Upload
milton
View
34
Download
0
Tags:
Embed Size (px)
DESCRIPTION
Lesson 4. What are the units for measuring radon?. Radioactivity units Picocuries (pCi). Measure activity (radioactive decays/time) 1 picocurie (pCi) = 0.037 decays/second = 1 decay/27 seconds = 2.22 decays/minute. Radon units Picocuries/liter (pCi/L). - PowerPoint PPT Presentation
Citation preview
Lesson 4
What are the units for measuring
radon?
Slide 4-2
Radioactivity unitsPicocuries (pCi)
Measure activity (radioactive decays/time)1 picocurie (pCi)
= 0.037 decays/second = 1 decay/27 seconds= 2.22 decays/minute
Slide 4-3
Radon unitsPicocuries/liter (pCi/L)
Measure activity (decays/minute) per volume (one liter of air)
1 pCi/L = 2.22 decays per minute per liter of air
EPA action level
= 4 pCi/L
= 8.88 decays/minute/liter
Slide 4-4
Hypothetical daily exposure
• Question– Assume that a client spent 10 hours/day
in a room with a radon level of 4 pCi/L– How many decays/liter would the client
be exposed to each day?
• Answer– 5,328 decays/day/liter
Slide 4-5
Medical X-Rays
Cosmic
Terrestrial
Consumer Products
Nuclear Medicine
InternalOther
Radon54%
U.S. exposure to radiation
Slide 4-6
International System (SI)
Radioactivity units1 becquerel (Bq)
= 1 decay/second= 27 pCi
1 pCi = 0.037 decays/
second= 0.037 Bq
Radon units1 pCi/L
= 37 Bq/m3
EPA action level= 4 pCi/L= 148 Bq/m3
Slide 4-7
Measuring radon decay products (RDPs)
Measure alpha radiation emitted by short-lived RDPs
Polonium-218
Bismuth-214
Polonium-214
Lead-214
Slide 4-8
Measuring RDPsWorking level (WL)
1 WL = Concentration of RDPs produced from
one liter of air that contains 100 pCi/L of radon
= Amount of short-lived RDPs that exists at a single moment if a container is kept at a constant 100 pCi/L
EPA action level = 4 pCi/L = 0.02 WL
Slide 4-9
EPA action level Summary
4 pCi/L = 148 Bq/m3 = 0.02 WL
Slide 4-10
Questions?
Slide 4-11
Factors that affect radon and RDP concentrations
• Some radon gas and RDPs escape as air flows out of home
• Remember RDP characteristics– Solid particles– Electrically charged– React chemically
• Some RDPs attach to (plate out on) solid objects, such as– Walls– Floors– Ceilings– Furniture
Plating out• Lowers RDP
concentration in air• Plated out RDPs
cannot be measured
• Only RDPs in air can be measured
• Factors that affect plating out also affect measurement of RDPs
Slide 4-12
Factors that affect radon and RDP concentrations
Air from open window
Air from open door
• Air circulation – Air moving within a
room
• Ventilation– Fresh air entering a
room
• Air filters• Particles suspended
in the air – Dust– Smoke– Aerosols
Some RDPs plated out
Slide 4-13
Air circulation
• Circulation = moving around air already in a room
• How would air circulation affect concentration of RDPs?
• May increase plating out, as RDP particles blow toward solid objects and attach to them
• As plating out increases, concentration of RDPs in the air decreases
Fans increase normal air circulation
Slide 4-14
Ventilation
• Ventilation = supply of fresh air
• How would ventilation affect concentration of RDPs?
• Ventilation likely to lower concentration of RDPs• May also reduce radon concentration, as gas
escapes from home
Open windows and doors increase
ventilation
Slide 4-15
Air filter
• How would air filters affect concentration of RDPs?
• Air filters may remove some RDPs, which– Are particles– Have electrical
charge– React chemically
ExampleFurnace air filter
• Air filters will not remove radon, which– Is a gas– Has no electrical
charge– Does not readily
react chemically
Slide 4-16
Particles suspended in air
• Examples– Dust– Smoke– Aerosols
• How would particles affect concentration of RDPs?
• RDPs are more likely to attach to particles• RDP concentration in air decreases
Slide 4-17
ReviewFactors that may affect
radon measurement
• Air circulation• Ventilation• Air filters• Particles in the air
Slide 4-18
Secular (eventual) equilibrium
Radon
Radon decay products
Radon
• In closed home, concentration of RDPs increases until secular equilibrium is reached– Means RDPs have same
level of radioactivity as radon itself
– Takes 3-4 hours– Measure home after it has
reached secular equilibrium
• At secular equilibrium, 1 WL = 100 pCi/L
Slide 4-19
A home inspector’s lament and pledge
Picocuries and becquerels; secular equilibrium.
Radon decaying has made my brain cells go numb.
But I do understand: breathing radon’s not healthy,
So I’ll master these concepts, though they won’t make me wealthy.
Convert all these measurements? Curse that uranium!
I’m working at levels that hurt my poor cranium.
I’ll learn proper techniques, use the right protocol,
To help prevent cancer: that’s the goal of my role.
Slide 4-20
SummaryEPA action level
4 pCi/L = 148 Bq/m3 = 0.02 WL
4 4 pCi/L = 148 Bq/m3 = 0.02 WL
See handout 4-1
Slide 4-21
SummaryFactors affecting measurement
• Air circulation• Ventilation• Air filters• Particles in the air
ImportanceFactors affect conditions for testing a
home
Slide 4-22
Questions?
Slide 4-23
Checkyour comprehension
• See handout 4-2