ML18143A445

Spent Fuel Pool Cooling

ML18143A445
Person / Time
Site:	Ginna
Issue date:	08/03/1978
From:	White L Rochester Gas & Electric Corp
To:	Ziemann D Office of Nuclear Reactor Regulation
References
Download: ML18143A445 (18)

Text

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REGULATORY INFORMATION DISTRIBUTION SYSTEM (AIDS)

DISTRIBUTION FOR INCOMING MATERIAL 50-244 REC: Z IEMANN D L ORG: WHITE L D DOCDATE: 08/03/78 NRC ROCHESTER GAS 8( ELEC DATE RCVD: 08/09/78 DOCTYPE: LETTER NOTARIZED: NO COPIES RECEIVED

SUBJECT:

LTR 1 ENCL 1 REQUESTING NRC APPROVAL TO EMPLOY THE EXISTING COOI ING SYSTEM FOR THE FULL CORE DISCHARGE SCHEDULE FQR EARLY SPRING 1979 AT SUBJECT FACILITY Pg+k~5'~<W<>~~~~

EXPANSION Ql= THE SPENT FUEI COOLING... W/ATT SUPPORTING INFO 8( DIAGRAMS.

PLANT NAME: RE GINNA UNIT REVIEWER INITIAL: XJM 1

DISTRIBUTOR INITIAL: ~

DISTRIBUTION OF THIS MATERIAL IS AS FOLLOWS GENERAL DI TRIBUT IQN FOR AFTER ISSUANCE OF OPERATING LICENSE.

(DISTRIBUTION CODF A001>

FOR ACTION: BR CHIEF ORB52 BC+4tW/7 ENCL INTERNAL: REG FII W/ENCL NRC PDR+>W/ENCL I h E~~~W/2 ENCL OELD~4LTR ONLY HANAUER<<~W/ENCL CORE PERFORMANCE BR>+W/ENCL AD FOR SYS 8c PROJ+%W/ENCL ENGINEERING BR+4W/ENCL REACTOR SAFETY BR+4W/ENCL PLANT SYSTEMS BR++W/ENCL EEB<<~W/ENCL EFFLUENT TREAT SYS+<W/ENCL J. MCGOUGH4HIW/ENCL EXTERNAL: LPDR S ROCHESTEIi> NY+4W/ENCL TERA~~W/ENCL NS IC~~W/ENCL ACRS CAT B>+W/16 ENCL DISTRIBUTION: LTR 40 ENCL 39 CONTROL NBR: 782220115 SIZE: 1P+ 12P THE END SF<<$ %%%%%4%%4%%%%%%%%%%%%%%%%%%%%%%

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ROCHESTER GAS AND ELECTRIC CORPORATION o 89 EAST AVENUE, ROCHESTER, N.Y. 14649 LEON D. WHITE, JR. TCLCPHONC VICK PRCSIDKNT ARCA CODC VIS 546-2700 August 3, 1978 V

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~CD na rll-Director of Nuclear Reactor Regulation Attention: Mr. D.L. Ziemann, Chief C. V Operating Reactor Branch 42 U.S. Nuclear Regulatory Commission Cl C3 Washington, D.C. 20555 ~

fll KIT

Subject:

Spent, Fuel Pool Cooling R.E. Ginna Nuclear Power Plant, Unit .No. 1 Docket No. 50-244

Dear Mr. Ziemann:

In early 1977, Rochester Gas and Electric Corporation (RG&E) expanded the fuel storage capacity of the Ginna spent fuel pool from 210 fuel assembies to 595 assembies. This modification was performed in order to provide storage through the late 1980's.

Amendment No. 17 to the Ginna Operating License, issued on November 17, 1976, included 'a discussion of the present spent fuel cooling system. The attachment to this letter enlarges upon the discussion presented by RGB'n its requests for storage capacity expansion (see RG&E letters of January 26, 1976 and June 3, 1976).

