ML20197A567

Submits 90-day Response for GL 97-04, Assurance of Sufficient NPSH for ECC & Containment Heat Removal Pumps

ML20197A567
Person / Time
Site:	Grand Gulf
Issue date:	12/17/1997
From:	Hagan J ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-97-04, GL-97-4, GNRO-97-00121, GNRO-97-121, NUDOCS 9712230092
Download: ML20197A567 (7)

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Entergy operations,Inc.

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December 17, 1997 ow e.

cc,o ca us, sm U.t1 Nuclear Regulatory Commission Mali Station P137 Washington, D.C. 20555 Attention:

Document Control Desk

Subject:

Grand Gulf Nuclear Station Unit i Docket No. 50-410 License No. NPF 29 Generic Letter (GL) 97-04, ' Assurance of Sufficient Net Positive Suction Head (NPSH) for Emergency Core Cooling and Containment Heat Removal Pumps",9&dsw Response GNRO-97/00121 Gentlemen:

On October 7,1997, the Nuclear Regulatory Commission issued the referenced generic letter regarding an issue which may have generic implications for Emergency Core Cooling System and Containment Heat Removal System pumps. The generic letter required, within 90 days, that licensees provide the information outlined below for each of their facilities:

1. Specify the general methodology used to calculate the head loss associated with the ECCS suction strainers

2. Identify the required NPSH and the available NPSH.

3. Specify whether the current design basis NPS'H analysis differs from the most recent analysis reviewed and spproved by the NRC for which a safety evaluation was issued,

- 4. Specify whether containment overpressure (i.e., containment pressure above the vapor pressure of the sump or suppression pool fluid) was credited in the

. calculation of available NPSH Specify the amount of overpressure needed and

• *j 9 the minimum overpressure available.

5. When containment overpressure is credited in the calculation of available NPSH, confirm that an appropriate containment pressure analysis was done to establish

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the minimum containment pressure.

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BEFORE THE UNITED STATES NUCLEAR REGULATORY COMMISSION LICENSE NO. NPF 29 DOCKET NO. 50-416 IN THE MATTER OF ENTERGY MISSISSIPPI and 1

SYSTEM ENERGY RESOURCES, INC.

and SOUTH MISSISSIPPI ELECTRIC POWER ASSOCIATION and ENTERGY OPERATIONS, INC.

AFFIRMATION 1, J. J. Hogan, being duly sworn, state that I am Vice President, Operations GGlsS af Entergy Operations, Inc.; that on behalf of Entergy Operations, Inc., System Energy Resources, Inc., and South Mississippi Electric Power Association I am authorized by Entergy Operations, Inc. to sign and file with the Nuclear Regulatory Commission, this 90-day responst, to Generic Letter 97-04; that i signed this response as Vice President, Operations GGNS of Entergy Operations, Inc.; and that the statements made and the matters set forth therein are true and correct to the best of my knowledge, information and belief.

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STATE OF MISSISSIPPI COUNTY OF CLAIBORNE SUBSCRIBED AND SWORy TO before me, a Notary Public, in and for the County and State above named, this l'?d day of sA ce s c,1997.

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. My commission expires: June 5. 1998

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GNRO 97/00121 Page 2 of 3 i

By this letter, Grand Gulf Nuclear Station is providing the required 90-day response, The

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information provided in this response is for the current ECCS Suction Strainer configuration,

- which is what the plant wu originally licensed to. It should be noted that portions of this information will be superseded when the new large passive strainer is installed during GGNS's next refueling outage in the spring of 1998 in response to NRCB 96-03. Following completion of this design change, the UFSAR is updated to reflect the changes made by i

installation of the strainer, including new NPSH calculations, The requested information is provided in the attachment, l

i Yours truly, JJH/WKH/RRJ attachment:

Generic Le er 97 04 Requested Information cc:

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GNRO 97/00121 Page 3 of 3 cc:

Ms. J. L. Dixon Herrity, GGNS Senior Resident (w/a)

Mr. L. J. Smith (Wise Carter) (w/a)

Mr. N. S. Reynolds (w/a)

Mr. H. L Thomas (w/o)

Mr. E. W. Merschoff (w/a)

Regional Administrator U.S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011 Mr. J. N. Donohew, Project Manager (w/2)

Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mall Stop 13H3 Washington, D.C. 20555 t

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Attachment to GNRO 97/00121 page 1 of 3 Attachment Generic Letter 97 04 Requested Information

1. Specify the general methodology used to calculate the head loss associated with the ECCS suction strainers.

The GGNS calculations determine the pressures at various locations along the ECCS pumps' suction piping and determine NPSH. For the calculations, a suppression pool water temperature with a corresponding vapor pressure was assumed for various plant conditions. As concluded from the calculations, adequate pressures exist along the suction piping to preclude local flashing under the worst postulated conditions. That k, the pressure at each point exceeds the vapor pressure of the fluid.

