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WMD-REALITI Level 1 Course Administrative Data R04: Radiation Sources Effective Date October 1, 2008 Academic Hours The Academic Hours required to teach this lesson are as follows: Hours/Methods 1.0 / Conference / Discussion Test 1.0 / End of Unit Exam Prerequisite Knowledge General Physics Student Study Assignments Study Class Notes Instructor to Student Ratio 1: Additional Personnel Requirements Assistant Lab Technician Equipment Required Name Quantity Laptop/LCD Projection or Overhead Projector 1 Projection Screen 1 Materials Required Instructor Materials:
- Lesson Plan
- Lecture Notes Student Materials:
- Notebooks
- Pencils/Pens Classroom/Area Requirements Classroom and Laboratory
INTRODUCTION
Motivator Discuss specific examples of radioactive materials found at waste facilities that could possibly be used as WMD. Terminal Learning Objective You will distinguish between various sources of radiation emitted from the ground, building materials, water and food, and other targets with 80% accuracy on a proctored exam. Enabling Learning Objectives: You will:
1. Differentiate between various sources of radiation emitted from technically-enhanced norms. 2. Apply the charts of radioactive materials found at various incident sites.
Natural Background Radiation: This section is further divided in to three categories based on their origin. Cosmic Radiation Terrestrial Radiation Internal Radiation Cosmic Radiation: The Earth and all living things on it are constantly bombarded by radiation from space, similar to a steady drizzle of rain. Charged particles from the sun and stars, mainly protons and some alphas, interact with the Earth’s atmosphere and magnetic field to produce a shower of radiation, typically beta, gamma, and neutron radiation. The capture of secondary neutrons produced in primary interactions of cosmic rays leads to two prominent radioactive nuclides in the atmosphere, 14 C and 3 H (tritium). (^14) N + n → 14 C + p and (^14) N + n → 12 C + 3 H The right arrow above indicates the direction of nuclear reaction. The nuclear reaction is bombarding neutrons (n) on to 14 N, which produces either 14 C and proton (p) or a 12 C and 3 H (tritium). Radioactive 14 C atoms combine with oxygen to form carbon dioxide. This is absorbed by plants during photosynthesis and eventually ends up in human bodies when food is consumed. Human bodies contain 14 C (^40 K as well as others from other origins) in about the same relative abundance as the air. The ratio of 14 C to all carbon atoms (^12 C, 13 C, and 14 C) in the environment was about 1.2 x 10-12^ which used to be a constant before the atmospheric nuclear explosions and burning of fossil fuels. The half-life of 14 C is 5730 years and is a pure -^ emitter with maximum beta particle energy of 157 keV. (^14) C → 14 N + - (^) + ( - antineutrino) Radioactive 3 H forms tritiated water (when one H is replaced by 3 H in a water molecule, H 2 O→^3 HHO) and is absorbed in human bodies when water is consumed. The ratio of 3 H to all forms of hydrogen atoms (H, 2 H, 3 H) in the environment is about 10-18. The half-life of tritium (^3 H) is 12.3 years and is also a pure -^ emitter with maximum beta particle energy of 18.6 keV. (^3) H → 3 He + - (^) + The dose from cosmic radiation varies in different parts of the world due to differences in elevation and to the effects of the Earth’s magnetic field. Secondary cosmic rays, formed by interactions in the Earth's atmosphere, account for about 45 to 50 millirem of the 360 millirem background radiation that an average individual receives in a year. Aurora displays are caused by high-energy particles from the sun entering the magnetosphere of the Earth, and following the magnetic field down to polar regions. Here, they strike molecules of air in the upper atmosphere at around 100 kilometers, causing the atoms to radiate light. This radiation gives aurora displays their characteristic colors, and the patterns of the magnetic fields give them their interesting shapes. Aurora displays appear in many forms including bands, arcs,
