ML16207A577: Difference between revisions

From kanterella
Jump to navigation Jump to search
(Created page by program invented by StriderTol)
(Created page by program invented by StriderTol)
Line 17: Line 17:


=Text=
=Text=
{{#Wiki_filter: STPEGS UFSAR    Q&R 2.1-1 Revision 13 Question 312.16  You imply that the public will use your heavy-haul road to obtain access to the public launch facilities at the end of this road. Please clarify this point. If the public is to use this road, also discuss your provisions for access control during routine operations and emergencies. Response  Section 2.1.1.2 no longer contains the implication that the heavy haul road will be used for access to public launch facilities located on the site. HL&P no longer intends public launch facilities to be available on the site. For these reasons, provisions for public access control, beyond that described in the STPEGS Security Plan, are not necessary.
{{#Wiki_filter:STPEGS UFSAR    Q&R 2.1-1 Revision 13 Question 312.16  You imply that the public will use your heavy-haul road to obtain access to the public launch facilities at the end of this road. Please clarify this point. If the public is to use this road, also discuss your provisions for access control during routine operations and emergencies. Response  Section 2.1.1.2 no longer contains the implication that the heavy haul road will be used for access to public launch facilities located on the site. HL&P no longer intends public launch facilities to be available on the site. For these reasons, provisions for public access control, beyond that described in the STPEGS Security Plan, are not necessary.
STPEGS UFSAR    Q&R 2.2-1 Revision 13  Question 312.1  Regarding the possible purchase of property near the north boundary of the STPEGS site for industrial development, provide an estimate of the distance of the development to the nearest plant safety-related structure and discuss the planned size of the development, the type of industry most likely to locate there, and any zoning or other restrictions which might apply. Response  Contacts with the property owners, Union Carbide and Dow Chemical, indicate that no definite plans for the property are available and the owners will not speculate on possible development options at this time.
STPEGS UFSAR    Q&R 2.2-1 Revision 13  Question 312.1  Regarding the possible purchase of property near the north boundary of the STPEGS site for industrial development, provide an estimate of the distance of the development to the nearest plant safety-related structure and discuss the planned size of the development, the type of industry most likely to locate there, and any zoning or other restrictions which might apply. Response  Contacts with the property owners, Union Carbide and Dow Chemical, indicate that no definite plans for the property are available and the owners will not speculate on possible development options at this time.
STPEGS UFSAR    Q&R 2.3-1 Revision 13  Question 372.1  The data period for determination of tornado frequencies (discussed on pages 2.3-3 and 2.3-4 of the FSAR) ended in 1972. Identify tornadoes that have occurred in the vicinity of the site since 1972, and provide estimates of the maximum wind speeds (based on observed structural damage), path lengths, and path areas. Response  In the period January 1973 through June 1978 a total of 24 tornadoes were reported within a 50-mile radius of the STPEGS site, an average of 4.36 tornadoes per year (NOAA, 1978). Six complete reports of path lengths and widths were available and the average computed tornado path area for the data period was 0.0725 square miles. Most of the incomplete or missing reports implied "short and narrow" tornado path dimensions. Wind speeds of 72 mph, and over 100 mph, were reported, but no severe-damage reports were documented for the 5.5 year period. Section 2.3 has been amended to incorporate the recent data. The Table Q372.1-1 sumarizes the data for the January 1973 through June 1978 period.  
STPEGS UFSAR    Q&R 2.3-1 Revision 13  Question 372.1  The data period for determination of tornado frequencies (discussed on pages 2.3-3 and 2.3-4 of the FSAR) ended in 1972. Identify tornadoes that have occurred in the vicinity of the site since 1972, and provide estimates of the maximum wind speeds (based on observed structural damage), path lengths, and path areas. Response  In the period January 1973 through June 1978 a total of 24 tornadoes were reported within a 50-mile radius of the STPEGS site, an average of 4.36 tornadoes per year (NOAA, 1978). Six complete reports of path lengths and widths were available and the average computed tornado path area for the data period was 0.0725 square miles. Most of the incomplete or missing reports implied "short and narrow" tornado path dimensions. Wind speeds of 72 mph, and over 100 mph, were reported, but no severe-damage reports were documented for the 5.5 year period. Section 2.3 has been amended to incorporate the recent data. The Table Q372.1-1 sumarizes the data for the January 1973 through June 1978 period.  
Line 54: Line 54:
Based on comparisons of Victoria data and of available STPEGS onsite data, it is concluded that the Victoria data for the period February 14, 1953, to January 1, 1956, are representative of long-term conditions and that Victoria data are representative of the four years of onsite STPEGS data. It is therefore concluded that the three years of Victoria data used by the Cooling Reservoir Fog Predictor (CRFP) model are representative of long-term conditions expected at the STPEGS site.   
Based on comparisons of Victoria data and of available STPEGS onsite data, it is concluded that the Victoria data for the period February 14, 1953, to January 1, 1956, are representative of long-term conditions and that Victoria data are representative of the four years of onsite STPEGS data. It is therefore concluded that the three years of Victoria data used by the Cooling Reservoir Fog Predictor (CRFP) model are representative of long-term conditions expected at the STPEGS site.   
(2) The CRFP model, as described in Section 2.3 of the UFSAR, inputs National Weather Service (NWS) observations of wind speed, wind direction, dry bulb temperature, wet bulb temperature, and cloud cover for use in calculations of the dissipation of heat from the thermally loaded reservoir and of the formation of elevated visible plumes and ground-level fog. In addition, solar and longwave radiant energy are STPEGS UFSAR  Q&R 2.3-11 Revision 13  Response (Continued)  calculated for each time period. The solar radiation term is calculated from an algorithm based upon the latitude of the reservoir, day of year, time of day, and cloud cover. The longwave radiant fluxes are calculated from the pond surface temperature and meteorological data including cloud cover. The onsite meteorological data set contains all parameters necessary for analyses of the Cooling Reservoir except for cloud cover, which would be required in the longwave radiation calculations. However, there are other factors influencing solar radiation received at the ground, such as atmospheric particulates and fog.
(2) The CRFP model, as described in Section 2.3 of the UFSAR, inputs National Weather Service (NWS) observations of wind speed, wind direction, dry bulb temperature, wet bulb temperature, and cloud cover for use in calculations of the dissipation of heat from the thermally loaded reservoir and of the formation of elevated visible plumes and ground-level fog. In addition, solar and longwave radiant energy are STPEGS UFSAR  Q&R 2.3-11 Revision 13  Response (Continued)  calculated for each time period. The solar radiation term is calculated from an algorithm based upon the latitude of the reservoir, day of year, time of day, and cloud cover. The longwave radiant fluxes are calculated from the pond surface temperature and meteorological data including cloud cover. The onsite meteorological data set contains all parameters necessary for analyses of the Cooling Reservoir except for cloud cover, which would be required in the longwave radiation calculations. However, there are other factors influencing solar radiation received at the ground, such as atmospheric particulates and fog.
References  1. Updated Final Safety Analysis Report - South Texas Project Units 1 & 2,  Vol. 2, Docket Nos. STN 50-498 and STN 50-499.
References  1. Updated Final Safety Analysis Report - South Texas Project Units 1 & 2,  Vol. 2, Docket Nos. STN 50-498 and STN 50-499.  
2. Turner, D. Bruce, "A Diffusion Model for an Urban Area", J. App. Meteorol., Vol. 3, No.1 (February 1964), pp.83-91.
: 2. Turner, D. Bruce, "A Diffusion Model for an Urban Area", J. App. Meteorol., Vol. 3, No.1 (February 1964), pp.83-91.
STPEGS UFSAR  Q&R 2.3-12 Revision 13  TABLE Q372.7-1  MONTHLY AND ANNUAL AVERAGE WIND SPEED  AT VICTORIA, TEXAS, FOR THREE PERIODS OF RECORD    (mph)
STPEGS UFSAR  Q&R 2.3-12 Revision 13  TABLE Q372.7-1  MONTHLY AND ANNUAL AVERAGE WIND SPEED  AT VICTORIA, TEXAS, FOR THREE PERIODS OF RECORD    (mph)
Period of Record      Month February 14, 1953 to January 31, 1956 July 21, 1973 to September 30, 1977 January 1, 1968 to December 31, 1977    January 11.2 10.2 10.5 February 12.0 11.1 10.9 March 11.5 12.4 11.9  
Period of Record      Month February 14, 1953 to January 31, 1956 July 21, 1973 to September 30, 1977 January 1, 1968 to December 31, 1977    January 11.2 10.2 10.5 February 12.0 11.1 10.9 March 11.5 12.4 11.9  
Line 173: Line 173:


Autumn -6.8 -13.5 9.8 -0.8 5.8 -0.9 -0.3 A large annual decrease (8.8 percent)(1) is observed in the frequency of very low wind speeds from the earlier to the later period. The majority of the decrease can be attributed to a decrease in the frequency of calms (6.0 percent).(2)  Also, it should be noted that there was a corresponding increase in the 4-6 knot frequency class, suggesting the lowest frequencies were "shifted" up one class. This shift of wind speed may have occurred as a result of different techniques in reporting calms or from changing to an anemometer with a lower threshold speed.   
Autumn -6.8 -13.5 9.8 -0.8 5.8 -0.9 -0.3 A large annual decrease (8.8 percent)(1) is observed in the frequency of very low wind speeds from the earlier to the later period. The majority of the decrease can be attributed to a decrease in the frequency of calms (6.0 percent).(2)  Also, it should be noted that there was a corresponding increase in the 4-6 knot frequency class, suggesting the lowest frequencies were "shifted" up one class. This shift of wind speed may have occurred as a result of different techniques in reporting calms or from changing to an anemometer with a lower threshold speed.   
 
: 1. A threefold decrease between the earlier and later periods. 2. A twofold decrease between the earlier and later periods.
1. A threefold decrease between the earlier and later periods. 2. A twofold decrease between the earlier and later periods.
STPEGS UFSAR    Q&R 2.3-42 Revision 13  Response (Continued)  Examination of the station history revealed that the Air Force operated the Victoria station during the earlier period and that it was turned over to the National Weather Service in 1961. Mr. Steve Doty of the National Climatic Center stated to us that, although it would be very difficult to document, he has found that Air Force stations tend to report a higher percentage of calms than do comparable National Weather Service stations.   
STPEGS UFSAR    Q&R 2.3-42 Revision 13  Response (Continued)  Examination of the station history revealed that the Air Force operated the Victoria station during the earlier period and that it was turned over to the National Weather Service in 1961. Mr. Steve Doty of the National Climatic Center stated to us that, although it would be very difficult to document, he has found that Air Force stations tend to report a higher percentage of calms than do comparable National Weather Service stations.   
: 3. Meteorological Differences Between the Two Periods - Finally, in order to determine if the changes in the frequencies of stable conditions were produced by real changes in the meteorology, a longer period of record from Victoria(3) was examined. Although the frequency distribution did not separate stability classes F and G, the percentages of low wind speeds can be compared to those of the two other data periods. The frequencies of wind speed classes for each of the data periods are shown in Table 2, below. Table 2 Wind Speed Class (Knots)  Period Calm    0-3  4-6      7-10  11-16 17-21      >21  9/53-8/58 (Earlier, 5 yr)  8.7    16.2 22.3    33.4    20.1  6.2      1.7 7/73-6/77 (Later, 5 yr) 2.7    7.4 32.4    30.8    23.0  5.4      1.1 1/65-1/74 (Longer, 10 yr) 2.8    7.0 30.4    32.2    24.2  5.2      1.0  As can be seen, the later period (7/73-6/77) corresponds very closely with the longer period of record. Conclusions - The investigation suggests that the shift of very stable conditions (G) to moderately stable conditions (F) from the earlier data period to the later period is a result of fewer calm conditions being reported during the later period. The decrease in calm conditions could be real or the result of changes in techniques and/or instruments used in determining wind speed; the evidence presented indicates the latter. Moreover, whether the differences are real meteorological changes or not, the later period is considered to be more representative of Victoria's climate because of its similarity to the longer 10-year record. 3. January 1965 through December 1974 period (three-hourly observations).
: 3. Meteorological Differences Between the Two Periods - Finally, in order to determine if the changes in the frequencies of stable conditions were produced by real changes in the meteorology, a longer period of record from Victoria(3) was examined. Although the frequency distribution did not separate stability classes F and G, the percentages of low wind speeds can be compared to those of the two other data periods. The frequencies of wind speed classes for each of the data periods are shown in Table 2, below. Table 2 Wind Speed Class (Knots)  Period Calm    0-3  4-6      7-10  11-16 17-21      >21  9/53-8/58 (Earlier, 5 yr)  8.7    16.2 22.3    33.4    20.1  6.2      1.7 7/73-6/77 (Later, 5 yr) 2.7    7.4 32.4    30.8    23.0  5.4      1.1 1/65-1/74 (Longer, 10 yr) 2.8    7.0 30.4    32.2    24.2  5.2      1.0  As can be seen, the later period (7/73-6/77) corresponds very closely with the longer period of record. Conclusions - The investigation suggests that the shift of very stable conditions (G) to moderately stable conditions (F) from the earlier data period to the later period is a result of fewer calm conditions being reported during the later period. The decrease in calm conditions could be real or the result of changes in techniques and/or instruments used in determining wind speed; the evidence presented indicates the latter. Moreover, whether the differences are real meteorological changes or not, the later period is considered to be more representative of Victoria's climate because of its similarity to the longer 10-year record. 3. January 1965 through December 1974 period (three-hourly observations).
Line 348: Line 347:
Response  FSAR Figure 2.5.C-25 has been developed as requested by the NRC. The figure shows the subsidence within the plant area as contours superimposed on piezometric decline contours. Although Question 361.10 addresses decline since 1973, the 1975 data obtained from plant area piezometers are more applicable. The 1973 groundwater data were obtained from other less site-sensitive sources. It is also important that the subsidence and groundwater data are derived for the same time period. The drawdown contours presented on Figure 2.5.C-25 reflect a bias due to the regional cycle of pumping and rebound. The January sampling period falls within a portion of the rebound cycle of the aquifer. The magnitude of the rebound cycle varies from year to year due to variations in the amount of pumping during the late fall of the previous year. The southwesterly trend of apparent differential drawdown at the site for this sampling period reflects a temporary late pumping cycle northwest of the site in the fall of 1978 and drawdown due to pumping of a site well (approximately 7000 ft southeast of the plant area) used for construction purposes. The interpreted subsidence contours reflect a regional subsidence of about 1.00 to 1.25 inches over the monitoring period (approximately three years). The net subsidence in the plant area has been less, due to heave associated with the construction excavation and rebound of the shallow aquifer due to rewatering. The interpretation of the regional near-surface subsidence monitoring is further addressed in UFSAR Section 2.5.C.5.5.2. It is evident that the construction activities have had overriding effects on the near-surface subsidence monitoring observations, in particular at monuments I, H, F, G, J, and L. These activities include heave caused by plant area excavation and other more local activities such as Cooling Reservoir embankment construction, material stockpiles, ECP, and ECP pipeline excavations. It is anticipated that the above identified monuments will continue to show deviating behavior due to ongoing plant construction, reservoir filling, and return of groundwater conditions to a natural state. The subsidence has not had any recognizable effects on the heave/settlement behavior of the plant structures as described in FSAR Section 2.5.C.4.5.
Response  FSAR Figure 2.5.C-25 has been developed as requested by the NRC. The figure shows the subsidence within the plant area as contours superimposed on piezometric decline contours. Although Question 361.10 addresses decline since 1973, the 1975 data obtained from plant area piezometers are more applicable. The 1973 groundwater data were obtained from other less site-sensitive sources. It is also important that the subsidence and groundwater data are derived for the same time period. The drawdown contours presented on Figure 2.5.C-25 reflect a bias due to the regional cycle of pumping and rebound. The January sampling period falls within a portion of the rebound cycle of the aquifer. The magnitude of the rebound cycle varies from year to year due to variations in the amount of pumping during the late fall of the previous year. The southwesterly trend of apparent differential drawdown at the site for this sampling period reflects a temporary late pumping cycle northwest of the site in the fall of 1978 and drawdown due to pumping of a site well (approximately 7000 ft southeast of the plant area) used for construction purposes. The interpreted subsidence contours reflect a regional subsidence of about 1.00 to 1.25 inches over the monitoring period (approximately three years). The net subsidence in the plant area has been less, due to heave associated with the construction excavation and rebound of the shallow aquifer due to rewatering. The interpretation of the regional near-surface subsidence monitoring is further addressed in UFSAR Section 2.5.C.5.5.2. It is evident that the construction activities have had overriding effects on the near-surface subsidence monitoring observations, in particular at monuments I, H, F, G, J, and L. These activities include heave caused by plant area excavation and other more local activities such as Cooling Reservoir embankment construction, material stockpiles, ECP, and ECP pipeline excavations. It is anticipated that the above identified monuments will continue to show deviating behavior due to ongoing plant construction, reservoir filling, and return of groundwater conditions to a natural state. The subsidence has not had any recognizable effects on the heave/settlement behavior of the plant structures as described in FSAR Section 2.5.C.4.5.
STPEGS UFSAR    Q&R 2.5-34 Revision 13  Question 361.12  The Cambe Geological Service Map No. T-7, provided in response to Request No. 361.1, indicates an additional site well not shown on PSAR Figure 2.5.1-32. This previously unidentified well (Robbins No. 1) is located approximately one mile east of Well No. 16 (PSAR Figure 2.5.1-32). Provide all pertinent data relative to the Robbins No. 1 Well. Revise appropriate portions of the FSAR accordingly.
STPEGS UFSAR    Q&R 2.5-34 Revision 13  Question 361.12  The Cambe Geological Service Map No. T-7, provided in response to Request No. 361.1, indicates an additional site well not shown on PSAR Figure 2.5.1-32. This previously unidentified well (Robbins No. 1) is located approximately one mile east of Well No. 16 (PSAR Figure 2.5.1-32). Provide all pertinent data relative to the Robbins No. 1 Well. Revise appropriate portions of the FSAR accordingly.
Response  The well identified as Robbins No. 1 represents a location registered with the Texas Railroad Commission. However, the well was never drilled and the location should be classified as abandoned.  
Response  The well identified as Robbins No. 1 represents a location registered with the Texas Railroad Commission. However, the well was never drilled and the location should be classified as abandoned.}}
}}

Revision as of 07:19, 19 May 2018

South Texas, Units 1 and 2, Revision 18 to Updated Safety Analysis Report, Q&R 2.1-1 Through Q&R 2.5-34
ML16207A577
Person / Time
Site: South Texas  STP Nuclear Operating Company icon.png
Issue date: 04/28/2016
From:
South Texas
To:
Office of Nuclear Reactor Regulation
Shared Package
ML16207A547 List: ... further results
References
NOC-AE-16003371
Download: ML16207A577 (89)
v • d • e


Text

STPEGS UFSAR Q&R 2.1-1 Revision 13 Question 312.16 You imply that the public will use your heavy-haul road to obtain access to the public launch facilities at the end of this road. Please clarify this point. If the public is to use this road, also discuss your provisions for access control during routine operations and emergencies. Response Section 2.1.1.2 no longer contains the implication that the heavy haul road will be used for access to public launch facilities located on the site. HL&P no longer intends public launch facilities to be available on the site. For these reasons, provisions for public access control, beyond that described in the STPEGS Security Plan, are not necessary.

