3F0489-08, Provides Supplemental Response to NRC Bulletin 88-004, Potential Safety-Related Pump Loss. Advises That Response on All Other Pumps Examined as Part of Bulletin Investigation Complete

Provides Supplemental Response to NRC Bulletin 88-004, Potential Safety-Related Pump Loss. Advises That Response on All Other Pumps Examined as Part of Bulletin Investigation Complete

ML20245A643
Person / Time
Site:	Crystal River
Issue date:	04/17/1989
From:	Widell R FLORIDA POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
3F0489-08, 3F489-8, IEB-88-004, IEB-88-4, NUDOCS 8904250310
Download: ML20245A643 (9)

Text

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Florida Power C O R PO R ATIO N April 17, 1989  ;

3F0489-08 U. S. Nuclear Regulatory Commission ]

Attn: Document Control Desk Washington, D.C. 20555

Subject:

Crystal River Unit 3 Docket No. 50-302 Operating License No. DPR-72 Supplemental Response To Bulletin 88-04:

Potential Safety-Related Pump Loss

Dear Sir:

Florida Power Corporation (FPC) is providing this response as a supplement to our letter dated December 9, 1988 which was in response to Bulletin 88-04. Item 2 of that letter stated that - pump minimum flow recommendations were being developed for Emergency Feedwater Pumps (EFP) EFP-1 and EFP-2 and Spent Fuel Cooling Pumps (SFP) SFP-1A and SFP-1B. Item 3 of the letter identified a potential concern may exist with the Decay Heat / Low Pressure Injection Pumps (DHP) DHP-1A and DHP-1B. As a result of the investigation into the DHPs, a 4-hour report was made on March 15, 1989 and LER 89-09 was submitted on April 14, 1989.

The results of FPC's investigations for the EF Pumps and the SF Pumps are discussed in Attachments 1 and 2, respectively. FPC's response on these pumps is now considered complete. Attachment 3 contains a description of the actions FPC has taken and information regarding DHP-1A and DHP-1B. The pump flow test described in the attachment was completed on April 14, 1989 and the preliminary test results indicate the DHPs met all of the acceptance criteria. FPC is evaluating the test data and will advise the NRC of the findings within 30 days after restart from the current outage.

8904250310 890417 PDR ADOCK 05000302 m-Q PDC g

'l GENERAL OFFICE: 3201 Thirty-fourth Street South

• P.O. Box 14042

• St. Petersburg, Florida 33 33 * (813) 866 5151 A Florida Progress Company

April 17, 1989 3F0489-08 Page 2 i FPC's response on all other pumps examined as part of the Bulletin investigation is considered complete.

Sincercly, kt Rolf C. Widell, Director Nuclear Operations Site Support RCW/JWT/sdr xc: Regional Administrator, Region II Senior Resident Inspector I

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STATE OF FIDRIDA COUNTY OF PINELLAS Rolf C. Widell states that he is the Director, Nuclear Operations Site Support for Florida Power Corporation; that he is authorized on the part . of said company to sign and file with the Nuclear Regulatory Commission the information attached hereto; and that all such statements made and matters set forth therein are true and correct to the best of his knowledge, information, and belief.

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I Rolf C. Widell, Director Nuclear Operations Site Support Subscribed and sworn to before me, a Notary Public in and for the State and County above named, this 17th day of April, 1989.

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Notary Public Notary Public, State of Florida at Large, 807Aff PUBLIC staff W FLORfDA My Commission Expires: av com issten t n xtv tr.isse 80WDCD IM U E MAAL IRS. UeD.

l ATTACHMENT 1 EMERGENCY FEEDWATER PUMPS PUMP DESCRIPTION Emergency Feedwater Pumps EFP-1 and EFP-2 are safety-related pumps having a minimum flow recirculation line with a piping configuration that does not prevent interaction between the pumps while in the recirculation mode.

PUMP EVALUATION On the basis of design reviews and vendor contacts, EFP-1 and EFP-2 have been evaluated for minimum flow considerations relative to single pump and parallel pump operation.

