NL-06-2496, Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information
| ML063170194 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 11/06/2006 |
| From: | Stinson L Southern Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-06-2496 | |
| Download: ML063170194 (22) | |
Text
L. M. Stinson (Mike)
Vice President Southern Nuclear Operating Company, Inc.
40 Inverness Center Parkway Post Office Box 1295 Birmingham, Alabama 35201 Tel 205.992.5181 Fax 205.992.0341 SOUTHERN COMPANY Energy to Serve Your World*
November 6, 2006 Docket Nos.:
50-321 50-366 NL-06-2496 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information Ladies and Gentlemen:
On August 29, 2006, Southern Nuclear Operating Company (SNC) submitted a request to revise the Edwin I. Hatch Nuclear Plant (HNP) licensing/design basis with a full scope implementation of an alternative source term (AST).
This letter provides information concerning the development of the atmospheric dispersion factors used in the AST analyses for the main control room and the technical support center. This information was requested via facsimile on September 29, 2006. It is noted that no changes have been made to the current licensing basis offsite atmospheric dispersion factors for the AST analyses.
The 10 CFR 50.92 evaluation and the justification for the categorical exclusion from performing an environmental assessment that were included in the August 29, 2006 submittal continue to remain valid.
(Affirmation and signature are on the following page.)
Aoo(
U. S. Nuclear Regulatory Commission N L-06-2496 Page 2 Mr. L. M. Stinson states he is a Vice President of Southern Nuclear Operating Company, is authorized to execute this oath on behalf of Southern Nuclear Operating Company and to the best of his knowledge and belief, the facts set forth in this letter are true.
This letter contains no NRC commitments. If you have any questions, please advise.
Respectfully submitted, SOUTHERN NUCLEAR OPERATING COMPANY L. M. Stinson Sworn to and subscribed before me this day of A) Ve,Ve e r-2006.
Notary Public My commission expires."
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Enclosures:
- 1) Atmospheric Dispersion Factor Information
- 2) ARCON96 Input Files
- 3) Compact Disc (CD) of Hourly Meteorological Data used for ARCON96 runs cc:
Southern Nuclear Operating Company Mr. J. T. Gasser, Executive Vice President Mr. D. R. Madison, General Manager - Plant Hatch RType: CHA02.004 U. S. Nuclear Regulatory Commission Dr. W. D. Travers, Regional Administrator Mr. R. E. Martin, NRR Project Manager - Hatch Mr. D. S. Simpkins, Senior Resident Inspector - Hatch State of Georgia Mr. L. C. Barrett, Commissioner - Department of Natural Resources
Enclosure I Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information NRC QUESTION 1 Provide the complete set of X/Q values from which it was determined that the X/Q values in the 08/29/2006 license amendment request are limiting.
SNC RESPONSE X/Q values at control room and technical support center (TSC) air intakes are presented in the following tables. Potential release points at the reactor vents (RV 1, RV2), main stack (S 1), turbine building railroad doors (T1, T2) and turbine building supply louvers (SLI and SL2) are depicted in Figures 1 and 2.
X/Q Values at the Control Room Air Intake Reactor Bldg.
Reactor Bldg.
Main Stack Averaging Time RV1 RV2 S1 0 - 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> 9.90E-04 1.26E-03 4.85E-06 2 - 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> 3.97E-04 3.87E-04 1.17E-06 8 - 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> 4.30E-04 4.17E-04 9.69E-07 1 - 4 days 3.22E-04 3.56E-04 8.27E-07 4 - 30 days 2.62E-04 2.37E-04 5.49E-07 Turbine Bldg.
Turbine Bldg.
Turbine Bldg.
Turbine Bldg.
Averaging Time T1 T2 SLI SL2 0 - 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> 3.82E-04 3.78E-04 6.03E-04 3.72E-04 2 - 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> 1.50E-04 1.20E-04 2.39E-04 1.11 E-04 8 - 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> 1.79E-04 1.23E-04 2.69E-04 1.19E-04 1 - 4 days 1.27E-04 1.06E-04 2.OOE-04 9.85E-05 4 - 30 days 1.08E-04 6.19E-05 1.64E-04 6.06E-05 I
Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information X/Q Values at the Technical Support Center Air Intake Turbine Bldg.
Turbine Bldg.
