Case Study: Impact of Above Ground

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Case Study Impact of Above Ground Spent Fuel
Storage on Nearby Meteorological Systems
NUMUG Meeting Charlotte, NC June 2008
Jim Holian SAIC
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Study
Evaluate the proposed Independent Spent Fuel
Storage Facility Installation (ISFSI) on the
meteorological monitoring system at the Cooper
Nuclear Station, Brownville, Nebraska
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Background

• Spent fuel pool near capacity
• Four potential ISFSI sites identified
• Numerous configurations examined
• Three sites eliminated after soils study
• Site selected is closest to Met Tower
• SAIC task with determining any potential impact

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ISFSI Facility

• 450-feet northeast of the Met Tower
• Concrete base elevated 10-feet
• 46 Horizontal Storage Modules (HSMs)
• Each HSM 10W X 20L X 18H
• Overall size is 40W X 260L
• 511sq-ft Storage Building south end

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• Impacts on Meteorological Data

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Meteorological Data Used in Analyses

• Five years of onsite data (2001-2005)
• 97 data availability
• Annual Wind Roses
• Joint Frequency Distributions (JFDs) for
  stability classification

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ISFSI Structure Impacts

• HSMs extend up to 28 feet above met tower base
• Distance to tower is approximately 450 feet
• Distance to height ratio of 161
• Structure impacts felt with wind direction from
  045-080 degrees (NE-ENE)
• Frequency is only 5.3 (5-year average)

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ISFSI Thermal Impacts

• NUHOMS TN-61BT HSMs to be installed
• By design, HSMs dissipate heat by natural
  conduction
• Air enters two openings at base, circulates, and
  vents out the top

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Two Specific Scenarios Studied

• (1) 46 HSMs with maximum heat load of 18.3
  kilowatts (kW)
• (2) 8 HSMs loaded first two years only
• Vary heat load from 18.3 kW to 9 kW
• Vary wind speeds from 1.0 m/s to 4 m/s
• Vary stability

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5-Year Stability at CNS

• A 6
• B 5
• C 6
• D 33

• E 29
• F 11
• G 10

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Thermal Plume

• G stability truncated cone volume and cross
  sectional area at met tower is 2,061,044 ft3 and
  8,500 ft2 respectively. (no ground reflection)
• D stability truncated cone volume and cross
  sectional area at met tower is 11,392,137 ft3 and
  46,700 ft2 respectively (with ground reflection)

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Assumptions

• HSM air temperature is linear to heat load (based
  on 51F rise at 24 kW load in NUHOMS ISFSI
  UFSAR)
• No conduction loss to ground around ISFSI
• No plume meander or mixing at edges (entrainment)

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Results
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Estimated Met Tower ?T (F) 46 HSM Casks Loaded
G Stability
HSM Heat kW Wind Speed (m/s) Wind Speed (m/s) Wind Speed (m/s) Wind Speed (m/s)
1 2 3 4
18.3 1.70 0.90 0.57 0.45
15 1.40 0.74 0.47 0.37
12 1.10 0.55 0.37 0.28
9 0.83 0.41 0.28 0.21
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Estimated Met Tower ?T (F) 46 HSM Casks Loaded
D Stability
HSM Heat kW Wind Speed (m/s) Wind Speed (m/s) Wind Speed (m/s) Wind Speed (m/s)
1 2 3 4
18.3 0.31 0.16 0.10 0.08
15 0.25 0.13 0.08 0.07
12 0.20 0.10 0.07 0.05
9 0.15 0.07 0.05 0.04
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Estimated Met Tower ?T (F) 8 HSM Casks Loaded
G Stability
HSM Heat kW Wind Speed (m/s) Wind Speed (m/s) Wind Speed (m/s) Wind Speed (m/s)
1 2 3 4
18.3 1.30 0.70 0.43 0.34
15 1.10 0.56 0.36 0.28
12 0.80 0.42 0.28 0.21
9 0.63 0.31 0.21 0.16
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Estimated Met Tower ?T (F) 8 HSM Casks Loaded
D Stability
HSM Heat kW Wind Speed (m/s) Wind Speed (m/s) Wind Speed (m/s) Wind Speed (m/s)
1 2 3 4
18.3 0.12 0.06 0.04 0.03
15 0.10 0.05 0.03 0.03
12 0.08 0.04 0.03 0.02
9 0.06 0.03 0.02 0.01
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Frequency of Occurrence of NE through ENE Sector
Wind

• G Stability - 0.5 with average wind speed of
  2.0 m/s
• D Stability 2.3 with average wind speed of 2.9
  m/s
• All Stabilities 5.3 with average wind speed of
  2.7 m/s

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Impacts

• Minimal over 95 of the time
• Separate study at CNS demonstrated that raising
  the 10-meter temperature 0.4 F changed the peak
  predicted downwind radiological doses by 90
  (worst case)

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Mitigation Options

• Move ISFSI site? no other acceptable location
• Move met tower? not practicable
• Erect new met tower in an acceptable location
  that preserves the long term meteorological data
  record
• Risk acceptable, do nothing

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CNS Decision

• Erect a new 100-meter tower
• Select an area that best reflects the original
  existing tower location
• Take into account current and future expansion of
  the plant
• Preserve the long term data record

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New 100-meter Tower

• New 100-meter tower will be nearly identical to
  existing tower and equipment
• Dual elevator system with sonic sensors
• Construction to begin 8/1/08
• 6 month comparison of data with existing
  100-meter tower to begin 9/15/08
• New tower to be declared operational by 4/1/09

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Then came the floods of 2008!
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Questions?