ML063470029
| ML063470029 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/07/2006 |
| From: | Morris G Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| TAC MD2621, TAC MD2622, TVA-SQN-TS-06-03 | |
| Download: ML063470029 (32) | |
Text
Tennessee Valley Authority, Post Office Box 2000, Soddy-Daisy, Tennessee 37384-2000 December 7, 2006 TVA-SQN-TS-06-03 10 CFR 50.90 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Gentlemen:
In the Matter of ) Docket Nos. 50-327 Tennessee Valley Authority ) 50-328 SEQUOYAH NUCLEAR PLANT (SQN) - UNITS 1 AND 2 - TECHNICAL SPECIFICATIONS (TS) CHANGE 06-03 "ULTIMATE HEAT SINK (UHS)
TEMPERATURE INCREASE AND ELEVATION CHANGES SUPPLEMENTAL INFORMATION" (TAC NOS. MD2621 & MD2622)
Reference:
TVA letter to NRC dated July 12, 2006, "Sequoyah Nuclear Plant (SQN) - Units 1 and 2 - Technical Specifications (TS) Change 06-03 'Ultimate Heat Sink (UHS) Temperature Increase and Elevation Changes'"
Pursuant to 10 CFR 50.90, Tennessee Valley Authority (TVA) submitted the above reference letter to change Licenses DPR-77 and DPR-79 for SQN Units 1 and 2. The referenced TS change was requested primarily to increase the UHS maximum limit and revise the minimum river elevation. The enclosure provides the additional information requested by NRC as discussed in a teleconference held on September 11, 2006, and via email dated October 10, 2006.
Printed on recycled paper
U.S. Nuclear Regulatory Commission Page 2 December 7, 2006 The supplemental information does not change the "No Significant Hazards Considerations" associated with the proposed change in the reference letter.
Additionally, in accordance with 10 CFR 50.91(b) (1), TVA is sending a copy of this letter and enclosure to the Tennessee State Department of Public Health.
There are no commitments contained in this submittal.
If you have any questions about this change, please contact me at 843-7170.
I declare under penalty of perjury that the foregoing is true and correct. Executed on this 7th day of December, 2006.
Sincerely, Glenn W. Morris Manager, Site Licensing and Industry Affairs
Enclosure:
TVA Response to NRC Questions cc: See page 3
U.S. Nuclear Regulatory Commission Page 3 December 7, 2006 Enclosure cc (Enclosure):
Mr. Lawrence E. Nanney, Director Division of Radiological Health Third Floor L&C Annex 401 Church Street Nashville, Tennessee 37243-1532 Mr. Douglas V. Pickett, Senior Project Manager U.S. Nuclear Regulatory Commission Mail Stop 08G-9a One White Flint North 11555 Rockville Pike Rockville, Maryland 20852-2739
ENCLOSURE TENNESSEE VALLEY AUTHORITY (TVA)
SEQUOYAH NUCLEAR PLANT (SQN)
UNITS 1 AND 2 TVA Response to NRC Questions TVA provides the following response to additional information requested by NRC as discussed in a teleconference held on September 11, 2006, and via email dated October 10, 2006.
Questions 1 through 6 reflect TVA's understanding of the questions during the teleconference and questions 7 through 12 were provided by NRC via email.
NRC QUESTION No. 1 Describe the basis for the revised ultimate heat sink (UHS) temperature limit of 87 degree Fahrenheit (°F) with regards to the applicable regulatory position of Regulatory Guide 1.27, "Ultimate Heat Sink."
TVA RESPONSE No. 1 TVA believes that the intent of this request for information (RAI) question is to address changes to meteorological conditions as described in Position 1 of the Regulatory Guide (RG), Revision
- 2. This information was not provided as-part of the July 2006 submittal because it was not required under Revision 0 .of the RG under which SQN was licensed. Meteorological conditions and historical river temperatures are described in the Final Safety Analysis Report (FSAR) Section 2.4.11.1 and were part of the Preliminary Safety Analysis Report (PSAR) Licensing Phase Circa 1976. The initial licensing phase proposed a UHS temperature of 81'F based on historical river temperature information. During initial startup of Unit 1, a new essential raw cooling water (ERCW) lift station was constructed on the bank of the Tennessee River in order to resolve several NRC concerns. A UHS temperature of 83°F was approved by NRC on July 15, 1981, once the new ERCW lift station was completed and placed in service.
Unit 1 began commercial operation on July 1, 1981; Unit 2 began commercial operation on June 1, 1982.
In relation to the current submittal, meteorological conditions have not significantly changed but other external factors that influence river temperatures have changed. TVA is the owner/operator of 49 dams and reservoirs in the Tennessee Valley, including nine projects on the Tennessee River that provide a commercially navigable waterway of 800 miles. SQN is located on one of these Tennessee River Reservoirs (Chickamauga). There are two other main river reservoirs upstream of Chickamauga in addition to numerous tributary projects, all of which provide E1-I
flow regulation for downstream locations, including SQN. TVA River Operations manages these 49 projects as an integrated system, accommodating multiple purposes including navigation, flood control, hydropower generation, water quality and aquatic habitat, recreation, and water supply for municipalities and industries (including thermal power production). TVA recently (2004) completed an extensive study (Final Environmental Impact Statement for the TVA Watershed) and adopted a new reservoir operating policy in response to the changing demands on the reservoir system. Significant changes in the policy as they impact SQN included extending summer reservoir levels on Chickamauga Reservoir until November 1 and adopting a tiered minimum flow regime from June through Labor. Day at the Chickamauga Dam. This requires increasing minimum average weekly flow requirements beginning with 13,000 cubic foot per second (cfs) in early June to 29,000 cfs by August 1 except in the driest of years when the flow requirement is only 25,000 cfs beginning August 1. Winter operating levels were also increased on many of the upstream tributary projects with no significant impact on flood control, but provides more carry-over storage which can help alleviate impacts of droughts.
TVA has determined that 87°F is the practical maximum. river temperature for SQN and is consistent with the environmental limitations (e.g., aquatic and National Pollutant Discharge Elimination System), summer base load needs of the region, and the river system flow requirements that are controlled by Chickamauga Dam. This management scheme provides the best business relationship with TVA's stakeholders (i.e., seven state wide, public, and private sector interest in TVA operations and economic development) while meeting their various demands. The new operating policy has been well received by TVA Valley stakeholders, and has been tested by both abnormally high flows (hurricanes Rita and Katrina in 2005,) and abnormally low flows (spring/summer 2006). Chickamauga Reservoir levels temporarily exceeded the published operating guide levels during high-flow regulation.
TVA plans to update the FSAR to describe the managed river temperature approach as part of the approved TS implementation.
Essentially, TVA has utilized a managed river temperature approach since 1988 when the UHS was increased to 84.5°F. TVA subdocument titled "Monitoring and Moderating Sequoyah Ultimate Heat Sink," within the TVA dam failure analysis document dated 2004, "Updated Predictions of Chickamauga Reservoir Recession Resulting From Postulated Failure of the South Embankment at Chickamauga Dam," describes the managing process. This process will remain intact.
The SQN UHS temperature limit was chosen to be 87°F based on practical limitations at SQN, as discussed in response number 3, as well as the environmental impacts and limitations, as E1-2
mentioned above. The quantity and quality of the 30-day supply of water, as required by the RG 1.27 Regulatory Position 1, is unchanged. The design basis temperature limits of safety-related equipment are not exceeded when operated with the UHS at 87°F and permits the safe shutdown and cooldown of both units. It is also possible to maintain the units in a safe shutdown condition with this proposed UHS temperature.
NRC QUESTION No. 2 Generic Letter (GL) 89-13, "Service Water System Problems Affecting Safety-Related Equipment," was issued to ensure the general design and quality assurance requirements were being met for service water systems. For SQN's 89-13 program describe the method allowed by the program to ensure identified components will perform as required. For those components that are subject to testing, describe to what extent the data is used? For comparison against specific acceptance criteria as well as any analytical analysis, do the results indicate a conservative conclusion?
TVA RESPONSE No. 2 Implementation of the SQN actions to GL 89-13 is provided in Technical Instruction (TI) 0-TI-SXX-000-146.0, "Program for Implementing NRC GL 89-13." The TI work practices, based on the recommendations provided in GL 89-13, assist to ensure compliance with the regulations. SQN has updated its program several times.
