ML20205A140

Responds to NRC 880629 Request for Addl Info Re Util Response to Generic Ltr 88-03.Util Considers Steam Binding of Emergency Water Booster Pumps Precluded by Design,Valve Configuration & Procedural Requirements

ML20205A140
Person / Time
Site:	Fort Saint Vrain
Issue date:	10/12/1988
From:	Robert Williams PUBLIC SERVICE CO. OF COLORADO
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
GL-88-03, GL-88-3, P-88318, NUDOCS 8810250402
Download: ML20205A140 (7)

Text

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h Public Service ~ nh October 12, 1988 [fgy"cbe Fort St. Vrain Unit No. 1 R.O. WILUAMS. JR.

P-88318 vce paEsoEnt NUCLEAR OPERATONS U.S. Nuclear Regulatory Comission ATTN: Document Control Desk Washington, D.C. 20555 Docket No. 50-267

SUBJECT:

Response to Request for Additional Information, Generic Letter 88-03 Fort St. Vrain

REFERENCE:

1. PSC letter dated May 27, 1988, Williams to Document Control Desk (P-88115)

2. NRC letter dated June 29, 1988, Michaud to Williams (G-88255)

3. NRC letter dated August 25, 1988, Heitner to Williams (G-88357)

Gentlemen:

Public Service Company of Colorado (PSC) responded to NRC's Generic Letter 88-03 in Reference 1. In Reference 2 the NRC submitted the following request for additional information:

"The emergency water booster pumps P-2109 and P-2110, were not included in the licensee's evaluation of Generic letter 88-03.

Although not used to supply water to the steam generators, these pumps would be used to provide the motive force to drive the helium circulators when using firewater. These pumps are also normally lined up such that two check valves provide the only isolation from the emergency feedwater system. The staff considers the unique aspect of these pumps and the system's configuration to warrant their inclusion in the evaluation of Generic Letter 88-03 for the Fort St.

Vrain Nuclear Generating Station."

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P-88318 ,

October 12, 1988  ;

2 PSC Response:

In the . request for additional information, a concern was identified i that only two check valves afford protection for the emergency water booster pumps (P-2109 and P-2110) from becoming steam bound. The NRC's Mr. Paul Michaud discussed with PSC personnel the flow path of concern whereby the emergency feedwater header f a postulated to cause reverse flow through the emergency condensate header which brings the . ,

discharge of P-2109 to emergency feedwater temperature causing P-2109 and/or P-2110 to become steam bound.

The points at which the two helium circulator water turbine drive a] supply lines (line L21219, loop 1, and line L21325, loop 2) ta off the emergency feedwater header (line L22291,PI-21-5,A-6)p could i contain hot water (approaching the temperature of the deaerator, 1 approximately 310 degrees F). This is based on emergency feedwater  ;

j continually flowing through the emergency feedwater header to provide makeup to the Bearing Water Surge Tanks (T-2104 and T-2105) and

! to l keeping 100 gpm thetotalbackup) flow . bearing water system pressurized (requiring 50 1

For hot water to flow from the emergency feedwater header into one of the helium circulator water turbine drive supply lines and on to the ,

emergency water booster pumps (P-2109 and P-2110), the water would  !

have to flow through approximately 340 feet of piping (based on  !

isometric drawings) varying in size from 10" to 3", which includes a l i' check valve, a stopcheck valve (e.g.; HV-21259 - '1B' circulator),

and many elbows, bends, and other flow restrictions.

Water in this path is normally stagnant, since paths off of the helium circulator su) ply lines from the emergency feedwater header  ;

j are isolated by bloc ( valves preventing back flow into the condensate j system. This provides assurance that when water is supplied to a i

helium circulator water turbine drive via the emergency feedwater '

I header, flow will not be diverted to other systems. Water from the emergency feedwater header does not supply the helium circulator l water turbine drives during normal plant operation.

