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laurenh468

NRC: Measuring Radiation - 0 views

www.nrc.gov/...measuring-radiation.html

Exposure

shared by laurenh468 on 08 Jun 14 - No Cached
  • Dose equivalent (or effective dose) combines the amount of radiation absorbed and the medical effects of that type of radiation. For beta and gamma radiation, the dose equivalent is the same as the absorbed dose. By contrast, the dose equivalent is larger than the absorbed dose for alpha and neutron radiation, because these types of radiation are more damaging to the human body. Units for dose equivalent are the roentgen equivalent man (rem) and sievert (Sv), and biological dose equivalents are commonly measured in 1/1000th of a rem (known as a millirem or mrem).
  • Exposure describes the amount of radiation traveling through the air. Many radiation monitors measure exposure. The units for exposure are the roentgen (R) and coulomb/kilogram (C/kg). Absorbed dose describes the amount of radiation absorbed by an object or person (that is, the amount of energy that radioactive sources deposit in materials through which they pass). The units for absorbed dose are the radiation absorbed dose (rad) and gray (Gy).
  • Radioactivity refers to the amount of ionizing radiation released by a material. Whether it emits alpha or beta particles, gamma rays, x-rays, or neutrons, a quantity of radioactive material is expressed in terms of its radioactivity (or simply its activity), which represents how many atoms in the material decay in a given time period. The units of measure for radioactivity are the curie (Ci) and becquerel (Bq).
laurenh468

Everyday Exposure - 0 views

people.chem.duke.edu/...exposure.html

Exposure

shared by laurenh468 on 03 Jun 14 - No Cached
  • Radioactive elements found in rock, soil, water, air, and in food from the earth make there way in our bodies when we drink water, breath air or eat foods which contain them. These naturally occurring radioisotopes such as carbon-14, potassium-40, thorium-223, uranium-238, polonium-218, and tritium(hydrogen-3) expose us to radiation from within our bodies.
  • Radioactivity in nature comes from two main sources, terrestrial and cosmic. Terrestrial radioisotopes are found on the earth that came into existence with the creation of the planet.
  • Terrestrial
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  • . In areas where surface rocks contain a high concentration of uranium, radon gas could enter a home through a crack in the foundation. A concern for homeowners is the possibility that radon gas could accumulate to dangerous levels. This is especially a problem during the winter months when windows and doors are tightly shut.
  • interaction of cosmic rays with the earth's upper atmophere. Cosmic rays permeate all of space and are composed of highly energized, positively charged particles as well as high energy photons.
  • Approaching the earth at near the speed of light, most cosmic rays are blocked by the earth's protective atmosphere and magnetic field. As a byproduct of the interaction between cosmic rays (i.e. particles) and the atmosphere, many radioactive isotopes are formed such as carbon-14.
  • Cosmic rays are also composed of high energy photons, and not all are prevented from reaching the earth's surface. It makes sense that the higher you are in altitude, the more you are exposed to cosmic radiation. In fact, the average amount of exposure to cosmic radiation that a person gets in the Unites States roughly doubles for every 6,000 foot increase in elevation.
  • lying can indeed add a few extra units of exposure to one's daily exposure. Of course, the amount of extra exposure you get depends on how high the plane flies and how long you are in the air.
  • Think about this : Estimate how much cosmic radiation that astronauts are exposed to during their flights. Recall that astronauts fly at heights of about 160 miles
  • The human production of tobacco products introduces another way for us to get exposure to radiation. Smokers recieve a dose of radiation from polonium-210 which is naturally present in tobacco. Smokers also recieve an additional dose of radiation from the decay product of radon gas, polonium-218. Polonium-218 clings to aerosols such as tobacco smoke, and eventually winds up in the lungs. Once in the lungs, polonium decays by alpha particle emission and in the process may damage cells.
  • For examples, the bricks, stones, cements and drywalls that we use for the building of our homes, schools, offices frequently contain uranium ores and are thus sources of radon.
  • This exposure results from the attempt to diagnose fractures or cavities using x-rays, or to diagnose or treat cancer using injected radioisotopes. Patients are exposed to nuclear radiation in the diagnosis and treatment of cancer. Additionally, radiologists routinely use radioisotopes of technetium or thorium to diagnose heart disease.
  • These higher risk occupations include underground miners, radiologists, medical technologists, nuclear plant operators, research scientists and pilots.
  • Any amount of radiation can be dangerous because of the potential effect that it has on living cells. Radiation can disrupt normal chemical processes of the cells, causing them to grow abnormally or to die. Cells that are altered by the radiation may go on to produce more abnormal cells - a process that could eventually lead to cancer. At low doses, such as have been described here, cells are able to repair any damage rapidly. Any cells that die due to exposure can be replaced by the body. If one receives a very high dose, unlike any exposure mentioned here, the cells may not be able to be replaced fast enough and tissues or organs may fail to function properly.
laurenh468

