05000029/LER-1987-002, Forwards LER 87-002-00

Forwards LER 87-002-00

ML20212J581
Person / Time
Site:	Yankee Rowe
Issue date:	02/05/1987
From:	St Laurent N YANKEE ATOMIC ELECTRIC CO.
To:	Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
NUDOCS 8703090059
Download: ML20212J581 (1)

LER-2087-002, Forwards LER 87-002-00

Event date:
Report date:
0292087002R00 - NRC Website

text

. i YANKEE ATOMIC ELECTRIC COMPANY r.i.ou an.t<,s><2<-s2e, Star Route, Rowe, Massachusetts 01367

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February 5, 1987 U.S. Nuclear Regulatory Commission Region I 631 Park Avenue King of Prussia, Pennsylvania 19406 Attention: Dr. Thomas E. Murley, Regional Administrator

Subject:

Licensee Event Report 50-29/87-02 Safety Injection Building Vent Fans PRV-1 and PRV-2 Inoperable

Dear Sir:

In accordance with 10 CFR 50.73(a)(2)(v), the attached Licensee Event Report is hereby submitted.

Very truly yours, hygd b 0 Wh Normand N. St. Laurent Plant Superintendent i

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On January 6, 1987, with the plant in made I at 100% power, while performing the recalibration of the temperature switches for the Safety Injection Building Ventilation System, ventilation fan PRV-1 failed to start. Attempts were made to start the redundant fan (PRV-2) manually.

PRV-2 started, then tripped. The fans support the operability of the ECCS system when outside ambient temperature is above 40 deg. F.

An immediate investigation determined that the thermal overload relavs in both PRV-1 and 2 starters had tripped. The fan tripping was attributed to the cold weather (ambient temperature range for the day was between 9 and 33 deg. F) which increased lubricant viscosity and increased bearing friction. The root cause of this event is still under investigation.

The fans were eventually started manually, and placed on a surveillance schedule to insure operability while corrective action is pursued. /t the time of discovery the ambient temperature did not exceed 40 deg.

Ft therefore there was no adverse effect to the public health or safety. This is the first occurrence of this nature.

Corrective actions include increasing the surveillance frequency, rep 1 acing the over1 cad heaters, and evaluating the motor ni2ing, j

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rixtin . w : _ w cs., .maren m On January 6, 1987, at 1450, with the plant in mode 1 at 100% power, while performing the recalibration of the temperature switches for the Safety Injection Building Ventilation System, ventilation fan PRV-1 failed to start. Attempts were made to start the redundant fan (PRV-2) manually. PRV-2 started, then tripped. The fans support the operability of the ECCS system when outside ambient temperature is above 40 deg. F.

An immediate investigation determined that the thermal overload relays in both PRV-1 and 2 starters had tripped. The fan tripping was attributed to the cold weather (ambient temperature range for the day between 9 and 33 deg. F) which increased lubricant viscosity and bearing friction. The root cause of this event is still under investigation.

On January 6, 1987, at 1600, PRV-1 was started and returned to service.

At 1635, PRV-2 was started and returned to service. Only one fan is required to support operation of the ECCS system when ambient temprature is above 40 deg. F. In order to assure continued operability the fans were manually started once per hour initially. As assurance of continued operability improved, the surveillance interval was increased to once per 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> shift. The fans have since started as required. The interval is expected to be extended to once per week.

To determine the cause of the failure and appropriate corrective actions, an extensive investigation was conducted. The following is a summary of the investigation and actions that have been, and will be.

taken to prevent a recurrence.

Doth PRV-1 and 2 fan motors are controlled by Gould, Inc. unitized combination starters equipped with Gould G30T32 (4.58-4.98 A) overloaa heaters set at 115%. The fan electrical motors are rated 3.0 hp.

230/460 V, 9.2/4.6A, 3 ph , 60 cy, 1775 rpm, S.F. 1.15, NEMA Code J, and operate at a running current of 4.3 A.

t In order to find the reasons for tripping, the fan motors were l disassembled, cleaned, inspected, provided with new bearings, and lubricated. The inspection revealed no mechanical problems. On November 9 1905, the fan bearings had bcon flushed and lubritated ui 9 Chevron SR12 lubricant for environmental qualification re.ssons.

Chevron SRI 2 lubricant has an excellent operating temperature range based on manufacturer's specification for any expected operating condition for the fans. Moreover, after the fan motors were reassembled, the starting time was recorded and found to be approximately the same as the previous recorded value (6.7 seconds).

The system design and operating conditions were reviewed, and conditions that apparently contributed to the fans tripping were noted l as follows:

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1. The fans starting time is excessively long due to the fans moment of inertia. This problem has not been detected earlier, (a) because the fans were started in mild weather, and (b) because prior to 1984, the motor starters were Westinghruse A2OO equipped with Type H32 heaters which, although similar to the actual Gould heaters, have somewhat longer trip times.

2. The cold weather on the day of the event added further load on the motors due to the belt's stiffness and somewhat more viscous lubricant.

An evaluation determined that at an ambient temperature of 40F or less, no active ventilation is required. This conclusion shows that during the time PRV-1 and PRV-2 were declared inoperable (average ambient temperature = 20F), operation of the ventilation system was not required to support ECCS operability.

To prevent a recurrence of this event, the following actions have been or will be taken:

A surveillance procedure will be developed and issued to check the safety injection building ventilation system operability once per 7 days when the ECCS system is required to be operable. Other clant procedures will be modified as necessary to insure the surveillance is carried out. The surveillance is, and will continue to be, carried out under the administrative control of the Operations Department until the procedures are in place.

The currently installed G30T32 (4.58-4.98 A) heaters shall be replaced with G30T35 (5.94-6.42 A) heaters set at 100% following reciept and acceptance of the new heaters. The replacement of the existing G30T32 thermal overload heaters with larger G30T35 heaters will help assure the completion of the safety-related function.

The replacemnnt will provide adequate protection of the fan motors on locked rotor and will not adversely affect the operation of tne fans. The G30T35 heaters will increase the tripping margin and are acceptable replacemento.

An evaluation of the motor fan sizing will be performed. This evaluation will consider the motor torque versus fan inertia durtng system starting and operation. Additionally. the evaluation will consider any environmental concerns associated with the operation of the ventilation system. If it is confirmed that the motor is marginally sized for the fan, a recommendation will be made, followed by a design change, if required, to correct the motor / fan sizing.

Dased on the above discussion, there was no adverso effect to the public health and safety.

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