Monitoring EquipmentAware Electronics RM-60 Geiger-Mueller detector. Aware Electronics Aw-Radw and Aw-graph software running on Windows XP. How it worksParticles (alpha, beta, and gamma) are emitted from unstable atoms of uranium, thorium, radium, and other elements, as they decay. Decay occurs in a random manner. As some of these particles strike the detector, an electronic pulse is produced, which is counted by the software. Every 60 seconds the accumulated count for that minute is recorded, and the webpage updated. What does it mean?For good health, we'd like the average count to be low. A healthy human body can repair cellular damage from being struck by a limited number of particles, but large quantities of particles can cause severe damage to cellular DNA, which can result in cancer or genetic mutations. Statistically, people living where the average radiation level is high experience a somewhat greater risk of cancer and birth defects. Average radiation background in the Southwestern US is typically 10-20 micro-Roentgens/hr, a reasonable value. Some of this comes from the sky, some from the earth. After certain solar events (sunspots), nuclear weapons tests, and accidents (e.g. Three Mile Island and Chernobyl), the count will rise sharply. How Radiation Affects the Human BodyTo our senses the human body seems quite dense and real, but at an atomic level it is made up of mostly space with atoms here and there. To affect the body, radiation particles must collide with either an electron or a nucleus of an atom. Even though we are constantly bombarded by radiation, due to the body being very "unsolid" most of the particles just pass right on through us. Only infrequently is there a collision causing the particle to transfer its energy to whatever it strikes, usually an electron. The electron reacts like a billard ball when hit by the cue ball which can knock the electron out of its orbit ionizing the atom. Nearby electrons will try to fill the vacancy, possibly joining several atoms into a compound. If this atom happens to be a part of a cell's DNA chain molecule, the chain is damaged, and the cell's instruction set contained in the DNA may be misinterpreted by the "reader" enzyme causing the cell to function incorrectly. In most cases if a cell is damaged, the body will kill it, and treat the remains as waste. Unfortunately, if the immune system is not healthy, damage to certain DNA can cause the cell to grow abnormally, yet be unaffected by the body's attempts to kill it off, possibly producing a tumor. In addition to cells becoming altered by radiation, water molecules within the body can become ionized by radiation, creating free radicals that can destroy good cells and create toxic chemical compounds within the body. Industrial uses of RadiationNowadays gamma radiation is used to sterilize hospital instruments and to give foods longer shelf life. The irradiated items do NOT become radioactive. In food irradiation, Ionization does occur, however, so atoms in the food combine in ways that can create carcinogenic compounds, and of course the essential enzymes are killed, making the food "dead", difficult to digest, and with reduced food value. Energetic Neutrons are produced from nuclear fission, such as found in a reactor. These neutrons interacting with the nucleus of a material can actually change one element to a different element, some of them highly radioactive. Very useful elements produced in this manner are Tritium (glow in the dark signs and wristwatch hands) and Americium (smoke detectors). These radioactive products do not contaminate the environment when their cases are intact. Most radioactive materials are poisonous...DO NOT EAT! Neutrons don't travel very far before they interact with various materials, so we don't need to monitor them in the environment. RadonAs uranium in the soil decays with a half-life of about 4.5 million years a continuous chain of new elements are produced. Most are of little concern, but as our homes become better sealed and insulated, one element has become a real problem. Radon. Radon is an invisible, odorless gas that is radioactive, which means that its atoms are unstable, so they decay, producing highly radioactive "daughter" products. Radon gas itself is relatively harmless, but its daughters, tiny solid particles, cling to dust and are breathed into the lungs where they can do serious damage. There are many websites with good information on how to deal with radon gas. Industries like cement plants and coal fired power plants release a lot of radon daughter products into the atmosphere. This can contaminate whole regions if not properly dealt with at the source. Educational LinksThe Nuclear Regulatory Commission (NRC) has good information on radiation. Envormental Protection Agency (EPA) for info on radon gas. College Physics Kenneth R. Koehler's great educational site. SLAC Stanford Linear Accelerator...lots of info. PDF-An Intro to Radioactivity excellent writeup by a Physicist. Radioactivity in Nature from Idaho State University.
Special LinksThanks to Bryan Boardman Aware Electronics Corp.