ML20133E484
| ML20133E484 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 01/03/1997 |
| From: | Jeffery Wood CENTERIOR ENERGY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| RTR-REGGD-01.099, RTR-REGGD-1.099 2429, GL-92-01, GL-92-1, TAC-M92668, NUDOCS 9701130050 | |
| Download: ML20133E484 (4) | |
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s CENTERDOR ENERGY a
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%01 N. State Route 2 419-249 2300 John K. Wood j
2 Oak Hart)or OH 43449 FAX: 419 3218337 W:;e Presdent Nuclear 1
Davis-Besse e
i Docket Number 50-346 i
License Number NPF-3 Serial Number 2429 January 3, 1997 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001
Subject:
Closeout for the Toledo Edison Company Response to Generic Letter 92-01, Revision 1, Supplement 1 for the Davis-Besse Nuclear Power Station (Closed TAC No. M92668)
Ladies and Gentlemen:
By letter dated August 13, 1996 (Toledo Edison Log Number 4893), the Nuclear Regulatory Commission (NRC) requested the Toledo Edison company to provide an assessment of the application of the ratio procedure, as described in Position 2.1 of Regulatory Guide 1.99, " Radiation Embrittlement of Reactor Vessel Materials," Revision 2, (RG 1.99) to Davis-Besse Nuclear Power Station (DBNPS) pressure-temperature limit curves and low temperature overpressure (LTOP) limits.
In Amendment 199 to Facility Operating License Number NPF-3 for the Davis-Besse Nuclear Power Station, Unit Number 1, dated July 20, 1995, the NRC provided approval of the current DBNPS pressure-temperature limit curves for 21 effective full power years (EFPY). The adjusted reference temperatures used.in the development of the 21 EFPY pressure-temperature limit curves are 155*F and 114*F at the 1/4 and 3/4 wall thickness locations in the reactor vessel wall, respectively. These adjusted reference temperatures are based on surveillance capsule data for critical welds. The weld chemistry of the surveillance capsule is 0.21 weight percent copper and 0.63 weight percent nickel. As reported in Babcock and Wilcox Topical Evaluation BAW-2257, Appendix B, Table 8, the best-estimate weld chemistry for weld wire is 0.24 weight percent copper and 0.63 weight percent nickel.
If the ratio procedure of RG 1.99 is applied to the weld wire data, the chemistry factor used in the calculation of adjusted reference temperatures will increase approximately five percent. Therefore, the use of the ratio procedure will result in calculated adjusted reference temperatures of 162*F and 118'F at the 1/4 and 3/4 wall thickness locations in the reactor vessel well, respectively.
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Dockst Number 50-346 Licensa Number NPF-3
' Serial Number 2429
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Page 2 The shift in the pressure-temperature limit curves that would result from using these revised adjusted reference temperatures is within the safety factors and margins included in the development of the 21 FFPY pressure-temperature limit curves for the DBNPS.
The curves are developed using the methodology provided in Appendix G to Section III of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code. These curves include additional margins beyond the level required by Appendix G.
A conservative differential pressure correction factor was applied over the entire temperature range of the pressure-temperature curves. The differential pressure correction factor provides correction for the pressure differential between the analyzed region of the reactor vessel and the location of the pressure sensing instrumentation. This pressure differential term includes correction for elevation differences and pressure drop due to flow resistance.
A value of -148 psid was conservatively selected based on operation with four j
reactor coolant pumps with a coolant temperature of 200*F and a density of 60.5 pounds per cubic feet.
The pressure differential due to elevation difference is only 30.4 psid. Only two reactor coolant pumps are operating at temperatures below 280*F and no reactor coolant pumps are operating below 260*F.
The pressure-temperature curves are conservative when the reactor coolant system temperature is below 280*F because the actual pressure drop is less than the pressure drop accounted for in developing the curves.
Low temperature overpressure protection is provided in two ways at the DBNPS.
i Once the pressurizer power-operated relief valve and the safety valves are no l
longer providing over-pressure protection (at approximately 315'F during cooldown and 353*F during heatup), administrative controls are used to assure protection within the existing pressure-temperature limits. These controls limit the reactor coolant system pressure, temperature, and the pressurizer level to ensure that a malfunction in the makeup system will not result in the reactor coolant system pressure approaching the pressure-temperature limits within 10 minutes of the malfunction initiation. Once the reactor coolant system temperature is below 280*F, a relief valve (DH-4849) in the Decay Heat Removal System suction piping is placed into service. Technical Specification 3.4.2,
" Safety Valves - Shutdown," requires this valve to be set less than or equal to 330 psig. This protects the reactor coolant system to below 140*F.
At that point the Makeup System is procedurally shutdown and can no longer impose an overpressure transient on the Reactor Coolant System (RCS).
Inadvertent initiation of High Pressure Injection is not considered credible since it would require multiple failures within the Safety Features Actuation
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System. Based on the above described conservative assumptions used in development of the pressure-temperature limits and the administrative controls used at the DBNPS, the revised adjusted reference temperatures would not impact low temperature overpressure protection.
Based on the above, it is concluded that sufficient margins exist in the pressure-temperature curve analyses so that application of the ratio procedure would not impact the currently approved pressure-temperature limits or the low j
temperature overpressure protection.
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Docket Number 50-346 Licanpa Number NPF-3
' Serial Number 2429 Page 3 Should you have any questions or require additional information, please contact Mr. James L. Freels, Manager - Regulatory Affairs, at (419) 321-8466.
Very truly yours,
.W/dle Enclosure cc:
A. B. Beach, Regional Administrator, NRC Region III A. G. Hansen, NRC Project Manager S. Stasek, DB-1 NRC Senior Resident Inspector Utility Radiological Safety Board
Dockst Number 50-346 Licanpa Number NPF-3
' Serial Number 2429 Enclosure Page 1 RESPONSE TO CLOSEOUT FOR THE TOLEDO EDISON COMPANY RESPONSE TO GENERIC LETTER 92-01 REVISION 1, SUPPLEMENT 1 i
FOR THE DAVIS-BESSE NUCLEAR POWER STATION l
i UNIT NUMBER 1 1
1 4
This letter is submitted in conformance with Section 182a of the Atomic Energy Act of 1954 as amended, and 10CFR50.54(f). Enclosed is Toledo Edison's Response to Closeout for the Toledo Edison Company Response to Generic Letter 92-01, Revision 1, Supplement 1, for the Davis-Besse Nuclear Power Station.
l By:
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// Wood,VicePresident-Nuclear J.
Sworn to and subscribed before me on this 3rd day of January, 1997.
en g pmv jw Notary Public / State of Ohio g
Nora Lynn Flood - My Commission expires September 3, 1997, O