United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #:  9410250232

TVA

OCT 17 1994

CDR-50-390                                        10 CFR 50.55(e)

U.S. Nuclear Regulatory Commission
ATTN: Document Control Desk
Washington, D.C. 20555

Gentlemen:

In the Matter of the Application of )        Docket Nos. 50-390 
Tennessee Valley Authority          )

WATTS BAR NUCLEAR PLANT (WBN) - RESIDUAL HEAT REMOVAL SYSTEM
MINIFLOW
CHECK VALVES IN IMPROPER ORIENTATION - CDR-50-390/94-11

The purpose of this letter is to provide a report in accordance with 10
CFR 50.55(e).  The subject deficiency, documented in Significant
Corrective Action Report WBSCA940046, was initially reported to the NRC
Operations Center on September 16, 1994.  The enclosure to this letter
contains TVA's final report on this subject.

If you have any questions, please telephone P. L. Pace at (615) 365-1824.

Sincerely,


Dwight E. Nunn
Vice President
New Plant Completion
Watts Bar Nuclear Plant

Enclosure
cc:  See page 2


U. S. Nuclear Regulatory Commission
Page 2

OCT 17 1994

cc (Enclosure):
     INPO Record Center
     700 Galleria Parkway
     Atlanta, Georgia 30339

     NRC Resident Inspector
     Watts Bar Nuclear Plant
     Rt. 2, Box 700
     Spring City, Tennessee 37381


     Mr. P. S. Tam, Senior Project Manager
     U.S. Nuclear Regulatory Commission
     One White Flint North
     11555 Rockville Pike
     Rockville, Maryland 20852

     U.S. Nuclear Regulatory Commission
     Region II
     101 Marietta Street, NW, Suite 2900
     Atlanta, Georgia 30323


                               ENCLOSURE 1

                    WATTS BAR NUCLEAR PLANT - UNIT 1
               RESIDUAL HEAT REMOVAL MINIFLOW CHECK VALVES
                            CDR 50-390/94-11
                              FINAL REPORT

DESCRIPTION OF DEFICIENCY

On July 15, 1994, during valve disassembly, WBN identified that the
Residual Heat Removal (RHR) system check valves were in the fully open
position and would not have closed to inhibit reverse flow, as required. 
These valves are Anchor Darling, 8 inch, tilting disk check valves and
are located in a vertical pipe run of the main lines, downstream of the
RHR system miniflow lines.

WBN purchase specifications identified that the valves would be used in a
vertical pipe run and Anchor Darling vendor drawings identified that the
supplied valves were acceptable for this application.  However, Anchor
Darling did not perform the required internal valve modification which
would allow the valve to operate in a vertical orientation.

SAFETY IMPLICATIONS

The residual heat removal (RHR) system at WBN is a safety-related system
designed to ensure adequate heat removal during shutdown conditions
(Modes 4, 5 and 6) and following a loss of coolant accident (LOCA) such
that the acceptable fuel design limits are not exceeded.  Following a
large break LOCA, the RHR system provides low head flow, from the
refueling water storage tank (RWST), to the reactor coolant system (RCS)
during the injection mode of cooling.  During the recirculation mode of
cooling following a large break LOCA, the RHR system provides the
capability to pump water from the containment sump to the RCS.

In the event of a small break LOCA, the RHR system remains available to
provide cooling should the RCS pressure drop below the setpoint for
initiation of the RHR system.  In the event of RHR system actuation
following a small break LOCA, the RHR pump discharge will be at a lower
pressures than the RCS, resulting in the check valve being closed and a
portion of the pump discharge flowing through the miniflow lines. 
However, the failure of the check valves could result in the stronger RHR
pump deadheading the weaker RHR pump with the potential for the
subsequent failure of the weaker pump.  Taking into account an additional
single failure, as required by 10 CFR 50.55e, this deficiency could
result in a loss of RHR capability at WBN.

CAUSE OF THE DEFICIENCY

This deficiency was a result of a failure of the vendor (Anchor Darling)
to ensure materials supplied to WBN met the required purchase
specifications.

                                  E1-1


                               ENCLOSURE 1

                    WATTS BAR NUCLEAR PLANT - UNIT 1
               RESIDUAL HEAT REMOVAL MINIFLOW CHECK VALVES
                            CDR 50-390/94-11
                              FINAL REPORT

CORRECTIVE ACTIONS

The following corrective actions have been taken to address the subject
deficiency:

1.   The field work for the internal valve modification required to
     ensure the RHR check valves will operate in a vertical configuration
     has been completed.

2.   TVA has reviewed the remaining active swing and tilting disc check
     valves to determine if they were procured to be installed in
     vertical pipe runs.  This review indicated no additional active
     check valves were specified for vertical installations.  Therefore,
     no other deficiencies were identified.

3.   TVA contacted a representative of Anchor Darling on September 29,
     1994 to inform the vendor of this deficiency.

                                  E1-2


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