STPEGS UFSAR Q&R 2.2-1 Revision 13 Question 312.1 Regarding the possible purchase of property near the north boundary of the STPEGS site for industrial development, provide an estimate of the distance of the development to the nearest plant safety-related structure and discuss the planned size of the development, the type of industry most likely to locate there, and any zoning or other restrictions which might apply. Response Contacts with the property owners, Union Carbide and Dow Chemical, indicate that no definite plans for the property are available and the owners will not speculate on possible development options at this time.

STPEGS UFSAR Q&R 2.3-1 Revision 13 Question 372.1 The data period for determination of tornado frequencies (discussed on pages 2.3-3 and 2.3-4 of the FSAR) ended in 1972. Identify tornadoes that have occurred in the vicinity of the site since 1972, and provide estimates of the maximum wind speeds (based on observed structural damage), path lengths, and path areas. Response In the period January 1973 through June 1978 a total of 24 tornadoes were reported within a 50-mile radius of the STPEGS site, an average of 4.36 tornadoes per year (NOAA, 1978). Six complete reports of path lengths and widths were available and the average computed tornado path area for the data period was 0.0725 square miles. Most of the incomplete or missing reports implied "short and narrow" tornado path dimensions. Wind speeds of 72 mph, and over 100 mph, were reported, but no severe-damage reports were documented for the 5.5 year period. Section 2.3 has been amended to incorporate the recent data. The Table Q372.1-1 sumarizes the data for the January 1973 through June 1978 period.

STPEGS UFSAR Q&R 2.3-2 Revision 13 TABLE Q372.1-1 TORNADO DATA FROM NOAA "STORM DATA" (PERIOD OF RECORD JANUARY 1973 THROUGH JUNE 1978)

No.

Place/County Date Path Length (mi) Path Width (yd) Path Area (mi2) Property Damage ($)

Comments 1. Brazoria County June 5, 1973 2 50 0.057 0 Tornado observed on ground 10 miles NE of Freeport. Area was open marsh so no damage occurred. 2. Garwood Colorado County June 13, 1973 Short Narrow - 0 Duration was short, several trees uprooted but no property damage occurred. 3. Hillje Wharton County June 13, 1973 7 Narrow - $500 to $5000 Tornado touched ground briefly uprooting trees and knocking one home from its foundation. The funnel lifted and moved HE and was sighted 3 mi NE of El Campo. 4. Calhoun County June 13, 1983 8 Narrow - $500 to $5000 The tornado was first reported on the ground on a ranch near Green Lake. It lifted as it moved NNE, then touched down briefly near Kamey, damaging a mobile home. 5. Ganado Jackson County April 30, 1974 1 ? - $50 to $500 Tornado damaged trailer, loud roaring noise. 6. Angleton Brazoria County September 13, 1974 ? ? - 0 Tornado touched down briefly about 10 miles north of Angleton. No visible signs were found in area. 7. Midfield Matagorda County September 28, 1974 ? ? - 0 Tornado was observed to touch ground briefly. No damage reports were received. 8. Sargent Matagorda County June 25, 1975 ? ? - 0 Tornado reported near Sargent. No damage over marshland. 9. Freeport Brazoria County June 27, 1975 ? ? - $50 to $500 Tornado touched down briefly near Surfside; minor damage. 10. Victoria Victoria County May 27, 1975 ? ? - 0 72 mph winds and pea-size hail were reported. Several unconfirmed reports of tornadoes were reported. No reported damage.

STPEGS UFSAR Q&R 2.3-3 Revision 13 TABLE Q372.1-1 (Continued) TORNADO DATA FROM NOAA "STORM DATA" (PERIOD OF RECORD JANUARY 1973 THROUGH JUNE 1978)

No. Place/County Date Path Length (mi) Path Width (yd) Path Area (mi2) Property Damage ($)

Comments 11. Victoria Victoria County October 15, 1975 ? ? - $50 to $500 Tornado reported 3 miles east of Victoria Victoria County Airport, moving south at 15 mph. Some minor damage to a few buildings. 12. Middle and Upper Texas Coast December 24, 1975 1 440 0.250 $3500 A line of thunderstorms with one tornado moved rapidly southeastward off Texas Coast. Funnel cloud touched down 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> 2 miles south of Ganado, Jackson county, damaging house and trailer. 13. Matagorda County August 3, 1975 ? ? - 0 Tornado reported 10 miles west of Matagorda. No damage reported. 14. Victoria Victoria County August 4, 1975 ? ? - 0 Tornado 10 miles SE of Victoria moving NW. No reported damage. 15. Telfener Victoria County and Edna Jackson County May 7, 1976 6 30 0.102 $5000 to $50,000 First signed as a funnel over downtown Victoria moving NE.

Touched down briefly between Telfener and Inez. Touched down again SE of Edna and moved toward Ganado for approximately 6 miles. 16. Pierce Wharton County July 14, 1976 Short Narrow - 0 Tornado touched down 15 miles SE of Pierce. 17. Richmond Fort Bend County September 2, 1976 ? ? - 0 Touched down briefly in an isolated area. 18. Alvin Brazoria County September 26, 1976 1/2 20 0.006 0 Moved from SW to NE. Touched down south of Alvin moving NE and lifted off ground 1/4 mile east of Alvin. 19. Bay City Matagorda County September 26, 1976 1/2 20 0.006 $5000 to $50,000 Funnel touched down briefly and damaged fences, outbuildings and windows. 20. College Park Matagorda County April 16, 1977 Short Narrow - 0 Funnel cloud touched down briefly near College Park.

STPEGS UFSAR Q&R 2.3-4 Revision 13 TABLE Q372.1-1 (Continued) TORNADO DATA FROM NOAA "STORM DATA" (PERIOD OF RECORD JANUARY 1973 THROUGH JUNE 1978)

No. Place/County Date Path Length (mi) Path Width (yd) Path Area (mi2) Property Damage ($)

Comments 21. Wadsworth Matagorda County September 10, 1977 ? ? - 0 Funnel cloud touched down briefly in open country. 22. El Campo Hungerford Wharton County November 8, 1977 ? 150 - $500 to $5000 A tornado from a fast moving thunderstorm touched down south of El Campo. El Campo airport registered over 100 mph winds at the time. 23. East Bernard Wharton County December 13, 1977 1/2 50 0.014 $50,000 to $5,000,000 Tornado touched down on outskirts of East Bernard. House was moved 20 ft from foundation. A 50 ft x 30 ft metal shed destroyed, damaging farm machinery inside the shed. 24. South Ganado Jackson County April 22, 1978 Short 20 - $5000 to $50,000 One barn destroyed, power lines broken, numerous trees uprooted, severely damaged crops in area.

STPEGS UFSAR Q&R 2.3-5 Revision 13 Question 372.3 Recent operating experience has identified various failures of systems from freezing temperature. Identify the design basis maximum and minimum air temperature (including frequency and duration) considered in the designs of systems and components such as heating and air conditioning systems, impulse lines, service water valves, steam isolation valves, etc. Also discuss the designs of systems and components with respect to combinations of phenomena such as moisture buildup coincident with freezing temperature.

Response The STPEGS HVAC design basis maximum and minimum outside ambient air temperatures are 95F and 29F, respectively. These design conditions are based on ASHRAE data.* Plant systems and components are protected from the effects of freezing temperatures by the following means:

1. Components are located in buildings or structure where the HVAC systems maintain the building environment above freezing temperatures by means of duct or unit heaters (refer to Section 9.4). Such components include, but are not limited to the main steam isolation valves (located in the MSIV structure) and the essential cooling water (ECW) pumps, strainers, and certain valves (located in the ECW intake structure), or 2. Components are located below ground (e.g., buried ECW piping), or
3. Certain components, such as instrument lines, which are directly exposed to potentially freezing conditions, are heat traced and insulated.

Another example of system design to prevent failures due to freezing conditions is illustrated in the Instrument Air System. As discussed in Section 9.3.1.2.2, the dual-tower, no-heat regenerative dryers for the Instrument Air System provide air at a design dew point of (-)40F thus precluding the possibility of condensation and subsequent freezing.

  • American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc., ASHRAE Handbook & Produce Directory - 1972 Fundamentals, N.Y., (1972).

STPEGS UFSAR Q&R 2.3-6 Revision 13 Question 372.4 The valves of solar radiation presented in FSAR Table 2.3-22 appear to be incorrect. The maximum daily solar radiation available in the area of the site at the beginning of July is about 975 cal. cm-2, which is equivalent to about 3600 Btu. ft-2. The daily solar radiation amounts presented in Table 2.3-22 exceed the maximum daily solar radiation available by over a factor of two, and exceed the average daily solar radiation for San Antonio in July by a factor of three. Clarify the solar radiation data used for preparation of Table 2.3-22, and discuss the effect of using incorrect solar radiation data in the calculation of minimum water cooling for the ultimate heat sink.

Response The values in Table 2.3-22 resulted from an assumption that the maximum hourly value occurs for the entire 24-hr period rather than from summing hourly values for each day. The effect of using higher solar radiation values would result in higher equilibrium temperature, resulting in higher pond temperatures. The use of higher solar radiation results in a conservative calculation of minimum water cooling for the ultimate heat sink.

STPEGS UFSAR Q&R 2.3-7 Revision 13 Question 372.5 Identify the dates of initiation and completion of the filling of the cooling reservoir, and the program proposed to examine possible effects of the reservoir on local meteorological conditions (e.g., fogging, icing, temperature, and humidity).

Response The cooling reservoir water level is currently being maintained at 28.0 MSL. During August 1985, filling operations will be initiated to raise the water level to 35.0 MSL. Subsequent filling operations have not been scheduled.

The response to Q372.6 discusses the status of programs related to predicting reservoir impacts on local meteorological conditions.

STPEGS UFSAR Q&R 2.3-8 Revision 13 Question 372.6 Indicate if a monitoring program for occurrences of fog at the STPEGS site has been operation or if such a program is planned for operation to confirm the estimates of increased fogging and icing resulting from the cooling reservoir.

Response As discussed in Section 5.1.5.1 of the STPEGS Environmental Report-Construction Permit Stage (ER-CP), approximately one-third of the land occupied by the STPEGS cooling reservoir was used in rice farming each year and was therefore flooded from March through October. Thus, it is expected that the increase in low visibility fogging occurrences from the cooling reservoir will be minimal and localized to the immediate lake vicinity where only very lightly travelled transportation routes might be briefly affected. However, calculations were made using the CRFP fogging model with meteorology from Victoria which has been shown to be representative of the site. The CRFP model has been verified (see ER-CP Section 6.1.3.2.3) using data gathered from studies performed at Dresden Nuclear Power Station in Illinois and Four Corners Power Plant in Arizona. Because the assessment of measured fogging at the STPEGS site has been performed using a twice verified model, there are no plans to assess the onsite occurrence during operation of fog of the cooling reservoir by performing a comprehensive onsite study.

STPEGS UFSAR Q&R 2.3-9 Revision 13 Question 372.7 FSAR Section 2.3.2.2 indicates that 3 years (February 1953 - January 1956) of meteorological data from Victoria, Texas, were used to provide estimates of increased frequency of fog resulting from operation of the cooling reservior.

1. Discuss the representativeness of the 3 years of Victoria data with respect to long-term conditions expected at the STPEGS site.
2. Four years (July 21, 1973, through September 30, 1977) of onsite meteorological data, including solar radiation information, are now available. Discuss utilization of these high-quality onsite meteorological data in the modeling of predicted impacts resulting from operation of the cooling reservoir. Response (1) Ten years of data, from January 1, 1968, through December 31, 1977, for Victoria, Texas, were used to determine the representativeness of the three-year period of Victoria data (February 1953 through January 1956) used in the analysis of fog potential related to the STPEGS Cooling Reservoir. Comparisons were also made to STPEGS data collected onsite as presented in Section 2.3 of the STPEGS UFSAR (Ref. 1). The conclusion of this study is that the February 1953 to January 1956 data used in the fog predictor model are representative of long-term conditions at the STPEGS site. Presented in Figures Q372.7-1, Q372.7-2, and Q372.7-3 are annual wind roses for Victoria, Texas for three time periods: February 14, 1953, to January 31, 1956; July 21, 1973, to September 30, 1977; and January 1, 1968, to December 31, 1977, respectively. Figure Q372.7-1 is based on the data period used in the fog predictor model; Figure Q372.7-2 based on the concurrent data period with the onsite STPEGS data presented in Section 2.3 of the UFSAR; and Figure Q372.7-3 represents a 10-year long-term average. Agreement between the three periods of record is good. Winds occur most frequently from the south for the long-term and site-concurrent periods (Figures Q372.7-2 and Q372.7-3) and from the south-southeast for the 1953-1956 period (Figure Q372.7-1). Calms occurred with a frequency of 2.46 percent for the site-concurrent period, and 6.67 percent for the period used in the fog study. The high frequency of calms recorded at Victoria as compared to the STPEGS onsite data (0.28 percent) is the result of the relatively high-threshold wind instruments at Victoria. From Figures Q372.7-2 and Q372.7-3 it is concluded that the wind data for the July 21, 1973, to September 30, 1977, period coinciding with the STPEGS onsite program are representative of long-term conditions. Comparison of Figure Q372.7-1 with the STPEGS wind rose for July 21, 1973, to September 30, 1977, (Figure Q372.7-4) yields to the conclusion that the Victoria wind data used in the fog predictor model are representative of the STPEGS site region. The annual average wind speed at Victoria was 9.6 mph for the February 14, 1953, to January 31, 1956, period compared to 10.7 mph at STPEGS for the July 21, 1973, to July 20, 1977, period. Monthly and STPEGS UFSAR Q&R 2.3-10 Revision 13 Response (Continued) annual average wind speeds for the three periods of Victoria data are presented in Table Q372.7-1. Presented in Table Q372.7-2 are monthly and annual averages of ambient temperature and dewpoint temperature for the three peiods of Victoria data (February 14, 1953, to January 31, 1956; July 21, 1973, to September 30, 1977; and January 1, 1968, to December 31, 1977) and for the STPEGS onsite data (July 21, 1973, to July 20, 1977). Agreement between average ambient temperatures and dewpoint temperatures for both sites is good, as presented in Table Q372.7-2. The differences are slightly cooler temperatures and higher dewpoints at the STPEGS site, because it is closer to the coast of the Gulf of Mexico than is Victoria.

Table Q372.7-3 presents monthly and annual values of average daily maximum and minimum temperatures and average diurnal temperature ranges for the three periods of Victoria data. Temperatures are slightly warmer and the diurnal range slightly larger for the 1953 to 1956 period than for the later periods. The monthly and annual stability class frequency distributions for Victoria are presented in Table Q372.7-4 for the three periods discussed in previous sections. For comparison, STPEGS annual stability class distributions are presented in Table Q372.7-5, which contains the information provided in Table 2.3-13 of the STPEGS UFSAR for the period July 21, 1973, to September 30, 1977. Differences between offsite and onsite distributions can be attributed to the different methods of stability classification. The stability distributions determined from Victoria data are based on the Pasquill-Turner approach (Ref. 2), which involves utilization of factors such as cloud cover, isolation, time of day, and wind speed to determine the stability class. The stability distribution determined from STPEGS data is based on the measured vertical temperature gradient, and classified in accordance with Regulatory Guide 1.23. Table Q372.7-4 shows that the Victoria data for the site-concurrent period are representative of long-term conditions. On an annual basis the occurrences of all stability classes are similar for each of the three periods.

Based on comparisons of Victoria data and of available STPEGS onsite data, it is concluded that the Victoria data for the period February 14, 1953, to January 1, 1956, are representative of long-term conditions and that Victoria data are representative of the four years of onsite STPEGS data. It is therefore concluded that the three years of Victoria data used by the Cooling Reservoir Fog Predictor (CRFP) model are representative of long-term conditions expected at the STPEGS site.

(2) The CRFP model, as described in Section 2.3 of the UFSAR, inputs National Weather Service (NWS) observations of wind speed, wind direction, dry bulb temperature, wet bulb temperature, and cloud cover for use in calculations of the dissipation of heat from the thermally loaded reservoir and of the formation of elevated visible plumes and ground-level fog. In addition, solar and longwave radiant energy are STPEGS UFSAR Q&R 2.3-11 Revision 13 Response (Continued) calculated for each time period. The solar radiation term is calculated from an algorithm based upon the latitude of the reservoir, day of year, time of day, and cloud cover. The longwave radiant fluxes are calculated from the pond surface temperature and meteorological data including cloud cover. The onsite meteorological data set contains all parameters necessary for analyses of the Cooling Reservoir except for cloud cover, which would be required in the longwave radiation calculations. However, there are other factors influencing solar radiation received at the ground, such as atmospheric particulates and fog.

References 1. Updated Final Safety Analysis Report - South Texas Project Units 1 & 2, Vol. 2, Docket Nos. STN 50-498 and STN 50-499.

