ML20154L542

Forwards Response to NRC 980824 Second Request for Addl Info Re Increased Spent Fuel Pool Storage Capacity,Per 980515 Application for Amend to License

ML20154L542
Person / Time
Site:	Nine Mile Point
Issue date:	10/13/1998
From:	Abbott R NIAGARA MOHAWK POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NMP1L-1369, TAC-MA1945, NUDOCS 9810190347
Download: ML20154L542 (5)

Text

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'NiagaraMohawk Richard B. Abbott , -

Vce President NuclearEngsneenng October 13, 1998 Ofice: (315) 349-1812 NMPIL 1369 Fax: (315) 349-4417 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 RE: Nine Mile Point Unit 1 Docket No. 50-220 DPR-63

Subject:

Supplemental Requestfor AdditionalInfonnation Reganting Increased Spent Fuel Pool Stomge Capacity at Nine Mile Point Nuclear Station Unit 1 (TAC No. MA1945)

Gentlemen:

By letter dated May 15,1998, Niagara Mohawk Power Corporation submitted an application to amend Nine Mile Point Unit 1 (NMP1) Technical Specification 5.5, Storage of Unirradiated and Spent Fuel. The changes reflect proposed modifications to increase the storage capacity of the NMP1 spent fuel pool from 2776 to 4086 fuel assemblies. The NRC's letter dated August 11,1998 requested additional information regarding our application. Our submittal of September 25,1998 provided our responses.

In your letter dated August 24,1998, the NRC provided their second request for additional information. The attachment to this letter provides this information.

Sincerely, db& ,

Richard B. Abbott

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, , , Vice President Nuclear Engineering [

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xc: Mr. H. J. Miller, NRC Regional Administrator Region I Mr. S. S. Bajwa, Director, Project Directorate I-1, NRR Mr. B. S. Norris, Senior Resident Inspector Mr. D. S. Hood, Senior Project Manager, NRR Mr. John P. Spath NYSERDA 286 Washington Avenue Ext.

Albany, NY 12203-6399 l Records Management

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ATTACIIMENT SUPPLEMENTAL REQUEST FOR ADDITIONAL INFORMATION

'REGARDING SPENT FUEL POOL MODIFICATIONS l NIAGARA MOHAWK POWER CORPORATION NINE MII E POINT NUCLEAR STATION UNIT 1 DOCKET NO. 50-220 PLANT SYSTEMS Ountinn 7:

I On page X-30 of the Updated Safety Analysis Report (UFSAR)for Nine Mile Point Nuclear l Station Unit 1 (NMP1), Niagara Mohawk Power Corporation (NMPC) stated that it l

" committed to the Nuclear Regulatory Commission (NRC), in Technical Specylcation l Amendment 54, that refueling and core opload operations would not begin untilit was i determined that spentfuelpool (SFP) cooling systems were operable, to ensure that the 125 *F \

pool temperature would not be exceeded. " In the May 15,1998 submittal,140 *F is used as  ;

the SFP temperature limit in the thermal-hydraulic analyses. Thus, it appears that the SFP l temperature limit is being raisedfrom 125 *F to 140 *F. If this is correct, please provide detailed evaluation ofthe efects of this elevated SFP temperature limit on the design and operation ofthe SFP cooling systems. This should include the afect upon operator reaction time before pool boiling would occur in the event of a loss of all mechanical cooling systems.

Recnoner As indicated in Amendment No. 54 and our May 15,1998 submittal, the NRC indicated acceptance of our existing thermal-hydraulic analysis based on the fact that with the maximum normal heat load assumed and one cooling train in operation, pool water is calculated to be 125*F which is below the 140*F limit recommended in Standard Review Plan (SRP) Section 9.1.3. Accordingly, the existing SFP temperature limit for this SRP case is 140*F. The analysis provided in Section 5, Attachment C of our May 15,1998 submittal indicated how the proposed change meets the requirements of the SRP (i.e.,140 F). The SFP temperature limit of 140*F is well within the 170*F SFP cooling system design temperature as well as the design temperature of the pool structure and liner.

As stated in item (iv) on page 5-1 of the Licensing Report, the time available for operators to respond to a complete loss of cooling (time-to-boil) is evaluated. The methodology for these ,

evaluations is presented in Section 5.5 (bottom of page 5-10 through page 5-11) with the results of the evaluations presented in Section 5.8 of the Licensing Report. Operators have in excess of 8.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> to respond to a complete loss of forced coohng even under the most l restrictive scenario. Neither this evaluation nor the results need to be revised. l l

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Quection 8:

