1. RADON MEASUREMENT OPERATORS PROFICIENCY COURSE
IN CONCERT WITH UNIVERSITY OF ILLINOIS AT CHICAGO AND
ILLINOIS DEPARTMENT OF NUCLEAR SAFETY
12/3/98
Illinois Department of Nuclear Safety

2. Physics of Radon and its Decay Products
The goal of this presentation is to give real estate professionals practical, field-tested techniques to address radon in a home purchase and sale transaction by answering the questions listed on this slide. Additionally, this presentation will acquaint professionals with federal, state and local resources available to them to address radon issues.
It is the goal of this program to sufficiently familiarize real estate professionals with the subject of radon, so they can address radon in as routine a manner as other minor defects are addressed at the time of sale. In other words, how not to make radon a deal buster or a liability concern by dealing with the concern in a straight forward, professional manner.
12/3/98
Illinois Department of Nuclear Safety

3. Introduction to Radon and Radioactivity
The goal of this presentation is to give real estate professionals practical, field-tested techniques to address radon in a home purchase and sale transaction by answering the questions listed on this slide. Additionally, this presentation will acquaint professionals with federal, state and local resources available to them to address radon issues.
It is the goal of this program to sufficiently familiarize real estate professionals with the subject of radon, so they can address radon in as routine a manner as other minor defects are addressed at the time of sale. In other words, how not to make radon a deal buster or a liability concern by dealing with the concern in a straight forward, professional manner.
12/3/98
Illinois Department of Nuclear Safety

4. Radon Characteristics
Colorless gas
Odorless gas
Tasteless gas
Naturally Occurring
Radioactive
Inert, does not chemically react (Noble Gas)

5. Simple Model of an Atom Atom comprised of: Nucleus Electrons (-)
Protons (+)
Neutrons (neutral)
Electrons (-)

6. The Nucleus
Made up of positively charged protons and neutral neutrons.
The number of protons and neutrons combined is called the “mass number” (or atomic mass).
The number of neutrons is generally more than the number of protons.
The number of protons is the atomic number (which identifies the element).
The number of electrons is normally equal to the number of protons, so that the total atom has no net charge.

7. Isotopes
An isotope is any atom with the same number of protons as another atom, but a different number of neutrons.
Radon-220 (thoron) is an isotope of Radon-222, since it also has 86 protons, but it has 134 rather than 136 neutrons.

8. Isotope Example 1P
1P, 1N
1P, 2N
Atomic # ?
Atomic Mass?

9. A Radon - 222 Nucleus Protons = 86 Neutrons Atomic Mass = 136
Atomic Number
This isotope of radon is further identified by its mass number, hence the name radon-222
= 222
= 136
= 86

10. Periodic Table of the ElementsRn 86
222

11. Radioactive Decay Occurs spontaneously
An atom changes identity due to change in number of protons. (-2)
Radiation is released in the process.
Radon-222
Alpha Radiation
Gamma
Radiation
Polonium 218

12. Radon Entry
Radon
Radium
Uranium

13. Abbreviated Uranium-238 Decay Series
Uranium-238 (solid)
4.47 billion years
Radium-226 (solid)
1,620 years
Radon-222 (gas)
3.8 days
Uranium decays to Radium and then to Radon.
Uranium and Radium as solids are trapped in soil, but radon gas can move.
The decay rate is expressed by “half life”.

14. The Meaning of Half Life
Half Life is the time required for half of the atoms to decay.
It is not the time for all of the atoms to decay.