Other canservative assumptions used for the calculations are:

a. Pump design maximu:1 runout flow rate

b. Atmospheric containment pressure (14.7 psia)

c. Minimum suppression poolwater level

+ for Modes 1,2, and 3, analyzed for suppression pool post LOCA drawdown level of 107' 6'

+ for Modes 4 and 5, analyzed for Tech Spec level of 105' 8" d, Maximum suction strainer pressure drop (from vendor flow test for 50% clogged strainers)

Calculations of NPSH in ECCS pumps NPSH (ft) = h, + h.i h,, - hr. AP..

A where:

h,= containment pressure, absolute (Note: minimum containment pressure is O psig (atmospheric); then h = 14.7 psla) h.i = net static head from minimum suppression poollevel @ minimum pool water density.

+ at 107' 6' elevation (post LOCA minimum drawdown level) to a point 3 ft above top of pump mounting flange at 212' F

+ at 105'-8' elevation (minimum Tech Spec level at Modes 4 and 5) to a point 3 ft above top of pump mounting flange at 200* F and 125'F.

h, =

a:aolute vapor pressure at corresponding suppression pool temperatures.

Attachment to GNRO 97/00121 i

page 2 of 3

• 14.7 psia @ 212* F for Modes 1,2, and 3 (212* F was used since that was the value GE specified the pumps to be able to pump. This in an extremely conservative assumption, since the maximum analyzod pool water temperature is 181* F)

• 11.5?,..:a @ 200* F and 1.96 psia @ 125' F were used for Modes 4 and 5.

h,, = line losses at maximum pump flow with the following considerations:

• pipe schedule for length of piping including the equivalent length associated with valves and fittings

• entrance losses AP = suction strainer AP (from vendor flow test for 50% clogged strainers) 2.

Identify the required NPSH (ft) and the available NPSH (ft).

The required NPSH is specific to each pump or pump type and is dependent on the flow s

rate at the time being evaluated. The required NPSH values are provided by pump vendors. The available NPSH is dependent on the containment overpressure credited (if any), number of pumps operating, piping configuration and the suppression pool and NPSH, for the limiting temperature at the most limiting condition. Therefore, NPSHa A

cases for pumps taking suction from the suppression pool following a design basis accident LOCA, are provided in the table below. No credit is taken for containment overpressure.

PUMPS NPSHn(ft H O)

NPSH (ft H OJ A

2 2

RHR A 2.0 6.0 RHRB 2.0 5.5 RHR C 2.0 5.7 LPCS 2.0 6.4 HPCS 2.0 7.0

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Attachment to GNRO-97/00121 page 3 of 3 3.

Specify whether the current design-basis NPSH analysis differs from the most recent analysis reviewed and approved by the NRC for which a safety evaluation was issued.

GGNS's current design-basis NPSH analysis is documented in UFSAR Appendix 6E.

There is one calculation that has been revised as fcilows.

UFSAR Appendix 6E states a minimum available NPSH of 4.7 ft at 3 ft above top of pump mounting flan 9e at 212' F for the HPCS pump. This calculation was based on a maximum runout flow of 9100 gpm for the HPCS pump. The actual maximum runout flow is 8175 gpm. Because of this discrepancy in runout flow, the minimum available NPSH was recalculateJ to be 6.9993 ft at 3 *t above pump mounting flange at 212' F; therefore, the current calculation in Appendix 6E is bounding.

This revissd calculation is documented in our corrective action program under Condition Report GGCR1997123300. The UFSAR is being updated by the design change which installs the new suction stralner to satisfy the requirements of NRC Bulletin 96-03.

4; Specify whether containment overpressure (i.e., containment pressure above the vapor pressure of the sump or suppression pool fluid) was credited in the calculation of available NPSH. Specify the amount of overpressure needed and the minimum overpressure available.

GGNS did not credit containment overpressure in the calculation of available NPSH.

5.

When containment overpressure is credited in the calculation of available NPSH, confirm that an appropriate containment pressure analysis was done to establish the minimum containment pressure.

Not Applicable

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