2. Turner, D. Bruce, "A Diffusion Model for an Urban Area", J. App. Meteorol., Vol. 3, No.1 (February 1964), pp.83-91.

STPEGS UFSAR Q&R 2.3-12 Revision 13 TABLE Q372.7-1 MONTHLY AND ANNUAL AVERAGE WIND SPEED AT VICTORIA, TEXAS, FOR THREE PERIODS OF RECORD (mph)

Period of Record Month February 14, 1953 to January 31, 1956 July 21, 1973 to September 30, 1977 January 1, 1968 to December 31, 1977 January 11.2 10.2 10.5 February 12.0 11.1 10.9 March 11.5 12.4 11.9

April 9.7 12.0 11.9

May 9.7 10.1 10.4 June 9.7 9.7 9.8

July 8.2 8.3 8.8

August 7.4 8.0 8.2

September 6.5 8.8 8.8

October 8.3 9.1 9.0

November 10.8 9.9 9.9

December 10.8 9.9 10.0 Annual 9.6 9.9 10.0 STPEGS UFSAR TABLE Q372.7-2 MONTHLY AND ANNUAL AVERAGE TEMPERATURE (T) AND DEW POINT TEMPERATURE (Td) FOR VICTORIA AND STP (F) Victoria STPEGS Period of Record February 14, 1953, to January 31, 1956 July 21, 1973, to September 30, 1977 January 1, 1968, to December 31, 1977 July 21, 1973, to July 20, 1977 T Td T Td T Td T Td January 56 47 52 44 53 45 53 47 February 58 46 58 46 56 45 58 48 March 65 54 65 55 63 53 64 57 April 71 62 70 60 70 60 68 62 May 76 67 76 67 75 66 74 68 June 82 71 80 71 80 71 79 72 July 84 73 81 72 82 72 81 74 August 83 73 81 72 82 72 80 73 September 80 70 77 69 78 70 75 68 October 72 61 69 60 71 61 69 61 November 62 50 61 53 61 51 63 55 December 56 45 54 45 56 47 54 46 Annual 71 60 69 60 69 59 68 61 Q&R 2.3-13 Revision 13 STPEGS UFSAR TABLE Q372.7-3 MONTHLY AND ANNUAL VALUES OF AVERAGE DAILY MAXIMUM (MAX), AVERAGE DAILY MINIMUM (MIN), AND AVERAGE DIURNAL TEMPERATURE RANGE FOR VICTORIA, TEXAS (F) Period of Record February 14, 1953 to January 31, 1956 July 21, 1973 to September 30, 1977 January 1, 1968 to December 31, 1977 Max Min Range Max Min Range Max Min Range January 67.0 47.1 19.9 62.5 44.3 18.2 62.7 45.3 17.4 February 69.2 49.3 19.9 69.6 48.7 20.9 66.9 47.6 19.3 March 75.7 57.4 18.3 74.5 57.3 17.2 72.8 54.9 17.9 April 81.3 63.8 17.5 78.5 62.5 16.0 78.5 62.4 16.1 May 85.2 68.4 16.8 83.7 69.2 14.5 83.4 68.0 15.4 June 91.6 73.7 17.9 88.3 73.4 14.9 88.1 73.4 14.7 July 94.1 76.3 17.8 90.3 75.0 15.3 90.9 75.3 15.6 August 93.3 75.9 17.4 90.5 74.8 15.7 91.0 74.9 16.1 September 90.6 72.0 18.6 86.8 70.6 16.2 87.0 71.4 15.6 October 83.3 63.0 20.3 80.1 61.1 19.0 81.0 62.4 18.6 November 73.2 52.7 20.5 72.0 52.9 19.1 71.7 52.1 19.6 December 66.9 46.8 20.1 65.1 45.1 20.0 66.7 47.6 19.1 Annual 81.1 62.4 18.7 79.0 61.9 17.1 78.4 61.3 17.1 Q&R 2.3-14 Revision 13 STPEGS UFSAR Q&R 2.3-15 Revision 13 TABLE Q372.7-4 MONTHLY AND ANNUAL STABILITY CLASS DISTRIBUTIONS FOR VICTORIA, TEXAS (%) 1 = February 14, 1953, to January 31, 1956 2 = July 21, 1973, to September 30, 1977 3 = January 1, 1968, to December 31, 1977 Stability Class Based on Pasquill-Turner Method A B C D E F G January 1 0.0 1.70 5.47 66.04 13.80 8.74 4.26 2 0.10 2.92 6.65 63.91 11.09 12.00 3.33 3 0.04 2.38 6.41 67.62 10.65 10.36 2.54 February 1 0.12 2.46 6.63 65.43 12.62 9.68 3.05 2 0.22 2.88 6.53 61.95 11.39 14.16 2.88 3 0.09 2.12 6.67 65.11 11.09 12.63 2.30 March 1 0.18 2.87 6.68 72.18 8.24 8.02 1.84 2 0.10 1.61 5.14 78.23 7.06 6.45 1.41 3 0.28 1.85 5.52 72.98 8.87 8.83 1.65 April 1 1.16 4.35 12.22 57.45 7.96 9.31 7.55 2 0.31 2.81 8.65 69.27 7.40 9.17 2.40 3 0.42 2.92 6.87 71.08 8.25 8.42 2.04 May 1 1.30 5.60 13.36 53.65 8.29 9.50 8.29 2 0.71 4.44 9.58 64.52 8.87 9.88 2.02 3 0.56 5.20 9.88 63.51 9.44 9.56 1.85 June 1 1.71 4.31 17.69 40.76 14.17 12.92 8.43 2 1.35 6.87 13.02 48.12 14.27 13.96 2.40 3 0.92 5.25 12.71 53.21 14.08 11.87 1.96 July 1 2.69 7.44 17.66 35.72 11.52 12.55 12.42 2 2.69 7.13 18.89 37.69 15.09 15.56 2.96 3 1.57 5.73 16.77 43.10 14.76 15.60 2.46 August 1 3.81 7.89 17.11 32.44 12.23 12.28 14.25 2 2.10 8.71 16.53 34.27 14.19 20.16 4.03 3 1.61 8.67 15.12 36.37 14.92 19.11 4.19 September 1 1.57 9.73 16.35 26.35 7.50 22.14 16.35 2 1.50 7.58 11.00 40.17 14.17 21.50 4.08 3 1.17 6.62 10.71 41.58 15.21 21.08 3.62 October 1 0.40 5.74 14.48 33.89 16.27 17.26 11.97 2 0.30 3.93 10.08 43.95 15.85 21.98 3.93 3 0.12 4.03 10.00 44.27 15.77 21.29 4.52 STPEGS UFSAR Q&R 2.3-16 Revision 13 TABLE Q372.7-4 (Continued)

MONTHLY AND ANNUAL STABILITY CLASS DISTRIBUTIONS FOR VICTORIA, TEXAS (%) 1 = February 14, 1953, to January 31, 1956 2 = July 21, 1973, to September 30, 1977 3 = January 1, 1968, to December 31, 1977 Stability Class Based on Pasquill-Turner Method A B C D E F G November 1 0.19 3.29 8.06 56.60 16.95 9.59 5.33 2 0.10 2.08 7.60 53.54 13.65 16.98 6.04 3 0.04 2.37 7.75 52.54 14.50 17.46 5.33 December 1 0.09 2.78 6.27 60.62 16.13 9.05 5.06 2 0.0 2.42 7.56 55.34 15.22 15.02 4.44 3 0.0 2.10 7.06 59.96 13.59 13.59 3.71 Annual 1 1.12 4.89 11.92 49.84 12.14 11.77 8.32 2 0.85 4.62 10.34 53.41 12.45 14.98 3.35 3 0.57 4.12 9.65 55.89 12.60 14.16 3.02 STPEGS UFSAR Q&R 2.3-17 Revision 13 TABLE Q372.7-5 STABILITY CLASS DISTRIBUTIONS BASED ON T (195 ft-33 ft) FOR THE STPEGS SITE (JULY 21, 1973 - JULY 20, 1977) TEXAS Period _______________Stability Class________________ A B C D E F G July 21, 1973 -

July 20, 1974 12.3 2.9 7.5 29.4 22.8 15.3 9.9 July 21, 1974 - July 20, 1975 12.8 2.7 6.5 32.2 23.1 12.6 10.0 July 21, 1975 - July 20, 1976 13.4 3.6 7.7 26.2 22.4 15.6 11.2 October 1, 1976 - September 30, 1977 4.5 2.2 6.1 40.9 24.0 12.9 9.5 July 21, 1973 - July 20, 1977 10.7 2.9 6.9 32.2 23.1 14.1 10.1

STPEGS UFSAR Q&R 2.3-18 Revision 13 Figure Q372.7-1 (See Q&R Figures)

STPEGS UFSAR Q&R 2.3-19 Revision 13 Figure Q372.7-2 STPEGS UFSAR Q&R 2.3-20 Revision 13 Figure Q372.7-3 STPEGS UFSAR Q&R 2.3-21 Revision 13 Figure Q372.7-4 STPEGS UFSAR Q&R 2.3-22 Revision 13 Question 372.8 Identify the primary data recording system (analog or digital) and indicate the fraction of data recorded by the analog and digital systems. Response The primary data recording system is digital via magnetic tape. During the first year of operation of the Onsite Meteorological Program, the digital system was not operational and data was extracted from the analog recordings. Approximate data utility from each recording device is shown in the table below.

Data Collection Rates by Device Percent Percent Time Period Digital Analog(1) July 21, 1973 - November 30, 1974 100 December 1, 1974 - November 30, 1974 NA(2) NA July 21, 1975 -

December 31, 1975 89.0 11.0 1976(3) 86.4 13.6 1977(4) 67.3 32.7

1. Includes Data Records Indicated as Missing 2. NA - Not Available from Existing Records
3. Includes Period of Limited Maintenance
4. Through September 30, 1977 STPEGS UFSAR Q&R 2.3-23 Revision 13 Question 372.10 Deleted.

STPEGS UFSAR Q&R 2.3-24 Revision 13 Question 372.11 Deleted.

STPEGS UFSAR Q&R 2.3-25 Revision 13 Question 372.12 Provide the results of the calibration findings, including adjustments and/or replacements of components in the data collection and recording system. Response Standard calibration procedures include recording "as found" values. Any significant discrepancies are corrected and the sensor recalibrated using standard calibration techniques. "As left" values are then recorded. Significant adjustments and replacement of components are listed as follows: Calibration Date Item Action November 4, 1974 Translator Card 30-10 DT Replaced and calibrated card; unable to reach calibration with old card.

January 21, 1975 30 M DT Probe Replaced probe; ice bath indicated -0.1F error from true. Pryanometer Replaced sensor; old sensor required new dessicant. April 9, 1975 60-10 DT Ice bath off -0.1F; recalibrated card. 30-10 DT Ice bath off +0.1F; recalibrated card. Pyranometer Electrical short; replaced sensor.

July X, 1975 30 M DT Probe Ice bath off -0.2F; replaced sensor November 12, 1975 No problems January 20, 1976 10 M WD Unacceptable changeover on dual potentiometer; replaced sensor. April 8, 1976 60 M WD Cable cover weathered; replaced cable. 10 M WD Cable cover weathered; replaced cable. 60 M WS Cable cover weathered; replaced cable.

60 M WS Cable cover weathered; replaced cable.

STPEGS UFSAR Q&R 2.3-26 Revision 13 Response (Continued) Calibration Date Item Action September 29, 1976 10 M AT Slight leakage to ground; replaced sensor.

Station had no routine maintenance during period of IBEW strike. Tower was completely recalibrated.

10 M WD Sensor had no signal; replaced sensor.

60 M DT Ice bath off 0.2F; replaced probe.

January 18, 1977 60 M WD Unable to determine "as found" values due to pulled shaft when installing calibrator; replaced sensor. 30-10 DT Ice bath indicated -0.2F error. Replaced probe at 30 M.

April 13, 1977 No problems

July 19, 1977 30 M DT Ice bath indicated defective probe; replaced sensor November 2, 1977 No problems

Abbreviations: DT - Delta Temperature AT - Ambient Temperature WD - Wind Direction WS - Wind Speed STPEGS UFSAR Q&R 2.3-27 Revision 13 Question 372.13 Data recovery for the onsite meteorological program has been extraordinarily high. Indicate if data from other levels have been used to substitute for data at the "primary" levels (i.e., wind speed and direction at the 10m level, and vertical temperature gradient between the 10m and 59.4m levels), and, if so, describe the procedures used for the substitutions. Response Data were not substituted from other levels to enhance data recovery. The high percentage data recovery is attributed to an intensive maintenance program including quarterly calibrations and three site visits per week by qualified instrument technicians. Generally, any problems encountered were solved immediately upon discovery or within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, resulting in minimal data loss.

STPEGS UFSAR Q&R 2.3-28 Revision 13 Question 372.14 Provide the dates and times of significant instrument outage, the causes of the outage, and the corrective action taken. Also discuss the reasons for the limited maintenance performed on the data collecting equipment during the July 21, 1976, through September 30, 1976, period. Response Dates and times of significant instrument outage in excess of 24 hrs and the corrective action taken for resolution of the outage are shown in Table Q372.14-1.

Limited maintenance was performed on the data-collecting equipment during the period July 21, 1976, through September 30, 1976, because of a strike by local union workers. No calibrations or routine site visits were performed during this period.

STPEGS UFSAR Q&R 2.3-29 Revision 13 TABLE Q372.14-1 SIGNIFICANT INSTRUMENT OUTAGES Days Problem Resolution Approximate Hrs of Data Lost 11/237/75 - 10/241/75 Rain gauge out Replaced Potentiometer 95 10/332/75 -

11/335/75 60m wind speed failure Replaced Sensor 73 14/334/75- 11/335/75 60m wind direction failure Replaced Sensor 22 3/10/76 -

10/20/76 10m wind direction failure Replaced Sensor 123 8/63/76 - 12/70/76 Solar radiation failure Replaced Sensor 173 0/218/76 - 16/219/76 End of tape

  • Replaced Tape 41 0/242/76 -14/243/76 End of tape
  • Replaced Tape 39 15/249/76 -

14/251/76 End of tape

  • Replaced Tape 48 5/260/76 -

11/266/76 End of tape

  • Replaced Tape 184 4/269/76 - 9/273/76 End of tape
  • Replaced Tape 101 12/266/76 - 10/274/76 10 m wind direction failure Replaced Sensor 190 10/333/76 - 11/334/76 10 m wind speed stopped due to freezing precipitation Natural Thaw 26 8/333/76 -

11/334/76- 60m wind speed stopped due to freezing precipitation Natural Thaw 28 STPEGS UFSAR Q&R 2.3-30 Revision 13 TABLE Q372.14-1 (Continued) SIGNIFICANT INSTRUMENT OUTAGES Days Problem Resolution Approximate Hrs of Data Lost 20/366/76 -

10/5/77 60m wind speed defective Replaced Sensor 65 11/45/77 -

7/115/77 30-10 T defective Replaced Sensor 1700 9/49/77 -

8/52/77 60m wind speed defective Replaced Sensor 72 18/161/77 -

16/201/77 30-10 T defective Replaced Sensor 958 7/165/77 -

11/168/77 Precipitation Replaced Potentiometer 76 18/252/77 -

18/264/77 Dewpoint off scale Adjust Dewpoint 289

  • End of Tape - Limited Maintenance Period STPEGS UFSAR Q&R 2.3-31 Revision 13 Question 372.16 The atmospheric dispersion model and procedures used to evaluate dispersion conditions to be used in an assessment of the consequences of design basis accidents described in Section 2.3.4 of the FSAR are based on Regulatory Guide 1.4 and Section 2.3.4 of the Standard Review Plan. After review of the results of recent atmospheric dispersion field experiments, we have developed a modified procedure for calculating short-term relative concentration (/Q) values which considers the following:
1. Lateral plume meander
2. Atmospheric dispersion conditions as a function of direction 3. Wind direction frequencies
4. Exclusion area boundary distances as a function of direction Enclosed is a copy of DRAFT Regulatory Guide 1.XXX, "Atmospheric Dispersion Models for Potential Accident Consequence Assessments at Nuclear Power Plants" (9/23/77), which describes the new procedure in detail. We believe that this model will provide an improved characterization of atmospheric dispersion conditions around the STPEGS site.

Enclosed is the interim branch technical position concerning use of these two models. During our review, we will examine /Q values for appropriate time periods for design basis accident evaluations using the modified model described in the enclosed DRAFT Regulatory Guide, and compare them with /Q values calculated using the model described in Regulatory Guide 1.4 and the procedures described in Section 2.3.4 of the Standard Review Plan. Therefore, provide exclusion area boundary distances as a function of direction using the procedure described in the DRAFT Regulatory Guide. Also provide a large-scale (for independent measurement) map of the site, similar to Figure 2.3-12, that also identifies the exclusion area boundaries, true north, and includes a scale of distances.

Response The table below presents exclusion area boundary distances as a function of direction. A large-scale map of the site is provided under separate cover. (ST-HL-AE-295).

STPEGS UFSAR Q&R 2.3-32 Revision 13 Response (Continued) Direction Distance * (meters) Distance Used in Calculations (meters) N 1430 1430 NNE 1430 1430

NE 1471 1430

ENE 1512 1430

E 1524 1430

ESE 1512 1430

SE 1471 1430 SSE 1430 1430

S 1430 1430

SSW 1430 1430

SW 1540 1430

WSW 1722 1430

W 1853 1430 WNW 1722 1430 NW 1540 1430

NNW 1430 1430

  • Minimum within + 22.5 degrees of the sector centerline STPEGS UFSAR Q&R 2.3-33 Revision 13 Question 372.17 The effects of spatial and temporal variations in atmospheric transport and diffusion conditions is of importance in describing the dose consequences of airborne routine releases of radioactivity. Sea breeze penetration at the STPEGS site is discussed on pages 2.3-14 and 2.3-15 of the FSAR with the conclusion that, because of the low frequency of occurrence of sea breeze penetration to the site, "the impact of sea breeze upon dose estimates for the STPEGS is expected to be insignificant". However, assessments of dose consequences to the population out to a distance of 80 km from the plant is required by Appendix I to 10 CFR Part 50, and the calculations of these doses may be affected by local circulation patterns such as the sea breeze in the area of the STPEGS site. Provide additional discussion of the effects of spatial and temporal variations in airflow of the estimates of annual average relative concentration (/Q) and relative deposition (D/Q) values out to a distance of 80 km from the site, and provide estimates of adjustments to /Q and D/Q values for consideration of these variations.

Response Comparison of /Q values for STPEGS with those for the Allens Creek Nuclear Generating Station (HL&P, 1973), located 110 km inland (97 km north of STPEGS), indicates long-term dispersion conditions tend to decrease (/Q increases) farther inland (see Tables Q372.17-l and Q372.17-2). A portion of this difference can be attributed to sea breeze. Under conditions favoring closed circulation, it is likely that a helical streak line, which moves northward up the coast line in time, will occur. This phenomenon results from (a) the sea breeze veering (turning to the right) with time due to the Coriolis effect, and (b) the amount of veering decreasing with height because the return flow is weaker than the onshore flow beneath; i.e., the return flow veers less than the surface flow. A helical streak line resulting from a sea breeze has not been observed. The sea breeze modeling results of McPherson (1968), however, clearly demonstrate a helical pattern such as described above. There is currently no methodology available to accurately account for sea breeze effects not already present in the STPEGS meteorological record.

STPEGS UFSAR Q&R 2.3-34 Revision 13 References 1. ss, S. L., 1959: Introduction to Theoretical Meteorology, Henry Holt and Company, New York, pp. 201.