15. Uranium 238 Decay Series Uranium-238 Radon-222 Bismuth-210 Thorium-234
a,g
a,g
b,g
Thorium-234
Polonium-218
Polonium-210
b,g
a,g
a,g
Protactinium-234
Lead-214
Lead-206
(Stable)
b,g
b,g
Uranium-234
Bismuth-214
a,g
b,g
Thorium-230
Polonium-214
Uranium 238
Decay Series
a,g
a,g
Radium-226
Lead-210
a,g
b,g

16. Radon Decay Product Characteristics
Source of cell damage in lungs
Short-lived decay products most significant
Have static charges
Chemically reactive
Solid particles
Heavy Metals

17. Fate of Indoor Radon Airborne Radon Decay Products Radon-222
Breathable
Measurable
Radon Decay
Products
Radon-222
Plated Out
Non-Breathable
Non-Measurable

18. Alpha Radiation (a)
Alpha radiation is a particle released when the nucleus kicks out 2 neutrons and 2 protons (mass number changes by 4 and atomic number changes by 2).
Alpha particle
relatively massive
relatively slow
total charge of +2

19. Beta Radiation (b) N P+ b-
Beta Radiation is a particle which is released when the nucleus changes a neutron into a proton and a beta particle (atomic mass number remains unchanged).
Beta particle
Relatively small mass
Relatively fast moving
Total charge of -1

20. Radon & Short-Lived Decay Productsb- b-
+1P
+1P Rn 86 Pb Bi Po At 82 83 84 85
-2 P
-2N
-2 P
-2N a a

21. Gamma Radiation (g)
Gamma radiation is pure energy. It is released from the nucleus whenever an alpha or a beta is emitted.
Gamma ray
No mass
Moves at the speed of light
No charge

22. Relative Penetrating Power
Alpha
Beta
Gamma
Paper
Concrete

23. Alpha Particles Are Strong Enough To Pit Plastic
Plastic chip from passive radon test (alpha track).
Magnified only 100 times.
3 months at EPA to Action Level of 4 pCi/L.
To provide an idea of just how destructive the particles that are released when the decay products radioactively decay, the picture above shows a piece of plastic from a radon testing device that was placed in a home for 3 months containing, on the average, 4.0 pCi/L of radon. During this period of time the air in the room would diffuse (no air pump) through a paper filter into a small container where the piece of plastic was housed. When radon, and its decay products, decay within the container the resultant alpha particles strike the plastic hard enough to create pits. These pits are large enough to be seen under relatively low magnification (100 power). Note that the plastic is similar to plastics used in some eyewear.
Consider, if the alpha particles are forceful enough to create pits in plastic they are certainly forceful enough to impact, penetrate, and damage soft tissue. This is what happens in the lungs. Also consider that the act of breathing causes approximately 20,000 liters of air to b inhaled and exhaled on a daily basis, thus bringing far more radon decay products into the lungs than would have diffused (drifted) through a paper filter and into the plastic casing that housed this piece of plastic.

24. Ionization Caused by Radiation can occur with a a, b, or g
Atom in air
Ion in air (net charge +1)
Before Collision
After Collision

25. Ion
Normally, the number of electrons orbiting the nucleus is equal to the number of protons inside the nucleus, so that the net charge of the atom is zero.
An ion is an atom that has either lost or gained electrons. It has a net positive or negative charge.

26. Impact of Ionization Caused by Radiation
Measuring ionization allows one to detect the presence of radiation:
Pulsed ion chambers, Electret ion chambers, Geiger counters
Ionization also contributes to overall health effects.

27. Radon Measurement Units
One picocurie per liter (pCi/L) is 2.22 disintegration's per minute within a liter
This comes from the fact that one Curie is 37 billion disintegration's per second (dps) and:
One picocurie is one trillionth of a Curie, or .037 decays per second
There are 60 seconds in a minute x .037=2.22, or 1 pCi/L is 2.22 dpm

28. International Radon Unit: The Becquerel
One Becquerel per cubic meter (Bq/m3) is one disintegration per second within a cubic meter
Becquerel = 1 disintegration per second
1 pCi/L = 37 Bq/m3
In other words:
pCi/L x 37 = Bq/m3, or
(Bq/M3)/37 = pCi/L
4pCi/l = 148Bq/m3

29. Radon Decay Product Units: The Working Level (WL)
1 Working Level is the total amount of energy which would be eventually released by the alpha particles coming from the short- lived RDPs.
1 WL is created by 100 pCi/L of radon
1 Working Level is the amount of short-lived radon decay products within one liter that would ultimately come from the complete disintegration of 100 pCi/L of radon (assuming all RDPs that are produced are measured).

