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Preliminary Dispersion Modeling for the NuStart Plant at Bellefonte

Preliminary Dispersion Modeling for the NuStart Plant at Bellefonte. Doyle E. Pittman and Kenneth G. Wastrack Tennessee Valley Authority. Introduction. Construction at Bellefonte halted in 1988 Two units placed in deferred status Site selected in 2005 by NuStart for new plant

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Preliminary Dispersion Modeling for the NuStart Plant at Bellefonte

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  1. Preliminary Dispersion Modeling for the NuStart Plant at Bellefonte Doyle E. Pittman and Kenneth G. Wastrack Tennessee Valley Authority 11th NUMUG Meeting - St. Louis 10/13/06

  2. Introduction • Construction at Bellefonte halted in 1988 • Two units placed in deferred status • Site selected in 2005 by NuStart for new plant • Old construction permit cancelled in 2006 • New plant: Passive-reactor design - Westinghouse AP1000 11th NUMUG Meeting - St. Louis 10/13/06

  3. Conceptual Layout at Bellefonte 11th NUMUG Meeting - St. Louis 10/13/06

  4. Meteorological Data Collection • Data collected onsite from 1972 to 1983 • Temporary towers until 1978 • Permanent 110 meter tower from 1975 • Wind flow study in 1993 • Tower removed • Building left • Training tower erected (55 meter) 11th NUMUG Meeting - St. Louis 10/13/06

  5. Elevation (meters-MSL) 400 300 200 4 105° 3 Distance (km) 2 Bellefonte Nuclear Plant 1 285° 0 1500 1000 500 Elevation (feet-MSL) Terrain Cross Section 11th NUMUG Meeting - St. Louis 10/13/06

  6. Examination of Monitoring History • Meteorological measurements at the local site reasonably represent conditions at surrounding locations and short-term measurements are representative of longer-term periods. • The last complete year of data collected at the permanent meteorological monitoring facility is more than 20 years old so it will not be acceptable as “the most recent 1-year period”. 11th NUMUG Meeting - St. Louis 10/13/06

  7. Exam Continued • Historical data were archived and are retrievable. • Meteorological data collected in the valley do not adequately represent meteorological conditions in the Bellefonte vicinity (10-mile EPZ) for emergency preparedness applications. 11th NUMUG Meeting - St. Louis 10/13/06

  8. Data Collection Renewed • Evaluated 55 meter tower – acceptable • Evaluated data needed for COLA submittal • Used guidance from ANS-3.11 (2005) • Installation begun in January 2006 • Operation began in April 2006 11th NUMUG Meeting - St. Louis 10/13/06

  9. Bellefonte Meteorological Tower 11th NUMUG Meeting - St. Louis 10/13/06

  10. Site Acceptability Evaluation • Westinghouse AP1000 Design Control Tier 1 Document identifies key site parameter specifications related to the design of safety-related aspects of structures, systems, and components for the AP1000. • An actual site is deemed acceptable if its site characteristics fall within these plant site design parameters. 11th NUMUG Meeting - St. Louis 10/13/06

  11. Evaluation Continued • Parameters include Atmospheric Dispersion Factors (χ/Q) for: • the site boundary, • for the low population zone, and • for Control Room and Heating Ventilation and Air Conditioning intakes for accident dose analysis. • Concern with the proximity of a portion of the site boundary at Bellefonte to the desired plant location (only 343 meters). 11th NUMUG Meeting - St. Louis 10/13/06

  12. TVA Analysis of χ/Q Values • Used onsite data from 1979-1982 • Design basis accidents were treated as ground-level releases • Utilized 10 meter wind speed and direction and the 10 to 46 meter temperatures for stability class • Used in-house model based on R. G 1.145 • Used geometric source data for the AP1000 • Compared results with NRC’s PAVAN model 11th NUMUG Meeting - St. Louis 10/13/06

  13. Results • Worst case site boundary χ/Q would exceed the site parameter specification by about a factor of 2 to 3 • Worst case condition was the 0-2 hour χ/Q that was exceeded 5% of the time. • Question was raised whether the site parameter specification was the 50th percentile or the 5th percentile value. 11th NUMUG Meeting - St. Louis 10/13/06

  14. Results Continued • Move plant or move site boundary? • Estimate what distance would be needed to meet the design specification for the existing site boundary - 700 meters • Verify that site parameter χ/Q is satisfied for relocated plant within the Bellefonte site. Site boundary distance of about 805 meters 11th NUMUG Meeting - St. Louis 10/13/06

  15. Bellefonte Arial View 11th NUMUG Meeting - St. Louis 10/13/06

  16. Conclusions • Availability of representative onsite data was critical to this analysis. • Important to ensure that key site design specifications are met before finalizing site selection and prior to completion of the combined operating license application. • Need a thorough understanding of the basis for the key site parameters. 11th NUMUG Meeting - St. Louis 10/13/06

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