NRC was informed of these changes by the following letters:
Browns Ferry (BFN), and Watts Bar (WBN) Nuclear Plants -
Response To Generic Letter (GL) 89-13, Service Water System Problems Affecting Safety-Related Equipment"
- 2. TVA letter to NRC dated October 24, 1990, "Sequoyah Nuclear Plant (SQN) - Revised Program Regarding NRC Generic Letter (GL) 89-13, 'Service Water System Problems Affecting Safety-Related Equipment'"
- 3. TVA letter to NRC dated September 22, 1995, "Sequoyah Nuclear Plant (SQN) - Revised Program and Status Update Regarding NRC Generic Letter (GL) 89 'Service Water System Problems Affecting Safety-Related Equipment'"
The September 1995 letter provides SQN's revised GL 89-13 program subsequent to recommendations from the Service Water System Operational Performance Inspection that was conducted in January and March of 1995. This letter provides the methods SQN employs to ensure identified GL 89-13 components will perform as required. Of particular interest, SQN presents the 1995 letter response to GL 89-13 Recommended Action Item 2 that start with, E1-3
"Conduct a test program to verify the heat transfer capability of all safety-related heat exchangers cooled by service water."
"SQN will maintain a program to verify the heat transfer capability of safety-related heat exchangers cooled by service water. The program consists of test, inspection, and/or maintenance. The program has a performance frequency of at least once every fuel cycle. Performance frequencies may be revised based on results of the periodic inspections after three fuel cycles.starting from the Unit 2 Cycle 4 refueling outage for Unit 2 and the Unit 1 Cycle 5 refueling outage for Unit 1. The trending of thermal performance tests and/or inspections is performed to identify degrading conditions and provide timely corrective actions. The results of SQN'S test/maintenance/inspectionprogram is documented and retained in appropriate plant records. The following is a list of each safety-related heat exchanger by major grouping and the type of program to be used.
A. Component Cooling Heat Exchangers - Thermal performance testing is periodically performed to verify heat transfer capability.
B. Engineered Safety Features (ESF) Room/Area Coolers - SQN has taken temperature measurements on the inlet and outlet piping of the ESF coolers. The temperature differentials across the ESF coolers, coupled with the currently available instrumentation for measuring bulk average air temperature, are insufficient to provide meaningful test data. Consequently, SQN considers testing to be impractical for the ESF coolers. Therefore, periodic maintenance and inspection is performed on the tube side (ERCW) for MIC, clams and mussels, silt, biofouling, and corrosion products, and on the air side for blockage and fouling. Periodic air flow testing is performed on the air side of the coolers to confirm minimum air flow requirements.
C. Lower Containment Vent Cool~rs - SQN has performed a total of 10 thermal performance tests on the lower compartment vent coolers. These tests were performed at shutdown for refueling, during unit start-up from refueling, and after normal cleaning. The inlet air temperature measurements varied as much as 50 degrees Fahrenheit. The margin of pass or fail was such that a 1- to 2-degree variance in average inlet air temperature significantly changed the final results. Consequently, SQN considers testing to be impractical for the lower compartment vent coolers. Periodic maintenance and inspection is performed on the tube side (ERCW) for MIC, E1-4
clams and mussels, silt, biofouling, and corrosion products, and on the air side for blockage and fouling.
Periodic air flow testing is performed on the air side of the coolers to confirm minimum air flow requirements.
D. Containment Spray Heat Exchangers - The shell side (ERCW) of the containment spray heat exchangers is maintained in a chemically controlled lay up condition with demineralized water and a corrosion inhibitor. Periodic monitoring of the water in the shell side of the heat exchangers is performed. Periodic maintenance and inspection is performed on the shell side (ERCW) for MIC, clams and mussels, silt, biofouling, and corrosion products.
E. Diesel Engine Coolers - These heat exchangers are in service typically once every month during regularly scheduled surveillance runs of the diesel generators.
During the monthly surveillance run, diesel engine coolant and lube oil temperatures are evaluated, recorded, and trended. Periodic maintenance and inspection is performed on the tube side (ERCW) for MIC, clams and mussels, silt, biofouling, and corrosion products.
F. Auxiliary Control Air Compressor After-cooler - Periodic maintenance and inspection is performed for MIC, clams and mussels, silt, biofouling, and corrosion products.
G. Condensers for Air-conditioning Packages (i.e., Main Control Room, Shutdown Board Room, Electric Board Room) -
Periodic maintenance and inspection is performed for MIC, clams and mussels, silt, biofouling, protective coating, and corrosion products.
H. Lube Oil Coolers - 1. Centrifugal charging, safety injection, and ERCW pump oil coolers: Oil bearing temperatures are evaluated, recorded, and trended in accordance with ASME Section XI pump tests. Periodic maintenance and inspection is performed for MIC, clams and mussels, silt, biofouling, and corrosion products on centrifugal charging and safety-injection pump oil coolers. 2. Air conditioner packages (i.e., main control room, shutdown board room, and electric board room):
Periodic maintenance and inspection is performed for MIC, clams and mussels, silt, biofouling, protective coatings, and corrosion products.
Safety-related heat exchangers cooled by SON's component cooling system are not included in a test inspection E1-5
program. Inspections were performed on the (component cooling side) of the component cooling heat exchangers, spent fuel pit heat exchangers, and post accident sampling facility sample coolers. The results of these inspections verified no fouling. Present chemistry programs are sufficient to ensure high-water quality for SQN'S component cooling system.
A summary of the program is documented in plant instructions and all testing inspection documentation is retained in appropriate plant records."
As informed in the Referenced 1995 letter and reprinted above, the components that receive routine thermal performance testing are the Component Cooling System (CCS) Heat Exchangers (HXs).
For these plate-type HXs, testing is performed and the results trended on a frequency that will detect fouling issues prior to adverse operability impact. The current testing frequency of CCS Train A HXs is quarterly. The current testing frequency of CCS Train B HXs is each refueling outage. CCS Train A normally supplies cooling for the spent fuel pool (SFP) and miscellaneous loads during plant operations; therefore, sufficient heat load exist for quarterly testing. The CCS Train B HX testing cannot be performed at a greater frequency due to a lack of sufficient heat load for meaningful test results during normal plant operation. However, sufficient heat load for testing the CCS Train B HXs is available when a unit goes on residual heat removal (RHR) shutdown cooling.
Test data is used to determine the CCS HX total fouling factor.
The test fouling factor is then compared against acceptance criteria fouling factor. The acceptance criteria fouling factor is determined using the design heat load, the worst-case actual available accident flow rates, and the TS maximum UHS value. The fouling factor determined from each test is compared to previous test data, and the rate of fouling factor change is observed and projected into the future. The CCS HXs' operability limits have been maintained for nearly 15 years and SQN has become more perceptive of fouling factor changes, such that HX fouling factors are more closely maintained near administrative limits prior to cleaning. Periodic cleaning, based on test results and engineering judgment, is performed to ensure that operability limits are maintained and that the HXs will meet their design function.
NRC QUESTION No. 3 By the analyses to support the proposed submittal, provide a summary of the equipment reviewed and their available cooling margins at 84.5 0 F and the new proposed value of 87°F. What equipment did not meet any marginal thresholds? How was this equipment made capable to performing at 87°F? Please describe E1-6
the elimination of nonessential loads and if this elimination provided for margin to other equipment. Also provide changes in methodology or assumptions in the analyses since 1988.
TVA RESPONSE No. 3 TVA developed calculation MDQ00006720020109, "ERCW System Sensitivity Review For 87 0 F, ESF & HVAC Equipment," to evaluate and compare the performance of the safety-related coolers and HXs at both 84.5 0 F and the proposed 87 0 F. The 1988 UHS basis of 0
84.5 F did not consider nor did it evaluate ERCW flow margins above the required design minimum flow with flow measurement uncertainties. At that time, as long as the minimum ERCW flow (a nominal value) was demonstrated (by testing) to the component or heat exchanger, then the design basis requirement was met.
