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

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

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

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

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

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.

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.

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

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

Periodic Table of the Elements Rn 86 222

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

Radon Entry Radon Radium Uranium

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”.

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.

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

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

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

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

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

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

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

Relative Penetrating Power Alpha Beta Gamma Paper Concrete

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.

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

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.

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.

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 60 x .037=2.22, or 1 pCi/L is 2.22 dpm

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

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).

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

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.

A Water Flow Experiment

At Equilibrium Water Flows are Equal

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.

At Secular Equilibrium the Decay Rates of RDPs and Radon are Equal Radon 222 - 3.8 days Po 218 - 3 min. Pb 214 - 27 min. Bi 214 - 19.7 min. Po 214 - .000164 sec. Pb 210 - 19.7 years

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

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... 100 pCi/L) to create 1 WL of RDPs. Therefore E.R. = = 0.5 0.5 WL 1.0 WL

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)

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 =

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 100 2 4 This could also be expressed as a percent by multiplying by 100, or 0.5 x 100 = 50%

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.

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

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

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