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Topic 11- Radiation Dosimetry

Internal Radiation Protection

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Atmospheric Pathways

  • Structure of the atmosphere
diagram

Structure of the Atmosphere

  • Troposphere
    • varies by season and latitidue
    • most weather formed here
  • Stratosphere
    • dry & cloudless
    • no real weather
    • lots of ozone
  • Mesosphere (warm layer)
  • Ionosphere
    • “densely ionized”

General Circulation of the Atmosphere

  • General circulation proposed in 1735
diagram

Prevailing Wind Patterns

diagram diagram

Temperature Profile of the Atmosphere

graph of temperature profile

Temperature Profiles of Specific Conditions

  • Superadiabatic conditions: vertical motions in atmosphere are accelerated & atmosphere considered unstable.
  • Inversion conditions: temperature increases with height and warm air over-runs cold; atmoshpere considered stable.

Atmospheric Stability & Stack Gas Behavior

diagram diagram

Atmospheric Dispersion and Removal Processes

diagram

Dispersion and Removal

  • Dispersion
    • diffusion and transport
  • Removal Mechanisms
    • Whatever depletes the plume
  • Rainout
    • gases/particulates are cause of precipitation
  • Washout
    • Removal by contact with precipitation
  • Dry Deposition
    • gravitational settling, impaction

Pasquill Stability Classes (1960s)

Class Description
A Ectremely unstable
B Moderately unstable
C Slightly unstable
D Neutral Conditions
E Slightly Stable
F Moderately Stable
G Highly Stable

 

Relation of Turbulence to Weather Conditions

  • A - summer day
  • B - sunny & warm
  • C - average day
  • D - heavy overcast day or night
  • E - average night
  • F - clear night
  • G - inversion, possible fumigation
Relation of Turbulence Types to Weather Conditionsa,b
  Daytime insolation Nighttime conditions
Surface wind speed
(m s-1)
Strong Moderate Slight Thin overcast or >= 4/8 cloudinessc <= 3/8 cloudiness
< 2 A A-B B    
2 A-B B C E F
4 B B-C C D E
6 C C-D D D D
>6 C D D D D
aFrom Gifford (1996).
bConditions: A, extremely unstable; B, moderately unstable; C, slighty unstable; D, neutral (applicable to heavy overcast, day or night); E, slightly stable; F, moderately stable.
cThe degree of cloudiness is defined as that fraction of the sky above the local apparent horizon that is covered by clouds


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