Since the ERCW system has excess capability, it is reasonable to utilize the available flow to offset an increase in UHS temperature-to the proposed value of 87 0 F. The referenced calculation determines the new design basis minimum flow requirements at 87 0 F. TVA flow models are developed for the various Unit 1 and Unit 2 large break loss-of-coolant accidents (LBLOCAs) conditions to predict what the actual flows will be to each ERCW-supplied component. The flow model is periodically validated by system flow balance test results. The required ERCW flows at 87°F were determined and compared to the modeled available flows under accident conditions with minimum safeguards. Flow measurement uncertainties of 5 percent were subtracted from the predicted flows. The installed flow orifices typically have a flow measurement uncertainty of 3 percent.
Therefore, using a measurement uncertainty of 5 percent is conservative. A flow marginal threshold was set equal to or greater than 1 percent. Instances of equipment having less than 1 percent remaining flow margin were identified for further evaluation to determine their acceptability and adequacy.
The following tables are extracts of Tables 3, 4, 5, 6, 8, and 9 of the abovementioned calculation. These tables provide an example of how the above methodology was applied to ensure available margin and to identify equipment for further analysis; Future revisions of the calculations may be compulsory. For example, as a result of equipment degradation, the margins may be revised to apply specific measurement equipment uncertainties to maintain overall system requirements. Tables 3, 4, 5, 6, and 9 detail the equipment evaluated, the cooling margin based on available ERCW flow, and the equipment which required additional evaluation to support an ERCW temperature increase to 87 0 F.
Table 8 contains the equipment that did not meet the margin threshold and provides additional validation of the equipment performance to ensure adequate operation and acceptability at the elevated ERCW temperature.
E1-7
Acronyms for Tables AFW = AUXILIARY FEEDWATER AUX CONT AIR COMPRESSOR & CLR A BAT = BORIC ACID TRANSFER BD = BOARD CCP = CENTRIFUGAL CHARGING PUMP CCS = COMPONENT COOLING SYSTEM CLR = COOLER COND :CONDENSER CONT = CONTROL CSS = CONTAINMENT SPRAY SYSTEM EDG = EMERGENCY DIESEL GENERATOR EGTS = EMERGENCY GAS TREATMENT SYSTEM ELECT = ELECTRIC HSB = HOT STANDBY, MODE 3 HX = HEAT EXCHANGER LCC = LOWER COMPARTMENT COOLER MCR = MAIN CONTROL ROOM PEN = PENETRATION PMP = PUMP RHR = RESIDUAL HEAT REMOVAL RM = ROOM SSC = Structures, Systems, and Components SFP = SPENT FUEL POOL SIS = SAFETY INJECTION SYSTEM TB = TURBINE BUILDING E1-8
TABLE 3 Extract SSC Evaluations For A Train Unit 1 LOCA and Unit 2 HSB a b d h i j k Design Available Required Margin Percent Detailed Flow Flow Flow Margin Review at Reduced by at 87 0 F at 870 F Required 84.5 0 F 5% at_87°Fa 87°_ Rqure (gpm) (gpm) (gpm) (gpm)
.Equipment 1 =d-h :i/h < 1%
669 PEN RM CLR 1A 13.0 50.4 15.5 34.9 224.9%
669 PEN RM CLR 2A 12.0 60.8 14.2 46.6 327.8%
690 PEN RM CLR 1A 8.25 28.9 9.8 19.2 196.4%
690 PEN RM CLR 2A 7.0 29.8 8.1 21.8 270.5%
714 PEN RM CLR 1A 18.0 28.7 21.8 6.9 31.6%
714 PEN RM CLR 2A 18.0 33.9 21.8 12.1 55.7%
AUX CONT AIR A 4.1 6.0 5.1 0.9 17.6%
BAT & AFW CLR 2A 55.0 73.5 70.1 3.4 4.8%
CCP RM CLR 1A 23.0 45.2 28.4 16.9 59.4%
CCP RM CLR 2A 23.0 51.4 28.4 23.0 81.0%
CCS & AFW CLR 1A 53.1 108.0 59.3 48.7 82.1%
CSS PUMP RM CLR 1A 9.0 25.0 9.9 15.1 151.6%
CSS PUMP RM CLR 2A 9.0 34.6 9.9 24.7 248.5%
EGTS 2A 8.0 14.5 8.8 5.7 65.6%
ELECT BD RM CHR A 136.0 189.8 163.9 26.0 15.8%
MCR CHILLER A. 83.0 130.3 95.4 34.9 36.6%
PIPE CHASE CLR 1A 21.0 60.9 24.2 3697 151.6%
PIPE CHASE CLR 2A 21.0 44.1 24.2 19.9 82.5%
RHR PMP RM CLR 1A 12.0 20.1 14.3 5.8 40.3%
RHR PMP RM CLR 2A 12.0 23.1 14.3 8.7 60.8%
SFP & TBBP CLR 1A 28.5 37.6 33.7 3.9 11.5%
SHUTDOWN BD RM CHR A 330.0 402.3 401.7 0.6 0.1%
SIS OIL CLR 1A 3.1 11.2 4.1 7.1 174.5%
SIS OIL CLR 2A 3.1 13.0 4.1 8.9 218.9%
SIS PMP RM CLR 1A 14.0 32.6 17.0 15.7 92.1%
SIS PMP RM CLR 2A 14.0 33.5 17.0 16.5 97.3%
Note 1 From the 1988 ERCW design basis flow requirements
= YES, See Table 8 E1-9
TABLE 4 Extract SSC Evaluations For B Train Unit 1 LOCA and Unit 2 HSB a b d h i j k Design Available Required Margin Percent Detailed Flow Flow Flow Margin Review at Reduced at 87°F at 87°F Required 84.5°F by 5%
(gpm) (gpm) (gpm) (gpm)
Equipment (Note 1) =d-h =i/h < 1%
669 PEN RM CLR lB 13.0 36.8 15.5 21.3 137.3%
669 PEN RM CLR 2B 12.0 58.7 14.2 44.5 313.2%
690 PEN RM CLR lB 8.3 30.8 9.8 21.1 216.0%
690 PEN RM CLR 2B 7.0 29.6 8.1 21.6 267.9%
714 PEN RM CLR lB 18.0 31.2 21.8 9.4 43.0%
714 PEN RM CLR 2B 18.0 32.5 21.8 10.7 49.3%
AUX CONT AIR B 4.1 6.9 5.1 1.8 36.0%
BAT & AFW CLR 2B 55.0 70.3 70.1 0.2 0.2%
CCP RM CLR 1B 23.0 36.7 28.4 8.3 29.3%
CCP RM CLR 2B 23.0 46.5 28.4 18.2 64.0%
CCS & AFW CLR lB 53.1 95.0 59.3 35.6 60.0%
CSS PUMP RM CLR 1B 9.0 25.5 9.9 15.6 156.6%
CSS PUMP RM CLR 2B 9.0 35.4 9.9 25.5 256.0%
EGTS 2B 8.0 14.2 9.2 5.0 54.6%
ELECT BD RM CHR B 136.0 201.4 163.9' 37.5 22.9%
MCR CHILLER B 83.0 218.2 95.4 122.8 128.8%
PIPE CHASE CLR lB 21.0 39.9 24.2 15.7 65.0%
PIPE CHASE CLR 2B 21.0 51.4 24.2 27.2 112.4%
RHR PMP RM CLR lB 12.0 16.3 14.3 1.9 13.5%
RHR PMP RM CLR 2B 12.0 20.5 14.3 6.2 4361%
SFP & TBBP CLR lB 28.5 34.1 33.8 0.4 1.1%
SHUTDOWN BD RM CHR B 330.0 383.8 401.7 (18.0) -4.5%
SIS OIL CLR lB 3.1 11.4 4.1 7.3 178.2%
SIS OIL CLR 2B 3.1 12.3 4.1 8.2 200.9%
SIS PMP RM CLR lB 14.0 29.0 17.0 12.0 70.3%
SIS PMP RM CLR 2B 14.0 35.4 17.0 18.4 108.4%
Note 1 From the 1988 ERCW design basis flow requirements 4 = YES, See Table 8 EI-10
