ML20217Q376
| ML20217Q376 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 04/08/1998 |
| From: | Alexion T NRC (Affiliation Not Assigned) |
| To: | Cottle W HOUSTON LIGHTING & POWER CO. |
| References | |
| TAC-MA0350, TAC-MA0351, TAC-MA350, TAC-MA351, NUDOCS 9804100414 | |
| Download: ML20217Q376 (6) | |
Text
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Mr. William T. Cottle April 8, 1998 President and Chief Executive Officer STP Nuclear Operating Company South Texas Project Electric Generating Station P. O. Box 289 Wadsworth, TX 77483
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION ON ALTERNATE OPERATION WITH REDUCED MEASURED REACTOR COOLANT SYSTEM FLOW, SOUTH TEXAS PROJECT, UNITS 1 AND 2 (TAC NOS. MA0350 AND MA0351)
Dear Mr. Cottle:
The Nuclear Regulatory Commission (NRC) staff is reviewing STP Nuclear Operating Company's (STPNOC's) December 31,1997, application for a license amendment to revise Technical Specifications 2.1 (Safety Limits),2.2 (Limiting Safety System Settings), and 3/4.2.5 (Departure from Nucleate Boiling Parameters) by including altomate operating criteria to allow continued plant operation with a reduced measured reactor coolant system flow rate, if necessary.
Based on its review, the staff has determined that additionalinformation is needed, as discussed in the enclosure.
Sincerely, ORIGINAL SIGNED BY:
Thomas W. Alexion, Project Manager Project Directorate IV-1 Division of Reactor Projects liiflV Office of Nuclear Reactor Reg alation Docket Nos. 50-498 and 50-499
Enclosure:
Request for AdditionalInformation i
cc w/ encl: See next page DISTRIBUTION:
Docket File PUBLIC PD4-1 r/f EAdensam (EGA1)
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April 8,1998 Mr. William T. Cottle President and Chief Executive Officer STP Nuclear Operating Company-South Texas Project Electric Generating Station P. O. Box 289 Wadsworth, TX 77483
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION ON ALTERNATE OPERATION WITH REDUCED MEASURED REACTOR COOLANT SYSTEM FLOW, SOUTH TEXAS PROJECT, UNITS 1 AND 2 (TAC NOS. MA0350 AND MA0351)
Dear Mr. Cottle:
The Nuclear Regulatory Commission (NRC) staff is reviewing STP Nuclear Operating Company's (STPNOC's) December 31,1997, application for a license amendment to revise Technical Specifications 2.1 (Safety Limits),2.2 (Limiting Safety System Settings), and 3/4.2.5 (Departure from Nucleate Boiling Parameters) by including attemate operating criteria to allow continued plant operation with a reduced measured reactor coolant system flow rate, if necessary.
Based on its review, the staff has determined that additional information is needed, as discussed in the enclosure.
Sincerely, f
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- EfW Thomas W. Alexion, Project Manager Project Directorate IV-1 Division of Reactor Projects til/IV Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499
Enclosure:
Request for AdditionalInformation cc w/ encl:.See next page
l
_ Mr. William T. Cottle STP Nuclear Operating Company South Texas, Units 1 & 2 cc:
Mr. David P. Loveless Jack R. Newman, Esq.
l Senior Resident inspector Morgan, Lewis & Bockius U.S. Nuclear Regulatory Commission 1800 M Street, N.W.
P. O. Box 910 Washington, DC 20036-5869 i
Bay City, TX 77414 Mr. Lawrence E. Martin
~
A. Ramirez/C. M. Canady Vice President, Nuc. Assurance & Licensing City of Austin STP Nuclear Operating Company Electric Utility Department P. O. Box 289 721 Barton Springs Road Wadsworth, TX 77483 Austin, TX 78704 Office of the Govemor Mr. M. T. Hardt ATTN: John Howard, Director Mr. W. C. Gunst Environmental and Natural 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 Mail Code: 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 Adi Jnistrator, Region IV Austin,TX 78756 U.S. Nuclear Esgulatory Commission 611 Ryan Plaza Drive, Suite 400 Jim Calloway Arlington, TX 76011 Public Utility Comrt 1sion of Texas Electric Industry Ar ilysis D. G. Tees /R. L. Balcom P. O. Box 13326 Houston Lighting & Power Co.
