ML17303B148

Forwards Description of Plant Design Characteristics & Responses to Items Discussed in Generic Ltr 88-03, Steam Binding of Auxiliary Feedwater Pumps. Procedures Discussed in Place & Will Be Maintained

ML17303B148
Person / Time
Site:	Palo Verde
Issue date:	05/27/1988
From:	Van Brunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
REF-GTECI-093, REF-GTECI-NI, TASK-093, TASK-93, TASK-OR 161-01057-EEVB, 161-1057-EEVB, GL-88-03, GL-88-3, NUDOCS 8806010234
Download: ML17303B148 (10)

Text

REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:8806010234 DOC.DATE: 88/05/27 NOTARIZED: YES DOCKET FACIL-STN-50-528 Palo Verde Nuclear Station, Unit 1, Arizona Publi 05000528 STN-50-529 Palo Verde Nuclear Station, Unit 2, Arizona Publi 05000529 STN-50-530 Palo Verde Nuclear Station, Unit 3, Arizona Publi 05000530 AUTH.NAME AUTHOR AFFILIATION VAN BRUNT,E.E.

Arizona Nuclear Power Project (formerly Arizona Public Serv RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Forwards description of plant design characteristics R

responses to items discussed in Generic Ltr 88-03.

L DISTRIBUTION CODE:

A063D COPIES RECEIVED:LTR ENCL SIZE-TITLE: Resolution of Generic Sfty Issue 93,"Steam Binding of Aux Feedwtr Pum~

NOTES:Standardized plant.

Standardized plant.

Standardized plant.

RECIPIENT ID CODE/NAME PD5 LA LICITRA,E INTERNAL ACRS NRR OLSHAN,L NRR/DEST/RSB 8E NRR/PMAS/ILRB12 OGC 15-B-18 EXTERNAL: LPDR NSIC NOTES:

COPIES LTTR ENCL 1

0 1

1 6

6 1

1 1

1 1

1 1

0 1

1 1

1 1

1 RECIPIENT ID CODE/NAME PD5 PD DAVIS,M ARM/DAF/LFMB NRR/DEST/PSB 8D NRR/DOEA 11-E-4 UBOGS-ABSTRACT REG I 01 NRC PDR COPIES LTTR ENCL 1

1 1

1 1

0 1

1 1

1 1

1 1

1 1

1 05000528 S 05000529 05000530j A

R,'OTAL NUMBER OF COPIES REQUIRED:

LTTR 23 ENCL 20 S

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Arizona Nuclear Power Project P.O. BOX 52034

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PHOENIX. ARIZONA85072-2034 161-01057-EEVB/JMQ May 27, 1988 Document Control Desk U.S. Nuclear Regulatory Commission Mail Station Pl-137 Washington, D.C.

20555

Reference:

Generic Letter 88-03 Resolution of Generic Safety Issue 93, "Steam Binding of Auxiliary Feedwater Pumps" dated February 17, 1988 to All Licensees, Applicants for Operating Licenses, an'd Holders of Construction Permits for PWRs

Subject:

Palo Verde Nuclear Generating Station Units 1, 2 and 3

Generic Letter 88-03 Steam Binding of Auxiliary Feedwater Pumps File:

88-005-026; 88-010-026 The referenced letter requested confirmation that procedures discussed in the Generic Letter 88-03 are in place and will be maintained.

Attached please find a

description of PVNGS design characteristics and'esponses to the items discussed in the Generic Letter.

Very truly you

%.F. ~

E.

E.

Van Brunt,,Jr.

Executive Vice President Project Director EEVB/JMQ/pvk cc:

J.

B. Martin E. A. Licitra A. C. Gehr T. J. Polich (all w/attach) 8806010234 880527'DR ADOCK 05000528 DCD

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STATE OF ARIZONA

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) ss.

COUNTY OF MARICOPA)

I, Edwin E.

Van

Brunt, Jr.,

represent that I am Executive Vice President Project Director of Arizona Nuclear Power

Project, that the foregoing document 'has been signed by me on behalf of Arizona Publi'c Service Company with full authority to do so, that I have read such document and

'know its

contents, and that to the best of my knowledge and'elief, the statements made therein are true.

Edwin E. Van Brunt,.Jr.

4-g Sworn to before me this~]

day of 1988.

E Q.

Notary Public -

My Commission Expires:

Vy Commission Expires Nov. 32, 1988

M aae

ATTACHMENT GENERIC LETTER 88-03 STEAM BINDING OF AUXILIARYFEEDWATER PUMPS PVNGS Desi n Characteristics The contributing factors to steam binding of the Auxiliary Feedwater (AFW) pumps are. leaking valves that allow, high temperature water to backflow into lower pressure areas and'lash into steam, and when this occurs in the AFW pump, it renders the pump inoperable.

'The problem is further complicated when the

-system has multiple pumps that share common suction, recirculation or discharge piping and'an potentially. disable all pumps resulting in a

common mode failure and loss of,all'afety-grade forced cooling for the steam generator.

The Palo Verde design does not rely solely on check valves for separation of the Seismic Category I

pumps from the steam generators, but has a normally closed gate valve and a normally closed globe valve in addition to three check valves.

The gate valve would prevent significant backflow and the globe valve would provide additional protection.

The Palo Verde design has completely separate suction and recirculation lines for each of the three pumps.

This design significantly reduces the potential for inoperable pumps since it eliminates shared piping which can transmit steam and hot water between pumps, resulting in a common mode failure.

The two Seismic Category I pumps are cross-tied to allow either pump to feed either or both steam generators, and the pumps are separated by the gate/globe valve combination on each cross-tie line.

These are effective in.preventing transmission

,between the two trains.

The Non-Seismic Category I AFW pump has no common piping with the Seismic, Category I AFW pumps.

The Non-Seismic Category I pump is more susceptible to backflow from the Main Feedwater (MFW) because the separation is made by two check valves,

however, the design of the recirculation line aids in avoiding steam binding.

The recirculation line is a

vertical riser two feet downstream of the pump discharge which allows any warmer backflow to rise into the recirculation

piping, avoiding the pump casing.

The recirculation line is open to the condensate storage tank while the pump suction is isolated by two normally closed butterfly valves and is an effective dead leg.

NRC Action Items 1.

Maintain procedures to monitor flui'd conditions within the AFW system 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 amb'ient levels.

PVNGS es onse In order to assure that the Non-Seismic Category I

pump is not

disabled, temperature indicators were added to the pump discharge piping to provide indication of backflow and procedures were modified to include temperature monitoring once per shift.

1527K/0054K

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The discharge gate valves on the Seismic Category I pumps close on limit switches

.and prevent significant backflow.

In the unlikely event that steam binding should

occur, temperature indicators added to the pumps discharge piping will provide indication of backflow.

Procedures have been modified to include temperature monitoring, once per shift.

NRC Action Item 2.

Maintain procedures for recognizing steam binding and for restoring the AFW system to operable status, should'team binding occur.

PVNGS Res onse Procedures for the Non-Seismic Category I pump have been revised to include identification of steam binding from increasing pipe temperature due to possible backleakage.

Also,procedures have been revised for restoring the AFW system to operable status should steam binding occur.

Similarily, the procedures affecting the Seismic Category I pumps have been revised.

~Summa u No further actions are proposed to be, taken,to prevent inoperable AFW pumps due to steam binding.

The installed temperature indicating tape on the pumps'ischarge piping will continue to be monitored and the procedures remain in place to vent the pumps should an increased temperature be indicated.

1.

Staff to perform the requested'onfirmation and follow up actions

- 22 manhours.

2.

Staff time to prepare requested documentation

- 25 manhours.

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