TABLE 5 Extract SSC Evaluations For A Train. Unit 2 LOCA and Unit 1 HSB a b d h i j k Design Available Required Margin Percent Detailed Flow Flow Flow Margin Review at Reduced at 87°F at 87"F Required 84.5 0 F by 5%
(gpm) (gpm) (gpm) (gpm)
Equipment (Note 1) =d-h =i/h < 1%
669 PEN RM CLR 1A 13.0 50.1 15.5 34.6 222.8%
669 PEN RM CLR 2A 12.0 53.2 14.2 38.9 273.9%
690 PEN RM CLR 1A 8.3 28.7 9.8 19.0 194.5%
690 PEN RM CLR 2A 7.0 26.1 8.1 18.1 224.5%
714 PEN RM CLR 1A 18.0 28.5 21.8 6.7 30.7%
714 PEN RM CLR 2A 18.0 29.7 21.8 7.9 36.3%
AUX CONT AIR A 4.1 5.9 5.1 0.9 16.9%
BAT & AFW CLR 2A 55.0 64.1 70.1 (6.0) -8.6%
CCP RM CLR 1A 23.0 45.0 28.4 16.6 58.4%
CCP RM CLR 2A 23.0 45.1 28.4 16.7 58.8%
CCS & AFW CLR 1A 53.1 107.4 59.3 48.0 80.9%
CSS PUMP RM CLR 1A 9.0 24.9 9.9 14.9 150.1%
CSS PUMP RM CLR 2A 9.0 30.4 9.9 20.4 205.5%
EGTS 2A 8.0 12.7 9.2 3.4 37.4%
ELECT BD RM CHR A 136.0 188.6 163.9 24.8 15.1%
MCR CHILLER A 83.0 129.5 95.4 34.1 35.7%
PIPE CHASE CLR 1A 21.0 60.5 24.2 36.3 150.3%
PIPE CHASE CLR 2A 21.0 *38.7 24.2 14.5 59.8%
RHR PMP RM CLR 1A 12.0 20.0 14.3 5.7 39.4%
RHR PMP RM CLR 2A 12.0 20.2 14.3 5.8 40.8%
SFP & TBBP CLR 1A 28.5 37.4 33.8 3.6 10.7%
SHUTDOWN BD RM CHR A 330.0 400.3 401.7 (1.4) -0.4%
SIS OIL CLR 1A 3.1 11.1 4.1 7.1 172.8%
SIS OIL CLR 2A 3.1 11.3 4.1 7.2 177.5%
SIS PMP RM CLR 1A 14.0 32.5 17.0 15.4 90.8%
SIS PMP RM CLR 2A 14.0 29.4 17.0 12.4 73.0%
Note 1 From the 1988 ERCW design basis, flow requirements
= YES, See Table 8 El-II
TABLE 6 Extract SSC Evaluations For B Train Unit 2 LOCA and Unit 1 HSB a b . d h i j k Design Available Required Percent Detailed Flow Flow Flow Margin Margin Review at Reduced at 87 0 F at 87°F Required 84.5°F by 5%
(gpm) (gpm) (gpm) (gpm)
Equipment (Note 1) =d-h =i/h < 1%
669 PEN RM CLR lB 13.0 39.4 15.5 23.9 153.8%
669 PEN RM CLR 2B 12.0 57.3 14.2 43.1 302.9%
690 PEN RM CLR lB .8.3 33.0 9.8 23.2 237.9%
690 PEN RM CLR 2B 7.0 28.9 8.1 20.9 258.8%
714 PEN RM CLR lB 18.0 33.3 21.8 11.5 53.0%
714 PEN RM CLR 2B 18.0 31.7 21.8 9.9 45.6%
AUX CONT AIR B 4.1 6.7 5.1 1.7 32.6%
BAT & AFW CLR 2B 55.0 68.5 70.1 (1.6) -2.3%
CCP RM CLR lB 23.0 39.2 28.4 10.8 38.1%
CCP RM CLR 2B 23.0 45.4 28.4 17.0 60.0%
CCS & AFW CLR lB 53.1 101.6 59.3 42.2 71.2%
CSS PUMP RM CLR lB 9.0 27.3 9.9 17.3 174.3%
CSS PUMP RM CLR 2B 9.0 34.5 9.9 24.6 247.4%
EGTS 2B 8.0 13.9 9.2 4.7 50.8%
ELECT BD RM CHR B 136.0 215.2 163.9 51.3 31.3%
MCR CHILLER B 83.0 233.2 95.4 137.8 144.4%
PIPE CHASE CLR lB 21.0 42.6 24.2 18.5 76.3%
PIPE CHASE CLR 2B 21.0 50.1 24.2 25.9 107.1%
RHR PMP RM CLR lB 12.0 17.4 14.3 3.1 21.5%
RHR PMP RM CLR 2B 12.0 20.0 14.3 5.7 39.6%
SFP & TBBP CLR lB 28.5 36.5 33.8 2.8 8.2%
SHUTDOWN BD RM CHR B 330.0 374.3 401.7 (27.4) -6.8%
SIS OIL CLR lB 3.1 12.2 4.1 8.1 198.3%
SIS OIL CLR 2B 3.1 12.0 4.1 7.9 193.1%
SIS PMP RM CLR lB 14.0 31.0 17.0 13.9 82.0%
SIS PMP RM CLR 2B 14.0 34.6 17.0 17.6 103.3%
Note 1 From the 1988 ERCW design basis flow requirements
= YES, See Table 8 El-12
TABLE 9 Series Extract Other SSC Evaluations Design Available Required Flow Flow Flow Flow Requirement at at Reduced Reduced at 87°F Met?
84.5°F by 5% See Basis (gpm) (gpm) (gpm) Y/N Calculation Equipment Note 1 SSC Evaluations For A Train Unit 1 LOCA and Unit 2 HSB CcP OIL CLR 1A 21.0 35.2 35.0 Y Note 5 CCP OIL CLR 2A 21.0 43.6 35.0 Y Note 5 CCS HX lAl/IA2 3,380.0 3,671.8 3,605.0 Y Note 6 CCS HX 2A1/2A2 945.0 1,601.8 1,348.0 Y Note 6 CSS HX 1A 3,400.0 3,850.4 3,400.0 Y Note 7 EDG lAl 350.0 444.8 365.0 Y Note 4 EDG 1A2 350.0 444.0 365.0 Y Note 4 EDG 2A1 350.0 486.6 365.0 Y Note 4 EDG 2A2 350.0 503.6 365.0 Y Note 4 SSC Evaluations For B Train Unit 1 LOCA and Unit 2 HSB CCP OIL CLR lB 21.0 37.1 35.0 Y Note 5 CCP OIL CLR 2B 21.0 52.8 35.0 Y Note 5 CCS HX OBI/0B2 945.0 5,285.9 3,365.0 Y Note 6 CSS HX lB 3,400.0 3,792.2 3,400.0 Y Note 7 EDG IBI 350.0 434.3 365.0 Y Note 4 EDG IB2 350.0 430.1 365.0 Y Note 4 EDG 2BI 350.0 464.1 365.0 Y Note 4 EDG 2B2 350.0 450.3 365.0 Y Note 4 SSC Evaluations For A Train Unit 2 LOCA and Unit 1 HSB CCP OIL CLR 1A 21.0 35.0 35.0 Y Note 5 CCP OIL CLR 2A 21.0 38.2 35.0 Y Note 5 CCS HX 1Al/IA2 945.0 2,449.2 1,348.0 Y Note 6 CCS HX 2A1/2A2 3,380.0 3,929.6 3,605.0 Y Note 6 CSS HX 2A 3,400.0 3,678.2 3,400.0 Y Note 7 EDG lAl 350.0 431.5 365.0 Y Note 4 EDG 1A2 350.0 430.7 365.0 Y Note 4 EDG 2A1 350.0 472.0 365.0 Y Note 4 EDG 2A2 350.0 488.3 365.0 Y Note 4 SSC Evaluations For B Train Unit 2 LOCA and Unit 1 HSB CCP OIL CLR lB 21.0 39.7 35.0 Y Note 5 CCP OIL CLR 2B 21.0 51.5 35.0 Y Note 5 CCS HX 0B1/0B2 2,850.0 5,184.5 3,365.0 Y Note 6 CSS HX 2B 3,400.0 3,630.6 3,400.0 Y Note 7 EDG IBI 350.0 443.2 365.0 Y Note 4 EDG 1B2 350.0 438.9 365.0 Y Note 4 EDG 2B1 350.0 473.4 365.0 Y Note 4 EDG 2B2 350.0 459.3 365.0 Y Note 4 El-13
TABLE 9 Series Extract (continued)
Other SSC Evaluations Design Available Required Flow Flow Flow Flow Requirement at Reduced at 87°F Met? See Basis 84.5°F by 5%
(gpm) (gpm) (gpm) Y/N Calculation Equipment Note 1 SSC Evaluations For A Train Unit 1 MSLB and Unit 2 HSB LCC lAA 200.0 1 304.5 1 200.0 Y Note 8 LCC lCA 200.0 1 272.7 200.0 Y Note 8 SSC Evaluations For B Train Unit 1 MSLB and Unit 2 HSB ILCC IBB 200.0 1 195.3 1 200.0 Y Note 9 LCC 1DB 200.0 258.9 200.0 Y Note 8 SSC Evaluations For A Train Unit 2 MSLB and Unit 1 HSB LCC 2AA 200.0 241.1 200.0 Y Note 8 LCC 2CA 200.0 202.2 200.0 Y Note 8 SSC Evaluations For B Train Unit 2 MSLB and Unit 1 HSB LCC 2BB 200.0 240.9 200.0 Y Note 8 JLCC 2DB 200.0 1302.5 1200.0 1 Y INote 8 Extracted Table Notes:
Note 1 - From 1988 ERCW design basis flow requirements Note 4 - See detailed thermal EDG evaluation MDQ 000 067 2003 0142 Note 5 - See detailed oil cooler evaluation SQN MEB KED53 0 HCG TBG 072682.