2. Houston Lighting & Power Company, 1973: "Preliminary Safety Analysis Report - Allens Creek Nuclear Generating Station", submitted to the Nuclear Regulatory Commission, Washington, D. C. 3. McPherson, R. D., 1968: "A Three-Dimensional Numerical Study of the Texas Coast Sea Breeze", Report No. 15, Atmospheric Science Group, The University of Texas, Austin, pp. 252. 4. McPherson, R. D., 1970: " A Numerical Study of the Effect of a Coastal Irregularity on the Sea Breeze", Journ. Appl. Met., 9, pp. 767-777.

Q&R 2.3-37 Revision 13 STPEGS UFSAR TABLE Q372.17-2 ALLENS CREEK NUCLEAR GENERATING STATION ANNUAL AVERAGE DILUTION FACTORS (SECONDS/METER3 AT THE MID-POINT OF THE STANDARD DISTANCES GROUND RELEASE - Affected Sector Distance (Miles) 0-5 1.5 2.5 3.5 4.5 7.5 15 25 35 45 N 4.9E-6 9.6E-7 4.7E-7 3.0E-7 2.1E-7 1.0E-7 4.1E-7 2.1E-8 1.4E-8 1.0E-8 NNE 3.4E-6 6.5E-7 3.2E-7 2.0E-7 1.4E-7 7.1E-8 2.8E-8 1.5E-8 9.7E-9 7.1E-9 NE 2.0E-6 3.8E-7 1.9E-7 1.2E-7 8.3E-8 4.1E-8 1.6E-8 8.5E-8 5.6E-9 4.1E-9 ENE 1.4E-6 2.6E-7 1.3E7 8.2E-8 5.8E-8 2.9E-8 1.1E-8 5.9E-8 3.9E-9 2.9E-9 E 1.5E-6 2.8E-7 1.4E-7 8.9E-8 6.3E-8 3.2E-8 1.3E8 6.7E-9 4.4E-9 3.3E-9 ESE 1.4E-6 2.6E-7 1.3E-7 8.4E-8 6.0E-8 3.0E-8 1.2E-8 6.4E-9 4.2E-9 3.1E-9 SE 1.9E-6 3.6E-7 1.8E-7 1.2E-7 8.3E-8 4.2E-8 1.7E-8 8.8E-9 5.8E-9 4.3E-9 SSE 2.8E-6 5.2E-7 2.6E-7 1.6E-7 1.2E-7 5.8E-8 2.3E-8 1.2E-8 7.9E-9 5.8E-9 S 4.6E-6 8.7E-7 4.3E-7 2.7E-7 1.9E-7 9.6E-8 3.8E-8 2.0E-8 1.3E-8 9.6E-9 SSW 3.6E-6 6.8E-7 3.3E-7 2.1E-7 1.5E-7 7.4E-8 2.9E-8 1.5E-8 1.0E-8 7.4E-9 SW 3.7E-6 7.1E-7 3.5E-7 2.2E-7 1.6E-7 7.8E-8 3.1E-8 1.6E-8 1.1E-8 7.7E-9 WSW 3.3E-6 6.35-7 6.1E-7 2.0E-7 1.4E-7 7.1E-8 2.8E-8 1.5E-8 9.7E-9 7.2E-9 W 2.9E-6 5.7E-7 2.8E-7 1.8E-7 1.3E-7 6.3E-8 2.5E-8 1.3E-8 8.5E-9 6.2E-9 WNW 2.8E-6 5.4E-7 2.7E-7 1.7E-7 1.2E-7 5.8E-8 2.3E-8 1.2E-8 7.8E-9 5.7E-9 NW 4.9E-6 9.8E-7 4.8E-7 3.0E-7 2.1E-7 1.1E-7 4.2E-8 2.2E-8 1.4E-8 1.1E-8 NNW 4.1E-6 8.2E-7 4.0E-7 2.5E-7 1.7E-7 8.6E-8 3.4E-8 1.7E-8 1.1E-8 8.4E-9 STPEGS UFSAR Q&R 2.3-38 Revision 13 Question 372.18 From the discussion of extreme winds presented in Section 2.3.1.2.1, of the FSAR it appears that the design wind velocity at 30 feet above ground with a 100-year recurrence interval should be 125 mph. As stated on page 2.3-3 of the FSAR, this value, when used with a gustiness factor of 1.3, provides an estimate of the highest instantaneous gust expected once in 100 years of 163 mph. Clarify the apparent discrepancy between the selection of the design wind velocity and gust factor used in Section 3.3.1 and the discussion of extreme winds and gust factors presented in Section 2.3.1.2.1.

Response The recorded 125 mph wind velocity (as was experienced by Corpus Christi during Hurricane Celia) is not considered to have occurred at the STPEGS site due to the reduction of wind velocity which occurs when hurricanes traverse over land (STPEGS PSAR Section 3.3.1.2). It is estimated that a wind velocity of 120 mph occured at the STPEGS site during Celia.

STPEGS UFSAR Q&R 2.3-39 Revision 13 Question 372.19 The response to Request No. 372.3 states that "The STPEGS design basis maximum and minimum outside ambient temperatures are 96F and 29F, respectively." Climatological data presented in Tables 2.3-14 through 2.3-20 indicate an observed maximum temperature of 110F at Victoria, with observed extreme maximum temperatures ranging from 101F to 105F at other climatological stations in the area. Temperatures in excess of 90F may be expected on an average of about 100 days each year. Similarly, an extreme minimum temperature of 8F has been observed at Galveston, with observed extreme minimum temperatures ranging from 9F to 13F at other climatological stations in the area. Temperatures of 32F or lower may be expected on an average of about 10 days each year. Provide further justification of the selected design basis maximum and minimum ambient air temperatures considering that extreme temperatures observed in the area are significantly different than the selected design basis values. Also discuss the effects on safety-related systems and components resulting from persistent (e.g., on the order of several hours) temperatures significantly different than the selected design basis values.

Response As described in the revised response to Question 372.3, the heating, ventilating and air conditioning (HVAC) design basis maximum and minimum outside ambient temperatures are 95F and 29F, respectively. These design conditions are based on ASHRAE data and are 99 percent (winter) and 1 percent (summer) temperature levels for Bay City, Texas. The summer design basis of 95F will be exceeded only 1 percent of the time in a normal summer and conversely there will be temperatures lower than 29F only 1 percent of the time in a normal winter. The outside design temperatures for safety-related HVAC, auxiliary systems, and components (95F and 29F) are considered long-term, steady state values. They are conservatively assumed to occur continuously during summer and winter, while extreme maximum and minimum temperatures are transient values of short duration.

Because of thermal inertia and due to the conservative design of HVAC systems, it is expected that persistent (e.g., on the order of several hours) temperatures outside the design basis values will have no impact on the normal temperature ranges delineated in Table 9.4-1. Thus, there will be no impact on safety-related systems and components located in structures served by HVAC systems. As described in the response to Question 372.3, components such as instrument lines that are located outside and hence are exposed to freezing conditions are heat traced and insulated. Therefore, there will be no impact on these components resulting from persistent temperatures different than the design basis values.

STPEGS UFSAR Q&R 2.3-40 Revision 13 Question 372.21 The annual frequencies of occurrence of moderately stable and extremely stable conditions (Pasquill types "F" and "G", respectively) are very important in the determination of relative concentration (/Q) values to be used in assessing the consequences of design basis accidents. A significant decrease (about 60 percent) in the annual frequency of extremely stable conditions at Victoria was observed for the period July 1973 through June 1977 (Table 2.3-12) compared to the annual frequency of these conditions observed for the period September 1953 through August 1958 (Table 2.3-11), particularly during the summer and fall seasons. Discuss possible explanations for this decrease in the occurrence of extremely stable conditions at Victoria, and discuss the significance of this decrease on the representativeness and conservatism of the onsite data collected during the period July 1973 through September 1977. Response The stability frequency distributions presented in Tables 2.3-11 and 2.3-12 were produced by the so-called "STAR" technique. This method of estimating thermal atmospheric stability is indirect, using wind speed, total amount of cloud cover, incoming solar radiation and time of day. With respect to moderately and extremely stable conditions (which can occur only at night) only wind speed and cloud cover are of interest. The scheme to estimate Pasquill "F" (moderately stable) and "G" (extremely stable) is shown below: Cloud Cover Wind Speed 50% <50% Very low (0-3 knots) F G Low (4-6 knots) E F Therefore, to produce an increase in "G" frequencies, an increase in occurrence of very low wind conditions or a decrease in amount of cloud cover must occur.

There are three possible explanations for these conditions:

1. Observations were reported once every three hours in the later period (7/73 - 6/77), whereas they were reported hourly in the earlier period (9/53 - 8/58). The later observations could produce biased low wind speed and/or cloud cover conditions.
2. A change in technique and/or instruments used to measure wind speed and cloud cover could have occurred between the two periods.
3. A real change in the meteorology could have occurred between the periods, indicating that one or both of the periods were not representative of the climatology of Victoria.

STPEGS UFSAR Q&R 2.3-41 Revision 13 Response (Continued)

Each of these possibilities will be discussed below. 1. Three-hourly vs Hourly Observations - In a study performed by the National Climatic Center of NOAA (Ref. 1) the percentage distributions of stabilities produced by the "STAR" method using hourly data and three-hourly data were compared. Using several statistical techniques, they concluded there were no significant differences between the frequencies produced by three-hourly and hourly data.

2. Change in Techniques and/or Instruments - Upon closer inspection of the two frequency distributions, a large decrease in the percentage of very low wind speeds (0-3 knots), and particularly in the percentage of calms, was found in the later data period. As shown above, this decrease in very low wind speeds would produce a decrease in the extreme stable conditions. Table 1, below, shows the change in percent of wind speed classes from the earlier data period and the later. Table 1 Wind Speed Class (Knots)

Period Calm 0-3 4-6 7-10 11-16 17-21 >21 Annual -6.0 - 8.8 10.1 -2.6 2.9 -0.9 -0.6 Winter -2.5 - 3.1 10.3 -3.2 0.2 -2.3 -1.8 Spring -5.3 - 7.7 4.1 -2.9 6.1 0.9 -0.5

Summer -9.7 -11.3 16.1 -3.5 -0.5 -0.9 0.1

Autumn -6.8 -13.5 9.8 -0.8 5.8 -0.9 -0.3 A large annual decrease (8.8 percent)(1) is observed in the frequency of very low wind speeds from the earlier to the later period. The majority of the decrease can be attributed to a decrease in the frequency of calms (6.0 percent).(2) Also, it should be noted that there was a corresponding increase in the 4-6 knot frequency class, suggesting the lowest frequencies were "shifted" up one class. This shift of wind speed may have occurred as a result of different techniques in reporting calms or from changing to an anemometer with a lower threshold speed.

1. A threefold decrease between the earlier and later periods. 2. A twofold decrease between the earlier and later periods.

STPEGS UFSAR Q&R 2.3-42 Revision 13 Response (Continued) Examination of the station history revealed that the Air Force operated the Victoria station during the earlier period and that it was turned over to the National Weather Service in 1961. Mr. Steve Doty of the National Climatic Center stated to us that, although it would be very difficult to document, he has found that Air Force stations tend to report a higher percentage of calms than do comparable National Weather Service stations.

3. Meteorological Differences Between the Two Periods - Finally, in order to determine if the changes in the frequencies of stable conditions were produced by real changes in the meteorology, a longer period of record from Victoria(3) was examined. Although the frequency distribution did not separate stability classes F and G, the percentages of low wind speeds can be compared to those of the two other data periods. The frequencies of wind speed classes for each of the data periods are shown in Table 2, below. Table 2 Wind Speed Class (Knots) Period Calm 0-3 4-6 7-10 11-16 17-21 >21 9/53-8/58 (Earlier, 5 yr) 8.7 16.2 22.3 33.4 20.1 6.2 1.7 7/73-6/77 (Later, 5 yr) 2.7 7.4 32.4 30.8 23.0 5.4 1.1 1/65-1/74 (Longer, 10 yr) 2.8 7.0 30.4 32.2 24.2 5.2 1.0 As can be seen, the later period (7/73-6/77) corresponds very closely with the longer period of record. Conclusions - The investigation suggests that the shift of very stable conditions (G) to moderately stable conditions (F) from the earlier data period to the later period is a result of fewer calm conditions being reported during the later period. The decrease in calm conditions could be real or the result of changes in techniques and/or instruments used in determining wind speed; the evidence presented indicates the latter. Moreover, whether the differences are real meteorological changes or not, the later period is considered to be more representative of Victoria's climate because of its similarity to the longer 10-year record. 3. January 1965 through December 1974 period (three-hourly observations).

STPEGS UFSAR Q&R 2.3-43 Revision 13 Reference

1. Doty, S. R., B. L. Wallace, and G. C. Holzworth, "A Climatological Analysis of Pasquill Stability Categories Based on 'STAR' Summaries", National Climatic Center, Federal Building, Asheville, NC, 1976.

STPEGS UFSAR Q&R 2.3-44 Revision 13 Question 372.22 A preliminary examination of onsite data for the period July 21, 1973, through September 30, 1977, provided on magnetic tape, indicates an inordinate number of occurrences of moderately unstable (Pasquill type "B") conditions defined by the vertical temperature gradient measured between the l0m and 30m levels. Although this interval of temperature gradient measurement is not the primary source of atmospheric stability information, the distribution of atmospheric stability conditions defined for this interval should generally resemble the distribution of stability conditions defined by the measurement of vertical temperature gradient between the l0m and 60m levels. Discuss the differences in the distribution of atmospheric stability conditions defined by these two intervals of measurement and indicate if problems with the data collection program are suspected.

Response Since the air near the ground (at l0m in this case) will respond more quickly to heating and cooling fluxes than air at either the 30m or 60m level, the lower temperature gradient measurements (i.e., the lower interval) will tend to respond quicker to temperature changes and indicate greater frequencies of very unstable atmosphere or (to a lesser extent) a more stable atmosphere. This is illustrated with data for the July 21, 1973, through September 30, 1977, data period in Table Q372.22-1. The data in this table compares the 30m to l0m temperature gradient classifications with the 60m to lOm temperature gradient classifications. As expected, the 30m to l0m level experiences more extremely unstable classes at the expense of the less unstable and neutral conditions. Unstable and neutral conditions account for approximately 53 percent of the observations at both levels of measurement, indicating that both levels are experiencing the same effects. Similarly, the extremely stable cases are more numerous at the 30m to l0m level than at the other level. Furthermore, the routine used to derive the frequency of various stabilities by use of RG 1.23 criteria has such a narrow range for "B" stability, that, for the 30m to l0m temperature gradients, "B" stability was not attainable at recording accuracies of 0.1 F (See Table Q372.22-2). For the 30m to l0m interval, only the (-)0.6F reading falls into a classification that is other than extremely unstable or neutral for temperature gradient readings of less than 0.0F.

STPEGS UFSAR Q&R 2.3-45 Revision 13 TABLE Q372.22-1 TEMPERATURE STABILITY CLASSIFICATION 1 -

July 21, 1973 - September 30, 1977* [Frequency (%)]

[60m - 10m Level]

A B C D E F G TOTAL (30m - 10m) A 11.03 2.67 6.15 8.65 0.53 0.13 0.02 29.18 B 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 53.57% C 0.06 0.04 0.27 3.80 0.12 0.01 0.00 4.30

D 0.24 0.08 0.29 15.23 4.09 0.14 0.02 20.09

E 0.11 0.03 0.07 3.30 13.54 1.48 0.13 18.66

F 0.16 0.00 0.01 0.40 4.10 7.54 0.89 13.10

G 0.02 0.00 0.00 0.04 0.11 4.97 9.45 14.59 Total 11.62 2.82 6.79 31.42 22.49 14.27 10.51 99.92**

(60m -,

10m) 52.65%

  • Period July 21, 1976, through September 30, 1976, omitted due to limited maintenance.
    • Not 100.00 due to round-off error.

STPEGS UFSAR Q&R 2.3-46 Revision 13 TABLE Q372.22-2 LAPSE RATE CLASSIFICATION SCHEME - Stability Class Lapse Rate C/100m Temperature Gradients Included (F) 30m - 10m (67 ft) 60m - 10m (162 ft) A T < -1.9 T < -.698 T < -1.698 B* -1.9 < T < -1.7 -.698 < T < -.625 -1.698 < T < -1.511 C** -1.7 < T < -1.5 -.625 < T < -.551 -1.511 < T < -1.333 D -1.5 < T < -0.5 -.551 < T < -.018 -1.333 < T < -.044 E -0.5 < < 1.5 -.018 < T < .551 - .044 < T < 1.333 F 1.5 < T < 4.0 .551 < T < 1.470 1.333 < T < 3.555 G 4.0 < T 1.470 < T 3.555 < T

  • This interval not attainable for 30m - 10m (67 ft) at accuracies of 0.1F.
    • Only -0.6F will be classified into this category for the 30m - 10m interval at accuracies of 0.1F.

STPEGS UFSAR Q&R 2.3-47 Revision 13 Question 372.24 During plant operation, the onsite meteorological tower should provide measurements of wind speed, wind direction, and atmospheric stability for estimates of atmospheric dispersion conditions from the point of release to the exclusion area boundary and LPZ distances during and following accidental and routine releases. Meteorological measurements, particularly wind speed and vertical temperature gradient, at the present tower location during winds from the south clockwise through south-southwest could be used to provide non-representative or misleading estimates of atmospheric dispersion, during and following accidental and routine releases, because of the long over-water fetch for airflow from these directions. Discuss the representativeness of the location of the onsite meteorological tower for describing atmospheric dispersion conditions from the point of release to the exclusion area boundary and LPZ distances, with particular attention to measurements of wind speed and vertical temperature gradient when winds are from the south clockwise through south-southwest directions. Indicate if the monitoring program identified in the response to Request No. 372.6 will be used to evaluate the representativeness of measurements at the current tower location.

Response During plant operation, the presence of the cooling reservoir is expected to result in decreased mechanically-generated turbulence (decreased ) and increased surface wind speed directly above, and for some distance downwind of, the reservoir. The magnitude of the changes in mechanically-generated turbulence and wind speed will depend upon several factors; e.g., fetch over the reservoir, distance and roughness characteristics downwind of the reservoir, and thermal stability. The upward flux of heat (convection) will decrease the vertical temperature gradient (decreased T) within the air over the reservoir, resulting in destabilization of the air nearest the water(1). The effect will be greatest near the outfall where the flux of heat is largest, and will decrease away from the outfall. When the wind speed is small, the effect will be limited to the vicinity of the reservoir. When the wind speed is not small, the effect will extend downwind of the reservoir. Both effects will diminish in space as the air becomes mixed with ambient air. These two effects are expected for any wind direction. However, when winds are from the south clockwise through south-southwest, the over-water fetch is longest with respect to the meteorological tower. It follows, then, that the probability of their detection at the meteorological tower will be greatest for these wind directions.