! l In order to heat up P-2109 or P-2110 to emergency feedwater l

temperature, water would need to flow through the pump to any of the  !

following:

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through the emergency condensate header back to P-3106 and t P-3106S (condensate pumps) which have normally closed valves to f prevent flow, HV-3133-2 and HV-3135-2 respectively,  ;

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P P-88318 ,

October 12, 1988

- through the emertency condensate header to loop 1 or loop 2 steam generators which have a normally closed valve (HV-2237 and HV-2238 respectively ) and a check valve (V-2257 and V-2256 respectively) to prevent flow.

- through the emergency condensate header to loop 1 or loop 2 cold reheat lines which have a nonnally closed valve to prevent flow, HV-2291 and HV-2290 respectively, and

- through the emergency condensate header to system 45 (fire water) which has two normally closed valves to prevent flow, HV-4519 and HV-4518.

- through the emer boiler feed pumps)gency condensate which has HV-31121, headerclosed a nonnally to system valve to84 (auxiliary prevent flow.

- through the emergency condensate header to system 45 which has HV-31122, a normally closed valve to prevent flow.

PSC recognizes that check valve leakage is considered to be a generic in a recent NRC letter concern dated in the August 25,nuclear industry),and 1988 (G-88357 asNRC notedInformation Notice No. 88-70 dated August 29, 1988.

The NRC letter dated August 25, 1988 notes that the primary cause of premature degradation of check valves is continuous fluctuation of the check valve disc when it is not finnly seated against its back seat by fluid force. However, there is a shut stop check valve (e.g.; HV-21259 '1B' Circulator) in this path, which is held closed by 90 to 100 psig instrument air, when under conditions of interest.

It is highly unlikely this stop check valve would leak quantities of water such that the emergency condensate header could heat up.

Assuming one of the stop check valves isolating the energency condensate supply to a water turbine drive from the emergency feedwater sup)ly did leak, the only driving force to direct flow of hot water to tie emergency condensate header would be leakage of emergency feedwater into the condensate system. This flow path would not direct water to the emergency water booster pumps, but to piping of the condensate system as the emergency water booster pumps are essentially dead ends.

P-88318 , -4r October 12, 1988 l l

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Based on the above it is inconceivable that water at high enough temperature to flash to steam could make its way to the emergency water booster pumps from the emergency feedwater header by means of r this flow path.

The emergency feedwater header can be aligned to supply water to either steam generator EES section, and also can be aligned to provide water directly to the Pelton wheel of any of the four helium circulators. The emergency feedwater header does not supply feedwater to the suction of either emergency water booster pump, since there is no need to boost feedwater pressure to drive a helium circulator on its Pelton wheel. Firewater can be lined up to supply the steam generator EES sections via the emergency feedwater header for Safe Shutdown Cooling. In establishing Safe Shutdown Cooling with the emergency feedwater header, firewater would be supplied to the emergency water booster pumps, P-2109 or P-2110, by opening manual valves V-211573 and V-211570.

PSC has evaluated the possibility of feedwater entering the emergency water booster pumps from the emergency feedwater header. The  ;

emergent.y feedwater supply to the helium circulator Pelton wheels is isolated from both emerge.'cy water booster pumps by nomally shut  :

manual valves V-211574 and V-211571, as well as check valves t Y-211575, V-211569 (P-2109), and V-211582 (P-2110). A tell-tale [

drain is positioned between the two nomally shut manual valves,  ;

V-211574 and V-211571. This configuration is more than adequate to assure hot water from the emergency feedwater header cannot enter i either emergency water booster pump, flash to steam, and interfere i with proper operation of the pump. The Integrated System Valve  !

Lineup and Checklist for System Operating Procedure 21-02, IVL 21-02,  !

requires operators to verify that V-211574 and V-211571 are closed prior to startup of the system. These measures provide adequate l assurance that hot water from the emergency feedwater supply to the ,

helium circulator Pelton wheels can not enter the emergency water  ;

booster pumps.