Averaging Time T2 SL2 0 - 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> 8.23E-04 9.71E-04 2 - 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> 2.53E-04 2.79E-04 8 - 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> 2.62E-04 3.24E-04 1 - 4 days 2.26E-04 2.75E-04 4 - 30 days 1.31E-04 1.79E-04 As shown in the above tables, the limiting case involves the potential release from RV2.
NRC QUESTION 2 Provide inputs to the ARCON96 computer runs or other methodologies (e.g., if a different methodology was used to calculate the elevated release X/Q values), along with a description of the assumptions used to make calculations for all the X/Q values.
SNC RESPONSE Input files used for the ARCON96 runs are provided in Enclosure 2.
Releases from RV 1, RV2, TI, T2, SL 1 and SL2 were assumed to occur at the ground level where they could be caught in the building wake. The wake region was assumed to result from the reactor building and the turbine building combined. Releases from RV 1 and RV2 were assumed to travel directly toward the air intake following the slant range path calculated by ARCON96. In other words, the releases would not follow the building outline (such as from the roof of the turbine building making a 90-degree turn downward to reach the air intake). This approach is conservative because it results in a shorter distance between the release point and the air intake.
Releases from RV 1 and RV2 were conservatively considered as ground-level releases because the release heights were lower than the estimated cavity height induced by the nearby buildings.
The potential releases from the turbine building were assumed to leak through the railroad doors located on the east side of the building (see Figure 2). The doors are located near each end of the turbine building. It was further assumed that these releases would travel over the turbine building and into the wakes at the lee side of the building. Compared to traveling around the comer of the building, this assumption yields a shorter distance between the release point and the air intakes; therefore, the assumption is conservative.
2 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information The elevated releases were assumed to originate at the main stack (see Figure 3). Since the main stack height (394 ft) is more than 2.5 times the height of the reactor building (154 ft),
releases from the main stack were treated as elevated by the ARCON96 model.
Because the distances between the TSC air intakes and release points TI, RV 1, RV2, SL 1, and the main stack are greater than those between the CR air intake and these points, X/Q values at the TSC air intake due to releases from the above points are expected to be smaller than those at the CR air intake. Thus, the impacts to the TSC air intake from the above releases were not modeled. However, the impacts to the TSC air intake were analyzed for releases from T2 and SL2 because these two release points are located relatively close to the TSC air intake.
NRC QUESTION 3 Provide an electronic copy of the ARCON96-formated hourly meteorological data used to determine the X/Q values.
SNC RESPONSE Hourly meteorological data used for the ARCON96 runs are included in a CD (see Enclosure 3).
NRC QUESTION 4 Provide figures which support the selection of the inputs and assumptions used to calculate all of the X/Q values. Include a figure of the general arrangement of plant structures, drawn approximately to scale and showing true north, sufficient to enable NRC staff to make confirmatory estimates of the selected inputs and assumptions and resultant X/Q values. For each accident, highlight the postulated Unit 1 and Unit 2 release and receptor locations as well as control room and TSC locations that may experience unfiltered inleakage.
Provide a table correlating the source and receptor locations by accident.
SNC REPONSE Figures 1 and 2 depict general arrangement of plant structures and the potential release point locations considered in the assessment. Figure 3 presents the main stack location in relation to other plant structures. The following table shows the distances between the source and receptor locations.
3 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information Release Point Intake Location Distance (m)
RV1 Control Room 69.5 RV2 Control Room 59.5 TI Control Room 112.5 T2 Control Room 106.5 SLI Control Room 92.4 SL2 Control Room 115.3 SL2 Tech Support Center 68.0 Main Stack Control Room 259 T2 Tech Support Center 70.6 NRC QUESTION 5 Regulatory Guide 1.194, "Atmospheric Relative Concentrations for Control Room Radiological Habitability Assessments at Nuclear Power Plants," recommends use of five years of meteorological data. Given that just three years were used (1996-1998), provide a brief discussion to justify that, overall, the meteorological data used in the assessment are of high quality and adequate for use in the assessment. Provide a comparison between the one year meteorological data set used previously and the three year meteorological data set used in the present AST license amendment request.
SNC RESPONSE In the previous assessment, the 1995 meteorological data set was used because it was the most recent year completed at the time of the study and a typically representative year.
Meteorological data collected onsite showed that during 1987-1996 the data are quite consistent each year. For the year 1995, all stability classes were within 2% for the 10-year average. For that year, the data recovery rate for the parameters selected averaged better than 99%.
