3/2003 Rev 1 I.4.1 – slide 1 of 33 Part I Review of Fundamentals Module 4Sources of Radiation Session 1Terrestrial Radionuclides Module I.4.1 IAEA Post Graduate Educational Course Radiation Protection and Safety of Radiation Sources

3/2003 Rev 1 I.4.1 – slide 2 of 33 Introduction  Natural terrestrial radiation will be discussed  Students will learn about natural radioactive decay chains, important radionuclides, radon and its significance, NORM and NARM

3/2003 Rev 1 I.4.1 – slide 3 of 33 Content  Terrestrial decay chains  Important radionuclides  Radon and its health significance  NORM  NARM

3/2003 Rev 1 I.4.1 – slide 4 of 33 Overview  Natural terrestrial radiation will be discussed  Sources of exposure from natural terrestrial radiation will be described

3/2003 Rev 1 I.4.1 – slide 5 of 33 Radioactivity in Nature  Primordial – existing since the creation of the Earth  Cosmogenic – formed as a result of cosmic ray interactions  Human produced – enhanced or formed due to human actions

3/2003 Rev 1 I.4.1 – slide 6 of 33 Primordial Nuclides NuclideHalf-life Natural Activity 235 U 7.04 x 10 8 yr 0.711% of all natural uranium 238 U 4.47 x 10 9 yr % of all natural U; 0.5 to 4.7 ppm total U in common rocks 232 Th 1.41 x yr 1.6 to 20 ppm in common rocks

3/2003 Rev 1 I.4.1 – slide 7 of 33 NuclideHalf-life Natural Activity 226 Ra 1,600 yr 16 Bq/kg in limestone and 48 Bq/kg in igneous rock 222 Rn 3.82 days Noble gas; average annual air concentrations in US range from 0.6 to 28 Bq/m 3 40 K 1.28 x 10 9 yr to 1.1 Bq/g in soil Primordial Nuclides

3/2003 Rev 1 I.4.1 – slide 8 of 33 Background Radiation  There are three decay “chains” that occur in nature:  the uranium series, beginning with 238 U  the thorium series, which originates with 232 Th  the actinium series, which originates with 235 U  Once upon a time there was also a neptunium series, which originated with 241 Pu, that has a half-life of only 14 years. The only remaining member of this series is 209 Bi with a half-life of 2E18 years.

3/2003 Rev 1 I.4.1 – slide 9 of U Decay Chain

3/2003 Rev 1 I.4.1 – slide 10 of 33 Natural Decay Series

3/2003 Rev 1 I.4.1 – slide 11 of 33 Natural Radioactivity in Soil Element* Assumed Activity** Mass of Element* Activity Uranium 25 Bq/kg 2,200 kg 31 GBq Thorium 40 Bq/kg 12,000 kg 52 GBq Potassium Bq/kg 2,000 kg 500 GBq Radium 48 Bq/kg 1.7 g 63 GBq Radon 10 kBq/m 3 11  g 7.4 GBq * Potassium-40 is a radionuclide** per kg of soil

3/2003 Rev 1 I.4.1 – slide 12 of 33 Terrestrial Gamma Ray Exposure in the United States

3/2003 Rev 1 I.4.1 – slide 13 of 33 Uranium Concentrations In United States Soil

3/2003 Rev 1 I.4.1 – slide 14 of 33 Thorium Concentrations in United States Soil

3/2003 Rev 1 I.4.1 – slide 15 of 33 Natural Terrestrial Dose Rate Map of Switzerland

3/2003 Rev 1 I.4.1 – slide 16 of 33 Natural Radioactivity in Building Materials (mBq/g) MaterialUraniumThoriumPotassium Granite Sandstone67414 Concrete Wallboard Gypsum Clay Brick

3/2003 Rev 1 I.4.1 – slide 17 of 33 Natural Radioactivity in the Oceans Nuclide* Assumed Activity PacificAtlantic All Oceans Uranium 33 mBq/L 22 EBq 11 EBq 41 EBq 40 K 11 Bq/L 7400 EBq 3300 EBq EBq 3H3H3H3H 0.6 mBq/L 370 PBq 190 PBq 740 PBq 14 C 5 mBq/L 3 EBq 1.5 EBq 6.7 EBq 87 Rb 1.1 Bq/L 700 EBq 330 EBq 1300 EBq *Uranium is an element

3/2003 Rev 1 I.4.1 – slide 18 of 33 Background Radiation - Radon  Radon is a noble gas (also called “inert”).  Radon is chemically like other members of this group of the periodic table, namely He, Ne, Ar, Kr and Xe. The noble gases do not readily form compounds due to their stable electron shell configuration. With the exception of helium, they all have 8 electrons in their outer shell (ns 2 np 6 for the chemists in the audience).

