ML20101E109
| ML20101E109 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 03/01/1996 |
| From: | Wadley M NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9603220140 | |
| Download: ML20101E109 (3) | |
Text
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Northern states Power Company 1717 Wakonade Dr. E.
Welch, MN 55089 Telephone 612-388-1121 March 1,1996 10 CFR Part 50 Section 50.90 J
U S Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 Supplement to License Amendment Request Dated May 4,1995 Pressurizer Safety Valves and Main Steam Safety Valves Lift Settina Tolerance Chanae and Safety Limit Curve Chanaes Pursuant to discussions with your staff regarding the subject License Amendment Request (LAR) and its supplement dated November 27,1995, Northern States Power Company provides the following supplemental information.
I The limiting plant transient for maximum Reactor Coolant System pressure and maximu'm main steam line pressure is the Loss of External Load Transient (Turbino Trip). These analyses assume that the reactor is operating at 102% of rated reactor power in addition to the assumptions described in the November 27,1995 supplement to this LAR.
The subject submittal states that, "The Main Steam Safety Valve (MSSV) capacity criteria is 110% of rated steam flow at 110% of the steam generator design pressure. " This was the criteria originally used to physically size the valves to assure that the pressure of the system is limited to 110% of the design pressure as required by the ASME Code. This LAR does not involve any physical changes to the valves so their size and relieving capacity has not changed. The pressures at which the valves open and achieve full relieving capability may be affected by this LAR.
This LAR requests that an as-found MSSV setting within 3% of the nominal setting will be considered an acceptable tolerance within the bounds of " normal" plant operation. This tolerance is acceptable because our analyses show that the 9603220140 960301 PDR ADOCK 05000282 P
PDR I
4 USNRC 4
.-0 M:rch 1,1996 i
Page 2 of 3 pressure is less than the ASME limit of 110% system design pressure for all l
analyzed conditions.
The transient which causes the highest steam generator pressure is the turbine trip transient where the steam generator pressure reaches 1153 psig (106.2% of i
design) and causes only the first three safety valves to open. The analysis assumes a 3% tolerance and 3% accumulation to full open. The initial reactor power is 102%
i and no credit is taken for the direct reactor trip upon a turbine trip or for power operated relief valves. Within the bounds of the USAR, all other transient analyses j
either assume that the turbine is available to remove heat or assume that the j
limiting conditions are at a power less than 102%. Thus, there are no USAR Chapter 14 transients or normal operating conditions that challenge the steam generator pressure limit.
l Also considered was the ATWS scenario where some initiating transient should f
result in a reactor trip but the reactor fails to trip. The ATWS analysis is considered l
to be a "best estimate" analysis so nominal conditions, nominal setpoints, and zero calibration errors are assumed in the analyses (Reference USAR 14.8.1 and j
WCAP-11992). Thus, changing the allowable setpoint tolerance of the main steam safety valves will not affect the ATWS analyses.
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in summary, allowing safety valve setpoint deviation as proposed in the subject LAR is acceptable since there are no design basis transients or ATWS transients l
affected by this change which exceed the ASME limit of 110% of the main steam j.
system pressure.
Revised Safety Evaluation, Significant Hazards Determination and Environmental
)
i Assessments have not been submitted with this supplemental information since these evaluations as originally presented in the May 4,1995 submittal continue to j
bound the proposed license amendment.
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If you have any questions related to this information in support of the subject license amendment request, please contact myself or Dale Vincent at 612-388-6758 X4107.
M. D. Wadley Plant Manager, Prairie Island Nuclear Generating Plant c:
Regional Administrator - 111, NRC NRR Project Manager, NRC Senior Resident inspector, NRC State of Minnesota Attn: Kris Sanda J E Silberg
l USNRC
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March 1,1996 Page 3 of 3 UNITED STATES NUCLEAR REGULATORY COMMISSION NORTHERN STATES POWER COMPANY PRAIRIE ISLAND NUCLEAR GENERATING PLANT DOCKET NO. 50-282 50-306 j
i REQUEST FOR AMENDMENT TO OPERATING LICENSES DPR-42 & DPR-60 LICENSE AMENDMENT REQUEST DATED May 4,1995 Northern States Power Company, a Minnesota corporation, provides this supplemental information in support of its license amendment request dated May 4, 1995. This letter contains no restricted or other defense information.
l NORTHERN STATES POWER COMPANY By M. D. Wadley Plant Manager Prairie Island Nuclear Generating Plant On this!
ay of
/ffb before me a notary public in and for said County, personc!!y appeah M. D. Wadley, Plant Manager, Prairie Island Nuclear Generating Plant, and being first duly sworn acknowledged that he is authorized to execute this document on behalf of Northern States Power Company, that he knows the contents thereof, and that to the best of his knowledge, information, and belief the statements made in it are true and that it is not interposed for delay.
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