35 gpm = 23 gpm lube oil cooler + 12 gpm gear oil cooler.
Note 6 - Flows at 670 Elevation. See detailed HX evaluation 70D53 0 HCGKBO 102287 and 70D53 EPMMCG 021290 Note 7 - See WCAP-12455 Rl Supplement 1R, Containment Integrity Re-analyses Engineering Report Note 8 - The LCC's design basis requires that for main steam line break (MSLB) 2 of 4 coolers operate with 200 gpm ERCW to each cooler and with 50,000 cubic feet per minute (cfm) air delivery from each cooler. At these conditions, the two coolers remove a total of approximately 3.5 MBTU/hr. which is greater than the required 2.8 MBTU/hr.
Note 9 - This LCC was evaluated at 192 gpm (24 gpm/coil) which is less than the minimum case of 195.3 gpm. It was determined that adequate heat removal is obtained for MSLB by two coolers at 192 gpm. At these conditions, the two coolers remove a total of approximately 3.4 MBTU/hr. which is greater than the required 2.8 MBTU/hr.
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TABLE 8 Extract Component evaluations details Required New Reqire Test Standard Margin ERCW EQ Determined LOCA Flow Flow at Over Min. Note Exit °F Temp Room Case Flow Equipment (Cpm) (gpm) 87°F (gpm) Increase Limit 'F Temp 'F
_____ (gpm)
BAT & AFW CLR 2B UIB 70.3 6.3 2A U2A 55.0, 64.1 64.0 0.1 1 +1 117 117.3 2B U2B 68.5 4.5 SDOWN BD RM CHR A UlA 402.3 72.3 CHR B UlB 383.8 53.8 330.0 330.0 2 0 NA NA CHR A U2A 400.3 70.3 CHR B U2B 374.3 44.3 Extracted Table Notes:
Note 1 The worst-case modeled ERCW flow (64 gpm) had the lowest flow value.
The other flow cases were greater. Base requirements are contained in design input. A Proto-HX evaluation is contained in the calculation.
Minimum design air cfm was also increased from 13,048 cfm to 14,000 cfm. Design heat removal requirement is 318,722 BTU/hr and was met at 87'F with fouling factors of .001 (air side & water side) including a 10% performance factor reduction. The resulting room temperature of 117.3°F is just 0.3°F above the established equipment qualification (EQ) limit. This is a very small temperature overage and it is not considered an EQ program change because the required heat load, fouling factors, degraded performance factor are conservatively determined. The 0.3°F increase has no significant impact on the overall EQ because the HVAC design methodology assumes that the UHS temperature will not remain at that maximum for the entire 100 days but will follow the seasonal rise and fall of the ambient profile.
The 1°F ERCW temperature increase (from 96.1°F to 97.0°F) is well below the 130'F design limit. DCN D21523 evaluates the Op Mode (Civil piping) impacts, if any.
Note 2 The minimum flow value for 91'F is established in calculation SQN031DO53EPMPJMII0493. Performance is conservatively based on the Electric Boardroom Condenser, and the SDBR Condenser has 15% more tubes for the same size vessel. Based on the values presented, 374 gpm is much greater than 330 gpm required.
Discussion of Table 8 Results Components *that had less than 1 percent flow margin for each of the various ERCW train conditions (limiting LOCA) are the shutdown board room (SDBR) chillers A and B and the Auxiliary Building coolers (BAT and AFW CLR 2A and 2B).
The available flow test flow values have been compared to the established limits in existing component design calculations.
For the Auxiliary Building coolers, the worst-case modeled ERCW flow is approximately 64 gallon per minute (gpm.) The other flow cases were greater. The minimum design air flow rate was increased from 13,048 cubic feet per minute (cfm) to 14,000 cfm for the BAT and AFW coolers. The design heat removal requirement of 318,722 BTU/hr is met at 87°F with fouling factors of .001 (air side & water side), including a 10 percent performance factor reduction. The resulting room temperature of 117.3 0 F is 0.3 0 F above the established EQ El-15
limit. This is a very small temperature overage and is not considered an EQ program change because the required heat load, fouling factors, degraded performance factor are conservatively determined. Also, the 0.3°F increase has no significant impact on the overall EQ because the heating, ventilating, and air conditioning (HVAC) design methodology assumes that the UHS temperature will not remain at that maximum for the entire 100 days but will follow the season rise and fall of the ambient profile. ERCW cooler discharge temperature is increased by 1IF (from 96.1°F to 97.0°F) which is insignificant and is below the 130'F piping design limit.
For the SDBR chillers, the cooling requirements are met at 87 0 F with margin at the ERCW flow rates. For example, at 87 0 F, the lowest ERCW test flow (after 5 percent flow uncertainty reduction) is 374,gpm for Unit 2 SDBR Chiller B. The chiller design calculation requires 330 gpm ERCW flow at 91°F for the basis heat load removal. This demonstrates a 44 gpm ERCW flow margin and a 4°F temperature margin for SDBR Chiller B.
Additional margin exists for SDBR Chiller A. Moreover, the chiller HXs physically have 15 percent more tubes (heat exchange area) than that evaluated in the calculation thus yielding additional uncredited capacity.
By this license amendment request (LAR), SQN has not proposed to eliminate any of the ERCW-supplied essential loads to retain margin during normal or accident plant conditions. SQN is planning to eliminate the nonessential control air compressors that are located in the Turbine Building. See response to question 9 for additional information.
The 1988 methodology that encompassed letting the UHS temperature increase from 83°F to 84.5 0 F allowed a general cascade effect throughout all the ERCW components. By this, TVA raised the ERCW inlet temperatures from 83°F to 84.5°F and allowed the resulting temperature increase at the outlet and downstream components.
The resulting exit water temperatures increased and that resulted in impacts on containment analysis, EQ (10 CFR 50.49) due to temperature profile shifts, and piping analysis revisions. The 2006 methodology eliminates the cascading effects by applying known and demonstrated ERCW flow margins to each component and calculating each individual component impact. Other assumption and methodology changes were integrated in the July 2006 submittal.
El-16
NRC QUESTION No. 4 In regards to the loss-of-downstream-dam event, what margins, if any, have been applied in your calculations? Why has the breach size been reduced?
TVA RESPONSE No. 4 A new and updated dam break analysis and resulting drawdown was performed in regards to General Design Criterion 44 of Appendix A to 10 CFR Part 50, "General Design Criteria for Nuclear POwer Plants," to show suitable redundancy in features provided for the cooling water system to assure that its safety function can be accomplished. This analysis was performed by TVA and is titled, "Updated Predictions of Chickamauga Reservoir Recession Resulting From Postulated Failure of the South Embankment at Chickamauga Dam." It is intended that the new dam break analysis will become the new basis for drawdown at SQN. Additional margins are created based on reduction in breach size and various margins are adjusted for tailwater discharge changes; however, the analysis initial river elevation of 670 feet (ft) and the long-term river elevation of 639 ft for loss of downstream dam are not changed.