rays and sheets. They may vary considerably in shape and brightness over timescales from seconds to minutes. A person will slightly increase his or her exposure to cosmic radiation when flying in an aircraft or by living in a place of higher altitude like Denver, Colorado. In-flight exposure will depend on the route, altitude, and aircraft type. However, on average, dose rates received will be in the order of: Concorde, 1.2 to1.5 millirem per hour; Long haul aircraft, 0.5 millirem per hour; Short haul aircraft, 0.1 to 0.3 millirem per hour dependent on the altitude reached. For airline passengers, the International Commission on Radiological Protection (ICRP) recommends a limit of 100 millirem per year. Figure 1: An Aurora display over Alaska skies. (Photo by Jeff Pederson) Please use the following link to read more information on this topic: http://www.britishairways.com/travel/healthcosmic/public/en_
Terrestrial Radiation average in continental US: 28 mrem per ye Terrestrial Radiation average in continental US: 28 mrem per yearar
Terrestrial Radiation average in continental US: 28 mrem per ye Terrestrial Radiation average in continental US: 28 mrem per yearar Figure 2: US Terrestrial Radiation Distribution
Annual terrestrial radiation doses in the world (Based on the UNSCEAR report 1993 and so forth. Please click the red mark on the map, to find some places and survey results.) Table 2 Area mean (mGy/year) maximum (mGy/year) Ramsar, Iran 10.2 *1^ (260) Guarapari, Brazil 5.5 *2^ (35) Kerala, India 3.8 *2^ (35) Yangjiang, China 3.51 (5.4) Hong Kong, China 0.67 (1.00) Norway 0.63 (10.5) France 0.60 (2.20) China 0.54 (3.0） Italy 0.50 (4.38) World average 0. India 0.48 (9.6) Germany 0. (3.8) Japan 0. (1.26) USA 0.40 (0.88) Austria 0.37 (1.34) Ireland 0.36 (1.58) Denmark 0. (0.45) *1 (^) High Levels of Natural Radiation 1996, M. Sohrabi, p57-p68 Elsevier Science B.V (1997) *2 (^) 1982 UNSCEAR report Source Reference: http://www.taishitsu.or.jp/radiation/index-e.html
Table 3 The Uranium Series (^238 U) of Naturally Occurring Radioactive Decays The Uranium Series (^238 U) Nuclide Half Life Decay Modes or (energy in MeV) Major Gamma Rays and their Energy in MeV Gamma Intensity (^238) U 4.5 x 10 (^9) y (4.2)
Th L X-rays (^234) Th 24.1 d - (^) (0.19)
Pa L X-rays 3.5%, doublet 4%, doublet 234mPa 1.17 m (1st^ excited state)
-^ (2.29)
U L X-rays 0.30 % 0.60 % (^234) U 2.47 x 10 (^5) y (4.8)
Th L X-rays 0.2 % (^230) Th 7.7 x 10 (^4) y (4.8)
Ra L X-rays 0.6 % 0.07 % 0.014 % 0.017 % (^226) Ra 1600 y (4.8)
Rn X-rays 4 % (^222) Rn 3.82 d (5.49) 0.510 0.07 % (^218) Po 3.05 m (6.00) (^214) Pb 26.8 m - (^) (0.65) 0.
(^214) Bi 19.9 m - (^) (1.5) 0.
(^14) Po 1.64 x 10-4 (^) s (7.7) 0.799 0.014 % (^210) Pb 22.26 y - (^) (0.016)
Bi L X-rays 4 % (^210) Bi 5.03 d - (^) (1.16) Po X-rays (weak)
The Uranium Series (^238 U) Nuclide Half Life Decay Modes or (energy in MeV) Major Gamma Rays and their Energy in MeV Gamma Intensity (^210) Po 138.4 d (5.30) 0.803 0.0011% (^206) Pb Stable Table 4 The Actinium Series (^235 U) of Naturally Occurring Radioactive Decays The Actinium Series (^235 U) Nuclide Half Life Decay Modes or (energy in MeV) Major Gamma Rays and their Energy in MeV Gamma Intensity (^235) U 7.04 x 10 (^8) y (4.38)
Th X-rays 9 % 5 % 11 % 54 % 5 % (^231) Th 25.5 h - (^) (0.30)
Pa L X-rays 2 % 10 %, complex (^231) Pa 3.25 x10 (^4) y (5.06)
Ac X-rays 6 % 6 %, complex (^227) Ac 21.6 y (0.046)
Th L X-rays 0.08 % (^227) Th 18.2 d (6.04)
Ra X-rays 8 % 15 %, complex 8 %, complex (^223) Ra 11 d (5.86)
Rn X-rays 10 %, complex 10 % 6 %, complex (^219) Rn 4 s (6.82)
Po X-rays 9 % 5 % (^215) Po 1.78 x10-3 (^) s (7.38) (^211) Pb 36.1 m - (^) (1.36) 0.