Austin, TX 78711 3326 P. O. Box 1700 Houston,TX 77251 Judge, Matagorda County Matagorda County Courthouse 1700 Seventh Street Bay City, TX 77414
REQUEST FOR ADDITIONAL INFORMATION ON ALTERNATE OPERATION WITH REDUCED MEASURED REACTOR COOLANT SYSTEM FLOW SOUTH TEXAS PROJECT. UNITS 1 AND 2 Introduction The licensee stated that the Technical Specifications are proposed to be changed to allow the minimum Reactor Coolant System flow rate to be reduced from 392,300 gpm to 380,500 gpm, a 3% reduction, while operating at full power. This is to be accomplished by using existing i
margins while still bounding the design ano licensing analyses.
The licensee stated that the purpose of their Safety Evaluation is to determine the effect of the 3% reduction in required minimum RCS flow rate on the design and licensing basis analyses presented in the South Texas Project Updated Final Safety Analysis Report (UFSAR). Their evaluation also considers the effect of the Thermal Design Flow reduction on the Reactor j
Coolant System mechanical systems and components.
The licensee's safety evaluations are presented for the following six item headings:
- 1) Loss of Coolant Accident Evaluations-
- a. Large Break LOCA
- b. Small Break LOCA
- c. LOCA Hydraulic Foremg Functions
- d. Hot Leg Switcho;4r and Post-LOCA Longterm Cooling j
- e. Rod Ejection Mass and Energy Releases i
- 2) Containment Response Evaluation:
- a. LOCA Mass and Energy Release
- b. Main Steam Line Break and Energy Release i
- c. Radiological Consequences and Post-LOCA Hydrogen Generation Evaluation
- 3) Non-LOCA Evaluations:
- a. Core Thermal Safety Limits, OTAT and OPAT Setpoints
- b. Evaluation of the Departure from Nucleate Boiling Ratio Criterion:
- 1. Category 1
- 2. Category 2
- 3. Category 3
- c. Evaluation of Non-Departure from Nucleate Boiling Criteria
- 4) Steam GeneratorTube Rupture Evaluation
- 5) NSSS Mechanical Systems and Equipment Evaluation:
- a. NSSS Components
- b. NSSS Systems
- 6) Design Transient Evaluation (including setpoint review of the followira):
- a. Overtemperature/ Overpower Delta-T
- b. Rod Control
- c. Steam Dump
- d. Pressurizer Level ENCLOSURE
l
.a 2
- e. Pressurizer Pressure f.
Steam Generator Level
- g. Feedwater Pump speed Questions 1.
In the six items above you indicate that the evaluation is done by several means, such as:
- 1) sensitivity studies,
- 2) recalculation and
- 3) " eve;ation."
When it is stated that the method used is by " evaluation," is it by 1) sensitivity studies, 2) recalculation or 3) by engineering judgement?
For example, on page 6 of Attachment 2, for Category 1, you state that " Evaluation of the current licensing-basis analysis results with the new Core Thermal Safety Limits (based on 3% flow reduction) confirms that the Departure from Nucleate Boiiing Ratio limit remains satisfied for each case." For Category 2 you state "Therefore, it is sufficient to evaluate, or re-calculate, the minimum Departure from Nucleate Boiling Ratio value for each of these events based on the transient statepoints from the current licensing-basis analyses with revised reference conditions based on a 3% flow reduction."
Please make clear which items are recalculated and which items are not based on a calculation or sensitivity analysis. Please explain what is meant in cases when the term
" evaluation" is used for an item in your letter of 12/31/97.
2.
When you state that the evaluation for accident or transient analysis is by sensitivity studies, please provide the sensitivity. For example, provide the change in departure i
from nucleate boiling ratio (DNBR) or pressure for the parameter compared to. Please i
provide the new value for DNBR and pressure expected from the change and also the limit value.- Also, provide the same for the results of any other sensitivity parameters.
3.
Where you state that there are minor changes in parameters (example, operating temperatures for Large Break LOCA on page 3 of Attachment 2), please explain by providing comparisons of the changes both by numerical values and by percent changes.
4.
Please provide the UFSAR sections for each of the accident and transient evaluations presented so that a cross reference can be more easily made for each of the evaluations
. and also to aid in checking for completeness.
5.'
On page 1 of Attachment 2:
- a. You state that "To offset the decrease in Departure from Nucleate Boiling [DNB)
. margin,
. (1) the upper end of the nominal T, range is reduced frrem 593 to 590 F, and
f 4-3 (2) the K, and K terms in the Overtemperature Delta-T (OTA T) and Overpower Delta-T (OPA T) reactor trip setpoints are reduced respectively.
(3) The Limiting Condition for Operation maximum T for the Reactor Coolant o
System is reduced from 598 'F to 595 'F."