The extended drawdown time is not credited for long-term-cooling, but is recognized for its relationship to the limiting design basis LOCA. ERCW flow to the CCS HX and the CSS HX are the only components flow balanced at a river level of 670 ft. All other ERCW-supplied components are balanced to a lake level of 639 ft.
ERCW flow rates for long-term cooling are established at a river elevation of 639 ft. No credit is taken for the extended drawdown on any design basis calculation.
The analysis concluded that experiential data for earthen filled dams produces a likely breach size (400 ft) that is significantly smaller than the basis used in the 1988 LAR (1000 ft). The reference "Prediction of Embankment Dam Breach Parameters," US Department of Interior 1998 (DSO 98 004), was the basis for re-estimating the breach size. Four different empirical relationships provided four different estimates of breach width; two were smaller than the 400 ft, one about the same as 400 ft, and one larger than 400 ft. None of these four estimators produced a breach width as large as 1000 ft. An additional discussion about conservatism in the hydraulic analyses will be more fully presented in response to NRC questions by letter to TVA dated November 22, 2006.
El-17
NRC QUESTION No. 5 Clarify why the river elevation of 639 ft is used in this submittal as compared to an elevation of 636 ft in the 1988 submittal.
TVA RESPONSE No. 5 The 636 ft elevation is related to the original sediment limit established for the ERCW intake pumping station's (IPS's) 100 foot wide approach channel. In 1993 and 1994, TVA established a new maximum sediment accumulation elevation at 635 ft which was based on operating experience data obtained from periodically monitoring and dredging of the ERCW intake channel. Variations and irregularities in the bottom contour were considered. The resulting Minimum required lake level following a loss of downstream dam (LODD) was 639 ft to ensure negligible sediment uptake into the ERCW. A river elevation of 639 ft is achieved by releasing a rate of water at 14,000 cfs through the Watts Bar Dam (upstream) about 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> after the dam breach (FSAR 2.4.11, "Low Water Considerations"). The analysis recession curves show that the predicted long-term river elevation to be 641 ft at the IPS, which is above the required 639 ft long-term minimum. The value of 639 ft is used as the low river analysis value and is referenced in TS Bases 3/4.7.5 as well as various FSAR sections.
A release rate of water at 14,000 cfs can be maintained through the Watts Bar Dam for 100 days following the LODD.
NRC QUESTION No. 6 Need additional discussion of the licensing basis of the spent fuel pool cooling.
TVA RESPONSE No. 6 The SQN spent fuel pit cooling and cleanup system (SFPCCS) is discussed in FSAR Section 9.1.3. The SFPCCS consists of two seismic Category I cooling trains, a purification loop, and a surface skimmer loop. Each train is equipped with one heat exchanger and one pump. A third pump is provided to serve as a backup to the pump of either train. The SFPCCS is analyzed to provide cooling for a bounding heat load of 45.3 MBTU/hr and 183°F as the maximum bulk water temperature in the SFP with only one train of SFPCCS operating following an unplanned core offload. Typical operations for a 'refueling outage discharge include limiting the heat load to 45 MBTU/hr with cooling provided by the nonoutage unit's CCS. For offloading the core, a specific decay heat analysis is developed to determine the acceptable point in time that the core offloading activities may commence without exceeding the design basis maximum allowable heat load (45.3 MBTU/hr) . This method ensures that the maximum SFP water temperature will not exceed 183°F if one train is out El-18
of service. In addition to the normal operation, SQN received approval from NRC on September 30, 2002, by letter titled "Sequoyah Nuclear Plant, Units 1 and 2 - Issuance of Amendments Regarding Technical Specification Change No. 00-06 (TAC NOS.
MB2972 and MB2973) (TSC 00-06)," to provide an alternative SFP cooling methodology that would increase the allowable SFP heat load to 55 MBTU/hr. This method takes credit for actual, rather than conservative, values to calculate thermal balances of the SFP such as lower CCS cooling water temperatures (i.e., less than 95°F,) and lower SFP heat exchange fouling factors.
In the event of an accident, such as loss of offsite power (LOOP) with a safety injection (SI), operating conditions include transferring the SFP cooling load to the nonaccident unit following the event. This action is directed by emergency operating procedures.
NRC QUESTION No. 7 On page El-15 of the submittal dated July 12, 2006, reference 8 is used in calculations, which is the recent dam break analysis at L=400 feet. The submittal indicates that four hours of cooling are available starting at a river elevation 674 feet before the level reaches 670 feet. The analysis credits these four hours to get to hot shutdown. The LCO (Limiting Condition for Operation) allows 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> to place the unit in hot shutdown, whereas the analysis indicates that only four hours are available before the river decreases below the level upon which design flows were established. "For equipment related to containment integrity . . . the ERCW (Essential Raw Cooling Water) system are balanced to a system configuration with the ERCW pumps operating at river elevation of 670 feet." Ref: El-11-12.
"For the remainder of the engineered safety feature (ESF) equipment tied to the ERCW system, that is needed long term following an accident, the system is balanced to the long-term river elevation of 639 feet." Ref: El-12.
The insert that was provided from the 1988 submittal states: "The time-independent heat loads (ESF room coolers, etc.) are balanced assuming a reservoir level of elevation 636." Ref; page 10.
The dam break analysis states that "TVA's 1988 computations used a south embankment bottom elevation of 630 ft-msl, and no compelling reasons emerged during this analysis to alter this assumption." Charts show a variety of different bottom levels based upon Watts Bar discharge.
a) Please confirm whether or not TVA is taking credit for the new dam break analysis. If credit is being taken, please provide appropriate justification and supporting analysis for El-19
NRC review. Also, discuss the impact that dam failure will have on the capability to achieve and maintain safe shutdown conditions consistent with existing Technical Specification LCO limitations that have been established.
b) This submittal credits a long term minimum river water level of 639 feet, whereas the previous studies used 636 feet.
Please explain the basis for this change and discuss any adverse impact that this will have on plant operation.
TVA RESPONSE No. 7 a) TVA's new and updated dam break analysis is the new basis record. The created margins are not credited for safe shutdown. The chart in the submittal provided a reference point of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> above 670 ft elevation for the limiting design condition which is the LBLOCA. A LODD is assumed concurrent with the LBLOCA. Under accident conditions, minimum safeguards and minimum ERCW capability (i.e., two pumps) is sufficient to remove the required accident and residual heat loads (i.e., LOOP and loss of an EDG train).
The bulk of the heat resulting from a LBLOCA is bounded within one hour and then proceeds to long-term cooling. The graph on page El-15, of the July 2006 letter, related timing of the LBLOCA conditions to that needed for long-term cooling just for the limiting accident and was not intended to be referenced for a nonaccident safe shutdown. Short-term (1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />) ERCW cooling loads (i.e., CCS and CSS HXs,) are' balanced assuming the river elevation is 670 feet and is conservative.
In contrast, for a LODD event and no accident, a dual unit safe shutdown would be required by TSs due to low UHS level.
Both units would be placed into hot standby (HSB), with subsequent cooldown of each unit to cold shutdown (CSD). SQN is licensed although, as a HSB plant for its safe shutdown design basis (NUREG-1232, "Safety Evaluation Report on Tennessee Valley Authority: Sequoyah Nuclear Performance Plan"). As such, the CCS is sized so that only one unit can be cooled down by RHR shutdown cooling at a time without overwhelming the CCS and ERCW at the CCS HXs. The other unit would, by system design, remain .at HSB until RHR shutdown cooling can be place in service. However, other available equipment (e.g., atmospheric relief valves) could be used to continue cooldown from HSB. The CCS HX outlet temperature design limits are 120OF for HSD, 104.5 0 F for LOCA recirculation, and 95 0 F for HSB.
TVA complies with the requirements of the TS shutdown times of 6 and 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> on the first unit. This is possible because the change in lake level to the minimum elevation 639 ft, resulting in an approximate 7 percent ERCW flow El-20
reduction, can be compensated by starting additional ERCW pumps, if needed. All ERCW pumps are assumed available for safe shutdown under the LODD event without other accident conditions. By this discussion, with offsite power.
available, all eight pumps are available for operation. As stated above, the 7 percent flow difference can be compensated for by starting ERCW pumps, if necessary.
