ML20154G131

Responds to Generic Ltr 88-03 Re Resolution of Generic Issue 93, Steam Binding of Auxiliary Feedwater Pumps. Probability for Steam Binding of Auxiliary Feedwater Pumps & Subsequent Disabling of Sys Very Low

ML20154G131
Person / Time
Site:	Callaway
Issue date:	05/12/1988
From:	Schnell D UNION ELECTRIC CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
REF-GTECI-093, REF-GTECI-NI, TASK-093, TASK-93, TASK-OR GL-88-03, GL-88-3, ULNRC-1774, NUDOCS 8805240244
Download: ML20154G131 (4)

Text

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- Umon Etscraic a

1901 Gratiot Street. St. Louis gg, y2, 399g U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Gentlemen: ULNRC-1774 DOCKET NUMBER 50-483 CALLAWAY PLANT RESPONSE TO GENERIC LETTER 88-03 RESOLUTION OF GENERIC SAFETY ISSUE 93, "STEAM BINDING OF AUXILIARY FEEDWATER PUMPS" Union Electric Company received the subject NRC Generic Letter 88-03 in February 1988. The Generic Letter requested that Union Electric provide a letter of confirmation indicating that the following procedures are in place and maintained:

(a) Procedures to monitor fluid conditions within the auxiliary feedwater system (AFW) each shift during times when the system is required to be operable. This monitoring should ensure that fluid temperature at the AFW pump discharge is maintained at about ambient levels.

(b) Procedures for recognizing steam binding and for restoring the AFW system to operable status, should steam binding occur.

At Callaway a combination of training, administrative controls and design features minimizes the possibility of steam binding in the auxiliary feedwater pumps. The training program incorporates a section on steam binding of auxiliary feedwater pumps in the auxiliary feedwater system lesson plan. This training is required of all equipment operators and licensed personnel.

The Operations Department procedure ODP-ZZ-00016, Watchstation Equipment Logs and Practices, requires a surveillance each shift to perform the following activities:

(a) Vent the auxiliary feedwater pumps to ensure no steam generator back-leakage to the pumps.

(b) Immediately notify the Shift Supervisor if any steam or hot water is vented from the pumps. }

I 8805240244 880512 PDR ADOCK 05000483 1

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P DCD Maarng Address P.U. Box 10, bl Louis. MO 63166

(c) Inspect for leakage from check valves between main feedwater and auxiliary feedwater systems.

I (d ) Check for high temperature in the piping at locations between the check valves.

) Monitoring for leakage and for high temperatures provide l recognition for a potential occurence of steam binding. Venting the pumps provides the corrective action necessary for restoration in the event steam binding should occur.

In add ition , the following Callaway design features minimize any problems due to a theoretical possibility of steam binding of the AFW pumps.

(a) Three check valves are utilized to isolate main feedwater from the auxiliary feedwater pumps. Although the additional valve does not preclude all backflow, it does reduce the possibility of having excess leakage.

(b ) The pumps are situated at a low point in the piping configuration. The steam would preferentially collect in the upper portions of the piping loop rather than travel down the pipe to the pump.

(c ) A minimum flow line is connected at the discharge of the pumps and rises above the pump to the condensate storage tank. Excess pressure and steam would relieve through this line if the steam travelled to the pump d isch arge . l (d ) A temperature sensor at the pump discharge line alarms at 190 deg. F for the control room operator.

This would signal the operator that feedwater is leaking past the check valves and that appropriate action must be taken.

In conclusion, the probability for steam binding of the APW pumps and subsequent disabling of the system is very low for j Callaway due to the combination of design features, procedures, j and training. Should steam hinding occur, adequate surveillances  !

are performed to recognize the situation, in addition to the j over-temperature alarm. Routinely venting the pumps provides the corrective action to ensure operability.  !

If additional information is required, please let us know. I Very truly ours, h .

Donald F. Schnell DJW/skn

STATE OF MISSOURI- )

) SS CITY OF ST. LOUIS )

Donald F. Schnell,.of lawful age, being first duly sworn upon oath says that he is Vice President-Nuclear and an officer of Union Electric Company; that he has read the foregoing document and

.knows the content thereof; that he has executed the same for and on behalf of said company with full power and authority to do so; and that the facts therein stated are true and correct to the best of his knowledge, information and belief.

I By. .

Donald F.' S61inell '

Vice President Nuclear SUBSCRIBED and r.aorn to before me this /o?@ day of b - , 198[.

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BARBARA J. PFAFF NOTARY PUBUC. STATE OF MISSOURI MY COMMISSION EXPlRES AFRtl 22, 1989 ST. LOUIS COUNTY ,

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e cc Gerald Charnoff, Esq.

Shaw, Pittman, Potts & Trowbridge l 2300 N. Street, N.W.

Washington, D.C. . 20037'

.Dr. J. O. Cermak CFA, Inc.

4 Professional Drive (Suite 110)

Gaithersburg, MD 20879 I

R. C. Knop Chief, Reactor Project Branch 1-U.S. Nuclear Regulatory Commission Region III 799 Roosevelt Road Glen Ellyn, Illinois 60137 Bruce Little Callaway Resident Office i U.S. Nuclear Regulatory Commission RRil- i Steedman, Missouri 65077 Tom Alexion (2)

Of fice of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop 316 o l

7920 Norfolk Avenue Bethesda, MD 20014 Manager, Electric Department ,

Missouri Public Service Commission l P.O. Box 360 Jefferson City, MO 65102

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