The pump minimum flow currently recommended by the vendor, Ingersoll-Rand, for continuous operation is 250 GPM. A review of EFP-1 and EFP-2 operating modes indicates two cases where this recommended flow is not met. The vendor has evaluated these cases and has concluded that the expected pump flows below 250 GPM are acceptable for limited operating durations (2 100 gpm; 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> / event), as tabulated below.

Expected Pump Cases Flows / Durations

1. Dual pump operation 2125 GPM on minimum flow recirc. 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> / event only (EFIC actuation)

2. Single pump operation 2185 GPM on minimum flow recirc. 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> / event only (Testing, EFIC actuation)

While these restrictions are consistent with the CR-3 systems' response, FPC will revise the plant operating procedures to include these recommended durations and instruct the termination of EF pump operation if plant conditions permit it. From both a design and operational standpoint, such suggested restrictions are appropriate and will not impact the successful accomplishment of any safety function. .

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ATTACHMENT 1 (Cont'd)

Although there is limited margin between some of the expected vs.

-recommended flowrates/ durations, this is' considered acceptable for the following reasons:

1. The specified 3-hour duration is a recommendation, not a required limit.

-2. Although the piping configuration does not physically prevent interaction between EFP-1 and EFP-2 in the minimum flow recirculation mode, hydraulic interaction between these pumps is essentially prevented by the. high pressure drop in each of the recirculation lines. Calculations show that, for an assumed 15%

difference in discharge head during parallel pump operation, the

" weaker" pump will operate at 2 100 GPM (analysis result is '107 GPM)'during minimum recirculation.

3. The ~ majority of EF pump operation below 250 GPM occurs during testing, which can be terminated without restriction. Only a small percentage of EF pump operation occurs as a result of an actual demand, with an even smaller percentage of this operation falling outside the continuous operation range recommended by the vendor.

EVALUATION RESULTS EFP-1 and EFP-2 are acceptable as is. Changes to the plant operating procedures should further limit the duration below the recommended continuous flow rates to acceptable levels.

FUTURE ACTION AND SCHEDULE The operational prccedure revisions will be made prior to restart from'the current plant-outage. The test procedures will be modified prior to next use.

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. . . l ATTACHMENT 2 SPENT FUEL COOLING PUMPS PUMP DESCRIPTION Spent Fuel Cooling Pumps SFP-1A and SFP-1B are safety-related pumps having no minimum flow recirculation mode of operation, but which have  !

a piping configuration that may not prevent pump interaction during i certain modes of operation. These modes could involve lower-than- j design flowrates. l PUMP EVALUATION On the basis of design reviews and vendor contacts, SFP-1A and SFP-1B have been evaluated for minimum flow considerations relative to single pump and parallel pump operation.

The pump minimum flow currently recommended by the vendor, 'Ingersoll-Rand, for continuous operation is 750 GPM. A review of SFP-1A, 1B operating modes indicates two cases (i.e. filling and draining the fuel transfer canal) where this recommended flow may not be met. To ensure that a flowrate 2750 GPM is maintained for these cases requires procedure changes to revise the position of certain SF system valves.

These changes do not impact the safety function of the system.

During parallel operation the expected flowrate is 2750 GPM per pump.

EVALUATION RESULTS With changes to the operating procedure, a flowrate 2750 GPM can be achieved during all modes.

FUTURE ACTION AND SCHEDULE The procedure revisions will be made by August 31, 1989. Filling and draining of the SF canal only occurs during refueling. The next scheduled Refuel is in the Spring of 1990, therefore, these procedure changes will take place in adequate time to support these modes of operation.

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ATTACHMENT 3 LOW PRESSURE INJECTION / DECAY HEAT REMOVAL PUMPS PUMP DESCRIPTION Low Pressure Injection / Decay Heat Removal Pumps DHP-1A and DHP-1B are safety-related pumps having a minimum flow recirculation line with a piping configuration that does prevent interaction with other pumps while in the recirculation mode.

PUMP EVALUATION A minimum flow evaluation of DHP-1A and DHP-1B is currently underway, but is not yet complete. Information received from the pump vendor, Dresser, indicates a concern in that the expected pump flows during certain modes of operation are below the values recommended.