1. Except, perhaps, near ground level, immediately downwind of the reservoir on a hot summer day.

STPEGS UFSAR Q&R 2.3-48 Revision 13 Response (Continued)

The effects of operation of the cooling reservoir, namely, increased wind speed and decreased atmospheric stability near the ground, would produce better atmospheric dispersion conditions (i.e., lower concentrations for ground level releases) than would exist in the ambient air without its operation. As the air moves away from the vicinity of the reservoir, the effects would diminish as the air mixes with ambient air until atmospheric dispersion conditions finally become that of the ambient air.

For winds from south clockwise through south-southwest, assume that the effects influence dispersion near the plant, but are not detected at the tower located 1.0 mi northeast of the plant; i.e., ambient conditions are measured at the tower. Because atmospheric dispersion conditions would be better near the plant than indicated by the tower measurements, ground level concentrations based on tower-measured wind speed and atmospheric stability would be:

1. overestimated from the point of release to the exclusion area boundary (0.9 mi); and
2. overestimated from the point of release to the LPZ distance (3.5 mi) because of the enhanced initial dilution taking place near the plant.

Next, assume that the effects influence dispersion near the plant, and are also detected at the tower (although mixing with ambient air would have diminished their influence at the tower distance); i.e., better-than-ambient dispersion conditions are measured at the tower. Item l, above, would still hold, and item 2, above, would generally hold. However, better-than-ambient atmospheric conditions measured at the tower (considered alone) would yield underestimates of ground level concentrations at the LPZ distance. If this condition dominated net dispersion such that the enhanced dilution taking place near the plant was cancelled out, underestimated ground level concentrations could result somewhere between the tower and the LPZ distance, and item l would not hold. It is anticipated that in any case, operation of the Cooling Reservoir will have little, if any, measurable effect on ground level concentrations beyond the LPZ.

The monitoring system for the fog model verification program will not be used to assess the impact of the reservoir on dispersion conditions. However, prior to completion of reservoir-filling operations, more than seven years of meteorological data will have been collected. Data collected following reservoir filling and operation of the plant will be evaluated to determine any significant changes in dispersion meteorology with respect to winds from the south and south-southwest sectors.

STPEGS UFSAR Q&R 2.3-49 Revision 13 Question 372.25 The control room display of meteorological parameters will include utilization of the Unit 1 and Unit 2 computers for CRT display or digital print-out. The response to Request No. 372.8 indicates a significant reliance (32.7%) on the analog data recording system for the period January through September 1977. Discuss the problems encountered in the digital data recording system and indicate if these difficulties would impair the reliability of the control room access to meteorological information.

Response The current digital recording system is a Climet CI-100 data logger coupled with a Kennedy 1600 Incremental tape recorder. The loss of digital data has been associated with the data logger's IBM encoder circuitry. A simultaneous problem with the tape drive caused difficulty in determining the exact nature of the problem. The present data logging system will not be used during plant operation. The data channels will be scanned and the data processed into hourly averages by the plant computer. The data will be transmitted from the meteorological tower to the plant computer via wireless technology. The current problems with the digital system should, therefore, have no impact on future digital data collection reliability. CN-2754 STPEGS UFSAR Q&R 2.4-1 Revision 13 Question 240.4N Provide a discussion of flood protection measures employed at STPEGS to preclude floodwater from entering safety-related buildings or areas; i.e., flood doors, hatches, covers, vent pipes (fuel oil), etc. The design basis flood for STPEGS results from the failure of the MCR embankment which would not allow any warning time to implement flood protection. Therefore, an alarm system is required to insure that flood closure mechanisms are normally closed. Provide a discussion of the alarm system. Also, all closure mechanisms must open into the direction of the flood water such that the force of the flood water will hold the door or cover in the closed position. Please discuss. Are there any emergency procedures associated with the flood protection measures? If so, please discuss.

Response As indicated in the response to NRC Question 240.1N, a detailed assessment of the Main Cooling Reservoir (MCR) facing the STPEGS Category I structures has demonstrated that the MCR embankment remains stable under all credible failure modes.

The instantaneous MCR breach is not considered a credible event; therefore the provision of single water-tight doors and other flood protection features (discussed in Section 3.4 and the responses to NRC Questions 240.1N through 240.3N) provide adequate protection against any credible flood. With respect to fuel oil vent pipes, these are more than 30 ft above the maximum design basis flood level. The water-tight doors will be under administrated control so they can be secured if conditions require (no alarm system is provided). (Note: the exterior doors are designed such that they open into the direction of the flood water.)

Ductbanks entering safety-related areas of Category I structures will be sealed at the manhole to block the flood path of flood waters.

STPEGS UFSAR Q&R 2.4-2 Revision 13 Question 240.5N Considering the existing or proposed reservoirs upstream of STP with storage capacities (top of dam) of 400,000 ac-ft or more, are there any of these dams that cannot safety pass (without overtopping) 40 percent of the PMF (or SPF) followed in 3 to 5 days by a PMF? If any of the larger upstream dams would be overtopped during the above postulated scenario, then you need to discuss the effects on other downstream reservoirs and/or STPEGS, considering concurrent rainfall (or SPF) on the intervening drainage areas.

Response See revised Section 2.4.

STPEGS UFSAR Q&R 2.4-3 Revision 13 Question 240.12N In determining ground-water velocity you used a gradient of 2.6 x 10-4 ft/ft for the lower shallow aquifer and 6.9 x 10-4 ft/ft for the upper shallow aquifer. How were these values determined? Response Section 2.4.13.3.2.1.1 has been revised in Amendment 44 to reflect anticipated post-construction hydraulic gradients for purposes of spill analysis. The gradients questioned in Q240.12N were based on pre-construction conditions and are no longer used in Section 2.4.13.3. A revised gradient of 1.58 x 10-3 ft/ft is used for the lower shallow aquifer. This gradient is computed using an assumed hydraulic head at the power block equal to ground surface (E1. 27), and a head of E1. 2 feet at the Colorado River. The distance used to compute the gradient is three miles, or 15,840 ft, the shortest distance from the Mechanical-Electrical Auxiliaries Building (MEAB) to the river. This gradient is believed to be conservative (greater than what could be expected to occur) because the piezometric surface in the lower shallow aquifer at the power block is expected to stabilize between E1. 17 ft and 26 ft. No gradient is determined for accidental spill in the upper shallow aquifer because the stabilized water level in the upper shallow aquifer will be lower at the power block than in the surrounding area (See response to Q240.19N).

STPEGS UFSAR Q&R 2.4-4 Revision 13 Question 240.15N You state that no significant erosion is expected in the spillway discharge channel due to flood flows. What is the expected velocity of flow in this channel? Provide assurance that the grassed channel will withstand this velocity.

Response The maximum expected mean velocity in the spillway channel is about 5.6 ft/sec. This corresponds to spillway flows resulting from probable maximum precipitation (PMP) on the Main Cooling Reservoir (MCR). The spillway discharge channel is grassed with a mixture of Bermuda grass, Bahia, and Gulf Rye. The soil is cohesive and erosion resistant. The permissible velocity under such conditions is about 8 ft/sec, which is well in excess of the maximum expected velocity in the spillway channel. No significant erosion of the spillway channel is, therefore, expected.

STPEGS UFSAR Q&R 2.5-1 Revision 13 Question 230.1N Provide a map showing the locations of all proposed and existing geothermal wells within 15 miles of the site. Examine if fluid injection or withdrawal may cause small magnitude earthquakes (Yerkes and Castle, 1976, Engineering Geology, v. 10, pp. 151-167). If the occurrence of these events is deemed reasonable, discuss ground motion resulting from such small earthquake(s) within 5 miles of the site and examine the effect upon estimate of earthquake hazard at the site and exceedence of the SSE response spectra.

Response Based on information from the Texas Railroad Commission, the responsible regulatory agency, no geothermal wells exist or are proposed within 15 miles of the site. The site is located on the northern edge of a geopressured, geothermal fairway in the Frio Formation in Matagorda County (Gustavson and Kreitler, 1976) which is unsuitable for geothermal development. As reported by Bebout, et al. (1978) this is due to "...limited lateral extent of reservoirs and lack of sufficient thickness of permeable sandstones." Therefore, future geothermal exploration within the STPEGS site vicinity is not anticipated.

Although the occurrence at the site of such earthquakes is not deemed reasonable, historically the earthquakes associated with fluid injection or withdrawal have been shallow and of small magnitude. Ground motions associated with such small magnitude earthquakes, even within five miles of the site, would not have an effect on the design basis for the STPEGS.

The low intensity seismic effects which accompany fluid extraction studied by Yerkes and Castle (l976) are attributed to differential compaction at depth, but they note that the relative effects of fluid extraction followed by injection are not easily separated. The nature and occurrence of the seismicity and faulting associated with this differential compaction is chiefly a function of: "... (l) the pre-exploitation strain regime, and (2) the magnitude of contractional horizontal strain centered over the compacting materials relative to that of the surrounding annulus of extensional horizontal strain ..."

Based on data presented in Section 2.5.2.4 it has been concluded that the Cenozoic and upper Mesozoic sequence underlying the site vicinity is incapable of storing significant amounts of strain energy. The magnitude of contractional horizontal strain is directly related to the extent of fluid withdrawal. Since the potential fluid withdrawal in the vicinity of the site is small, based on data presented in Section 2.5.l.l.6.6.7.2, it is concluded that the magnitude of contractional horizontal strain is also small. Therefore, since the chief functions of seismicity associated with fluid withdrawal or injection are small, it is expected that the seismicity will be of small magnitude. An earthquake of this small magnitude would not have an effect on the design basis for the STPEGS.

STPEGS UFSAR Q&R 2.5-2 Revision 13 Response (Continued)

A paragraph that reports the absence of geothermal wells and summarizes the potential for geothermal development in the STPEGS site vicinity has been included in Section 2.5.1.1.6.6.7.2. Section 2.5.2.3 has been amended to include a discussion of the potential for ground motion due to fluid injection. References 1. Bebout, D.G., R. G. Loucks, and A. R. Gregory, "Frio Sandstone Reservoirs In The Deep Subsurface Along The Texas Gulf Coast - Their Potential For Production of Geopressured Geothermal Energy", Bureau of Economic Geology, Report Investigation No. 91, University of Texas, Austin, 1978. 2. Gustavson, Thomas C., and Charles W. Kreitler, "Geothermal Resources Of The Texas Gulf Coast - Environmental Concerns Arising From The Production And Disposal Of Geothermal Waters", Bureau Of Economic Geology, Geologic Circular 76-7, University Of Texas, Austin, 1976. 3. Yerkes, R. F., and R. O. Castle, "Seismicity And Faulting Attributable To Fluid Extraction", Engineering Geology, Vol. 10 (1976), pp. 151-167.

STPEGS UFSAR Q&R 2.5-3 Revision 13 Question 230.3N Examine and provide the interpretation including figures of any seismic reflection lines which may have been shot within five miles of the site, Post CP Safety Evaluation Report.

Response Sections 2.5.1.2.5 and 2.5.4.4 have been updated to include seismic information obtained in l983 and its interpretation. The sharper definition of the newer seismic lines have reinforced the earlier interpretation and only changed minor details off-site in the geologic structure. (Figures 2.5.1-6 through 2.5.1-12 have also been added.)

STPEGS UFSAR Q&R 2.5-4 Revision 13 Question 230.4N In the FSAR, you have indicated that growth faults are not a source of earthquakes. Provide a discussion, including supporting basis which you have used to support your statement. Discuss this in light of the article by Mauk, Sorrel's and Kimball, 1981. (Fifth Geopressured Geothermal Energy Conference, Baton Rouge, La). Response Growth "faults" are not associated with seismic activity capable of generating earthquakes which could cause damaging ground motion at STPEGS. As noted in Section 2.5.2.4: "The microseismic ground motion which may result from nontectonic sources such as growth "faults" is considered insignificant in relation to the ground shaking that may result from tectonic sources in basement rocks... The upper Mesozoic and Cenozoic sequence in which growth "faults" are known to occur are incapable of storing significant amounts of strain energy."

Based on an evaluation Texas Gulf Coastal Plain geology, growth "faults" flatten at depth and do not extend into basement rock, which is evidence that they are not caused by tectonic forces nor are they an extension upward of basement faults. It is therefore concluded that growth "faults" are the result of gravitational forces acting on the poorly consolidated sediments overlying downwarping basement rock (Section 2.5.1.1.6.6.6). Mauk, et. al. report microearthquake activity associated with growth "faults" in Brazoria County, Texas and Parcperdue, Vermillion Parish, Louisiana. This activity may be either high-stress-drop microearthquakes associated with the top of a geopressured zone* or low-stress-drop microearthquakes associated with gravity slide phenomenon. In either case this activity is: "... very low and the size (magnitude) of the events is very small. No events have been recorded with magnitudes larger than 1.5 (Mauk, et al, P. 106)."

Therefore, it is concluded that ground motion that might be generated by growth "faults" will not result in shaking which will affect plant design at the STP site.

Section 2.5.1.1.6.6.6 has been revised to reflect this conclusion. The observation that nontectonic, microseismic activity may be associated with growth "faults" is clarified in revised Section 2.5.2.4.

  • A geopressured zone exists where fluid pressure in the aquifer exceeds normal hydrostatic pressure of 0.465 pounds per square inch per foot of depth.

STPEGS UFSAR Q&R 2.5-5 Revision 13 Question 230.5N Recent installations of seismic networks in the Central U. S. have resulted in significant additions to the history of the site area (of East Texas Seismic Network operated by the University of Texas). Many of the earthquakes listed in Tables 2.5.2-3 and 2.5.2-4 of the STP PSAR have been relocated and/or reevaluated. For instance the 1964 earthquakes in the vicinity of Hemphill, East Texas are considered a swarm of events with approximately the same epicenter, the largest of which had an estimated magnitude of 4.4 (mb) (Ref. 1). On November 5, 1963 an earthquake occurred in the Gulf of Mexico with a magnitude of mb = 4.8 (determined from instrumental data). Update the above earthquake listings and maps to show the most recent information regarding both historical and instrumental seismicity. Include magnitude estimates wherever possible. Sources include references 1, 2, 3 and 4.

Response See revised Section 2.5.2 which incorporates the updated seismic history. Most of the data on earthquakes in the PSAR and UFSAR have been superseded by these more recent catalogs. For those few events for which no updated source information was found, the original PSAR and UFSAR source was retained. In particular, this includes events for which the best current information is DOC (Docekal, 1970).

STR is a compilation of earthquake data cataloged by state by Stover of the U.S. Geological Survey. Other source information from the USGS is designated GS.

EQH represents the updated Earthquake History of the United States published by NOAA (1982). Finally, the Oklahoma Gelophysical Observatory has a compilation of local events which inlcude sources OKO (their own event locations) and OKU (epicenter information taken from U. S. Earthquakes).

In combining all the different catalogs, a hierarchy was developed so that the best information was always retained. In order of most to least preferred, this hierarchy is: DEG,; PEN, CAR; NUT, SLU; EUS, STR; OKU, OKO, BOL; EQH; CGS, PDE, GS, G-R; and DOC, where sources within a common set of semicolons have comparable weights.

No change resulting from this reevaluation results in a change in the arguments leading to the Project design basis earthquake.

STPEGS UFSAR Q&R 2.5-6 Revision 13 References

1. Barstowm, N. L., K. G. Brill, O. W. Nuttli, P. W. Pomeroy. "An Approach to Seismic Zonation for Siting Nuclear Electric Power Generating Facilities in the Eastern United States" (NUREG/CR-1557), May 1981. 2. Carlson, Steven M., "Investigations of Recent and Historical Seismicity in East Texas". MA thesis May, 1984 University of Texas, Austin Texas.
3. Dewey, J. W. and D. W. Gordon, 198, "Seismicity of the Eastern United States and Adjacent Canada, 1925-1976"; to be published as a U. S. Geological Survey Professional Paper.
4. NGSDC, National Geophysical and Solar-Terrestrial Data Center, 1981 Earthquake Data File listing of magnetic tape. 5. Coffman, J. L. and C. A. Von Hake, Earthquake History of the United States, Publication 41.1, revised edition (through 1970), 1982 reprint with supplement (1971-1980), U. S. Department of Commerce, NOAA. 6. Pennington, W. D. and S. M. Carlson, "Observations from the East Texas Seismic Network", Bureau of Economic Geology, University of Texas, Austin, Texas 1984.

STPEGS UFSAR Q&R 2.5-7 Revision 13 TABLE Q230.05N-1 ALL TECTONIC EARTHQUAKES WITHIN 200 MILES OF THE SITE 1 - Year DateMo Dy Hr Time (GMT) Mn Sec Lat Lon Mag Int Sou DistMi 1873 5 1 4 30 0.0 30.25 97.60 3.6 4.0 CAR 137.4 1887 1 5 17 57 0.0 30.15 97.06 3.6 5.0 CAR 111.8 1887 1 31 22 14 0.0 30.53 96.30 3.8I 4.0 CAR 120.7 1902 10 9 18 0 0.0 30.10 97.60 3.6 5.0 CAR 130.1 1910 5 8 17 30 0.0 30.10 96.00 3.6 4.0 CAR 90.1 1910 5 12 0 0 0.0 30.10 96.00 3.6 0.0 NUT 90.1 1914 12 30 1 0 0.0 30.50 95.90 3.5 4.0 CAR 117.9 1925 0 0 0 0 0.0 29.60 94.80 3.8I 4.0 CAR 93.4 1952 10 17 15 48 0.0 30.10 93.80 3.8 4.0 CAR 162.4 1956 1 7 0 0 0.0 29.30 94.80 3.8I 4.0 EUS 82.9 1956 1 8 0 35 0.0 29.30 94.80 3.8 0.0 NUT 82.9 1959 10 15 15 45 0.0 29.80 93.10 3.8 0.0 NUT 190.6 1964 6 3 9 37 0.0 31.00 94.00 3.6 4.0 NUT 195.3 1966 3 24 23 45 0.0 30.00 94.00 3.0 0.0 NUT 148.6 1970 2 3 0 0 0.0 31.00 97.00 3.8 0.0 NUT 162.5 1973 12 25 2 46 0.0 28.82 98.20 3.8N 4.0 CAR 130.9 1974 4 20 23 46 0.0 28.80 98.20 0.0 0.0 CAR 130.9 1974 6 24 18 3 0.0 28.80 98.20 0.0 0.0 CAR 130.9 1974 8 1 13 34 0.0 28.80 98.20 0.0 0.0 CAR 130.9 1975 10 26 21 41 0.0 28.80 98.20 0.0 0.0 CAR 130.9 1982 3 28 23 24 32.9 28.83 98.19 3.0 0.0 CAR 130.3 1983 7 23 15 24 39.1 28.83 98.19 3.4 5.0 CAR 130.3 1983 7 23 22 41 0.0 28.83 98.19 3.3I 3.0 CAR 130.3

NOTE: All reported magnitudes are mb or its equivalent mblg unless otherwise noted. I - After magnitude indicates that the magnitude value has been calculated from intensity based on Nuttli (1974): mb = 1.75 + 0.5*Io. N - Indicates magnitude from Nuttli's catalog in Barstow et al. (1981).