Therefore, there is sufficient ERCW flow capacity to meet the cooldown requirements.
The basis pertaining to the 670 ft river elevation sets the ERCW system flow balance point for minimum safeguards (two ERCW pumps) at the CCS HXs for accident conditions. To this end, the river elevation is not a controlling factor for nonaccident safe shutdowns; however, the capacity (size) and limitations of the CCS components limit the capability to obtain cold shutdown for the second unit resulting in time potentially exceeding the required 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. However, other available equipment would be used to continue cooldown from HSB to comply with TSs. The CCS and ERCW are monitored to ensure that the design limits are not exceeded as the total heat load is managed.
As a result of the updated dam break model, no other TS changes are required and no other LCO's are impacted to achieve and maintain safe shutdown conditions.
b) Please see TVA Response No. 5 for the change in river elevation. There are no adverse impacts to plant operations as a result of this change.
The long-term minimum river elevation following a LODD utilized by TVA SQN for analysis purposes at the intake structure is 639 ft and is based on Tennessee River channel flows and assuming a 14,000 cfs discharge from Watts Bar Dam.
Current river modeling under these conditions actually produces a river water elevation of 641 ft at the SQN IPS, although this higher elevation is not credited.
NRC QUESTION No. 8 Page El-17 of the July 12, 2006 submittal, under Piping Impacts, states that "The evaluation showed the CCS (Component Cooling System) and ERCW do not exceed any piping design temperature limit."
However, on page 118 of the calculation, "SQN-CCS Plate Heat Exchangers OBI & OB2 Train B ERCW Flow Requirements," in the Summary of Results and Discussion, it states that "These cases
[8,15,33,34,35,36,37,38,39,40] show that at the design ERCW temperature of 87 degrees F, and the restraints on the CCS System El-21
Temperatures leaving the CCS HX (95, 104.5, 120 degrees F) the high heat loads cannot be removed by the OBI/OB2 pair of plate heat exchangers (PHEs) without exceeding CCS piping temperature limitations of 145 degrees F." Similarly, page 201 of this calculation states that "These cases show that at the design ERCW temperature of 87 degrees F, and the restraints on the CCS System temperatures leaving the CCS HX (95,104.5,120'F), the high heat loads cannot be removed by the lAl/1A2 or 2A1/2A2 pair of PHEs without exceeding the CCS piping temperature limitations of 145 0 F."
Also, page El-17 of the July 12 submittal states that "The auxiliary feed water pumps (AFWPs) are supplied by the ERCW following a switchover [from] the non-safety related condensate storage tanks (CSTs)." The criterion is to cooldown the RCS (Reactor Coolant System) to hot shutdown conditions within eight hours.
a) Please explain and justify the apparent discrepancies that exist between the information that was provided in the July 12, 2006, amendment request and the supporting calculation that is referred to above, including a complete description of any operator actions that will be credited and the time that i. available to complete these actions.
b) Please describe the impact that the proposed increase in the UHS temperature limit will have on AFW system temperature and how this compares with AFW system design limitations. Also, please describe any operator actions that will be credited and the time that is available for completing these actions.
c) Please discuss what impact the proposed temperature increase will have on the capability of the AFW system to perform its specified functions.
TVA RESPONSE No. 8 a) The design basis calculation "SQN-CCS Plate Heat Exchangers OBI & OB2 Train B ERCW Flow Requirements," evaluates the thermal performance of the HXs under various heat load conditions. The cases [8, 15, 33, 34, 35, 36, 37, 38, 39, and 40] demonstrate the equipment is capable of transferring these heat loads from the RHR HX. However, in some of these conditions, the CCS piping design temperature (RHR HX exit) of 145°F can be exceeded. Therefore, heat removal rate is controlled by regulating primary coolant and CCS flow through the RHR HXs. This method is used to ensure that the CCS piping temperature is not exceeded. Procedural controls for this practice are contained in Operation's procedure 0-SO-74-I, "Residual Heat Removal System," and is captured in Section 3.0, "Precautions and Limitations" by the following El-22
statement, "RHR HX CCS outlet temperature shall not exceed 145 0 F due to limitations on piping and support analyses.
(Ref: 47W859-4) CCS flow rate or RHR flow rate through the RHR HX shall be adjusted as necessary to meet this limitation." In regards to the CCS Train A HXs cases on page 201 of thecalculation, these cases are outside of design basis of the ERCW System. However, similar actions to those above, could be taken to limit the heat removal rate so~that the CCS piping design temperature of 145°F is not exceeded.
This practice is described in Section 5.3.2, "Residual Heat Removal System," of NUREG-0011. The actions required to maintain CCS outlet temperature are part of the normal process of placing RHR in service, which involves various operator actions. The proposed change does not result in new procedure requirement(s) for placing RHR in service.
For additional information, see FSAR 9.2.2, "Essential Raw Cooling Water" and FSAR 3.1, "Conformance with NRC General Design Criteria."
b) The AFW system is designed to deliver feedwater from the preferred water source (i.e., the condensate storage tank
[CST]); the ERCW system (i.e., qualified source); or in a flood above plant grade, the fire protection system can be connected downstream the motor-driven AFW pumps to supply raw water to the steam generators. The flood above plant grade requires manual operator actions to align the fire protection system to AFW.
The design operating temperature range for the AFW system is 40°F to 120 0 F. There are no impacts to the AFW system because the proposed ERCW temperature increase is within the existing design limits of the AFW system. Further discussion of the AFW can be found in FSAR Section 10.4.7, "Condensate -
Feedwater System." SQN's Operations department. has established procedures for manuallyswapping feed from the CST to ERCW, if necessary. Swap-over from CST to ERCW is also accomplished automatically on low AFW suction pressure.
c) The proposed temperature increase will not have a negative impact on the AFW system functional requirements to remove primary system stored and residual core energy following a loss of main feedwater. SQN submitted and received approval of an LAR to increase the usable volume of the Units 1 and 2 CST's for plant cooldown for new Unit. 1 steam generators in 2002. As part of this change, revised analysis assumptions were used to determine the volume of water necessary to support plant cooldown. One of these assumptions included the use of a higher AFW temperature of 120 0 F. The proposed UHS temperature increase will not have a negative impact on the AFW system functional requirements to remove primary El-23
system stored and residual core energy following a loss of main feedwater. The UHS temperature increase has no.new impact on AFW capability or its functions. AFW system has always been bounded by the CST upper temperature and the ERCW lower temperature. The ERCW feed to the turbine driven AFW pump originates for the ERCW supply header and may be as low as 35°F were as the motor driven pumps receive ERCW feed originates from the ERCW discharge header and may be as high 0
as 126 F.
NRC QUESTION No. 9 The cover page for the mini-calc for ERCW flow states that "This mini-calc revises the parent calculation to fully open certain manual throttle valves and isolate the station air compressors by closing valves O-FCV-67-205 and O-FCV-67-208. . . . some of these valves must be open for ERCW system to meet the minimum required design flows at the ultimate heat sink temperature of 87 degrees F."
The licensee discusses the process for isolating the station air compressors under DCN D21523. On page El-18 & 19 of the July 12 submittal, the report mentions that the Control Room AC chillers are supplied by ERCW. The analysis indicates that s§ufficient flow is maintained by eliminating non-safety related station air compressor loads in the turbine building.
a) Please clarify if the "certain manual throttle valves" will be permanently maintained in the open position or if other manual or automatic actions will be required to achieve the necessary alignment.
b) Please discuss how the proper positioning of the "certain manual throttle valves" will be assured, such as through changes to alignment and surveillance procedures and use of locking mechanisms.
c) Please discuss how isolation of ERCW flow to the station air compressors will be accomplished, including single active failure considerations, operator actions that will be relied upon, and the time that is available for operators to complete these actions.
TVA RESPONSE No. 9 a) ERCW small-bore manually-set throttle/balancing valves in the Auxiliary Building (except for valves 1-67-680 & 2-67-680 to the auxiliary control air compressors) have been fully opened to increase overall ERCW flows. Overall, ERCW flow gains were achieved and ERCW Multiflow modeling confirmed the effectiveness of the change. The governing procedure has El-24
been revised to ensure the position of the manual valves is controlled. The affected throttle valves have been repositioned.
b) The positions of the "certain manual throttle valves" in the Auxiliary Building, with the above noted exceptions, have been changed to full open. The ERCW valve positions are controlled by their respective system operating procedures.
