ML20209B353

Informs NRC That All Actions Associated with NRC Bulletin 96-003, Potential Plugging of ECC Suction Strainers by Debris in Bwrs, Has Been Completed.Summary of Actions Completed & Other Pertinent Info Is Provided in Attachment

ML20209B353
Person / Time
Site:	Nine Mile Point
Issue date:	06/25/1999
From:	Abbott R NIAGARA MOHAWK POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
IEB-95-002, IEB-95-2, IEB-96-003, IEB-96-3, NMP1L-1444, NUDOCS 9907060415
Download: ML20209B353 (4)

Text

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! i Niagara $ Mohawk' l

l Richard B. Abbott June 25,1999 mone: 31s 349.1812 l Vice President NMPIL 1444 Fax: 315.349.4417 1 Nuclear Engineering U. S. Nuclear Regulatory Commission Attn Document Control Desk Washington, DC 20555 l

l RE: Nine Mile Point Unit 1 Docket No. 50-220 DPR-63

Subject:

NRC Bulletin 96-03, " Potential Plugging ofi ergency Core Cooling Suction Strainers by Debris in Boiling-Water Reactor Gentlemen:

On May 6,1996, the Commission issued NRC Bulletin 96-03, " Potential Plugging of Emergency Core Cooling Suction Strainers by Debris in Boiling-Water Reactors."Bulletin 96-03 requested that licensees implement appropriate procedural measures and plant modifications to minimize the potential for clogging of emergency core cooling system (ECCS) suppression pool suction strainers by debris generated during a loss-of-coolant accident (LOCA). All jf licensees were requested to implement certain actions by the end of the first refueling outage 'l starting after January 1,1997.Bulletin 96-03 also required licensees to 1) report to the Commission within 180 days whether and to what extent the requested actions would be taken and 2) notify the Commission within 30 days of completion of all requested actions along with a summary of the actions taken. M,>

By letters dated October 4,1996, November 4,1996, August 4,1997, and November 25, 1997, Niagara Mohawk power Corporation responded to Bulletin 96-03 and delineated its proposed actions and schedule. The purpose of this letter is to inform the NRC that all actions associated with Bulletin 96-03 have been completed. A summary of actions completed and other pertinent information is provided in the Attachment.

Very truly yours, n

02001a &# .g 9907060415 990625 -

0

[A Richard B. Abbott Vice President Nuclear Engineering l

l l RBA/IAA/ kap Attachment l

xc: Mr. H. J. Miller, NRC Regional Administrator i

, Mr. S. S. Bajwa, Section Chief PD-I, Section 1, NRR Mr. G. K. Hunegs, NRC Senior Resident Inspector Mr. D. S. Hood, Senior Project Manager, NRR  !

Records Management I Nine Mile Point Nuclear Station P0. Box 63, Lycoming, New York 13093-0063

• www.nimo.com

ATTACHMENT

SUMMARY

OF ACTIONS COMPI FTFD AND OTHER PERTINENT INFORMATION The following is a summary of actions completed and other pertinent information concerning Bulletin 96-03 for Nine MPc Point Unit 1 (NMP1).

I. Actinne Completed The following actions were :ompleted at NMP1 during refueling outage 15 (RFO15) to assure that post-LOCA debris will lot adversely affect the operation of the emergency core cooling systems (ECCS):

A. Passive, large capacity ECCS suction strainers were installed on the Core and Containment Spray Systems torus suction nozzles.

B. The NMP1 torus was dewatered and given a thorough cleaning. This included a water washdown of the entire torus interior and of the external surfaces of the individual downcomers and vent headers. Essentially all sludge was removed.

C. Retired in place containment monitoring equipment was removed from the vent header as it represented a direct debris source to the torus.

D. The drywell (containment) was thoroughly cleaned. Specific goals and objectives I included the removal of dust and dirt from the support steel and overhead areas, removal of foreign material, and coating inspections along with subsequent repairs / removal.

E. Insulation in the drywell was inspected for damage and proper installation. Defects were corrected to minimize the potential for generation of operational debris.

II. ECCS Suction Strainer Design Canability The newly added ECCS strainers are designed to meet the worst case debris loading expected ,

to be generated during pipe break accidents, in accordance with the BWROG's Utility l Resolution Guidance (URG) document for ECCS Suction Strainer Blockage, while still meeting the Core Spray and Containment Spray System Pumps Net Positive Suction Head (NPSH) and filtration requirements. The new ECCS strainer design accounts for the generation, transport, and accumulation of debris during accident mitigation. The ECCS strainers and their supports are designed to the ASME Boiler and Pressure Vessel Code and are Seismic Category I, safety-related components.

III. Imnact on Previous Resoonses to Bulletins 95-02 and 96-03 With the installation of the large capacity suction strainers on the Core and Containment Spray Systems, previous commitments made in response to NRC Bulletin 95-02, " Unexpected Clogging of a Residual Heat Removal (RHR) Pump Strainer While Operating in Suppression Pool Cooling Mode," and NRC Bulletin 96-03 need to be revised, as explained below.

I

n 1 NMPC's response dated November 16,1995, to NRC Bulletin 95-02, contained a commitment to inspect one ECCS (Core and Containment Spray Systems) discharge strainer quarterly and l to trend discharge strainer differentir.1 pressure data to ensure early detection of discharge strainer fouling. The NRC's' safety evaluation dated August 15, 1996, incorporated both of these commitments. However, with the installation of the ECCS suction strainers, these commitments are no longer applicable as the strainer baskets and the differential pressure instruments have been removed.

NMPC's October 4,1996 respnse to NRC Bulletin 96-03, committed to validate free movement of raw water intertie check valve disks quarterly using a torque wrench. This interim compensatory action was implemented as the containment spray raw water system

- provides an alternate path for water injection into the reactor vessel. This alternate flow path ,

gave additional assurance for coping with ECCS strainer clogging until NMPt ' could comply )

with NRC Bulletin 96-03's requested actions by installing high capacity suctic 1 strainers. { '

With the installation of ECCS high capacity suction strainers, it is no longer necessary to continue with the interim compensatory action. ,

I IV. Conclusion Based on the above information, NMPC considers the actions required to meet NRC Bulletin l 96-03 to be completed. NMPC will continue to adhere to its commitments relative to NRC  !

Bulletin 95-02 to periodically inspect and clean the tarus, i

l 2 l i

UNITED STATES NUCLEAR REGULATORY COMMISSION l

In the Matter of ) l

)

Niagara Mohawk Power Corporation ) Docket No. 56 220

)

Nine Mile Point Unit 1 )

(

Richard B. Abbott, being duly sworn, states that he is Vice President Nuclear Engineering of Niagara Mohawk Power Corporation; that he is authorized on the part of said Corporation to sign and file with the Nuclear Regulatory Commission the document attached hereto; and that the document is true and correct to the best of his knowledge, information, and belief.

/'

Richard B. Abbott Vice President Nuclear Engineering Subscribed and sworn before me, in and for the State of New York and the County of Osm ,

this ./d day of June,1999.

My Commission expire::: ffdeoo fm~s 6. 7%

NOTARY PUBLIC Eunice B. Naklick #4964683 Notary Public, State of New York Qualified in Jefferson County My Commission Expires April 2_p2dQO L