STPEGS UFSAR Q&R 2.5-8 Revision 13 TABLE Q230.05N-2 ALL TECTONIC EARTHQUAKES WITHIN 600 MILES OF THE SITE WITH INTENSITY V AND GREATER MAGNITUDE 3.5 AND GREATER - Year Date Mo Dy Hr Time (GMT) Mn Sec Lat Lon Mag Int Sou DistMi 1699 12 25 13 0 0.0 35.20 90.00 4.3I 5.0 EUS 566.0 1780 2 6 0 0 0.0 30.40 87.20 4.8I 6.0 STR 543.4 1843 1 5 2 45 0.0 35.50 90.50 6.0 8.0 NUT 564.6 1843 2 17 5 0 0.0 35.50 90.50 4.8 5.0 NUT 564.6 1873 5 1 4 30 0.0 30.25 97.60 3.6 4.0 CAR 137.4 1875 10 28 3 0 0.0 35.10 90.00 3.8 0.0 NUT 560.8 1879 9 26 3 10 0.0 35.30 90.30 3.9 4.0 NUT 560.6 1880 7 14 2 30 0.0 35.30 90.30 4.1 4.0 NUT 560.6 1881 10 7 16 52 0.0 35.10 90.00 3.8 4.0 NUT 560.8 1882 10 22 22 15 0.0 34.00 96.00 5.5 6.0 CAR 358.7 1883 6 11 18 16 0.0 35.10 90.00 4.2 6.0 NUT 560.8 1883 12 5 15 20 0.0 36.30 91.20 4.6 5.0 NUT 589.2 1884 11 30 5 0 0.0 35.50 89.70 4.0 4.0 NUT 592.8 1886 2 5 1 0 0.0 32.80 88.00 5.3I 5.0 EQH 551.9 1887 1 5 17 57 0.0 30.15 97.06 3.6 5.0 CAR 111.8 1888 11 3 0 0 0.0 35.40 90.40 3.8 4.0 NUT 562.5 1889 7 20 1 32 0.0 35.20 90.00 3.8 6.0 NUT 566.0 1891 1 8 6 0 0.0 31.70 95.20 3.8 6.0 CAR 206.5 1891 1 14 0 0 0.0 35.10 90.00 3.6 4.0 NUT 560.8 1898 1 27 1 35 0.0 34.60 90.60 3.8 4.0 NUT 512.5 1899 12 1 18 50 0.0 36.80 94.40 3.8 4.0 NUT 560.0 1900 12 0 0 0 0.0 36.00 96.80 3.8 4.0 NUT 498.6 1902 10 9 18 0 0.0 30.10 97.60 3.6 5.0 CAR 130.1 1905 2 3 0 0 0.0 30.50 91.10 4.3I 5.0 STR 319.6 1907 1 11 7 45 0.0 37.10 97.00 3.8 4.0 NUT 575.2 1910 5 8 17 30 0.0 30.10 96.00 3.6 4.0 CAR 90.1 1910 5 12 0 0 0.0 30.10 96.00 3.6 4.0 NUT 90.1 1911 3 31 16 57 0.0 33.80 92.20 4.3 6.0 NUT 413.0 1911 3 31 18 10 0.0 33.80 92.20 3.8 5.0 NUT 413.0 1914 12 30 1 0 0.0 30.50 95.90 3.5 4.0 NUT 117.9 1915 10 8 16 50 0.0 35.70 95.30 3.7 3.0 NUT 477.9 1917 3 24 0 0 0.0 35.30 101.20 4.2 5.0 NUT 540.7 1917 3 27 19 56 0.0 35.30 101.30 3.8 6.0 NUT 544.0 1917 3 28 13 56 0.0 35.30 101.30 4.8I 6.0 DOC 544.0 1917 3 28 17 38 0.0 35.30 101.30 4.8I 6.0 DOC 544.0 1917 6 29 20 23 0.0 32.69 87.50 4.3I 5.0 BOL 574.5 1917 6 30 1 23 0.0 32.70 87.50 4.3I 5.0 EQH 574.8 1918 0 0 0 0 0.0 35.50 97.70 3.6 3.3 NUT 472.2 1918 9 10 16 30 0.0 35.50 98.00 3.6 6.0 NUT 476.1 1918 9 11 8 0 0.0 35.51 97.95 4.8I 6.0 DOC 476.1 1918 9 11 6 30 0.0 35.50 97.90 3.6 6.0 NUT 474.8 1918 10 4 9 21 0.0 34.70 91.70 4.4 5.0 NUT 480.5 1918 10 13 9 30 0.0 36.10 91.00 3.8 0.0 NUT 583.1 1918 10 16 3 30 0.0 35.20 89.20 4.3I 5.0 EQH 596.5 1919 4 8 12 30 0.0 36.20 91.30 3.6 4.0 NUT 580.5 STPEGS UFSAR Q&R 2.5-9 Revision 13 TABLE Q230.05N-2 (Continued) ALL TECTONIC EARTHQUAKES WITHIN 600 MILES OF THE SITE WITH INTENSITY V AND GREATER MAGNITUDE 3.5 AND GREATER . Year Date Mo Dy Hr Time (GMT) Mn Sec Lat Lon Mag Int Sou DistMi 1919 11 3 20 40 0.0 36.30 91.00 3.6 5.0 NUT 594.9 1923 3 27 8 0 0.0 34.60 89.70 3.9 4.0 NUT 547.1 1923 10 28 17 10 0.0 35.50 90.40 4.5 7.0 NUT 568.0 1923 11 26 23 25 0.0 35.50 90.40 4.1 4.0 NUT 568.0 1924 1 1 1 5 0.0 35.40 90.30 4.6 5.0 NUT 566.0 1925 1 27 22 42 0.0 36.20 91.70 3.8 3.0 NUT 569.7 1925 7 8 16 0 0.0 36.20 93.20 3.9 4.0 NUT 536.6 1925 7 29 11 30 0.0 34.50 101.20 3.8 4.0 NUT 496.8 1925 7 30 8 0 0.0 34.50 100.30 4.2 5.0 NUT 466.3 1925 7 30 12 17 0.0 35.40 101.30 4.9 6.0 NUT 549.6 1926 1 20 0 0 0.0 35.60 94.90 4.2 5.0 NUT 473.8 1926 6 20 14 20 0.0 35.60 94.90 4.2 5.0 NUT 473.8 1927 5 7 8 28 0.0 35.70 90.60 4.8 7.0 NUT 572.5 1927 11 13 16 21 0.0 32.30 90.20 3.8 4.0 NUT 423.7 1927 12 15 4 30 0.0 28.90 89.40 3.9 4.0 NUT 402.6 1928 11 1 4 12 49.0 27.00 105.50 6.3 0.0 G-R 591.3 1928 11 10 6 20 0.0 36.10 91.10 3.8C 4.0 NUT 580.2 1928 12 26 3 25 0.0 36.10 91.10 3.8 4.0 NUT 580.2 1929 7 28 17 0 0.0 28.90 89.40 3.8 4.0 NUT 402.6 1929 12 28 0 30 0.0 35.50 97.90 4.0 6.0 NUT 474.8 1930 1 26 21 0 0.0 36.10 91.10 3.8 4.0 NUT 580.2 1930 3 27 8 56 0.0 35.10 90.10 3.5 4.0 NUT 557.1 1930 10 19 12 12 0.0 30.10 91.00 4.2 6.0 NUT 316.9 1930 11 16 12 30 0.0 34.30 92.80 3.3 5.0 NUT 424.8 1931 8 16 11 40 21.0 30.60 104.10 5.8C 8.0 NUT 500.1 1931 8 19 1 36 0.0 30.60 104.10 4.2 5.0 NUT 500.1 1931 12 17 3 36 0.0 34.10 89.80 4.7 7.0 NUT 519.0 1932 4 9 10 17 0.0 31.70 96.40 3.9 6.0 CAR 201.4 1933 8 19 19 30 0.0 35.50 98.00 3.4 6.0 NUT 476.1 1933 12 9 8 50 0.0 35.80 90.20 3.2 6.0 NUT 591.3 1934 4 11 17 40 0.0 33.90 95.50 3.9 5.0 NUT 353.3 1934 7 3 3 10 41.0 35.20 90.00 3.8 4.0 NUT 566.0 1936 3 14 17 20 0.0 34.00 95.20 3.6 5.0 NUT 362.2 1936 6 20 3 24 3.5 35.31 100.77 4.5 5.0 D&G 527.6 1937 5 17 0 49 46.0 36.10 90.60 4.3 5.0 NUT 595.2 1937 6 8 14 26 0.0 35.30 96.90 3.6 4.0 NUT 451.2 1938 4 26 5 42 0.0 34.20 93.50 3.8 4.0 NUT 401.6 1938 9 18 3 34 28.3 35.41 90.25 4.8 5.0 D&G 568.3 1939 6 1 7 30 0.0 35.00 96.40 4.3 4.0 NUT 428.2 1939 6 19 21 43 12.0 34.10 92.60 4.3 5.0 NUT 418.3 1940 12 2 16 16 0.0 33.00 94.00 3.8 4.0 NUT 314.2 1941 6 28 18 30 0.0 32.30 90.80 3.6 4.0 NUT 394.9 1941 10 18 7 48 0.0 35.40 99.00 3.2 5.0 NUT 487.1 1941 11 15 3 7 0.0 35.10 90.00 3.8 4.0 NUT 560.8 1941 11 17 3 8 0.0 35.50 89.70 4.7 6.0 NUT 592.8 STPEGS UFSAR Q&R 2.5-10 Revision 13 TABLE Q230.05N-2 (Continued) ALL TECTONIC EARTHQUAKES WITHIN 600 MILES OF THE SITE WITH INTENSITY V AND GREATER MAGNITUDE 3.5 AND GREATER Year Date Mo Dy Hr Time (GMT) Mn Sec Lat Lon Mag Int Sou DistMi 1942 6 12 4 50 0.0 36.40 97.90 3.7 3.0 NUT 535.2 1947 9 20 21 30 0.0 31.90 92.60 4.0 4.0 NUT 296.8 1947 12 15 3 27 0.0 35.60 90.10 4.0C 5.0 NUT 583.8 1950 3 20 13 23 0.0 33.30 97.80 3.8 4.0 CAR 327.5 1950 9 17 5 48 0.0 35.70 89.90 3.8 4.0 NUT 596.2 1951 6 20 19 37 10.0 35.00 102.00 4.5 6.0 NUT 552.5 1952 4 9 16 29 29.0 35.40 97.80 5.1 7.0 NUT 466.7 1952 4 11 20 30 0.0 35.40 97.80 3.9 4.0 NUT 466.7 1952 4 16 5 58 0.0 35.40 97.80 3.9 3.0 NUT 466.7 1952 4 16 6 5 0.0 35.40 97.80 3.9 5.0 NUT 466.7 1952 6 16 0 30 0.0 35.40 97.80 3.8 4.0 NUT 466.7 1952 7 17 0 30 0.0 35.40 97.80 3.6 4.0 NUT 466.7 1952 7 17 2 0 0.0 35.40 97.80 3.6 4.0 NUT 466.7 1952 8 14 21 40 0.0 35.40 97.80 3.8 4.0 NUT 466.7 1952 10 8 4 15 0.0 35.10 96.50 3.8 4.0 NUT 435.4 1952 10 17 15 48 0.0 30.10 93.80 3.8 4.0 CAR 162.4 1953 3 16 12 50 0.0 35.40 97.90 3.4 3.0 NUT 468.1 1953 3 17 13 12 0.0 35.60 98.00 3.8 5.0 NUT 482.8 1953 3 17 14 25 0.0 35.60 98.00 4.2 6.0 NUT 482.8 1953 5 12 18 50 0.0 35.60 90.30 3.8 4.0 NUT 576.9 1953 6 6 17 40 0.0 34.70 97.70 3.8 4.0 NUT 408.8 1954 4 11 0 0 0.0 35.00 96.40 3.8 4.0 NUT 428.2 1954 4 12 23 5 0.0 35.00 96.403 3.8 4.0 NUT 428.2 1954 4 13 18 48 0.0 35.10 96.40 3.8 4.0 NUT 435.1 1954 4 27 2 9 27.0 35.10 90.00 4.3I 5.0 EUS 560.8 1954 4 27 4 9 0.0 35.10 90.00 4.4 5.0 NUT 560.8 1955 1 27 0 37 0.0 30.60 104.50 3.8 4.0 NUT 523.4 1955 2 1 14 45 0.0 30.40 89.10 4.4 5.0 NUT 432.1 1956 1 8 0 35 0.0 29.30 94.80 3.8 4.0 NUT 82.9 1956 2 16 23 30 0.0 35.40 97.30 4.1 6.0 NUT 461.2 1956 4 2 16 3 18.0 34.20 95.60 3.7 5.0 NUT 373.4 1956 9 27 14 15 0.0 31.90 88.40 3.8 4.0 NUT 504.0 1956 10 30 10 36 0.0 36.20 95.90 4.2 7.0 NUT 510.5 1957 3 19 0 16 38.0 32.00 95.00 4.1 5.0 OKU 229.5 1957 3 19 16 37 38.0 32.60 94.70 4.3 5.0 CAR 274.2 1958 1 26 16 56 0.0 35.20 90.00 4.3I 5.0 EQH 566.0 1958 5 20 1 25 0.0 35.50 90.40 3.8 4.0 NUT 568.0 1958 11 6 23 8 0.0 29.90 90.10 3.8 4.0 NUT 366.5 1958 11 19 18 15 0.0 30.50 91.20 3.3 5.0 NUT 314.1 1959 2 10 20 5 0.0 35.50 100.90 4.5 5.0 NUT 542.6 1959 6 15 12 45 0.0 34.70 96.70 4.0 5.0 NUT 408.8 1959 6 17 10 27 10.6 34.64 98.05 4.3 6.0 D&G 419.8 1959 10 15 15 45 0.0 29.80 93.10 3.8 4.0 NUT 190.6 1960 5 4 16 31 32.0 34.20 92.00 3.8 4.0 NUT 442.3 1961 1 11 1 40 0.0 34.90 95.50 3.8 5.0 NUT 422.0 STPEGS UFSAR Q&R 2.5-11 Revision 13 TABLE Q230.05N-2 (Continued) ALL TECTONIC EARTHQUAKES WITHIN 600 MILES OF THE SITE WITH INTENSITY V AND GREATER MAGNITUDE 3.5 AND GREATER Year Date Mo Dy Hr Time (GMT) Mn Sec Lat Lon Mag Int Sou DistMi 1961 4 26 7 5 0.0 34.60 95.00 3.8 3.0 NUT 404.8 1961 4 27 7 30 0.0 34.90 95.30 4.1 5.0 NUT 423.0 1963 9 10 19 40 8.3 28.90 104.00 4.2 0.0 CGS 482.4 1963 9 13 10 51 57.9 29.10 105.90 4.7 0.0 D&G 597.2 1963 11 5 22 45 3.4 27.49 92.58 4.8 0.0 D&G 299.5 1964 2 2 8 23 0.0 35.10 99.70 4.2 5.0 NUT 484.7 1964 4 24 1 20 54.2 31.38 93.81 3.7 5.0 D&G 222.8 1964 4 24 7 33 51.9 31.42 93.81 3.7 4.0 D&G 225.0 1964 4 28 0 30 45.7 31.40 93.82 3.4 53.0 D&G 223.5 1964 4 28 21 18 35.0 31.20 93.90 4.0N 5.0 CAR 209.7 1964 5 7 20 1 39.0 31.20 94.00 3.2 5.0 CAR 206.1 1964 6 2 23 0 0.0 31.30 94.00 4.2 5.0 CAR 211.6 1964 6 3 0 0 0.0 31.30 94.00 4.2 5.0 CAR 211.6 1964 6 3 9 37 0.0 31.00 94.00 3.6 4.0 CAR 195.3 1964 7 23 23 57 55.1 20.10 96.40 4.2 0.0 PDE 598.4 1964 8 16 11 33 31.0 31.40 93.80 3.0 5.0 NUT 224.2 1965 4 13 9 35 46.0 30.30 105.10 4.2 0.0 NUT 555.0 1965 8 30 5 17 38.0 32.10 102.30 3.5 4.0 NUT 437.3 1966 3 11 10 24 20.3 21.70 95.40 4.7 0.0 PDE 489.6 1966 7 20 9 4 58.8 35.64 101.33 3.8 5.0 D&G 564.1 1966 8 14 15 25 52.0 31.70 103.10 4.3 6.0 NUT 467.0 1966 8 19 4 15 44.6 30.30 105.60 4.1 0.0 CGS 584.6 1966 8 19 7 38 53.6 30.20 105.70 3.9 0.0 CGS 589.6 1966 8 19 8 38 21.9 30.30 105.60 4.0 0.0 CGS 584.6 1966 8 20 6 36 2.7 30.10 105.50 4.3 0.0 CGS 576.9 1966 8 21 2 57 25.2 30.00 105.60 4.1 0.0 CGS 582.1 1966 11 28 2 20 57.3 30.40 105.40 3.8 0.0 CGS 573.8 1966 12 5 10 10 37.8 30.40 105.40 4.2 0.0 CGS 573.8 1967 6 4 16 14 12.6 33.55 90.84 4.5 6.0 D&G 449.7 1967 6 29 13 57 6.5 33.55 90.81 4.0 5.0 D&G 450.9 1968 1 4 0 0 0.0 34.90 95.50 3.8 4.0 NUT 422.0 1968 6 4 22 13 18.0 27.33 102.96 4.4 0.0 CGS 434.2 1968 10 14 14 42 54.0 34.00 96.80 3.5 6.0 NUT 361.5 1969 1 1 23 35 38.7 34.99 92.69 4.5 6.0 D&G 470.2 1969 4 13 6 27 51.0 34.20 96.30 3.5 0.0 NUT 372.8 1969 5 2 11 33 21.7 35.29 96.31 4.0 5.0 D&G 447.9 1969 10 19 11 51 34.3 30.81 105.76 3.8 0.0 D&G 599.8 1970 1 7 17 45 0.0 35.20 89.90 3.8 4.0 NUT 569.7 1970 2 3 0 0 0.0 31.00 97.00 3.8 4.0 NUT 162.5 1971 3 14 17 27 54.6 33.18 87.84 3.9 0.0 D&G 572.6 1971 3 15 14 53 22.0 32.80 88.30 3.5 0.0 NUT 536.5 1971 3 16 2 37 28.0 32.80 88.30 3.7 0.0 NUT 536.5 1971 7 31 14 53 49.4 31.65 103.12 3.8 4.0 D&G 466.7 1971 10 1 18 49 38.5 35.77 90.49 4.1 6.0 D&G 580.0 1973 1 8 9 11 37.0 33.80 90.60 3.5 3.0 NUT 471.7 STPEGS UFSAR Q&R 2.5-12 Revision 13 TABLE Q230.05N-2 (Continued) ALL TECTONIC EARTHQUAKES WITHIN 600 MILES OF THE SITE WITH INTENSITY V AND GREATER MAGNITUDE 3.5 AND GREATER Year Date Mo Dy Hr Time (GMT) Mn Sec Lat Lon Mag Int Sou DistMi 1973 12 25 2 46 0.0 29.00 98.30 3.8 4.0 NUT 137.6 1974 2 15 13 33 49.2 36.40 100.69 4.6 5.0 D&G 589.9 1974 2 15 22 32 38.2 34.04 92.98 3.6 3.0 D&G 404.2 1974 2 15 22 35 46.6 34.07 93.12 3.6 3.0 D&G 402.4 1974 2 15 22 49 4.4 34.03 93.04 4.0 5.0 D&G 402.0 1974 11 28 3 35 20.5 32.31 104.14 3.9 0.0 GS 539.9 1974 12 10 6 1 32.7 31.35 87.47 3.0 5.0 PDE 542.6 1974 12 13 5 3 58.0 34.70 91.90 3.4 5.0 NUT 474.3 1974 12 30 8 5 27.1 30.92 103.11 3.7L 0.0 STR 448.8 1975 6 24 11 11 36.6 33.70 87.84 3.8 4.0 D&G 591.2 1975 8 1 7 27 43.8 30.57 104.49 4.8 0.0 D&G 522.4 1975 9 13 1 25 5.6 34.13 97.22 3.4 4.0 D&G 374.2 1975 11 29 14 29 44.9 34.68 97.42 3.5 4.0 D&G 413.6 1976 1 16 19 42 56.9 35.90 92.16 3.3 5.0 D&G 539.7 1976 1 25 4 48 28.5 31.90 103.09 4.1 5.0 D&G 472.1 1976 3 25 0 41 20.0 35.60 90.50 5.0 6.0 NUT 570.2 1976 3 25 1 0 12.0 35.60 90.50 4.5 0.0 D&G 570.2 1976 3 25 23 5 7.1 20.62 99.09 5.0 0.0 PDE 593.8 1976 4 19 4 42 46.9 36.06 99.79 3.5 4.0 D&G 545.2 1976 9 25 14 6 55.8 35.58 90.47 3.6 5.0 D&G 570.1 1977 2 12 6 51 44.6 28.34 105.13 3.7 0.0 GS 553.1 1977 5 4 2 0 24.3 31.95 88.44 3.6 5.0 D&G 503.5 1977 6 2 23 29 10.6 34.56 94.17 4.0 6.0 D&G 412.3 1977 6 7 23 1 25.0 33.13 100.94 3.5 0.0 D&G 416.8 1977 11 28 1 40 50.5 32.95 100.84 3.5 0.0 PDE 404.0 1978 3 2 10 4 53.0 31.55 102.50 3.5L 0.0 D&G 430.5 1978 5 3 23 35 15.2 25.79 103.05 4.4 0.0 PDE 477.8 1978 6 16 11 46 56.0 32.99 100.88 4.4 5.0 D&G 407.6 1978 7 24 8 6 16.9 26.38 88.72 4.9 0.0 D&G 478.7 1978 8 31 0 31 0.3 33.61 89.42 3.5 5.0 PDE 513.5 1978 9 23 7 34 3.7 33.96 91.92 3.2 5.0 D&G 431.3 1978 12 11 2 6 50.1 31.91 88.47 3.5 5.0 D&G 500.5 1979 2 27 22 54 54.8 35.96 91.20 3.4 6.0 D&G 569.0 1979 3 14 4 37 0.0 35.50 97.80 4.3I 5.0 EQH 473.5 1979 6 25 17 11 13.8 35.56 90.45 3.0 5.0 D&G 569.6 1979 7 25 3 16 0.0 34.00 97.60 4.3I 5.0 EQH 370.3 1980 6 9 22 37 0.0 35.50 101.10 4.3I 5.0 EQH 548.9 1980 11 2 10 1 0.0 35.50 97.80 4.3I 5.0 EQH 473.5 1980 11 13 23 55 48.2 34.37 97.08 2.7 5.0 OKO 389.1 1981 6 26 8 33 27.0 35.85 90.08 3.6 5.0 SLU 598.1 1981 7 11 21 9 21.8 34.85 97.73 3.5 5.0 OKO 429.0 1981 11 6 12 36 41.0 31.92 95.20 3.2C 5.0 PEN 221.2 1982 1 4 16 56 8.1 31.18 102.49 3.9 3.0 PDE 420.0 1982 1 20 14 1 30.6 35.22 92.20 3.5 3.0 PDE 496.8 1982 1 21 0 33 54.3 35.18 92.25 4.5 5.0 SLU 493.1 STPEGS UFSAR Q&R 2.5-13 Revision 13 TABLE Q230.05N-2 (Continued) ALL TECTONIC EARTHQUAKES WITHIN 600 MILES OF THE SITE WITH INTENSITY V AND GREATER MAGNITUDE 3.5 AND GREATER Year Date Mo Dy Hr Time (GMT) Mn Sec Lat Lon Mag Int Sou Dist Mi 1982 1 21 15 45 39.0 35.18 92.15 4.1 0.0 SLU 495.8 1982 1 22 23 54 22.6 35.25 92.29 3.7 0.0 SLU 496.3 1982 1 24 3 22 45.2 35.22 92.18 4.3 5.0 SLU 497.4 1982 2 24 19 27 15.3 35.30 92.25 3.9 5.0 SLU 500.4 1982 3 1 0 12 11.7 35.20 92.11 4.3 5.0 SLU 498.0 1982 3 21 9 39 16.0 25.18 101.05 4.4 0.0 PDE 396.3 1982 5 3 7 54 48.6 33.99 96.47 3.0 6.0 OKO 358.9 1982 5 31 17 49 19.9 35.20 92.24 3.6 4.0 PDE 494.6 1982 5 31 18 21 19.4 35.20 92.25 3.6 0.0 PDE 494.3 1982 7 5 4 14 50.1 35.19 92.23 3.8 0.0 SLU 494.2 1982 9 25 23 17 5.5 35.21 92.23 3.5 0.0 SLU 495.4 1983 7 23 15 24 39.1 28.83 98.19 3.4 5.0 CAR 130.3