The purpose of this letter is to request approval by the NRC to employ the existing cooling system for the full core discharge schedule for early Spring 1979 at Ginna.

Very truly yours, t

78222Ogg5 SD

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Spent Fuel Pool Cooling August 1978

In early 1977, Rochester Gas and Electric Corporation (RG&E) expanded the fuel storage capacity of the Ginna spent fuel pool from 210 fuel assemblies to 595 assemblies. This modification was performed in order to provide storage through the late 1980's.

Ammendment No. 17 to the Ginna Operating License, issued on November 17, 1976, included a discussion of the present spent fuel cooling system. The purpose of this attachment is to enlarge upon the discussion presented by RG&E in its requests for storage capacity expansion (see RG&E letters of January 26, 1976 and June 3, 1976) and to describe how the existing cooling system will be used for the full core discharge schedule for early Spring 1979 at Ginna.

It was recognized that increasing the number of fuel assemblies stored in the spent fuel pool would increase the loading on the spent fuel pool cooling system (SFPCS). The modification was approved by the NRC with the Technical Specification limit that the pool temperature remain below 150'F during normal operation and that, if the pump or heat exchanger in the cooling system were to fail, sufficient time would be available to bring backup equipment into service so that the pool temperature would not exceed 180'F. Estimates provided by RG&E indicated that, in all cases, backup equipment could be installed in 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> and it determined that, in 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />, the pool temperature would not exceed was 180'F. The NRC Staff found this acceptable. All the design basis analyses performed to obtain these results were performed assuming a conservatively high service water (Lake Ontario) temperature of 80'F.

Analyses for a normal, nominally one-third core, refueling showed and continue to show that the pool temperature will remain below 150'F even with 80'F service water and that, sufficient time (at least 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />) is available to bring backup equipment into service in the event of a pump or heat exchanger failure.

In the event of a full core discharge, a substantial length of time, approximately 30 days assuming full power operation prior to shutdown, is required between plant shutdown and the comple-tion of the full core discharge if the service water is at 80'F in order to maintain the pool temperature below 150'F. For general design purposes, it remains appropriate to consider the situation of 80 F service water. In this regard, RG&E is in the process of developing design criteria for a new spent fuel pool cooling system who.ch will meet these and other requirements. We expect to submit the details of this system to the NRC for approval in the next few months. Installation of this new system could not be accomplished prior to the 1979 shutdown.

The reactor vessel inservice inspection for 1979 requires a full core discharge. Because the time of year of this full core dis-charge is preplanned, it is not, necessary to assume the service water temperature will be 80'F and require, therefore, the extra critical path time for decay heat reduction. Rather, the full core discharge can be accomplished earlier in the shutdown, with

I'I direct shortening of the entire outage, if the historical records of intake temperature (service water) are used to develop a conservative upper limit of service water temperature for the time of year that the full core discharge will take place.

The following paragraphs describe the SFPCS and backup systems with detailed justification of service water .temperature and spent. fuel pool temperature inoperable.

if portions of the SFPCS become The SFPCS is illustrated on Figure 1. The system consists of a single loop containing a pump and heat exchange. Water is drawn from the spent fuel pool (SFP) by the SFP pump, forced. through the heat exchanger, and returned to the SFP. The heat exchanger is cooled by service water. Approximately 10% of the water from the SFP bypasses the heat exchanger and is passed through a demineralizer and filter.

The temperature of the service water going into the SFP heat exchanger is a controlling factor in determining the heat transfer capability of the SFP cooling system. The service water temperature is the same as the intake (lake) water temperature except during the winter months when recirculation is used as necessary to maintain a water temperature of approximately 37'F.

The 1979 refueling outage is tentatively scheduled for March 2, 1979. Based on this shutdown date, and on full power operation up to this point, by April 1, the full core discharge could be completed and the SFP would not exceed 150'F even with 80'F service water. For completion of the full core discharge prior to April 1, credit must be taken for lower lake temperature.

