ML20204C428
| ML20204C428 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 03/17/1999 |
| From: | Alexion T NRC (Affiliation Not Assigned) |
| To: | Cottle W HOUSTON LIGHTING & POWER CO. |
| References | |
| TAC-MA1911, TAC-MA1912, NUDOCS 9903230083 | |
| Download: ML20204C428 (5) | |
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'T Mr. Willi m T. Cottis March 17, 1999 President and Chief Executive Officer STP Nuclear Operating Company South Texas Project Electric Generating Station P. O. Box 289 Wadsworth, Texas 77483
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION ON PROPOSED AMENDMENT TO REFLECT REACTOR COOLANT SYSTEM FLOW DIFFERENCES WITH THE REPLACEMENT STEAM GENERATORS - SOUTH TEXAS PROJECT, UNITS 1 AND 2 (STP) (TAC NOS. MA1911 AND MA1912)
Dear Mr. Cottle:
The Nuclear Regulatory Commission staff is reviewing STP Nuclear Operating Company's May 7,1998, application on the above subject. This amendment is associated with the Replacement Steam Generator Project.
Based on its review, the staff has determined that additional information is needed, as discussed in the enclosed request for additional information (RAl). This request was discussed with Mr. Mark VanNoy of your staff on Fnbruary 24,1999, and a mutually agreeable target date of a response to the RAI by May 20,1999, was established. The staff appreciates the efforts expended w? respect to this matto'..
Si.1cerely, ORIGINAL S11NED BY:
Thomas W. Aiexion, Project Manager Project Directe rate IV-1 Division of Lic snsing Project Management Office of Nuc. ear Reactor Regulation Docket Nos. 50-498 and 50-499
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,o March 17, 1999 Mr. William T. Cottle President and Chief Executive Officer STP Nuclear Operating Company South Texas Project Electric Generating Station P. O. Bor. 289 Wadsworth, Texas 77483
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION ON PROPOSED AMENDMENT TO REFLECT REACTOR COOLANT SYSTEM FLOW DIFFERENCES WITH THE REPLACEMENT STEAM GENERATORS - SOUTH TEXAS PROJECT, UNITS 1 AND 2 (STP) (TAC NOS. MA1911 AND MA1912)
Dear Mr. Cottle:
The Nuclear Regulatory Commission staff is reviewing STP Nuclear Operating Company's May 7,1998, application on the above subject. This amendment is associated with the Replacement Steam Generator Project.
Based on its review, the staff has determined that additional information is needed, as discussed in the enclosed request for additional information (RAl). This request was discussed with Mr. Mark VanNoy of your staff on February 24,1999, and a mutually agreeable target date of a response to the RAI by May 20,1999, was established. The staff appreciates the efforts expended with respect to this matter.
Sincerely,
()a w J-Sna Thomas W. Alexion, Project Manager Project Directorate IV-1 Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-439
Enclosure:
As stated cc w/ enc!: See next page
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Mr. William T. Cottle STP Nuclear Operating Company South Texas, Units 1 & 2 cc:
Mr. Cornelius F. O'Keefe Jack R. Newman, Esq.
Senior Resident inspector Morgan, Lewis & Bockius U.S. Nuclear Regulatory Commission 1800 M Street, N.W.
P. O. Box 910 Washington, DC 20036-5869 Mr. T. H. Cloninger Vice President A. Ramirez/C. M. Canady Engineering & Technical Services City of Austin STP Nuclear Operating Company Electric Utility Department P. O. Box 289 721 Barton Springs Road Wadsworth,TX 77483 j
Austin, TX 78704 Office of the Governor
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Mr. M. T. Hardt ATTN: John Howard, Director
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Mr. W. C. Gunst Environmental and Natural l
City Public Service Board Resources Policy P. O. Box 1771 P. O. Box 12428 San Antonio,TX 78296 Austin, TX 78711 Mr. G. E. Vaughn/C. A. Johnson Jon C. Wood Central Power and Light Company Matthews & Branscomb P. O. Box 289 -
One Alamo Center MailCode: N5012 106 S. St. Mary's Street, Suite 700 Wadsworth,TX 74483 San Antonio, TX 78205-3692 INPO Arthur C. Tate, Director Records Center Division of Compliance & Inspection 700 Galleria Parkway Bureau of Radiation Control Atlanta, GA 30339-3064 Texas Department of Health 1100 West 49th Street Regional Administrator, Region IV Austin,TX 78756 U.S. Nuclear Regulatory Commission l
611 Ryan Plaza Drive, Suite 400 Jim Calloway Arlington,TX 76011 Public Utility Commission of Texas Electric Industry Analysis D. G. Tees /R. L Balcom P. O. Box 13326 Houston Lighting & Power Co.