Note: All reported magnitudes are mb or its equivalent mblg unless otherwise noted.

I - After magnitude indicates that the magnitude value has been calculated from intensity based on Nuttli (1974): mb = 1.75 + 0.5*Io. L - After magnitude indicates that the magnitude value is local magnitude M1 as defined by Richter (1958). C - Indicates magnitude from Carlson (1984).

N - Indicates magnitude and intensity from Nuttli's catalog in Barstow (1981).

STPEGS UFSAR Q&R 2.5-14 Revision 13

Figure Q230.05N-1 STPEGS UFSAR Q&R 2.5-15 Revision 13

Figure Q230.05N-2 STPEGS UFSAR Q&R 2.5-16 Revision 13 Question 230.6N Carlson (Reference 1) reports that the 1932 Mexia earthquake (31.7N96.4W; mb = 3.9), the 1957 Gladewater earthquake (32.6N94.7W; mb = 4.3) and the 1983 Fashing earthquake (28.83N98.19W; mb = 3.0) occurred near large oil and/or gas fields, suggesting that a relation between seismicity and fluid withdrawal could exist. In what ways were the conditions which led to these or other "induced" earthquakes similar to or different from those in the oil/gas fields surrounding the site. What is the potential of ground motion at the site from induced shallow earthquakes. Response Carlson (Reference 2.5.2-45) discusses low level seismicity possibly associated with fluid withdrawal and fluid injection. He indicates the proximity of several small earthquakes (Mexia, 1932; Gladewater, 1957; and Fashing, 1932) to large oil and/or gas fields suggests a possible relationship to fluid withdrawal. Carlson also suggests the possibility of a correlation of small events with fluid injection for secondary or enhanced recovery of hydrocarbons or salt water. The mechanism proposed by Carlson is stick-slip failure along normal faults near or within oil/gas fields. Failure is proposed to occur either because of increased shear stress along the faults or increased resistance to sliding along the fault surface associated with a decrease in pore pressure. The second mechanism is essentially the opposite of that proposed to explain injection-induced seismicity.

As Carlson acknowledges, evidence for such a mechanism at Mexia and Gladewater is circumstantial at best. Rough coincidence of these earthquakes with the area of highest hydrocarbon production is the strongest argument in favor of some casual association. However, small earthquakes are noted in the Mexia area that are not associated with oil fields, and the size and felt area of the Gladewater events argue for a focal depth well below the oil producing horizons. Carlson does not rule out the possibility of a tectonic origin for either.

Although some instrumental data is available for the 1983 Fashing earthquake, its location is again principally dependent on a survey of felt effects. Carlson postulates a shallow focal depth (about 3.5 km), not far below gas producing depths. Pore pressure has decreased in this field from 1956 to 1982, and Carlson proposes that gradual movement occurring aseismically on the Fashing-Edwards fault nearby may now be occurring episodically and causing small earthquakes.

The general geologic setting and the oil/gas production characteristics of the site area can be compared to those areas discussed by Carlson; however, an evaluation of the potential for similar events due to similar causes near the site must necessarily be qualified. Both the phenomenon of induced by fluid withdrawal earthquakes and the proposed mechanism causing them, if they do in fact occur, are conjectural.

STPEGS UFSAR Q&R 2.5-17 Revision 13 Response (Continued)

Total and annual hydrocarbon production rates at the times of the earthquake clusters reviewed by Carlson are substantially greater than for any fields near the site. For example, by 1932, Mexia field production was running three million barrels annually, 90 million barrels total; annual production for 1983 from the Fashing gas field was over 16,000,000 mcf. In contrast, the total combined 1983 production for all fields within approximately seven miles of the Plant Site was 7,500,000 mcf of gas and 28,000 barrels of oil.

Hydrocarbon extraction in those fields with possible induced seismicity discussed by Carlson is from relatively more component, Cretaceous rocks of the Ouachita Seismotectonic Province, and the hydrocarbon traps occur along faults which is part of that province's structural system.

The most important difference between the site area and those cases studied by Carlson is that there are no known earthquakes near the site area oil/gas fields. This lack of seismicity together with the small magnitudes of all the earthquakes considered by Carlson indicate that the current seismic design basis is adequate to supersede any fluid withdrawal induced events in the site area.

References 1. Carlson Steven M., (1984) "Investigations of Recent and Historical Seismicity in East Texas". MA thesis (May 1984) University of Texas at Austin STPEGS UFSAR Q&R 2.5-18 Revision 13 Question 230.7N The site is considered to be located in the Gulf Coast Seismotectonic province (FSAR Figure 2.5.2-4). The historic earthquake with the highest intensity within this province was determined to be the October 19, 1930, Donaldsonville, Louisiana earthquake. Table 2.5.2-3 of the STP PSAR lists the intensity as VII (Rossi-Forel). Barstow (Reference 2) list the intensity as VI (Modified Mercalli) and the magnitude as 4.7 (mb). The largest instrumentally recorded earthquake within this province is November 5, 1963 event located in the Gulf of Mexico (magnitude mb = 4.8).

In discussing the maximum earthquake potential specific mention is made that local soil conditions probably influenced the reported intensities of the 1930, Donaldsonville earthquake (of FSAR pp. 2.5.2-15, 19, 20). Ground motion estimates for the seismic design of the STP were based on intensity-peak acceleration relationships (Reference FSAR p. 2.5.2-18). Selecting the appropriate maximum earthquake based on magnitude estimates, and using distances of 10 to 15 km, compare the South Texas Design Spectrum to spectra derived from published magnitude-acceleration/velocity relationships such as Nuttli et at (References 5 and 6). To obtain the appropriate spectral acceleration and velocity ordinates refer to amplification factors proposed by Newmark and Hall (Reference 7). Compare design spectra to the 84th percentile ground motion estimates and discuss the significance of exceedances if any.

Response The southern boundary of the Gulf Coast Seismotectonic Province is generally not well defined and may, in fact, exclude the November 5, 1963, earthquake located in the Gulf of Mexico. Frolich (1982) considers a number of earthquakes in the Gulf of Mexico and concludes that they may be caused by flexure of the deep crust due to loading of the lithosphere by Mississippi River deltaic sediments. There is no evidence that such a mechanism is characteristic of the Gulf Coast Seismotectonic Province where the South Texas Project site is located. The crustal stress regime implied by a focal mechanism solution from an earthquake in the Gulf of Mexico in 1978 is shallow thrusting along planes parallel to the Gulf Coast. This is exactly the opposite of the shallow stress regime implied by coastal geologic structures.

Appropriate maximum magnitudes for the Gulf Coast Seismotectonic Province are in the 4.6 to 4.8 range (mb scale) independent of whether these magnitudes are based on an interpretation of the 1930 Donaldsonville earthquake or the 1963 Gulf of Mexico event. The appropriate focal depth are about 10 km (see Section 2.5.1.1.6.3.2). Nuttli and Herrmann (1984) give the following attenuation formulas:

1/2 log10 ah (cm/sec²) = 0.57 + 0.50 mb - 0.83log10(R²+h²) -0.00069R 1/2 log10 vh (cm/sec) = -3.60 + 1.00 mb - 0.83log10(R²+h²) -0.00033R STPEGS UFSAR Q&R 2.5-19 Revision 13 Response (Continued)

Where ah and vh are arithmetic averages of peak horizontal acceleration and velocity and R and h (distance and depth) are in kilometers. Substituting h = 10 km, R = 10, 15 km, and mb = 4.8, the results are ah ranges 0.08 to 0.10g and vh ranges 1.42 to 1.74 cm/sec. Average values are ah = 0.09g and vh = 1.58 cm/sec.

These peak values may be multiplied by appropriate amplification factors using the method of Newmark and Hall (1978) to derive 84 percent response spectra. For 5 percent critical damping these factors are 2.71 and 2.30 for acceleration and velocity, respectively. The transition from amplified peak acceleration to amplified peak velocity takes place, according to Newmark and Hall, at about 8 Hz. The South Texas Design Spectrum is clearly conservative at all frequencies and is particularly conservative at long periods (Figure Q230.7N-1).

For completeness it should be noted that the peak acceleration value obtained above depends in part on convention in the derivation of design values. For example, details of regression method and formula application can affect the derived value and, especially at very small distances, there are inadequate data to resolve all uncertainty. Fundamentally, however, it is worth emphasizing that the design earthquake at South Texas is essentially one of intensity VI on the Modified Mercalli scale and that this intensity is not expected to cause any damage to any safety-related structures designed to the criteria of STPEGS.

References 1. Frohlich, Cliff (1982). "Seismicity of the Central Gulf of Mexico. Geology", V. 10, p. 103-106. 2. Newmark, N. M. and W. J. Hall (1978). "Development of Criteria for Seismic Review of Selected Nuclear Power Plant", NUREG/CR-0098

3. Nuttli, O. W. and R. B. Herrmann (1984). "Strong Ground Motion of Mississippi Valley Earthquakes", Journal of Technical Topics in Engineering Vol 110 No.1 May 1984 STPEGS UFSAR Q&R 2.5-20 Revision 13 Figure 230.07N-1 STPEGS UFSAR Q&R 2.5-21 Revision 13 Question 231.1N Present a summary, with conclusions, of Houston Lighting and Power Company's post-CP Safety Evaluation Report geologic and seismologic efforts relative to updating the South Texas Project FSAR through November l981. This summary is to include information derived/produced by both the applicant as well as by others. Please revise appropriate sections of the FSAR (Sections 2.5.1, 2.5.2, 2.5.3 and relevant appendices) accordingly.

Response Chapter 2.5 has been revised to incorporate additional data including information developed during post-CP Safety Evaluation Report (SER) efforts undertaken in response to NRC Questions. The additional information has been incorporated in the appropriate subsection or appendix of the UFSAR and is summarized below. The geologic and seismologic data acquired subsequent to the CP SER and incorporated in Chapter 2.5 through November l98l continues to support the original conclusion presented in the CP SER. Geologic data generated by post-CP SER efforts and incorporated in Section 2.5.1 concern the following topics and are summarized below:

  • Strain energy in Gulf Coast sediments.
  • Update and indicate significance of oil and gas production within 15 miles of the site.
  • Seismic reflection geophysical data.

The sedimentary units in the vicinity of the site have been evaluated in regard to elastic properties and capability to store strain energy. It is concluded that there are effective mechanisms for plastic release of stresses within all elements of the sedimentary rock sequence, precluding the possible accumulation of elastic strain energy even within the more elastic stratigraphic units. This evaluation supports the conclusion that geologic units that are younger and shallower than the Jurassic basement in the Texas Gulf Coast do not provide the conditions required for the storage and release of strain energy sufficient to produce an earthquake of engineering significance to the STPEGS site.

The UFSAR has been updated to provide information on oil and gas production in the site area through December 1983. The significance of this production in terms of regional subsidence has also been considered. This survey indicates a decline in production in the immediate vicinity of the site (South Duncan Slough and Petrucha fields). This production has no effect on plant safety or operation. There has been no subsidence in Matagorda County attributed to the withdrawal of oil and gas as of 1983. (The discussion of oil and gas production in the site vicinity has been updated in response to NRC Q23l.02N).

STPEGS UFSAR Q&R 2.5-22 Revision 13 Response (Continued)

The subsurface geological model at the site, developed from seismic reflection geophysical data, paleontological data, and well log analyses, has been evaluated through comparison with copyrighted and proprietary structural contour maps purchased from geological data services. The data service maps substantiate the broad interpretations of the model. Additional seismic reflection lines, shot subsequent to the CP SER, are being examined and compared with PSAR data. The corresponding section of the UFSAR has been updated in response to NRC Q230.03N.

In addition, portions of the UFSAR text on regional stratigraphy were revised to refine nomenclature and description.

Section 2.5.2 has been revised to clarify terminology and to incorporate additional data on seismic history and new evaluations of earthquake intensity/ground acceleration relationships. The seismic history for the site has been updated through December 3l, 1982. The post-CP SER update indicated that no earthquakes were recorded or reported within a 200-mile radius of the STPEGS site. The site seismologic design bases have not changed. (The seismic history has been updated through December 31, 1982, in response to NRC Q230.2N).

