ML20024E456

Comments on Changes to Spent Fuel Pool Makeup Line Per 830722 Telcon Request.Table of Flow Rates Encl.Slower Heatup Rate Will Reduce Thermal Gradients & Concrete Cracking, Assuring Overall Pool/Support Sys Integrity

ML20024E456
Person / Time
Site:	Big Rock Point File:Consumers Energy icon.png
Issue date:	08/09/1983
From:	Bordine T CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	Crutchfield D Office of Nuclear Reactor Regulation
References
NUDOCS 8308150069
Download: ML20024E456 (4)

Text

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l Constimers Power Company General offices: 1945 West Parnall Road, Jack son, MI 49201 * (517) 788 0550 August 9, 1963 Dennis M Crutchfield, Chief Operating Reactors Branch No 5 Nuclear Reactor Regulation US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT - SPENT FUEL POOL MAKEUP LINE DESCRIPTION Consumers Power Company comrritment to provide sufficient make-up water to the spent fuel pool to limit inside pool wall surface temperatures to 150 F was identified in our letter of January 10, 1983. Since the then existing makeup line did not have sufficient capacity to limit the temperature to 150*F during power operation assuming a fully loaded spent fuel pool, Consumers Power Company proposed to upgrade the makeup system to increase its flow rate.

Specifically, we committed not to return to power operation following any refueling outage until the calculated decay heat load is less than that permitted by the known makeup flow rate and temperature. The following description of the changes to the makeup line is provided in response to a telephone request on July 22, 1983 from a member of your Staff.

The spent fuel pool makeup line (described during our June 1982 spent fuel pool hearings) consists of 190 feet of one-inch diameter pipe. Approximately 115 feet of this line has been changed to two-inch diameter schedule-80 pipe.

The two inch pipe replacement commences at a point approximately 4 feet 7-1/2 inches from the existing tie to our four-inch diameter core spray recircula-tion pipe. The attached figure provides a plan view of the makeup line indi-cating the location of the two-inch pipe replacement.

The flow capacity of the modified line was determined by the "FLOWNET" computer program. Standard hydraulic techniques were used in FLOWNET to determine the makeup line flow rato under a variety of conditions. Two FLOWNET models were developed:

(1) a model of the makeup line and the core spray system as they would be lined up to recirculate water from the contain-ment floor to the reactor and spent fuel pool following a LOCA; and, (2) a model of the makeup line and fire protection system as it could be lined up to feed the spent fuel pool with a fire pump. Using the model No 1 several cases were run for various possible configurations of the core spray system to oc0783-0235a142 8308150069 830809 s

PDR ADOCK 05000155 g

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D M Crutchfield, Chief 2

Big Rock Point Plant SFP Makeup Line Description 3

August 9, 1983 determine the minimum flow to the spent fuel pool assuming the worst active single failure in accordance with 10CFR50 Appendix A; as well as to verify adequate flow to the reactor through the core spray lines. To assure that the makeup line had been modeled correctly, a measurement of actual flow through the makeup IIne from the fire pumps was performed and compared to that predicted by model No 2.

Consumers Power Company intends to perform a similar test of the makeup line each refueling outage in order to verify makeup line functionability and the makeup flow. Predicted and measured actual flow for configurations of interest are summarized in the attached table. The minimum expected flow assuming the worst active single failure was determined to be 28 gpm.

The following evaluation of the cooling capability of the makeup line during the upcoming fuel cycle is provided to illustrate the design margin inherent in the new line. Assuming the current refueling outage lasts the scheduled 89 days (May 13, 1983 - August 9, 1983), the heat load in the pool from the twenty-two newly discharged assemblies and the 132 assemblies which were discharged in previous years is estimated to be 76,500 watts at the time of plant startup. Assuming makeup water is supplied at the minimum rate of 28 gpm, the bulk pool water temperature will not exceed 119'F.

This upper temperature value was arrived at by assuming that the makeup water enters the pool at 100*F and an equal amount leaves by overflowing at the bulk water temperature. Energy loss by conduction through the pool walls and evaporation from the surface were not considered.

I If the makeup water cannot be supplied to the spent fuel pool and if the normal heat removal systems are not operating, the bulk water temperature will

~

reach 150*F in approximately 150 hours0.00174 days <br />0.0417 hours <br />2.480159e-4 weeks <br />5.7075e-5 months <br /> (assuming an initial temperature of 100*F) as compared to 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> which was assumed in NUS Structural Analysis.

This heatup rate of approximately 0.33*F per hour is significantly less than the l'F por hour assumed-in the NUS Structural Analysis. The slower heatup-rate will significantly reduce the thermal gradients through the spent fuel pool walls and floors.

This reduction in thermal gradients will be accompanied by a commensurate reduction in out-of plane moments which implies less concrete cracking and greater assurance of overall structural integrity of the pool / support system.

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w Thomas C Bor'd ne

. Staff Licensing Engineer CC Administrator, Region III, USNRC NRC Resident Inspector-Big Rock Point

. Attachment oc0783-0235a142 w,

.e TABLE Spent Fuel Pool Cooling Makeup Line Flow Rates Recirculation Cases (No Single Failures) 1.

Nozzle Flow 408 gpm (296 gpm required)

Fuel Pool Flow 32 gpm 2.

Sparger Flow 373 gpm (292 gpm required)

Fuel Pool Flow 35 gpm Recirculation Cases (with worst active single failure -

containment spray valve open) 1.-

Nozzle Flow-360 gpm (296 gpm required)

Containment Spray Flow 79 gpm (M0 7064)

Fuel Pcol Flow 29 gpm 2.

Nozzle Flow 341 gpm (296 gpm required)'

Containment Spray Flow 99 gpm (MO 7068)

Fuel Pool Flow 28 gpm 3.-

Sparger Flow 325 gpm (292 gpm required)-

Containment Spray Flow 94 gpm (MO 7064)

Fuel Pool Flow 31 gpm

4. Sparger Flow 303 gpm (292 gpm required)

Containment Spray Flow 132 gpm (MO 7068)

Fuel Pool flow.

29 gpm Fire Protection System Cases (No LOCA, One Fire Pump)-

~(with test apparatus connected)

1. Fuel Pool Flow

-40 gpm*~

Fuel pool Heat Exchanger Flow 400 gpm*

• Verified by test-nu0883-0235d142 e

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