Radioactive materials radon

Care must be taken in handling radon, as with other radioactive materials. The main hazard is from inhalation of the element and its solid daughters which are collected on dust in the air. Good ventilation should be provided where radium, thorium, or actinium is stored to prevent build-up of the element. Radon build-up is a health consideration in uranium mines. Recently radon build-up in homes has been a concern. Many deaths from lung cancer are caused by radon exposure. In the U.S. it is recommended that remedial action be taken if the air in homes exceeds 4 pCi/1. 

Although the nucleus of the uranium atom is relatively stable, it is radioactive, and will remain that way for many years. The half-life of U-238 is over 4.5 billion years the half-life of U-235 is over 700 million years. (Half-life refers to the amount of time it takes for one half of the radioactive material to undergo radioactive decay, turning into a more stable atom.) Because of uranium radiation, and to a lesser extent other radioactive elements such as radium and radon, uranium mineral deposits emit a finite quantity of radiation that require precautions to protect workers at the mining site. Gamma radiation is the... 

Use nuclear power, medical X-rays, medical diagnostics, scientific research, cancer treatment, cathode ray tube displays Source radon, X-rays, radioactive materials produce alpha, beta, and gamma radiation, cosmic rays from the sun and space Recommended daily intake none (not essential)... 

When thorium emits alpha particles, it disintegrates into other daughter radionuclides (radioactive materials), such as radium-226 and radon-222 (from thorium-230 in the uranium-238 decay series) or radium-228 and thoron (radon-220 from thorium-232 in the thorium decay series). It eventually decays to stable lead-208 or -206, which is not radioactive. More information about the decay of thorium can be found in Chapter 3. The toxicological characteristics of radon, radium, and lead are the subject of separate ATSDR Toxicological profiles. 

Radioactive materials such as uranium, thorium, and radon gas are released to the environment during coal combustion (51, 52). The amounts of radioactivity are often in excess of that released by many modern nuclear power plants but, nevertheless, are well below established radiation standards (52). 

Over the next decade, many scientists worked to find out more about radioactive materials. Curie and her husband, Pierre Curie (1859-1906), isolated two new radioactive elements, polonium and radium. In 1900, German physicist Friedrich Ernst Dorn (1848-1916) found a third radioactive element radon. 

The name comes from the Latin radius, meaning ray. It was discovered by Marie and Pierre Curie in 1898 when they were studying uranium and other radioactive materials found in pitchblende. There is about 1 g of radium in 7 tons of pitchblende, but it is 3xl05 times more radioactive than uranium. It was isolated as a metallic element in 1911 by Marie Curie and Andre-Louis Debieme (1874-1949). Radium exists in small quantities associated with uranium ores. Radium is phosphorescent, so it has been used to make luminous paint, especially for watch dials, but, because it is highly radioactive, most uses are related to nuclear medicine or the energy industry. Radon gas is produced from radium and is a harmful by-product. 

As can be seen in Figure 1, radon itself and its polonium daughter products are alpha emitting nuclides, while the isotopes of lead and bismuth produced are beta/ gamma emitters. The short half-lives of the daughter products prior to Pb (Table 2) result in the rapid production of a mixture of airborne radioactive materials which may attain equilibrium concentrations within a relatively short time. The half-life of °Pb is 22 years and at this point in the decay chain any activity inhaled is largely removed from airways in which it is deposited before any appreciable decay occurs. 

In 1903, with the scientist Frederick Soddy, Rutherford concluded that radiation was caused by atoms of radioactive material breaking apart. The tiny bits that broke off were the a and (3 rays. This was a revolutionary idea, since it had been a basic principle of physics and chemistry that atoms were the smallest possible particles of matter and therefore indivisible. Rutherford went on to demonstrate that a-particles were, in fact, a form of the helium atom. He did this by placing a delicate glass bulb containing radon gas, which emitted a-particles, in an evacuated tube. The particles would penetrate the glass of the bulb but not escape the tube, and could then be analyzed. 

The number of counts recorded in a radiochemical analysis includes a contribution from sources other than ihe sample. Background activity can be traced lo the presence of minute quantities of radon radionuclides in Ihe atmosphere, to ihe materials used in construction of the laboratory, to accidental contamination wiiliin the laboratory, lo cosmic radiation, and to the release of radioactive materials into ihe Earth s atmosphere. To obtain an accurate determination, then, it is necessary to correct the measured counting rate for background contributions. The counting period required to establish the background correction frequently differs from the counting period for the sample. As a result, it is mure convenient to employ counting rates as shown in Equation 32-15. 

Although the chemistry of radium is relatively simple (like barium), the fact that it produces a radioactive gas (radon) complicates its handling. The decay of radon produces "airborne" radioactive atoms of At, Po, Bi, and Pb. Since uraniiun is a common element in rocks (see 5.4) it is also a common constituent of building materials. Such material emits Rn, as discussed further in 5.6. Work with radium compounds should be carried out within enclosures to avoid exposure to Rn and its daughters. 

The laboratory also may be required to report to the ERA its radionuclide quantities or to monitor airborne emission from operating stacks and by other discharges under the National Emission Standards for Hazardous Air Pollutants (NESHAPS). Subpart H protects the public and the environment from radioactive materials (other than radon) emission at DOE facilities and subpart I applies to other federal facilities, including NRC licensees. The basic criteria are that the annual effective dose equivalent to any individual... 

HDI value is 10 for oil put into the oceans, 15 for lead and 0.7 for mercury release corresponding to the human generated movement of 5 million tons of oil put annually into the oceans and also almost 400 000 tons of lead and 20 000 tons of mercury released into the environment. In the context of large natural inventory of radioactive materials in the earth and significant continuous release of natural radon gas to the atmosphere, additions made by nuclear power have a negligible impact on the natural radioactive baseline situation. 

These effects depend upon the nature of the radioactive material, its route of entry and concentration in a particular tissue, and due mainly to cr or p particles. Lung cancer has been observed in miners following inhalation of radon, and severe anaemia and bone tumour following ingestion of radium in luminising dial painters. 

NORM—Naturally occmring radioactive materials includes naturally occurring uranium-235 and daughter products such as radium and radon. 

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