SQN TS Limiting Condition for Operation 3.7.4, "Essential Raw Cooling Water," contains a surveillance requirement to ensure the proper valve positioning.
c) Under the current limiting design basis LOCA, ERCW at 84.5 0 F with a concurrent seismic event, operators are required to identify and isolate an ERCW pipe break in the nonseismic turbine building header to the station air compressors (SACs). By the proposed ERCW change to 87 0 F, ERCW flow will be normally isolated to the Turbine Building. The mentioned design change, DCN 21523, will change the normal position of the ERCW isolation valves to the SACs to be closed. These existing valves are located in the Auxiliary Building and are seismically qualified. This new configuration eliminates an Operator action following a seismic event. In addition, it is anticipated that electrical power will be removed from the motor operators (Train A and Train B) to preclude any negative effects of a single active valve failure or spurious operation. Cooling water to the SACs is nonessential and will be provided by the raw cooling water system in the Turbine Building. The design change will include ERCW as a manually aligned back up supply to the SACs.
NRC QUESTION No. 10 Page El-Il of the July 12 submittal states: "The evaluation credited the excess ERCW flow rates to ensure that the existing heat loads and discharge temperatures are maintained." It also states: "... the UHS increase is offset by an increase in the cooling water supply for ESF room coolers."
In the calculation, "ERCW System Calculation Review for 87 Degrees F, ESF & HVAC Equipment," Table 7 summarizes the cases where there is less than 1 percent margin. The ERCW sensitivity study shows the required flow for "A" train Unit 2 LOCA and Unit 1 HSB (Hot Standby) to the BAT (Boric Acid Tank) & AFW CLR 2A does not satisfy the flow requirement of 70.1 gpm. Available flow was only 67.5 gpm, and 5% reduced flow was 64.1 gpm. Table 8 shows worst case modeled ERCW flow at 64 gpm, which resulted in a temperature of 117.3 degrees F, 0.3 degrees above the EQ limit.
To achieve this result the minimum designed air flow was increased from 13,048 cfm to 14,000 cfm.
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Please explain how the increased air flow was achieved, and how this capability will continue to be assured over time.
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TVA RESPONSE No. 10 The existing air flow is greater than 14,000 cfm. TVA is using some of the available flow margin and by design calculation showing that the required demonstrated heat removal capability is met. The change, involves increasing the existing design minimum air flow requirement from 13,048 cfm to 14,000 cfm for 87°F.
Periodic Instruction 0-PI-SFT-030-755.0, "Equipment Cooler Operability Test," performs periodic assessment of this fan. The last two performances of the surveillance showed 14,265 cfm and 14,733 cfm. Should the surveillance value be less than design, a degraded condition would exist that requires a functional evaluation, coil cleaning, or repair/replacement in accordance with the Corrective Action Program. Flow measurements are taken using calibrated Measuring and Test Equipment (M&TE). Air flow measurement uncertainties are not typically considered in thermal calculations; however, for these coolers, a 10 percent performance reduction is utilized in establishing the design thermal performance minimum requirements.
NRC QUESTION No. 11 On page 202 of the calculation, "SQN-CCS Plate Heat Exchangers Train 1A/2A ERCW Flow Requirements," the ERCW flow rate was increased from 3455 gpm (Table 85) to 4670 (Table 88) to compensate for an increase in heat exchanger fouling from 0.0003 to 0.001 hr-ft2 °F/Btu. The calculation concluded that if approximately 1250 gpm flow margin exists in the ERCW flow to the PHE heat exchanger pair, then fouling up to 0.001 can be tolerated.
In the calculation, "Emergency Diesel Generator (EDG) ERCW Heat Exchanger Evaluation for 87 degrees F;" assumption 4.4 states that "Design and actual calculated fouling factors are used.
Fouling factors of 0.0013 and up to 0.0016 are reasonable for river water (based on GL-89-13 inspections and SQN history for these heat exchangers per discussion with the SQN System Engineer." Section 6.10 Proto-HX Model #3, shows the required flow for EDG coolers with 5% tube plugging is 425. gpm.
Actual surveillance test data for the Watts Bar plant shows that the overall fouling resistance can reach approximately 0.00214 hr-ft 2 °F/Btu. In the EDG calculation, design fouling factors of
.0013 hr-ft 2 °F/Btu and actual of .0016 hr-ft 2 °F/Btu are used as reasonable values. Watts Barr uses .014 hr-ft2 oF/Btu for the tube side fouling resulting in an overall fouling of .00216 hr-ft2 °F/Btu. Using TEMA recommendations, fouling can reach
.003372 hr-ft2 0F/Btu.
Since both Watts Bar and Sequoyah have the same UHS, it would appear reasonable that Sequoyah can experience the same degree of El-27
fouling of their heat exchangers as does Watts Bar. Describe how the fouling resistances were determined for the Sequoyah application, including measures that will be taken to assure that the assumed maximum value will not be exceeded.
TVA RESPONSE No. 11 Various different fouling factors are utilized at SQN based on actual experienced values seen at the various components since these components are different and they operate under different local conditions between SQN and WBN. Specifically, SQN has CCS plate heat exchangers that operate incontinuous, high velocity, turbulent service. These were supplied with a very low design fouling factor based on the original equipment manufacturer's extensive operating experience worldwide. WBN does not have CCS plate heat exchangers but rather shell and tube heat exchangers with different operating characteristics. The SQN HXs are in pairs with the capability to be cleaned online or plates added or replaced. As stated in response to other RAI questions, the plate HXs are monitored and trended for fouling factors and these are projected to ensure that actual fouling factor limits will not be exceeded. The calculation design values establish the expected operating normal basis.
The SQN EDG HXs are a two-pass tube and shell HX, where as WBN has a single pass. SQN performs visual inspections of the tubes under GL-89-13, but monitors and trends EDG operations on a frequent basis. Tube cleaning has typically not been required for SQN. A EDG thermal performance calculation was specially prepared to support the 87 0 F TS change. The calculation was based on data from a periodic instruction to determine the cooling capacity of the HXs. Actual fouling factors were conservatively determined using Proto-HX modeling software and documented in calculation MDQ00006720030142, "Emergency Diesel Generator (EDG) Heat Exchanger Evaluation for 87 0 F."
The established EDG HX design fouling factor is greater than the actual measured values and it is believed to be reasonable for this application.
The basis for the SQN fouling factors have been justified for use based on actual operating conditions and experience. The Tubular Exchanger Manufacturers Association, Inc. (TEMA) industrial standards and values were considered during the design evaluations (calculations). No additional design validation testing is planned to be performed now or in the future.
NRC QUESTION No. 12 On page El-18 of the submittal letter dated July 12, 2006, it states: "Uncertainties in the ERCW.flow rates have been incorporated into the engineering analysis." Page El-24 states; EI-28
"A temperature averaging scheme (reference 2) has been part of the SQN licensing basis and has been applied since 1988 as delineated in the 1988 SER." The 1998 submittal on page 10 under Surveillance Requirements to "TVA has proposed to keep the current SR 4.7.5 for the water temperature."
Please describe how the uncertainties in UHS temperature monitoring are accounted for to assure conservative results.
TVA RESPONSE No. 12 TVA has used nominal temperature values in its UHS monitoring for compliance with the surveillance requirement since original licensing of the units. The safety significance of this practice in ERCW was originally addressed in Standard TS, Section 3.0, Technical Specification Limits Generically Acceptable Tolerances, issued October 1, 1978. As such, measurement of the UHS temperature was obtained using the best industrial device available at the time and no inaccuracies were applied to the value since this was neither a reactor protection nor an engineering safety feature setpoint. However, in the spring of 2003, the validity of using a nominal temperature value for the UHS as a safety limit was entered into the SQN Corrective Action Program for evaluation. This LAR is one of the corrective actions determined appropriate during the evaluation.
For the 87°F TS submittal, TVA has conservatively applied loop measurement uncertainties to the UHS temperature surveillance requirement. The existing platinum resistance temperature detector (RTD) measurement devices have a loop uncertainty of
+1.160 F. The plant instrument may be replaced at a future date to further reduce the measurement uncertainties. Portable M&TE is commercially available for this application with uncertainties as low as 0.1°F.
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