3/2003 Rev 1 I.4.1 – slide 19 of 33 Background Radiation - Radon  The average dose from radon-222 ( 222 Rn) is approximately 2000  Sv per year. Radon is an alpha emitter. Many of the radon decay products are also alpha emitters.  Radon is produced from the radioactive decay of 238 U, an isotope of uranium which is naturally present in the environment. In fact, in some areas of the western US, the concentration of natural uranium is high enough that it is mined to provide a source of uranium for reactors.

3/2003 Rev 1 I.4.1 – slide 20 of 33 Production of 222 Rn by Decay of 238 U

3/2003 Rev 1 I.4.1 – slide 21 of 33 Background Radiation - Radon  Just as helium can diffuse through a balloon, radon can diffuse through the soil and foundations of homes. The diffusion is greater when the soil has low moisture content.  Radon is a radiological hazard because the decay products are alpha emitters. Since they are formed by emission of alpha particles, the resulting decay products have an electrostatic charge and are attracted to particulates in the air. These may become deposited in the lung. These particles then decay by alpha emission, which results in a dose to the lung.

3/2003 Rev 1 I.4.1 – slide 22 of 33 Radon Diffusion Through Soil

3/2003 Rev 1 I.4.1 – slide 23 of 33 Radon Transport Into Homes

3/2003 Rev 1 I.4.1 – slide 24 of 33 Background Radiation - Radon  The concern is really not with the radioactive decay of radon, but with the radon progeny (also called “daughter products”), that are produced when radon decays. Since radon decays by alpha emission, the radon “daughters” have a ++ charge and so are electrostatically attached to particulates in the air. These decay products are also radioactive, and many decay by alpha particle emission.  The alpha particle energy delivers a dose to the lung where the particles are deposited. The dose to the lung is associated with the development of lung cancer in uranium miners (hence the regulatory limits for radon and radon daughter concentrations).

3/2003 Rev 1 I.4.1 – slide 25 of 33 Radon in Air in the United States

3/2003 Rev 1 I.4.1 – slide 26 of 33 Relative Risk from Radon

3/2003 Rev 1 I.4.1 – slide 27 of 33 Radionuclides Found in Your Body Nuclide* Total Mass of Nuclide Found in the Body Total Activity of Nuclide Found in the Body Daily Intake of Nuclides Uranium 90  g 1.1 Bq 1.9  g Thorium 30  g 0.11 Bq 3  g 40 K 17 mg 4.4 kBq 0.39 mg Radium 31 pg 1.1 Bq 2.3 pg 14 C 95  g 15 kBq 1.8  g *Uranium, Thorium and Radium are elements

3/2003 Rev 1 I.4.1 – slide 28 of 33 Natural Radiation Exposure Around the World

3/2003 Rev 1 I.4.1 – slide 29 of 33 Effective Dose Equivalent to a Member of the Population of the United States Source Average Annual Effective Dose Equivalent, μSv Inhaled (radon and decay products) Other Internally Deposited Radionuclides 390 Terrestrial Radiation 280 Cosmic Radiation 270 Cosmogenic Radioactivity 10 Rounded Total from Natural Sources 3000 Rounded Total from Artificial Sources 600 Total3600

3/2003 Rev 1 I.4.1 – slide 30 of 33 Sources of Radiation Exposure In the United States

3/2003 Rev 1 I.4.1 – slide 31 of 33 NORM and NARM  NORM Naturally Occurring Radioactive Material  NARM Naturally Occurring and Accelerator-Produced Radioactive Material

3/2003 Rev 1 I.4.1 – slide 32 of 33 Summary  Natural terrestrial radiation was discussed  Important radionuclides and their distribution was discussed  Radon in particular and its significance was discussed  NORM and NARM were defined

3/2003 Rev 1 I.4.1 – slide 33 of 33 Where to Get More Information  Cember, H., Johnson, T. E., Introduction to Health Physics, 4th Edition, McGraw-Hill, New York (2008)  Martin, A., Harbison, S. A., Beach, K., Cole, P., An Introduction to Radiation Protection, 6 th Edition, Hodder Arnold, London (2012)  Eisenbud, M., Gesell, T. F., Environmental Radioactivity from Natural, Industrial and Military Sources, 4 th Edition, Academic Press Inc., New York (1997)  Firestone, R.B., Baglin, C.M., Frank-Chu, S.Y., Eds., Table of Isotopes (8 th Edition, 1999 update), Wiley, New York (1999)