The radioactive materials listed in the last three tables and other long half-life radioactive elements such as 40 K are found in: Soil Water Vegetation Thus, the radioactive materials are found throughout nature. It is in the soil, water, vegetation, and air. Water also contains a tiny fraction of radioactive tritium water as mentioned in the cosmic radiation section. Vegetation and food also contain radioactive 14 C, which was also discussed in the cosmic radiation section. Low levels of uranium, thorium, and their decay products (see the tables above) are found everywhere. Some of these materials are ingested with food and water, while others, such as radon in air, are inhaled. The dose from terrestrial sources also varies in different parts of the world. Locations with higher concentrations of uranium and thorium in their soil have higher dose levels. This high dose level is mainly due to the daughter product radon from the uranium and thorium decay series. The major isotopes of concern for terrestrial radiation are uranium and the decay products of uranium, such as thorium, radium, and radon. Internal Radiation: In addition to the cosmic and terrestrial sources, all people also have radioactive 40 K (potassium-40), 14 C (carbon-14), 210 Pb (lead-210), and other isotopes inside their bodies from birth and consumption of food. The variation in dose from one person to another is not as great as the variation in dose from cosmic and terrestrial sources. The average annual dose a person receives from internal radioactive material is about 40 millirems/year. Man-made Sources of Radiation: Although all people are exposed to natural sources of radiation, there are two distinct groups exposed to man-made radiation sources. These two groups are: Members of the public Occupationally exposed individuals Members of the Public: A member of the public is defined in 10 CFR (Code of Federal Regulations) Part 20 as any individual except when that individual is receiving an occupational dose. Occupational dose is the dose received by an individual in the course of employment in which the individual’s assigned duties involve exposure to radiation or to radioactive material. This does not include the dose received from background radiation, from any medical administration the individual has received, from exposure to individuals administered through radioactive materials from voluntary participation in medical research programs, or as a member of the public.
Man-made radiation sources that result in an exposure to members of the public include: Tobacco Televisions Medical X-rays Smoke detectors (^241 Am) Lantern mantles (^232 Th) Nuclear medicine (see below) Building materials (Concrete contains 238 U, 235 U, 232 Th and their daughter products such as radium and radon; Glass contains 40 K) By far, the most significant source of man-made radiation exposure to the public is from medical procedures, such as diagnostic X-rays, nuclear medicine, and radiation therapy. Some of the major isotopes would be I-131, Tc-99m, Co-60, Ir-192, Cs-137, and others. Brachytherapy Sources in Nuclear Medicine Brachytherapy is a specialized form of radiotherapy where a radiation source is placed close to the target tissue. This results in a high radiation dose to the target, while at the same time minimizing damage to adjacent, normal tissue. There are two types of brachytherapy sources: sealed and unsealed sources. Unsealed sources (e.g. 131 I and 32 P) are used commonly in the treatment of thyroid and bone marrow disease, respectively. Sealed sources are used in various forms of implants (e.g. gynecological cancer). Figure 4: A brachytherapy source.
Figure 6: Cassini Spacecraft to the Saturn is powered by a 238 Pu RTG.
Figure 7: A Radioisotope Thermoelectric Generator used in terrestrial application. The final sources of exposure to the public would be shipment of radioactive materials and residual fallout from nuclear weapons testing and accidents, such as Chernobyl. Occupationally Exposed Individuals: Occupationally Exposed Individuals work in the following environments: Fuel cycle Radiography X-ray technicians Nuclear power plant U.S. NRC inspectors Nuclear medicine technicians Occupationally exposed individuals are exposed according to their occupations and to the sources with which they work. These individuals are monitored for radiation exposure with dosimeters so that their exposures are well documented in comparison to the doses received by members of the public. Some of the isotopes of concern would be uranium and its daughter products, cobalt-60, cesium- 137, americium-241, and others.
