United States Nuclear Regulatory Commission - Protecting People and the Environment

                         EVENT NOTIFICATION WORKSHEET

Notification Time:  Fri 03 Nov 95 1800

Facility:           Watts Bar Unit 1, 2

Caller's Name:      P. L. Pace

Caller's Number:         (615) 365-1824

Event Date:         13 Oct 95

Regulation:         10 CFR 50.55(e)

Description:        The deficiency identified a fan shaft failure initiation mechanism on Ellis
and Watts safety-related coolers and a condenser.  Specifically, the components identified as
having damage are 1-PMCL-30-175-A (1A-A RHR pump room cooler), 2-COND-31-289 (480
V board room condenser 2B-B), 1-PMCL-30-183-A (1A-A CCP room cooler A-A),
2-PMCL-30-190-A (CCS pump and Unit 1 AFW pump cooler A-A), and 1-PMCL-30-191-B
(CCS pump and Unit 1 AFW pump cooler B-B).  Unit 1 was in cold shutdown, prior to Mode 6
(initial fuel loading).

During an accident, individual pump room coolers will start with their respective pumps to
provide cooling and assure safe pump function.  Pump coolers start on auxiliary building
isolation signal or when area temperature is greater than set point.  The 480 volt board room
condenser is intended for continuous operation and is controlled by room thermostats.  Failure of
these components may potentially lead to overheating and failure of the equipment they serve.

The mechanism of failure was the bearing moving relative to the fan shaft.  Overtensioning of
belts was identified as the cause.  Maintenance Instruction (MI)-0.16, "Maintenance Guidelines
For Belt Driven Equipment," had been initiated in 1988 as a result of deficiencies written on air
handling equipment.  The instruction provided a belt tensioning method base on belt deflection
(Browning Belt Manufacture guidance).  This resulted in high forces/loads on the shaft and

Because of the identified condition, the required 100 days of continuous operation to support safe
shutdown following a design basis accident may not be assured, since potential fan running time
before failure could not be determined.  However, the fans had not failed prior to removal from
service for repairs.

Forty one safety-related/quality-related Ellis and Watts belt driven fans required for Unit 1
operation have been identified.  As part of this review, eighteen were determined to be required
to be inspected prior to mode 6.  Inspection has been performed on the eighteen units plus
2-ConD-31-289.  Five of the nineteen were identified to have damaged shafts and have been
repaired.  The corrective actions include a change to the method of tightening the belts for
avoiding shaft damage.  The remaining twenty-two fans will be inspected prior to Mode 4 entry.

Reference:  II-W-95-17
            CDR 95-07
Page Last Reviewed/Updated Monday, January 27, 2020