In their initial response to FPC regarding NRC Bulletin 88-04, Dresser provided pump minimum flow recommendations of 2350 GPM for continuous operation and 1200 GPM for durations up to 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> per year. A review of DHP-1A and DHP-1B operating modes indicated neveral cases not enveloped by the above recommendations, the most s< vere of which occurs when DHP-1A or DHP-1B is in the minimum flow recirculation mode and the expected pump flow is calculated to be 100-112 GPM. Dresser was requested to evaluate this case in more detail and, as a result, provided a supplemental recommendation to allow a pump flow of 80 GPM for a cumulative operating duration of two hours on the pump shaft and/or bearings, after which these parts must be replaced and the two hour time limit is renewed. This recommendation has been incorporated into appropriate plant procedures.

A review of other DHP-1A and DHP-1B operating modes was subsequently conducted by FPC, and resulted in the following flow requirements for each of these pumps:

._1500 GPM -

For all normal DH system operations.

> 500 GPM For LPI flow after a SBLOCA.

When Dresser was asked to evaluate these conditions for continuous or limited duration operation, their response was that they had no information to offer other than the flowrates already provided.

Dresser further stated that, to obtain such information would require testing which they could perform, with a completion date sometime in l 1990. i l

Based on the foregoing response from Dresser, FPC decided to pursue l field testing of one of our Decay Heat Removal Pumps to establish that the pumps can remain operable with flows less than those recommended by the vendor. A general description of this test is outlined as follows:

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. . 4 ATTACHMENT 3 (Cont'd)

1. The pump was tested in a recirculation mode to the Borated Water Storage Tank.

2. The pump was tested over.a range of flows, starting at 3000 l

GPM and decreasing in increments to approximately 100 GPM.

The pump was operated long enough at each flow increment'to collect data, except that it was run for ten hours at a total pump flow of 400 GPM. This was based on an expected " worst-case" pump flow of 500 GPM during the postulated SBLOCA, adjusted.for a 100 GPM margin.

3. The parameters monitored during the test include:

a. Pump suction and discharge pressures.

b. Pump. flow to the BWST.

c. Flow in the pump minimum recirculation line,

d. Pump suction and discharge temperatures.

e. Motor. current.

f. Pump bearing cooling water inlet and outlet temperatures.

g. Overall and filtered horizontal and vertical vibration at all four bearings.

h. Overall and filtered axial vibration at inboard end of pump.

4. Satisfactory operation of the pump was assessed at each flow increment. Some of the key acceptance criteria (not all-inclusive) for this test were:

a. Vibration 10.7 inches /second.

b. Pump delta T $15 0F.

5. The pump will be disassembled and inspected after the test.

This inspection will include the casing and stuffing box rings, volute tongues, shaft and shaft sleeve, impeller (vanes, wear rings, shroud, tightness), and bearings. A new rotating assembly will be installed in the pump after the test.

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ATTACHMENT 3 (Cont'd)

It should be noted that, in the case of DHP-1A and DHP-1B, there has been a significant change in vendor recommendations on pump minimum flow in that their previous recommendation was 800 GPM for continuous operation and 80 GPM for 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> at a time up to 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br /> total within the life of the pump. It should also be noted that the minimum flow of 2350 GPM currently recommended by Dresser for continuous operation appears to be quite conservative within the pump industry.

The 2350 GPM value represents 78% of best efficiency point (BEP) flow for DHP-1A and DHP-1B, whereas other pump vendors are recommending minimum continuous flowrates of 25% to 50% of BEP flow.

EVALUATION RESULTS The test was performed on April 14, 1989 and the criteria in items 1 through 4 above were included in the test procedure. During the test, the pump did not exceed the acceptance criteria. An evaluation of the test data is underway and disassembly of the pump will occur shortly.

FUTURE ACTION AND SCHEDULE The additional actions planned for DHP-1A, and DHP-1B are outlined below, including expected completion dates.

1. 4/28/89 -

Evaluate pump testing results and make preliminary assessment of pump low-flow capability.

2. Prior to -

Make final determination of pump low-flow plant re- capability. Evaluate whether procedure start changes and/or hardware changes are necessary.

3. Restart + -

Advise NRC of results in accordance with 30 days Bulletin Action #5.

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