ML20195J328

Forwards Application for Amend to License DPR-63,proposing Changes to TS Set Forth in App a of Mentioned License. Supporting Info & Analyses Demonstrating Proposed Changes Involve No Significant Hazards Consideration,Encl

ML20195J328
Person / Time
Site:	Nine Mile Point
Issue date:	11/16/1998
From:	Mueller J NIAGARA MOHAWK POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML17059C356	List: ML20195J328
References
NMP1L-1382, NUDOCS 9811240241
Download: ML20195J328 (2)

Text

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NiagarahMohawk' John H. Mueller Phone: 315.349.7907 Senior Vice President and I'*:3'53"3'33' Chief Nuclear Officer * # ""' ***

November 16, 1998 NMPIL 1382 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 RE: Nine Mile Point Unit 1 Docket No. 50-220 DPR-63 Gentlemen:

Niagara Mohawk Power Corporati,on (NMPC) hereby transmits an Application for Amendment to Nine Mile Point Unit 1 (NMP1) Operating License DPR-63. Also enclosed are the proposed changes to the Technical Specifications (TS) set forth in Appendix A of the above mentioned license included as Attachment B is a hand-marked version of the proposed changes. Supporting information and analyses demonstrating that the proposed changes involve no significant hazards consideration pursuant to 10CFR50.92 are included as Attachment C.

General Design Criterion (GDC) 12 of 10CFR50 Appendix A requires that the reactor core and associated coolant, control, and protection systems be designed to assure that power oscillations, which can result in conditions exceeding specified acceptable fuel design limits, are not possible or can be reliably and readily detected and suppressed. Operating experience has shown that under certain operating conditions, Boiling Water Reactors (BWRs) are susceptible to coupled neutronic/ thermal-hydraulic instabilities which can compromise established j

fuel safety limits. Such instabilities are characterized by periodic core power and hydraulic oscillations. For most plants, the existing Neutron Monitoring System f

(NMS) features of the Reactor Protection System (RPS) may not assure automatic protection against this class of events.

The BWR Owners' Group (BWROG) defined several stability long-term solutions which meet the GDC stated above. The Option ll solution demonstrates that Cldd/

existing quadrant-based Average Power Range Monitor (APRM) trip systems will initiate a reactor scram for a postulated reactor instability and avoid violating the Minimum Critical Power Ratio (MCPR) safety limit. The quadrant-based APRM system is unique to BWR/2 designs (e.g., NMP1) in that Local Power Range Monitor (LPRM) instrument assignments to the APRMs are arranged in separate quadrants of the reactor.

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9811240241 981116 PDR P ADOCK 05000220 PDR i

Nine Mde Point Nuclear Station R0. Box 63, Lycoming New York 13093-0063

I Page 2 NMPC's letter to the NRC dated December 15,1995, stated that NMPC would implement the BWROG Option ll solution. However, plant-specific analysis supporting Option ll implementation at NMP1 indicated that changes to the APRM flow biased neutron flux scram settings (TS 2.1.2) would be required. The changes are required to limit the oscillation magnitude at reactor trip, thereby limiting the associated Critical Power Ratio (CPR) change and, in conjunction with MCPR operating limits, assure compliance with the MCPR safety limit. The change to the APRM flow biased neutron flux scram will be implemented by APRM Flow Control Trip Reference (FCTR) cards and by making the required changes to the APRM flow biased neutron flux scram (and rod block) TS. These changes implement more restrictive TS flow biased scram trip (and rod block) settings in the low flow regions of the power / flow operating map (i.e., the operating conditions most susceptible to reactor instabilities).

In addition, changes are proposed which willincrease the APRM flow biased neutron flux scram and control rod block settings to allow plant operation in the previously approved Extended Load Line Limit Analysis (ELLLA) region. NMP1 is currently restricted from full use of the ELLLA region of the power / flow map .

because of the flow biased rod block setpoints. The required setpoint methodology I assigns a penalty to account for drift of the power and flow measuring instruments. This reduces the as-left setpoints of the rod block which causes it to fallinto the allowable ELLLA region. Consequently, NMP1 is forced to operate at higher core flows to avoid nuisance rod block alarms. Full use of the ELLLA region .

will allow for optimum core power distributions throughout the operating cycle and l a gain in cycle energy. Regaining the full power operating map will save NMP1  ;

approximately $250,000 a year while having negligible impact on transient or  !

accident event results. Operation in the ELLLA region was approved by '

Amendment No. 92 dated March 24,1987.

Pursuant to 10CFR50.91(b)(1), NMPC has provided a copy of this license amendment request and the associated analyses regarding no significant hazards consideration to the appropriate state representative.

Very truly yours, Jdhn H. Mueller i Senior Vice President and I Chief Nuclear Officer JHM/JMT/ kap i Attachments xc: Mr. H. J. Miller, Regional Administrator, Region l Mr. G. K. Hunegs, Senior Resident inspector Mr. D. S. Hood, Senior Project Manager, NRR Mr. S. S. Bajwa, Director, Project Directorate I-1, NRR Mr. John P. Spath NYSERDA 286 Washingtor, Avenue Ext i Albany, NY 12203-6399 Records Management