Please state the total offset in DNS :nargin and the contribution to margin that is obtsined from each of the above three modifications.
b.' You state that "To ensure that the NSSS component analyses remain bounding, the lower end of the nominal Reactor Coolant System [RCS) average temperature (T,)
range is raised from 582.3 to 583.3 'F."
Please explain how this 1*F increase in T, temperature ensures that the NSSS component analyses remains bounding.
6.
On page 3 and 4 of Attachment 2:
- a. For
- Power Capability Parameters," you state that you have evaluated for two RCS T, levels of 583.2 'F for a lower bound and 590 'F for a upper bound. The lower bound has been increased by 0.9 'F and the upper bound has been decreased by 3 *F.
Please explain the background on how the lower ard upper bound average temperatures are arrived at and also what instrumentation is used to measure T,.
- b. For "Large Break LOCA and Small Break LOCA," you state that "The reduced flow results in very minor changes in operating temperatures throughout the Reactor j
Coolant System. The changes in these operating temperatures were evaluated based on plant-specific sensitivity studies performed to support the current operating
]
temperature range for South Texas Project Units 1 and 2."
1 Please give an example of a minor change in operating temperature and a corresponding sensitivity study application.
7.
On page 6 of Attachment 2:
- a. For Category 2, please explain the statement " based on the transient statepoints from the current licensing-basis analyses."
- b. You state that sufficient margin has been identified for the 5 events listed. Please provide these values and state from what variables they are obtained from.
8.
_On page 7 of Attachment 2:
You state that several current non-LOCA analyses for South Texas Project Units 1 and 2 have very little margin available and refer to Table 3. Table 3 is entitled " Sensitivity Analyses Performed With a 3 % Reduction in Reactor Coolant System Flow." The events
a 4
listed in Table 3 are loss of load, loss of feedwater, station blackout, feedline break, and rod ejection. The corresponding limiting parameters for each event are listed in Table 3.
Please provide the results from the analyses for these limiting parameters.
9.
On page 8 of Attachment 2:
Under the heading " DESIGN TRANSIENT EVALUATION" you state "Using the Thermal Hydraulic Reactor Coolant System Parameters listed in Table 1, an evaluation of the Design Transients used for the Reactor Coolant System Component Fatigue Analysis was conducted for the South Texas Project. The altemate full power nominal T range o
coupled with the altemate Reactor Coolant System flow continue to maintain the plant T-hot and T-cold values within the operating range defined for the current plant design basis used in the development of the NSSS design transients. Therefore, the transient response of the NSSS parameters used in the component fatigue analysis (T-hot, T-cold, Reactor Coolant System flow, Reactor Coolant System and pressurizer pressure, pressurizer spray and surge flow, and steam knd feedwater flows and temperatures) do not need to be revised from those included in the present design transients. There is also no impact on the installed capacity of the major Reactor Coolant System pressure-relieving devices (i.e., pressurizer spray, pressurizer power-operated relief valves and safety valves, and the steam generator safety valve's); the Reactor Coolant System flow changes do not require changes in the required relieving capacities."
in Table 1, which is labeled "NSSS Power Capability Parameters With a 3% Reduction In Thermal Design Flow," the parameters are provided for two temperatures, 590*F T and m
583.2'F Tg. For each of these two temperatures there are parameter values for two steam gem AM tube,%gging (SGTP) conditions of 0% and 10 %.
J a Discuss the basis for the two temperatures (590*F and 583.2*F).
- b. For the two changes in T, (590'F and 583.2'F) in Table 1:
- 1) Please discuss the methodology for determining the change, and the reasons for the change, in reactor coolant system temperatures for the 6 affected parameters listed in Table 1. Also, it is indicated that SGTP does not affect the parsmeters.
Please explain.
- 2) Please discuss the methodology for determining the change, and the reasons for the change, in steam pressure, steam temperature, and steam flow. Also, it is indicated that SGTP 1831 affect the parameters. Please explain.
L 10.'
On page 1 of Attachment 3, it is stated that the original Thermal Design Flow (TDF) rate was 381,600 gpm and the proposed new TDF rate is reduced by 3% to 370,00 gpm, a reduction of 11,600 gpm. You state that the new TDF rate is for altemate operations
" based on the 10% Steam Generator Tube Plugging limit of the current Licensing Basis."
Please explain how the 11,600 gpm reduction in TDF is obtained. If from reduced j
margins please provide the tabulation of items from where the 11,600 gpm was gained.
Has this reduction of 11,600 gpm been arrived at by a recalculation of analysis codes? If so, please provide the name(s) of the approved code (s) used, i