.
Had the core spray system been called upon to function under design basis LOCA conditions, both the core spray and core spray booster pumps would have received simultaneous start signals since it would appear to the core spray booster pumps that the core spray pumps had started and established at least a 100 psig discharge pressure. Had the core spray pump failed to start or to operate properly, the booster pump would have rapidly depressurized the core spray pump discharge line, thereby resetting the RV29B and D switches.
This would have caused the primary core spray pump to trip and the redundant pump to start after 5 seconds.
It should be noted that had a staa t signal been applied to the booster pump, it would have continued to run until such time as a " trip" signal was applied. Once the RV29s reset, power is not available to the trip logic; hence, the pump would have continued to run through the event. When the RV29s again trip due to the successful operation of a core spray pump, the trip logic is reestablished and the booster pu=p would then be subject to the normal system interlocks.
It is concluded that the core spray system would have performed its intended function although the sequence of events to achieve this end would have been slightly different than the nomal mechanisms.
To prevent a repetition of this occurrence, the set point of the RV29B and D swi:.ches was increased to a nominal trip value of 150 psig with a reset of 90 psig. The system had been tested with these set points with satisfactory results.
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Mr. Giambusso June 6, 1974
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e Enclosed are forty copies of this letter.
i Very truly yours,
)f W Donald A.: Ross 6
Manager, Nuclear Generating Stations
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Enclosures cc:
Mr. J.
P.' O'Reilly,- Director Directorate of Regulatory Operations,- Region I -
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