PSC has also evaluated the possibility of feedwater entering the emergency water booster pumps from the normal feedwater header. For feedwater to reach either P-2109 or P-2110, it would have to flow in the wrong direction through check valve V-2257 and then through normally closed motor operated valve HV-2237 (Loop 1), or it would have to flow in the wrong direction through check valve V-2256 and  ;

then through normally closed motor operated valve HV-2238 (Loop 2).

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HV-2237 (emergency condensate to Loop 1 steam generator EES sectior.)

is electrically interlocked with the Loop 1 feedwater block valve,  ;

HV-2201, such that HV-2237 cannot be opened unless the normal supply of feedwater is isolated to Loop 1. Likewise. HV-2238 (emergency cundensate to Loop 2 steam generstor EES section) is electrically i interlocked with the Loop 2 feedwater block valve such that HV-2238 cannot be opened unless the normal supply of feedwater is isolated to Loop 2. This provides adequate assurance that het feedwater will not i' flow into P-2109 or P-2110, flash to steam, and intarfere with proper pump operations.

PSC has e. valuated numerous other f'ew paths for the possibility of l hot water or steam ingress to the eneraency water bouster pumps in  ;

addition to tH feedwater and tuergency feedwater. headers. All the flowpaths evaluated contain adeauate protection to prevent steam binding of the emergency water A . pu "p ,

Even if P-2109 and P-2110 e s t.o W ~ r e m bound, it is unlikely this would prevent these pump from , .cf .iits theie safety function durinq Safe St'utduwn Cooling, ihn ' '.f.i ,utdown fooling procedures, 4 whirn rely upoa one of the eners'nt;/ wa te hcoster pinps (SSC-03, 1 SSC-04, and 3SC-05) to provlle o#.te peer to a helium circulator Pelton Nheel, all require dep.es:wiv.th.< ct the neam generator EES  !

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tion to be utilized for coldcor. befo'e 60 minutes into an

, interruption of forced circuiction. The emergency water booster pump '

would be started no later than 90 minutes. af ter the interruption of forced circulation. The interval tetween feedwater system depressurization and Felium circulctor restart (approximately 35 minutes to I hour) should permit steam in a,. emergency water booster pump to condense.

When the emergency water booster pump is started, it is being supplied with relatively cold firewatcr from a firewater pump (125 4

psig rated discharge pressure). If any steam were present in the pump it would quickly be condensed by cold water, PSC considers that steam binding of tre e.nergency water booster pumps t has been precluded by design, valse configuration and procedural }

requirements. PSC has maintained and will continue to maintain these design features and procedural requirements as necessary to preclude .

f steam binding from becoming a p .r/emi at FSV.

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P-88318 . r &- October 12, 1988 If there are any questions, please contact Mr. M.H. Holmes at (303) 480-6960.

Sincerely, f

R.0. Williams, Jr.

Senior Vice President Nucletr Operations R0W/JRJ:jw cc: Regional Administrator, Region IV ATTN: Mr. T.F. Westerman Chief, Projects Section B Mr. Robert Farrell Senior Resident Inspector Fort St. Vrain i

UNITED STATES OF AMERICA i

NUCLEAR REGULATORY COMMISSION  ;

! In the Matter ,

1 i Public Service Company of Colorado Docket No. 50-267 Fort St. Vrain Unit No. I l

AFFIDAVIT  !

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R. O. Williams, Jr. being first duly sworn, deposes and says: i That te is Senior Vice President, Nuclear Operations, of Public i Service Company of Colorado, the Licensee herein, that he has read  !

the information presented in the attached letter and knows the i contents thereof, and that the statements and matters set forth therein are true and correct to the best of his knowledge,  ;

information and belief. l I

• R. O. Williams, Jr.  :

Senior Vice President  ;

Nuclear Operations

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STATE OF$/#tado I COUNTY OF r3er, /su .  ;

Subscribe and sworn to before me, a Notary Public on this

/d & day of &#fxA _ ,198].  :

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(Yl)f A M/)A Motary Public F- l 1.1, ta) ,

l My commission expires 4[/L ,193 i

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