ML20202F802

Provides 120-day Response to GL 96-06, Assurance of Equipment Operability & Containment Integrity During DBA Conditions

ML20202F802
Person / Time
Site:	Monticello
Issue date:	02/02/1998
From:	Hammer M NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-96-06, GL-96-6, TAC-M96835, NUDOCS 9802190301
Download: ML20202F802 (4)

Text

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N:rthem States Power Company Monticeno Nuclear Generating Plant 2807 West County Road 76 Monticello, MN $5362 February 2,1998 Generic Letter 96-06 US Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 Revised Response to Generic Letter 96-06 (TAC NO. M96835) i On Janum! 28,1997 Northern States Power provided the required 120 day response to Generic Letter 96-D.," Assurance of Equipment Operability and Containment Integrity During Design-Basis Accident Conditions." By this letter, NSP made the following commitment.

'Monticello willinstallpressure relisving devices or other equivalent means to resolve the overpressure conditions identified by this submittalprior to stertup from the next refueling outage. The next refueling outage is currently scheduled for January 1998."

By a January 21,1998 conference call with the NRC staff, NSP identified problems meeting this commitment for four penetrations and requested additional time. Our commitment for all other penetrations remhins unchanged. We are therefore revising our commitment to the followin?

'Monticello willinstall pressure relieving devices or other equivalent means to resolve the overpressure ccnditions identified by NSP's January 28,1997 submittal prior to startup from the 1998 refueling outage witis the exception of the RHR Shutdown coo ling line and the instrument air / alternate N2 system which will be resolved during the 1999 refueling outage.

The 1998 refueling outage is currently scheduled for March 1998 and tne ~I999 outage for November 1999."

A time extension for the shutdown cooling line is requested due to a conflict with a modification currently planned to the reactor water cleanup system that will improve safety and reduce personnel exposure. Since either shutdown cooling c, reactor water cleanup is required for core cooling during the refueling outage, modifications on both these systems dunng the 1998 refueling outage increases the complexity and risk of maintaining core cooling. Continued opera 0on of the shutdown cooling line in its current 7nfiguration until the 1999 refueling outage is considered acceptable as the RHR Shutdown cooling line meets ASME Section lil, Appendix F operability critena. , ,,

. ..,6 a v m A time extension for the air / alternate N2 line is being requested due to the difficulty in developing an acceptable design and obtaining suitable parts. Please no'.e that this system meets its current 9802190301 980202 ~

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design criteria; nowever,.NSP feels it prudent to proceed with trying to provide additional margin if cost effective. See attachment A for additional discussions.

Please contact Sa,a Shirey, Sr. Licensing Engineer, at (612) 295-1449 if you require additional infoimation related to this regtiest.

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Michael F. Hammer Plant Manager Monticello Nuclear Generating Plant T Regional Administrator - 111, NRC NRR Project Manager, NRC Sr. Resident inspector, NRC State of Minnesota Attn: Kris Sanda J. Silberg Affidavit to the US Nuclear degulatory Commission Attachment A: Monticello Nuclear Generating Plant Additional Information for Revised Response to Generic Letter 96-06 (TAC NO. M96835) e t

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I UNITED STATES NUCLEAR REGULATORY COMMISSION NORTHERN STAMS POWER COMPANY MONTICELLO NUCLEAR GENERATING PLANT DOCKET NO. 50-263 ,

REVISED RESPONSE TO GENERIC LETTER 96-06 (TAC NO. M96835)-

Northern States Power Company, a Minnesota corporation, by letter dated February 2, _

1998, provides the attached revised response to NRC Generic Letter 96-06 dated September 16,1997. This letter contains no restricted or other defense information.

NORTHERN STATES POWER COMPANY By A41A41/A./

Michael F. Hammer Plant Manager .

Monticello Nuclear Generating Plant On this1 day of Echwm \DB before me a notary public in and for said County, personally appeared Idchael F. Hammer, Plant Manager, Monticello Nuclear Generating Plant, and being first duly sworn acknowledgsd that he is authorized ,

to execute this docurr.ent on behalf of Northern States Power Company, that he knows the contents thereof, and that to the best of his knowledge, informrdion, and bel:af the statements made in it are true and that it is not interposed for delay.

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(Sarnuel 1. Shirey L ~'SAMUEb. SHIREY

. Notary Public - Minnesota C < no1AnysusuC MINNESOTA Shert'urne County wco t a an u.2000

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My Cummission Expires January 31,2000

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Attachment A

. Monticello Nuclear Generating Plant Additional Information for Revised Response to Generic Letter 96-06 (TAC NO. M96835)

X-12: RHR Shutdown Cooling Piping componerts were analyzed between inboard containment isolation valve MO-2029 and outboard containment isolation valve MO-2030 inclusive. The peak calculated internal pressure foi the maximum Drywell ac::ident temperature conditions was 2,743 psig. The piping and components were qualified to the ASME Section ill A . undix F operabiity criteria for a maximum expected internal pressure of 3,306 psig.

Since 3,306 psig is greater than the peak calculated internal pressure of 2,743 psig, the components of this penetration meet the ASME Section ill Appendix F operability criterist X-22: Instrument Air, X-34A: Altemate N2 Supp9 to SRVs and X-105B-G: Alternate N2 Supply to SRVs These three penetrations contain instrt. ' ant air and nitrogen supply pressure.

In accordance with the USAR, Table 5.2-7, " Assumptions for the LOCA Containment Evaluathn," initial drywell temperature is assumed to be 135'F. The initial pressure is assumed to be the N2 supply regulator setpcint. SBA LOCA Drywell temperature and pressure ale 335'F and 21.9 psig, respectively, in accordance with the USAR figures 5.2 25 and 5.2-26.

Using the perfect gas law, the line pressure outside the drywell is calculated to be 145.2 psig and the line pressure inside the Drywell is 145.2 psig - 21.9 psig = 123.3 psig.

The pressure ratings of all components in the subject pneumatic supply systems are 125 psig or greater.

Allowable stress levels of ANSI B31.1 " Power Piping" are met for tr 2se components.

Schedule For Completion Of Modificatioy To meet the ANSI B31.1 code allowables, pressure relieving devices will be installed on 4 penetrations X-17, X-18 and X-19 at the next refueling outage currently scheduled for March,1998. Penetration X-12 will be evaluated or corrected during the 1999 refueling outage currently scheduled for Navember 1999.

A method to increase margin between postulated pressure and design pre. ;ure on penetrations X-22, X-34A, and X-105B-G will also be evaluated and/or implemented during the 1999 refueling outage.

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