Intensity/ground acceleration relationships proposed subsequent to the CP SER have been evaluated for the STPEGS site. This evaluation has not altered the conclusions regarding the seismic analysis. In summary, the earthquake producing the maximum vibratory ground motion at the site is conservatively estimated to be of Intensity VI (Modified Mercalli). The epicentral acceleration associated with an intensity VI (Modified Mercalli) earthquake is 0.07g.

STPEGS UFSAR Q&R 2.5-23 Revision 13 Question 231.8N Provide a general summary of the near site oil and gas exploration/production that has taken place in the site area since December, 1982. Designate by appropriate text and FSAR figure revision the locations of any completed or newly-permitted exploratory test wells and seismic reflection lines and any changes in the structural interpretation of the site area resulting from these new data. Include in this response the completion dates of all post-CP exploratory wells and seismic reflection surveys including the four TXO/Sies Pros Inc. lines shown on FSAR Figure 2.5.1-6.

Response Near site oil and gas production information is periodically updated upon issuance of the Texas Railroad Commission Oil and Gas Division Annual Report each June. Section 2.5.1.1.6 has been revised to present production data through December, 1985. Section 2.5.1.1 has been revised to include data on Post-CP hydrocarbon exploration including test and production wells and seismic exploration. Information such as locations and dates are provided on Table 2.5.1.1 and Figure 2.5.1-1A.

Other seismic reflection lines near the Plant Site have been shot subsequent to 1982. Two lines are of a quality that makes them potentially useable data. These lines are identified on Figure 2.5.1-1A as Jaecon 1984 and Southwest Minerals. The most recent review of seismic data for the response to NRC Q230.3N resulted in only minor revisions to the interpretation northwest of the site, and no changes at the site itself. It is concluded that the Jaecon 1984 line is in essentially the same location as previously obtained data, and the Southwest Minerals line is located in an area surrounded by previously interpreted data. Any refinement that the Southwest Minerals line would provide will not affect the basic geologic structural interpretation under the plant area. The response to NRC Q231.7N provides information on the post-1975 oil/gas exploration and production drilling.

STPEGS UFSAR Q&R 2.5-24 Revision 13 Question 231.18N Since much of the information presented in Appendix Geotechnical Monitoring, has not been amended for some time (for example, Figure 2.5.C-25B, Regional Subsidence and Deep Aquifer Piezometer Differential Decline, has not been revised since March 1983), please update this appendix and other appropriate FSAR sections to reflect the most current data and conclusions. Response The geotechnical monitoring portions of the UFSAR are currently updated on an annual basis through June of each year and submitted to the NRC during the first quarter of the following year. Review of the various monitoring data has indicated that the performance of Category I foundations is within criteria, and there is no unusual or unexpected behavior in any of the various geotechnical elements monitored.

STPEGS UFSAR Q&R 2.5-25 Revision 13 Question 231.19N Using guidance contained in the Standard Review Plan conduct a lineament analysis of an area within at least five miles of the site using imagery derived from Landsat, Skylab and other appropriate sources not included in the PSAR lineament study (PSAR Figure 2.5.1-44). In addition to identification, discuss the possible origin and address the safety significance of any lineament which may be structurally controlled. Conduct field truth investigations as required. As indicated by the Standard Review Plan, provide the staff with a copy of the imagery used in your analysis.

Response Section 2.5.1.2.5.5 has been revised to incorporate the results of a lineament study conducted Summer, 1985, using post CP imagery. Lineaments identified during this study were reviewed using field checks and comparison with other project data. None of the lineaments identified are correlated with geological structure. Section 2.5.1.2.5.5 describes the scope of the study and provides a location map (Figure 2.5.1-15) of the lineaments. The 1985 lineament study was performed as a confirmatory review to supplement the extensive CP multi-spectral study. The present study used NASA U-2 false-color infrared imagery flown in 1979, based on the evaluation that these data provide the best overview of the five-mile radius study area. Other post-CP imagery was identified. Several Landsat Multispectral Scanner scenes obtained subsequent to 1975 are available (February 1976; December 1976, October 1980; and April 1984, with site area at edge); however, as in the CP study (refer to PSAR Figures 2.5.1-44 and 2.5.1-44A) this imagery was not considered to be appropriate to review within the five mile study radius because of its scale. Side-looking airborne radar imagery was flown along the Texas coast by Litton Aerospace in late 1976 for speculation. This imagery in the form of a composite mosaic was reviewed. Given the mosaic scale (1:400,000) and the relatively low relief of the terrain, it was concluded that the 1976 radar imagery does not represent an improvement over the site-specific radar flown with multiple look-directions for the STP site in 1973. High-altitude black and white photography of approximately the same scale as the false-color U-2 imagery was flown for the ASCS in 1979. The U-2 imagery were considered to provide the better coverage over the low-relief site area. The false-color photography are also a better tool for identifying surface soil tonal, soil moisture, and vegetation features than black and white photography. Aerial photography in the form of black and white sheets at an approximate scale of 1:12,000 flown in 1981 for the USDAs "Agriculture Stabilization and Conservation Service" (ACSC) as well as color-slides at an approximate scale of 1:8000 flown annually for crop monitoring is on file at the ASCS in Matagorda County. This photography was not used in the lineament analysis but the black and white photographs and the slides from 1985 were inspected during a field review of the previously identified lineaments. No new lineaments were observed on these photographs.

STPEGS UFSAR Q&R 2.5-26 Revision 13 This information was previously provided to the NRC in letter ST-HL-AE-1499 dated October 31, 1985. It should be further noted that remote sensing images were transmitted in ST-HL-AE-1262 dated June 5, 1985.

STPEGS UFSAR Q&R 2.5-27 Revision 13 Question 240.16N No sustained pumping (from the deeper aquifer) is permitted within a 4,000 ft radius of the plant area. What is the purpose of this restriction? Is any pumping (other than sustained) permitted.

Response The 4,000 ft sustained pumping exclusion radius is to restrict the withdrawal of significant amounts of groundwater from directly beneath the plant area in order to minimize the potential for regional subsidence resulting from lowering of the groundwater level in the deep aquifer. The relationship between subsidence and groundwater withdrawal is discussed in Section 2.5.1.2.9.6.1. One deep aquifer well is located about 3,200 ft due east of Unit 1. The well (680 ft deep) is to provide the potable water supply and fire training water supply at the Emergency Operations Center (EOC). Water requirements are low and intermittent. Average pumping rate for normal use is anticipated to be 2 gal/min; there is no sustained pumping from this well. Groundwater usage from the EOC well will not have a significant impact on regional subsidence.

STPEGS UFSAR Q&R 2.5-28 Revision 13 Question 241.1N The measured settlement data given in Appendix 2.5.C of the South Texas Project FSAR is provided only up to June 1979. Provide time vs. settlement plots of up-to-date settlement data obtained for all Category I structures where settlements are being monitored. Tabulate values of the measured maximum differential settlements and show comparisons of the measured data with anticipated settlements assumed in the analysis of these structures and their appurtenances, and evaluate the impact of any differences between the measured and anticipated settlements on the design and construction of these structures and appurtenances. Staff requires that the settlement of safety related structures and appurtenances be monitored for a period of at least five years after the issuance of the operating license and the impact of observed settlement, if any, on the design limits of category I structures be evaluated periodically. (6 months, 2 years and 5 years after OL issuance). Response The evaluation of settlement monitoring data is periodically updated and is provided in Section 2.5.4 and Appendix 2.5.C.

The experienced differential movements between buildings are plotted on Figures 2.5.C-11 and 2.5.C-11A for Unit 1, and on Figures 2.5.C-12 and 2.5.C-12A for Unit 2. The differential movements within individual buildings are shown on plots for representative dates on FSAR Figures 2.5.C-13A and 2.5.C-13B for Unit 1, and on Figures 2.5.C-14 and 2.5.C-14A for Unit 2. The design criterion for allowable differential movements between buildings is defined in Section 2.5.4.11 (item 1) as one-inch, which is applicable after the pipe installation. Recording of differential movements between buildings started when adjacent portions of two building foundations had been completed. The differential movement plots and tabulations should, therefore, not be directly compared with the design criteria, and they only provide geotechnical information of the relative settlement behavior of the adjacent foundations and allow evaluations of the trends of movements. For purpose of evaluation of measured settlement, January 1985 will be the assumed date of pipe connection.

(Note: The previously described evaluation of Unit l Essential Cooling Water System piping installation at the Mechanical-Electrical Auxiliary Building [MEAB] has been deleted [see amended Section 2.5.C.4.6] as the pipes have been disconnected).

The design criteria for allowable tilt across individual buildings are defined in Section 2.5.4.11 (item 3). The tilt criteria applies to piping after final installation and connections.

Notwithstanding that the design criteria are not applicable in the early part of building construction and before installation of interconnected systems, as described above, it is an objective to minimize deviations throughout the construction period in order to avoid adverse trends. For this reason the effects of actual settlement behavior have been analyzed for the Unit 2 MEAB (see amended Figure 2.5.C-14A, section Q3, June 1980). The tilt and curvature STPEGS UFSAR Q&R 2.5-29 Revision 13 Response (Continued) of the foundation have been conservatively derived, as described above, and this case is recognized as the most severe situation experienced. However, the differential movements were found not to have any detrimental effect on the building. Category I piping systems were only partially installed in the Unit 1 MEAB in 1979, and no piping installations had been made in Unit 2 MEAB in 1980. The excursion within Unit 2 MEAB, as discussed above, was corrected by load modifications as described in letter to NRC on February 3, 1981 (ST-HL-AE- 616). An excursion is also noted within the Unit 1 MEAB in June 1979 which was "self-correcting" in the normal course of construction. The predicted heave/settlements are shown in comparison to the actual movements for the Reactor Containment, Fuel Handling and Mechanical-Electrical Auxiliary Buildings of Unit l on amended Figure 2.5.C-9 and 2.5.C-9A. The actual heave/settlement for the Unit 2 buildings are shown on Figure 2.5.C-10 and 2.5.C-10A.

Settlement monitoring for safety related structures and appurtenances after the issuance of the operating license will be performed as requested. Existing Table 2.5.C-1 in the UFSAR defines the monitoring frequency which meets the requirements of Question 241.1N.

The following Sections, and Figures have been revised.

Sections: 2.5.4.11 2.5.C.3 2.5.C.4 2.5.C.4.5 2.5.C.4.6 Figures: 2.5.C-9, 9A, 10, 10A, 11, 11A, 12, 12A, 13A, 13B, 14, 14A, 15 STPEGS UFSAR Q&R 2.5-30 Revision 13 TABLE Q241.01N-1 MEASURED DIFFERENTIAL SETTLEMENT Between Buildings Date Started Measured Diff. Settlement (in.) Oct. 1978 June 1979 Dec.

1980 Oct.

1982 Apr.

1983

Unit l FHB vs RCB July l976 0 0.2 0.l 0.4 0.3 MEAB vs RCB Oct. l977 0.l 0.3 0.3 0.2 0.1 MEAB vs FHB Oct. l977 0.l 0.l 0.6 0.5 0.6 MEAB vs DGB Dec. l979 - - 0.2 0.l 0.0 IVC vs RCB Dec. l977 0.6 0.6 0.l 0.l 0.2

Unit 2 FHB vs RCB March l977 0.3 0.6 0.5 - MEAB vs RCB April l979 0.4 0.l 0.6 -

MEAB vs FHB May l979 0.l 0.2 0.5 -

MEAB vs DGB Dec. 1982 (l) - - - -

IVC vs RCB July l979 0.3 0.2 0.4 -

1. DGB-2 mat constructed December l982.
2. See Figure 2.5.C-ll and 2.5.C-11A for Unit l differential movement plots. 3. See Figure 2.5.C-l2 and 2.5.C-12A for Unit 2 differential movement plots.

STPEGS UFSAR Q&R 2.5-31 Revision 13 TABLE Q241.01N-2 MEASURED END-TO-END TILT ) Buildings Direction Measured End-to-End Tile (in.) Oct. 1978 June 1979 Dec.

1980 Oct.

1982 Apr.

1983 Unit l RCB E-W 0.3 0.4 0.3 0.2 0.l RCB N-S 0 0.l 0.2 0.3 0.2 FHB E-W 0 0 0 0.l 0.2 FHB N-S 0.3 0 0.4 0.4 0.4 MEAB E-W N Portion 0.6 0.6 0.5 0.6 0.7 MEAB E-W S Portion 0.3 0.2 0.4 0.4 0.4 MEAB N-S E Portion 0.4 0.7 0.5 0.2 0.2 MEAB N-S W Portion 00 .l 0.l 0.l 0.l DGB E-W (l) (l) 0 0 0.l DGB N-S (l) (l) 0 0.2 -

Unit 2 RCB E-W 0.2 0.3 0.2 0 - RCB N-S 0 0 0 0.l - FHB E-W 0 0.l 0.2 0 - FHB N-S 0.2 0.7 0.7 0.8 0.7 MEAB E-W N Portion 0.l 0.2 0.2 0.7 0.4 MEAB E-W S Portion 0.2 0.2 0.7 0 -

MEAB N-S E Portion 0.7 0.7 0.l 0.l 0.0 MEAB N-S W Portion 0.l 0.l 0.l 0.2 - DGB E-W (2) (2) (2) (2) -

DGB N-S (2) (2) (2) (2) - l. DGB, Unit l, construction started in December l979.

2. Construction of DGB, Unit 2 started December l982. 3 See Figures 2.5.C-l3A and 2.5.C-l3B for differential movement profile within Unit l buildings. 4 See Figure 2.5.C-l4 and 2.5.C-l4A for differential movement profile within Unit 2 buildings.

STPEGS UFSAR Q&R 2.5-32 Revision 13 Question 361.8 Piezometric level declines (deep aquifer) experienced at the STPEGS site generally exceed the estimates shown on PSAR Figure 2.5.1-15G. This figure indicates a projected six foot decline between January 1973 and June 1978. The actual decline, utilizing the data presented in PSAR Figure 2.5.1-16D and FSAR Figure 2.5.C-22, ranges from 7 ft at Piezometer 607 to 27 ft at Piezometer 604. Eleven feet of decline has occurred directly beneath the plant site in a 2-1/2 year period (November 1975 to June 1978). Discuss the impact of this rapid groundwater decline (especially directly beneath the structures area) on the subsidence estimates given on FSAR page 2.5.1-125. Discuss the significance, if any, of this decline with respect to site safety.

Response The regional decline in the piezometric level within the deep aquifer has been, on the average, 11 ft between 1973 and 1979. The projected decline shown on PSAR Figure 2.5.1-16G is 11.5 ft. Withdrawals occur on a cyclic basis because of seasonal needs. Evaluations must, therefore, be made at the same cyclic points from year to year. For example, Piezometer 607 shows a decline of about 4 ft between March 1975 and March 1978. Localized larger drawdown has been experienced near the well which has been pumped since the spring of 1976 for construction purposes (near Piezometer 604, as described in Sections 2.5.C.5.5.5, 2.5.C.5.6, and 2.5.4.6.8). This localized drawdown is temporary and will recover when construction withdrawal is reduced and normal plant operation begins. A further interpretation of the current (March 1979) groundwater conditions within the deep aquifer is provided by amendment to Sections 2.5.C.5.5.5 and 2.5.C.5.6. The changes in groundwater elevations with regard to regional subsidence and site safety are addressed in the response to Question 361.10.

STPEGS UFSAR Q&R 2.5-33 Revision 13 Question 361.10 Provide a composite figure incorporating subsidence contours derived from observations taken from the monuments shown on FSAR Figure 2.5.C-1 and piezometric levels derived from the deep aquifer piezometers shown on FSAR Figure 2.5.C-18. The 1973 piezometric levels (PSAR Figure 2.5.1-16D) are to be used as a base for the piezometric decline. We request that revisions to this figure be submitted periodically to coincide with the submittal of the combined Horizontal Strain-Regional Subsidence Monitoring data described in Request No. 361.9, above. With each subsequent submittal, describe the suspected relationship between the observed subsidence and the deep aquifer piezometric level decline.

Response FSAR Figure 2.5.C-25 has been developed as requested by the NRC. The figure shows the subsidence within the plant area as contours superimposed on piezometric decline contours. Although Question 361.10 addresses decline since 1973, the 1975 data obtained from plant area piezometers are more applicable. The 1973 groundwater data were obtained from other less site-sensitive sources. It is also important that the subsidence and groundwater data are derived for the same time period. The drawdown contours presented on Figure 2.5.C-25 reflect a bias due to the regional cycle of pumping and rebound. The January sampling period falls within a portion of the rebound cycle of the aquifer. The magnitude of the rebound cycle varies from year to year due to variations in the amount of pumping during the late fall of the previous year. The southwesterly trend of apparent differential drawdown at the site for this sampling period reflects a temporary late pumping cycle northwest of the site in the fall of 1978 and drawdown due to pumping of a site well (approximately 7000 ft southeast of the plant area) used for construction purposes. The interpreted subsidence contours reflect a regional subsidence of about 1.00 to 1.25 inches over the monitoring period (approximately three years). The net subsidence in the plant area has been less, due to heave associated with the construction excavation and rebound of the shallow aquifer due to rewatering. The interpretation of the regional near-surface subsidence monitoring is further addressed in UFSAR Section 2.5.C.5.5.2. It is evident that the construction activities have had overriding effects on the near-surface subsidence monitoring observations, in particular at monuments I, H, F, G, J, and L. These activities include heave caused by plant area excavation and other more local activities such as Cooling Reservoir embankment construction, material stockpiles, ECP, and ECP pipeline excavations. It is anticipated that the above identified monuments will continue to show deviating behavior due to ongoing plant construction, reservoir filling, and return of groundwater conditions to a natural state. The subsidence has not had any recognizable effects on the heave/settlement behavior of the plant structures as described in FSAR Section 2.5.C.4.5.

STPEGS UFSAR Q&R 2.5-34 Revision 13 Question 361.12 The Cambe Geological Service Map No. T-7, provided in response to Request No. 361.1, indicates an additional site well not shown on PSAR Figure 2.5.1-32. This previously unidentified well (Robbins No. 1) is located approximately one mile east of Well No. 16 (PSAR Figure 2.5.1-32). Provide all pertinent data relative to the Robbins No. 1 Well. Revise appropriate portions of the FSAR accordingly.

Response The well identified as Robbins No. 1 represents a location registered with the Texas Railroad Commission. However, the well was never drilled and the location should be classified as abandoned.

Retrieved from "https://kanterella.com/w/index.php?title=ML16207A577&oldid=672300"