Table l illustrates the monthly average of the daily minimum, average, and maximum intake water temperatures for the first four months of the year.

Table 2 presents lists of the minimum and maximum intake water temperatures that occur at any time during those month.

The intake water temperature has been recorded since December l969. The data show the following:

the monthly average of the daily average temperature has not exceeded 43'F from January through April.

2. the monthly average of the daily maximum temperature has not exceeded 44'F from January through April.

3. the instantaneous daily maximum temperature has not exceeded 56'F from January through April. The temperature exceeded 50'F for only two days, April 18 and 19, 1974 during this period.

4. the instantaneous daily maximum temperature has not exceeded 50'F from January through March.

Therefore, a conservative service water temperature for January through March would be 50'F and for January through April would be 60'F. (The May temperature also has not exceeded 60'F.)

The design capacity of the SFPCS was calculated to be 9.3 x 10 BTU/hr with a SFP temperature of 150'F and a service water temperature of 80'F. If the service water temperature is 50'F,6 the design capacity is calculated to be approximately 13.2 x 10 BTU/hr. If the service water temperature is 60'F the design capacity is calculated to be 12.0 x 10 BTU/hr.

Figure 2 illustrates the decay heat generated by the l979 Full Core Discharge and the decay heat generated by the fuel assemblies stored in the SFP. The decay heat was calculated using the equa-tions presented in the Branch Technical Position APCSB 9-2, "Residual Decay Energy for Light. Water Reactors for Long Term Cooling." The calculations were done assuming finite assembly burnup based on actual group average burnups.

Based on Figure 2 and a 12.0 x 10 BTU/hr heat removal capacity, approximately 15 days of cooling is required before the entire core can be placed in the SFP. ]Fuel movement can begin prior to 15 days as 1gng as the 12.0 x 10 BTU/hr limit is maintained.)

At 12.0 x 10 BTU/hr the SFP will go from 150 to 180'F in approxi-mately 5.$ hours versus the 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> if the SFPCS is lost.

13.2 x 10 BTU/hr heat removal capacity is used from Figure 2, If the approximately 12 days of cooling is required before the entire core can be placed in the SFP.

The SFPCS is designed such that backup equipment can be used should the normal components not be operable. A portable pump is available should the SFP pump not be operable. In the event. the SFPCS heat exchanger is lost, cooling can be provided using temporary connections to one of the component cooling heat exchangers.

Since the component cooling system contains chromated water, the heat exchanger must be isolated and drained before for spent fuel pool cooling.

it can be used Figure 3 illustrates the connection of the portable pump to the SFPCS. The dashed lines indicate the portable pump and temporary connections. The following steps would be employed in connecting the portable pump:

l. Stop SFPCS pump

2. Close valves 781, 782, 789, 790, 804, 787, 785

3. Drain system

4. Close SFPCS pump spectacle flange

5. Remove blind flanges ECC1 and ECC2

6. Connect hose from ECC2 to suction side of portable pump

7. Connect hose from ECC1 to discharge side of portable pump

8. Open valves 781 and 785

9. Start portable pump It is estimated that approximately 45 minutes would be required to position the portable pump and approximately 45 minutes to install the pump.

Figure 4 illustrates the connection of the "A" Component Cooling heat exchanger to the SFPCS. The dashed lines indicate the tem-porary connections to the heat exchanger. The following steps would be employed in connecting the heat exchanger:

l. Place "A" Component Cooling heat exchanger in standby

2. Stop SFPCS pump

3. Isolate SFP purification loop by closing valves 789, 790, 804 Close valves 733A and 734A S. Drain Component. Cooling heat exchanger by opening valve 806C

6. Close valves 787 and 785

7. Remove blind flanges ECC3, ECC4, ECC5

8. Connect temporary hoses between ECC3 and ECCS, between ECC4 and SFP

9. Close valve 806C

10. Start SFPCS pump ll. Maintain SFP temperature by throttling valve 4619 It is estimated that 2 to 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> would be required before the component cooling heat exchanger would be operational in the SFPCS. The following table provides the SFP temperature after 1.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> in the case of the portable pump and after 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> for the component cooling heat exchanger for a service water tempera-ture of 80', 60', and 50'F.