For the AST assessment, performed in 2000, newer meteorological data (1996-1998) were used. Those data are good quality, the overall (wind speed, wind direction and AT between 10 and 60 meters) data recovery rates are presented in the following table.
Hatch Nuclear Power Plant Meteorological Data Recovery Rates Year 1 0-m Level 60-m Level 1996 99.1%
98.8%
1997 97.8%
97.6%
1998 99.5%
94.2%
4 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information The 1995 meteorological data are compared with the 1996-1998 period meteorological data.
As described, both data sets have relatively high data recovery rates. For convenience, the wind roses from these periods are compared to show the representativeness of the data. The 10-m and 60-m wind roses for 1995 are presented in Figures 6 and 7; wind roses for 1996-1998 are also presented in Figures 4 and 5, respectively.
Although it is normal for meteorological data to show yearly variations; however, for data with good quality collected at the same site, similarities are expected. Figure 4 indicates the prevailing winds for the 10-m level combined 3-year (1996-1998) are from NE and SW directions. Figure 6 shows the same pattern from the single year (1995) observations collected at the I 0-m level. Figure 5 shows the prevailing wind directions are from NE and W for the 60-m level combined 3-year. Similarly, Figure 7 also shows the same prevailing wind directions for the single year observations collected at the 60-m level. In conclusion, the combined 3-year wind roses depict similar patterns as those for the single year wind roses.
5 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information 298' 113.3' 115.5' 160.5' FIGURE 1.
BUILDING DIMENSIONS 6
Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information Reactor Building Vent (163' above ground)
A TB Supply Louver TSC intake elevation is 139' 1.5".
SL1 is 60' above ground.
SL2 is 55' above ground.
TSC - Tech. Support Center TI, T2 - Railroad Doors CB - Control Bldg RV 1 - Reactor Vent 1 RV2 - Reactor Vent 2 TB - Turbine Bldg.
FIGURE 2.
Postulated Release Points at the Turbine Building and Reactor Building Vents 7
Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information FIGURE 3.
STACK LOCATION 8
Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information FIGURE 4. 1996-1998 10-m Level Wind Rose
'NORTH4 15%A 1261.
WEST
~--
r-I-
EAST'
- SOUTH WIND SPEED (Knots)
>22 m 17-21 11 17 7 11
[
47 1-4 Calms: 0.95%
9 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information FIGURE 5.
1996-1998 60-m Level Wind Rose NORTH...
AIL" 10%/
4, EAST'
'SOUTH WIND SPEED (Knots)
M
'= 22 M
17-21 m
11-17 7-11 F-1 4-'7 m
1-4 Calms. 2.05%
10
Enclosure I Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information FIGURE 6. 1995 10-m Level Wind Rose X + 0 H H H-mmn N=
-2 SMMMM M rrr 2 rnnr D
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ZZD0 1 A)U II Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information FIGURE 7.
1995 60-m Level Wind Rose mmmm n-rn mrmm zC W 4-M,*
CaD Zn =rO CDt 12 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information ARCON96 Input Files Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information ARCON96 Input Files CR X/Q Estimates for Reactor Building Release (Release Point -
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CR X/Q Estimates for Reactor Building Release (Release Point -
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I Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information CR X/Q Estimates for Reactor Building Release (Release Point RV2) 3 c: \\hatch\\hatch96.met c: \\hatch\\hatch97.met c: \\hatch\\hatch98.met 10.00 60.00 1
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CR X/Q Estimates for Main Stack Release 3
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2 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information CR X/Q Estimates for Turbine Building Release (Release Point -
SLI) 3 c: \\hatch\\hatch96.met c: \\hatch\\hatch97.met c: \\hatch\\hatch98.met 10.00
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CR X/Q Estimates for Turbine Building Release (Release Point -
SL2) 3 c: \\hatch\\hatch96.met c: \\hatch\\hatch97.met c: \\hatch\\hatch98.met 10.00 60.00 1
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3 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information CR X/Q Estimates for Turbine Building Release (Release Point -
Tl) 3 c:\\hatch\\hatch96.met C:\\hatch\\hatch97.met c:\\hatch\\hatch98.met 10.00 60.00 1
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4 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information TSC X/Q Estimates for Turbine Building Release (Release Point -
SL2) 3 C: \\hatch\\hatch96.met c: \\hatch\\hatch97.met c: \\hatch\\hatch98.met 10.00 60.00 1
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5 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Atmospheric Dispersion Factor Information Compact Disc (CD) of Hourly Meteorological Data used for ARCON96 runs