In the thermal-hydraulic analysis (Section 5.0 ofAttachments C and F ofyour submittal)for the unplanned (abnormal) full-core opload scenario, HOLTEC, International assumed, in part, that 36 days q)ter 148 spentfuel assemblies (SFAs)from the previous planned refueling were discharged to the SFP, afull core was transferred to the pool, beginning no sooner than 150 hours0.00174 days <br />0.0417 hours <br />2.480159e-4 weeks <br />5.7075e-5 months <br /> after reactor shutdown. Table 5.5-1 of the SFP Re-racking Licensing Report indicates that after each planned refueling, 200 SFAs would be left in the pool. Therefore, it appears that the thermal-hydraulic analysisfor the unplannedfull-core ofload scenario should be revised using 200 SFAs as the previously discharged SFAs. If this is correct, provide the revised results (i.e., decay heat load, SFPpeak temperature, etc.). If this is not correct, explain why you consider the use of148 SFAs to be acceptablefor the unplannedfull-core scenario.

l Resnonse:

As stated in the fourth paragraph on page 5-4 of the Licensing Report, the unplanned full-core offload scenario does not represent an actual discharge scenario at NMP1. This scenario is  ;

included to demonstrate compliance with SRP 9.1.3, which stipulates that the SFP temperature l under this scenario should not result in bulk pool boiling.

The full core discharge of 532 assemblies causes the SFP temperature to rise less than 35*F l above the temperature at the start of the discharge. Given that the calculated margin against boiling is 77*F (Licensing Report Section 5.8), the addition of 52 assemblies to the previous discharge batch would not cause the SRP 9.1.3 limit (212 F boiling temperature) to be exceeded. Accordingly, the use of 148 SFAs is acceptable for the unplanned full-core scenario.

Question 9:

As indicated in the SFP Re-racking Licensing Report, the heat removal capability of the SFP cooling system heat exchangers is afunction of the temperature of the reactor building closed loop cooling (RBCLC) water system. To maintain the SFP water below the temperature limit of140 *F, the reactor shutdown time required before any SFAs are discharged to the SFP varies with RBCLC water temperature. Specifically, thefollowing reactor shutdown times required before discha ging SFAs to prevent the SFPfrom exceeding the 140 *F temperature limit during a plannedfull-core ofload (normal refueling) operation have been established with RBCLC water atjour temperatures:

RBCLC Water SFAs in Reactor Decay Temnerature. *F Time Reouired. Hrs.

40 72 60 116 80 405 95 916 2 of 4

.m _

i Provide .the.follpwing infonnation:

1

a. Has single activefailure of the SFP cooling system been considered in establishing the above constraints?

b. HOLTEC, International recommends that the above constraints tofuel discharge ,

operations be incorporated into appropriate plantprocedures. What is NMPC's l position regarding the establishment ofproceduresfor thesefuel discharge constraints?

c. What is NMPC's position and reasoning as to whether snese restrictions should be included in the NMP1 TS?

Response

a. A single active failure is considered in the evaluation of Licensing Report Case 3, l actual end-of-cycle refueling. This is stated in the third paragraph on page 5-5 and i

item (i) on page 5-6 of the Licensing Report in which we discuss one (versus two) fuel l'

pool cooling trains operating (i.e., a single failure).

i b. As stated in Section 5.4.v of the Licensing Report, since the maximum temperature of the RBCLC system depends on the lake temperature, coincident decay heat in the pool and other system heat loads, cycle specific evaluations shall be performed. These l '

evaluations will ensure that with specific RBCLC temperatures and decay heat inventory in the pool, the required hold times shall be such that the bulk SFP temperature will be maintained at or below 140*F with one spent fuel pool cooling train operating. The requirement to perform these cycle-specific evaluations is in NMP1 administrative procedures. The approprir.te NMP1 operating procedure will be revised prior to each refueling outage to reflect the appropriate fuel discharge constraints.

c. The subject restrictions need not be included in the NMP1 Technical Specifications (TS). As indicated in Response 9b, the constraints to fuel discharge operations will be incorporated into the appropriate plant procedures. Except for TS 5.0, Design Features, the NMP1 TSs are silent regarding the SFP. As indicated by its title, TS 5.0 is meant to convey important design information, not to provide operational guidance.

Therefore, incorporating these constraints into plant procedures versus the NMP1 TSs is appropriate.

Question 10:

Discuss the procedures to be utilized by NMPC staf to monitor and control SFP water temperature and decay heat load so that these parameters will remain within the design basis limiting valuesforplanned or unplannedfull core ofload events.

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l Response: ,

. .. l Refueling and core offloading procedures at NMP1 will be revised to ensure that the SFP bulk temperature is maintained at or below 140*F. The results from the cycle-specific analysis  ;

discussed in Question 9.b. will be used to determine the core off-loading start time and offload rate to ensure SFP bulk water temperature will be maintained at or below 140*F. The total number of offloaded SFAs in the pool at any specific time during the offload, SFA in-reactor l

decay times and RBCLC heat loads for a given full core offload will be placed into the l appropriate refueling and core offloading procedures. The SFP high temperature alarm I provides temperature indication for the operators to ensure that the temperature is maintained I at or below 140*F. I l

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