ML20205A588

Forwards Request for Addl Info Re Submittal Requesting Rev of pressure-temperature Limits & Surveillance Capsule Withdrawal Schedule

ML20205A588
Person / Time
Site:	Monticello
Issue date:	03/24/1999
From:	Lyon C NRC (Affiliation Not Assigned)
To:	Richard Anderson NORTHERN STATES POWER CO.
References
TAC-MA4532, NUDOCS 9903310022
Download: ML20205A588 (4)

Text

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Mr. Rogsr O. And:rson, Director Nucimr Energy Engineering

(

Northern States Power Company .

414 Nicollet Mall '

Minneapolis, Minnesota 55401

SUBJECT:

MONTICELLO NUCLEAR GENERATING PLANT - REQUEST FOR ADDITIONAL INFORMATION RELATED TO SUBMITTAL REQUESTING REVISION OF PRESSURE-TEMPERATURE LIMITS AND SURVEILLANCE CAPSULE WITHDRAWAL SCHEDULE (TAC NO. MA4532)

Dear Mr. Anderson:

By letter dated December 31,1998, Northern States Power Company submitted a request for a Technical Specification change to modify the Monticello reactor pressure vessel (RPV)

, pressure-temperature limits and to modify the RPV surveillance program. These modifications ,

were requested based upon your acquisition of additional surveillance data from Monticello i specimens that had been inserted into the Prairie Island RPV for irradiation. Based upon our  !

review of the information submitted in the original package and additional discussion with your i staff during telephone conferences on February 18 and March 10,1999, the staff has j developed the enclosed request for additional hformation. d The enclosed request was discussed with Mr. M. Voth of your staff on March 18,1999. A mutually agreeable target date of April 23,1999, for your response was established. If circumstances result in the need to revise the target date, please contact me at (301) 415-2296 at the earliest opportunity.

Sincerely, ,

ORIGINAL SIGNED BY Carl F. Lyon, Project Manager Project Directorate ill-1 Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-263 I

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c Mr. Roger O. Anderson, Director Monticello Nuclear Generating Plant Northern States Power Company a

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J. E. Silberg, Esquire Commissioner Shaw, Pittman, Potts and Trowbridge Department of Public Service 2300 N Street, N. W. 121 Seventh Place East Washington DC 20037 Suite 200 St. Paul, Minnesota 55101-2145 U.S. Nuclear Regulatory Commission Resident inspector's Office Adonis A. Nebiett 2807 W. County Road 75 Assistant Attomey General Monticello' Minnesota 55362

, Office of the Attorney General 445 Minnesota Street Plant Manager Suite 900 Monticello Nuclear Generating Plant St. Paul, Minnesota 55101-2127 ATTN: Site Licensing Northem States Power Company .

2807 West County Road 75 Monticello, Minnesota 55362-9637 Robert Nelson, President Minnesota Environmental Control Citizens Association (MECCA) 1051 South McKnight Road St. Paul, Minnesota 55119 Commissioner Minnesota Pollution Control Agency ,

520 Lafayette Road St. Paul, Minnesota 55119 Regional Administrator, Region 111 U.S. Nuclear Regulatory Commission

, 801 Warrenville Road Lisle, Illinois 60532-4351 Commissioner of Health Minnesota Department of Health 717 Delaware Street, S. E.

Minneapolis, Minnesota 55440 Darla Groshens, Auditor / Treasurer Wright County Government Center 10 NW Second Street '

Buffalo, Minnesota' 55313 u.e me

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l REQUEST FOR ADDITIONAL INFORMATION REGARDING THE PROPOSED AMENDMENT TO THE l PRESSURE-TEMPERATURE LIMITS I MONTICELLO NUCLEAR GENERATING PLANT DOCKET NO. 50-263 1

I (1) Provide a complete description of the methodology used at Monticello Nuclear Generating Plant (MNGP) for the determination of reactor pressure vessel (RPV) fluences. This should include information on the neutron transport code models (their spatial mesh refinement, angular quadrature, energy group divisions, differencing i schemes, cross-sectional libraries, etc.) and on the analysis and application of dosimeter wire measurements for establishing best-estimate fluences. In particular, this should address if and/or how the dosimeter wire measurements are used to modiiy the results of the neutron transport code analyses. The staff notes that preliminary staff guidance on determining RPV fluences was published as draft Regulatory Guide (RG)-1053.

(2) Summarize the results of the last end-of-cycle fluence analysis that was performed at MNGP to demonstrate how the methodology described in (1) is applied for the purpose of establishing RPV leak test pressure-temperature (P-T) limits.

(3) Describe the current status of the MNGP RPV surveillance program.

(a) How many surveillance capsules remain to be withdrawn from the MNGP RPV and when are these capsules scheduled to be removed?

(b) What basis or criteria will be used to determine when the remaining surveillance capsules will be withdrawn? Licensees have been permitted to remove surveillance capsule withdrawal requirements from their technical specifications (TS), but in those cases a definitive program has been addressed in the facility's Updated Safety Analysis Report to ensure that the facility continues to comply with the provisions of Title 10 of the Code of Federal Regulations Part 50, Appendix H.

(c) Explain what actions MNGP is taking to address the lack of unirradiated baseline data for your RPV surveillance weld.

(4) Regarding the revised Figures 3.6.1,3.6.2,3.6.3, and 3.6.4 in your submittal package:

(a) Confirm that the margin term (proposed in your submittal as 34 *F) used to calculate the limiting adjusted reference temperature after a period of operation is directly incorporated into Figure 3.6.1 for determining "RTa Shift."

(b) Figures 3.6.2,3.6.3, and 3.6.4 indicate that the temperature scale on the vertical axis is relative to the " minimum vessel metal temperature."

ENCLOSURE

2-(1) Explain how the instrumentation used to monitor the cond%ons in the RPV is used to determine the " vessel metal temperature."

(2) Indicate how instrument uncertainties are included when relatirr 7.nt conditions to the P-T limits.

(c) For Figures 3.6.3 and 3.6.4, explain:

(1) What heatup or cooldown rates these curves are valid for (e.g., less than or equal to 100 'F/hr) and indicate where the limits on how rapidly the MGNP RPV can heatup or cooldown are located.

(2) Explain how the through-wall thermal gradients in the RPV are determined when defining the heatup and cooldown P-T limits.

(3) Explain how the contribution of the thermal stresses developed during heatup and cooldown was' calculated and provide the Ky values used for determining the heatup and cooldown curve.

(4) The staff has noted that the methodology for establishing heatup and cooldown P-T limits in your TS is based on an evaluation of the 1/4T flaw location. During heatup, since the tensile stresses occur on the outside of the vessel, the 3/4T flaw location may be limiting depending upon the heatup rate, the through-wall temperature gradient, the water l temperature, and the RT, of the 1/4T and 3/4T location. l l Is the 3/4T flaw limiting at any point during the most severe heatup transient permitted by your TS? If so, explain how the methodology l proposed in your TS results in the generation of P-T limits which are t

bounding for the most severe heatup transient permitted by your TS.

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