Austin, TX 78711-3326 P. O. Box 1700 l
Houston,TX 77251 Judge, Matagorda County Matagorda County Courthouse 1700 Seventh Street i
Bay City, TX 77414
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Reauest for Additionalinformation Reaardina Technical Soecifications to Reflect Reolacement Steam Generator Reactor Coolant Flow Differences South Texas Project. Units 1 and 2 1.
Page 2 refers to two changes made to reduce vertical uplift forces on the reactor core:
(1) removal of the reactor vessel head flow nozzle plugs (T-cold conversion), and (2) removing thimble plugging devices on the fuel assemblies. Please provide or reference drawings showing each of these modifications.
2.
Page 3 discusses modifications to the reactor core safety limits. Page 12 discusses determination of [overtemperature delta temperature] OTAT and [ overpressure delta temperature] OPAT trip setp&ts. Discuss or provide reference to the methods that were used. Justify that the safety limits and setpoints are adequate to provide for departure from nucleate boiling ratio (DNBR) protection.
3.
Page 6 states that a specified number of reactor vessel head flow nozzle plugs will be removed to increase cooling flow to the upper head region so that the vessel inlet temperature (T-cold) will be achieved in that region. Discuss and justify how this number will be determined.
4.
Page 12 describes DNB-related events that were reanalyzed in the following categorias of events using RETRAN.
I Feedwater system malfunctions Spectrum of steam system piping failures inside and outside containment Loss of external electricalload/ turbine trip a.
The Final Safety Analysis Report for South Texas Project lists several spedo transients and accidents that were analyzed in each of the above categories.
We understand that not all of these events were reanalyzed for the reactor coolant flow technical specification revision. What specific events were reanalyzed, what specific events were not reanalyzed, and provide justification for not reanalyzing the other events (a separate discussion for each event not
)
reanalyzed is being requested).
b.
The staff understands that DNBR was evaluated in RETRAN using a partial derivative method as discussed in WCAP-14882 P (Westinghouse RETRAN topical report). Provide values for the partial derivatives used and justify that these values are conservative for DNBR analysis of South Texas.
c.
In the case of main steamline break (MSLB), asymmetrical cold leg temperatures and a stuck control rod might result in a skewed neutron flux shape. Discuss how skewed flux shapes were evaluated. Discuss how initial core fuel and cladding temperatures were determined for input to RETRAN. What minimum DNBR was determined for the MSLB and for what break size, power level and single failure assumptions.
ENCLOSURE
d d.
Page 7 states that reducing the minimum feedwater temperature from 440 "F to 390 *F has been included in the evaluation to account for a feedwater heater being out of service. If continuous operation with a feedwater heater out of service is planned, was the single failure of a second feedwater heater evaluated as part of the DNBR evaluations? What would be the effect on DNBR from failure of the second feedwater heater?
5.
Page 16 provides a table of minimum measured flow and thermal design flow including the expected core bypass for the two steam generator types. Describe how these flow rates were determined.
l 6.
Of the non-LOCA transients and accidents that were reanalyzed in NOC-AE-0080, for which event was the minimum DNBR calculated? What was the change in DNBR from this event for the steam generator replacement and how does the new value compare to the DNBR limits for the South Texas Project. For which event was the maximum reactor system pressure calculated? What was the change in calculated reactor pressure for the steam generator replacement and how does the new pressure compare to the maximum allowable reactor system pressure for the South Texas Project.
7.
In the conclusion section of the NRC staff safety evaluation report for WCAP-14882-P, several conditions are listed for use of RETRAN. These conditions describe the 1
boundaries and the extent of the stch's review based on the supporting information provided by Westinghouse. Wease address each of these conditions.
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