United States Nuclear Regulatory Commission - Protecting People and the Environment

This document is typed from a poor original 50.55(e) telephone
and fax report.

                         EVENT NOTIFICATION WORKSHEET

Notification Time:  28 Sep 1995 1330

Facility:           Watts Bar Unit 1

Caller's Name:      P. L. Pace

Caller's Number:         (615) 365-1824

Event Date:         20 August 1995

Regulation:         10 CFR 50.55(e)

Description:        Significant check valve chatter and pipe
vibration for
both Unit 1 motor driven auxiliary feedwater (AFW) pumps were
observed during
hot functional testing at low feedwater flow.

AFW system performance is essential for mitigation of several of
the events
which form the licensing basis for WBN.  The AFW system consists
of two motor
driven AFW pumps and one steam turbine driven pump configured
into three
trains.  Each motor driven pump feeds two steam generators and
the steam
turbine driven pump supplies a common header capable of feeding
all steam
generators.  The AFW system removes reactor coolant system (RCS)
heat by
assuring the required supply of water to the steam generators
(SGs) when the
main feedwater (MFW) system is not available and the RCS is above
operational pressure and temperature limits of the residual heat
removal (RHR)

Piping vibration could cause the loss of both motor driven AFW
trains and a
single failure in the turbine driven AFW pump would render all
AFW inoperable
and unable to remove decay heat via the steam generators.

Subsequent testing, with the internals removed from the discharge
check valve
of the B train motor driven auxiliary feedwater pump and with
additional pipe
support shims installed, indicated stable pump performance with
no abnormal
pressure pulsations or pipe vibrations.  Evaluations have
determined that
Nuclear Safety is not affected with the check valve internals

Reference:  CDR 95-06, TDN 95-0832

Handwritten remark:  One of these in series to prevent feeding a
faulted S.G.
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