Table 6 Radiation Exposure to the U.S. Population Exposure Source Population Exposed (millions) 230 Average Dose Equivalent to Exposed Population (millirems/year) Average Dose Equivalent to U.S. Population (millirems/year) Natural: Radon 230 200 200 Other 230 100 100 Occupational 0.93 230 0. Nuclear Fuel Cycle^1 - - - - - - 0. Consumer Products: Tobacco^2 50 - - - - - - Other 120 5 – 30 5 – 13 Environment 25 0.6 0. Medical: Diagnostic X-rays^3
Nuclear medicine^4
Approximate Total 230 - - - 360 1 - Collective dose to regional population within 50 miles of each facility. 2 - Difficult to determine a whole body dose equivalent. However, the dose to a portion of the lungs is estimated to be 16,000 millirems/year. 3 - Number of persons unknown. However, 180 million examinations performed with an average dose of 50 millirems per examination. 4 - Number of persons unknown. However, 7.4 million examinations performed with an average dose of 430 millirems per examination. Sources of Technologically Enhanced, Naturally Occurring Radioactive Material (TENORM): TENORM is an acronym for Technologically-Enhanced, Naturally-Occurring Radioactive Materials. This refers to certain radionuclides that are naturally present in rocks, soils, minerals, as well as radionuclides that human industrial activities have concentrated or exposed to the accessible environment. (Transuranic elements (Pu, Am, Cf,) or “man made” elements with atomic number above 92 (Uranium), are treated separately at the end of Sources of Radiation at Nuclear Power Plants). The following link will provide up-to-date information from the Environmental Protection Agency (EPA) Website about TENORM: http://www.epa.gov/radiation/tenorm/faq.htm
Over the past 20 years, the EPA and other environmental organizations have identified an array of materials that present a radiation hazard to people and the environment. Many of these materials were products or by-products of manufacturing, water treatment, or mining operations--products of some “human activity”. Over time, environmental organizations began to consider this collection of individual problems as part of a single, larger, and more complex problem, which came to be known as “TENORM.” TENORM can be found in all 50 states--anywhere industrial processes (such as mining) that generate it take place. For example, most uranium mining has occurred west of the Mississippi in states such as Arizona, New Mexico, Texas, Colorado, Utah, and Wyoming. The production of phosphate for fertilizer and associated TENORM waste is predominately in the southeastern U.S. (particularly in Florida and North Carolina), but also includes some Western states such as Idaho, Montana, Utah, and Wyoming. TENORM waste from oil and gas production is of greatest concern in the Gulf States, upper Midwest, and some Appalachian states. Also, geothermal energy production in the states of California and Hawaii is known to generate radioactive TENORM wastes. TENORM is generated by certain industrial activities such as mining and the production of fertilizers, oil, and gas. Trace amounts of TENORM may be found in some consumer products when certain minerals are used in the manufacturing process. The following link will provide a list of TENORM Sources: http://www.epa.gov/radiation/tenorm/sources.htm The total annual generation of TENORM wastes in the United States may be in excess of 1 billion tons. In many cases, the levels of radiation are relatively low compared to the large volume of material. Managing this waste presents a dilemma. The cost of disposing of radioactive waste is very high, while in many cases the value of the product separated from the TENORM is relatively low. In addition, few landfills or other licensed disposal locations can accept radioactive waste. As a result, large quantities of TENORM wastes remain at many of the thousands of pre-1970s abandoned mine sites and processing facilities located around the nation. Radium-226 (^226 Ra) is the principal source of human exposure to radiation from natural surroundings. It is a decay product of uranium and thorium and has a half-life of 1600 years. Radium-226 (^226 Ra) is commonly found in TENORM materials and wastes. Concentrations in TENORM materials range from undetectable amounts to as much as several hundred thousand picocuries per gram (pCi/g). Typical concentrations in U.S. soils range from less than 1 to slightly more than 4 picocuries per gram. It is also found in basement of houses due to material used in construction of homes or offices as well as the soil beneath them. The problem is the decay of 226 Ra into 222 Rn, and the high concentrations of radon in homes and workspaces. Because of low air exchanges in these areas the concentration of radon (Rn) gas is higher. The solution is more air exchanges to purge the radon from the confined spaces.