SFP Temp. when Service Water Initial SFP Heat Up Backup Becomes Condition Temperature Temperature Rate Operational oF oF F/hr oF Portable Pump 80 150 157 CCHE 80 150 163 Portable Pump 60 150 5.6 158 CCHE 60 150 5.6 167 Portable Pump 50 150 6.2 159 CCHE 50 150 6.2 169 As can be seen, the increased heat. load has negligible effect on the SFP temperature when backup cooling is available.

In addition to the conservatism found in the decay heat calcula-tion, margin is available in other areas. First, the refueling shutdown is scheduled for March. The expected service water temperature is less than 40'F, rather than the 50'F or 60'F assumed in the analysis. The spent fuel pool cooling system

cleanup system removes 10% of the water before the heat exchanger.

If required, and for a short period of time, the cleanup system could be isolated with the result that additional cooled water would be discharged to the pool.

Based on these results, we request approval to use the existing SFPCS for the Spring 1979 shutdown. Because we cannot predict, at this time, the exact shutdown time or the power level for the balance of the cycle, we propose that decay heat levels be cal-culated using BTP APCSD 9-2. For shutdowns on or before March 6 2, 1979, we would propose using a SFPCS capability of 13.2 x 10 BTU/hr (i.e., 50'F) and for shutdowns on or before May 2, 1979, a SFPCS capability of 12.0 x 10 BTU/hr (i.e., 60'F).

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TABLE 2 HINIHUM AND MAXIMUM MONTHLY INTAKE WATER TEMPERATURE oF GINNA STATION 1970 1971 1972 1973 1974 1975 1976 1977 1978 min max min max min max min max min max min max min max min max min ~max Jan 30 39 32 43 32 40 32 39 33 53 35 42 34 40 33 40 34 39 Feb 31 35 32 37 32 37 32 37 32 36 34 43 34 39 33 39 34 37 Mar 31 35 NR NR 32 39 33 '41 34 48 34 39 35* 42* 33 44 34 42 Apr 39 45 NR NR 33 42 36 45 36 56 34 47 40 48 37 45 37 47 May 40 46 40 48 NR NR 40 48 42 52 43 64 43 53 39 59 41 58 NR = data not recorded-

• = data taken for only 12 days

Figure 1 Spent Fuel Pool Cooling System Service Water I

787 SFPCS Hx ECC3 ECCl 785 ~

from D. I 804 To D.I ECC2 789 Bypass 781 Spectacle SFPCS Flange Pump SFP 790 782

FIGURE 2 SFP Heat Load 1979 Full Core Discharge 4

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8 8J 10 15 20 25 30 Time from Reactor Shutdown cooldown days

Figure 3 Connection of Portable Pump to SFPCS

+ Service ~ater 787 SFPCS Hx Normal Path ECC3 ECCl

,78S From D.X. ~<

IT'empo'rary Hose To D.i. ())

bypass 189 I

Portable

/90 Pump ECC2 781 782 To D.X.

I SFP SFPCS Spprtacle Pump

Figure 4 Connection of "A" CC lix to SFPCS 4619 II A II 4617 Service Water Outlet CC Flx ~~~Service Water Inlet ECC4 ECC5 gl I

l 734@, 733A ECC1 806C ECC3 CC water 787 Normal Patl Drain SFPCS Hx I

.7785 CC water (IJ

~l ECC2 Temporary Hose 789 )

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+7790 781 Bypass P~

To D.I. SFPCS 782 Pump SFP