30. Radon Decay Product Units: A More Practical Definition
1 Working Level is the amount of short-lived radon decay products that exist at any one moment within one liter if a room, or container, is constantly maintained at 100 pCi/L (assuming all RDPs that are produced are measured.)
1 WL
100 pCi/L

31. Secular Equilibrium
The condition where the short-lived Radon Decay Products (RDPs) have each reached the same radioactivity ( in picocuries per liter) as the radon forming them.
It takes 4 hours for this to occur.

32. A Water Flow Experiment

33. At Equilibrium Water Flows are Equal

34. At Equilibrium Water Flows are Equal
The waterfalls would be measured in gallons/minute.
Replace waterfalls with radioactive decay in decays/minute, or picocuries.
The volume of water in the buckets is analogous to the number of atoms of each isotope with the short lived isotopes having the least number of atoms at any one time.

35. At Secular Equilibrium the Decay Rates of RDPs and Radon are Equal
Radon days
Po min.
Pb min.
Bi min.
Po sec.
Pb years

36. Equilibrium Ratio (ER)
Plated out
RDPs
Suspended
The equilibrium ratio describes the fraction of RDPs that are suspended in the air, and therefore measurable, to the total RDPs created.
ER =
Measured RDPs
Total RDPs

37. Equilibrium Ratio Example
Assume that you measured the RDPs suspended in the room with a working level meter and determined there were 0.5 WL in the room.
Assume that you measured the radon and determined that there was enough radon (i.e pCi/L) to create 1 WL of RDPs.
Therefore E.R. = = 0.5
0.5 WL
1.0 WL

38. Another Equilibrium Ratio Equation
Since the total RDPs can be found by measuring the radon, the total RDPs part of the equilibrium ratio equation can be replaced by:
Total RDPs = Radon (in pCi/L)
100 pCi/L per WL
This provides a more useful equation:
ER = Measured RDPs (in WL)
Radon (in pCi/L)

39. Equilibrium Ratio Equation
Canceling units and moving the “100” gives:
RDPs (in WL) x 100
Radon ( in pCi/L)
This equation allows one to determine an equilibrium ratio, and to convert from Radon to Working Levels, or vice versa.
ER =

40. Equilibrium Ratio Calculation Example
Simultaneous measurements of radon and radon decay products indicate 4.0 pCi/L and .02 WL respectively. What is the equilibrium ratio?
ER = = = 0.5
.02 x 4
This could also be expressed as a percent by
multiplying by 100, or 0.5 x 100 = 50%

41. Factors Affecting Equilibrium Ratio
Air circulation
Increases plate-out, thereby decreasing ER
Electronic air filters
Decreases RDPs attached to dust particles, thereby decreasing ER
Suspended dust, smoke
Increases sites for RDPs so fewer plate-out
Recent ventilation
Inadequate time for RDPs to have been formed
0.3 < ER < 0.7 in homes.

42. The Equilibrium Ratio Assumption
EPA and IDNS often assumes that, if nothing else is known about the home, an ER of 0.5 (50%) is a reasonable assumption.
Remember that the ER can be different, not only from house to house, but also within the same house.
Equilibrium ratios in homes range from 0.3 to 0.7

43. Other Versions of the Equilibrium Equation
WL x 100
pCi/L
ER =
pCi/L =
WL =
WL x 100
WL x 100 ER ER
pCi/L
ER x pCi/L
100

44. Dynamic Equilibrium
Once the radon entry rate into a building has been altered, time is needed for radon and RDP levels to stabilize.
12 hours is normally sufficient for dynamic equilibrium to occur in a home.
12 Hours Rn WL
Measurable Radioactivity
Time
House
Open
House Closed