Radiation sickness Symptoms - Diseases and Conditions - Mayo Clinic - 0 views

www.mayoclinic.org/...con-20022901

Exposure

shared by laurenh468 on 04 Jun 14 - No Cached
  • The severity of signs and symptoms of radiation sickness depends on how much radiation you've absorbed. How much you absorb depends on the strength of the radiated energy and the distance between you and the source of radiation.
  • The absorbed dose of radiation is measured in a unit called a gray (Gy). Diagnostic tests that use radiation, such as an X-ray, result in a small dose of radiation — typically well below 0.1 Gy, focused on a few organs or small amount of tissue. Signs and symptoms of radiation sickness usually appear when the entire body receives an absorbed dose of at least 1 Gy. Doses greater than 6 Gy to the whole body are generally not treatable and usually lead to death within two days to two weeks, depending on the dose and duration of the exposure.
gabb_03

Precision radiation therapy may improve survival rates of patients with inoperable earl... - 0 views

www.utsouthwestern.edu/...western-physicians-report.html

radiation therapy Medicine

shared by gabb_03 on 12 Jun 14 - No Cached
  • In a study appearing in the March 17 issue of The Journal of the American Medical Association, primary lung cancer did not recur in nearly 98 percent of the 55 participants who received stereotactic body radiation therapy (SBRT). More than half of these patients – 56 percent – were alive three years after diagnosis, while less than 20 percent ultimately died of metastatic lung cancer.
  • SBRT is a noninvasive procedure that delivers radiation beams to a tumor in a concentrated, extremely precise manner.
gabb_03

Radiation Therapy | MemorialCare Health System | Orange County | Los Angeles County - 0 views

www.memorialcare.org/...radiation-therapy

radiation therapy Medicine

shared by gabb_03 on 11 Jun 14 - No Cached
  • gabb_03 on 11 Jun 14
     
    Types of cancer treated by radiation therapy
gabb_03

Radiation Therapy for Cancer - National Cancer Institute - 0 views

www.cancer.gov/...radiation

radiation Medicine

shared by gabb_03 on 04 Jun 14 - Cached
  • gabb_03 on 04 Jun 14
     
    What is radiation therapy
wizardbrown

Nuclear meltdown - Wikipedia, the free encyclopedia - 0 views

en.wikipedia.org/...Nuclear_meltdown

nuclear-meltdown

shared by wizardbrown on 06 Jun 14 - No Cached
  • A core melt accident occurs when the heat generated by a nuclear reactor exceeds the heat removed by the cooling systems to the point where at least one nuclear fuel element exceeds its melting point. This differs from a fuel element failure, which is not caused by high temperatures. A meltdown may be caused by a loss of coolant, loss of coolant pressure, or low coolant flow rate or be the result of a criticality excursion in which the reactor is operated at a power level that exceeds its design limits
  • Once the fuel elements of a reactor begin to melt, the fuel cladding has been breached, and the nuclear fuel (such as uranium, plutonium, or thorium) and fission products (such as cesium-137, krypton-85, or iodine-131) within the fuel elements can leach out into the coolant. Subsequent failures can permit these radioisotopes to breach further layers of containment. Superheated steam and hot metal inside the core can lead to fuel-coolant interactions, hydrogen explosions, or water hammer, any of which could destroy parts of the containment. A meltdown is considered very serious because of the potential for radioactive materials to breach all containment and escape (or be released) into the environment, resulting in radioactive contamination and fallout, and potentially leading to radiation poisoning of people and animals nearby.
  • In a loss-of-coolant accident, either the physical loss of coolant (which is typically deionized water, an inert gas, NaK, or liquid sodium) or the loss of a method to ensure a sufficient flow rate of the coolant occurs. A loss-of-coolant accident and a loss-of-pressure-control accident are closely related in some reactors. In a pressurized water reactor, a LOCA can also cause a "steam bubble" to form in the core due to excessive heating of stalled coolant or by the subsequent loss-of-pressure-control accident caused by a rapid loss of coolant. In a loss-of-forced-circulation accident, a gas cooled reactor's circulators (generally motor or steam driven turbines) fail to circulate the gas coolant within the core, and heat transfer is impeded by this loss of forced circulation, though natural circulation through convection will keep the fuel cool as long as the reactor is not depressurized.[6]
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  • Nuclear power plants generate electricity by heating fluid via a nuclear reaction to run a generator. If the heat from that reaction is not removed adequately, the fuel assemblies in a reactor core can melt. A core damage incident can occur even after a reactor is shut down because the fuel continues to produce decay heat. A core damage accident is caused by the loss of sufficient cooling for the nuclear fuel within the reactor core. The reason may be one of several factors, including a loss-of-pressure-control accident, a loss-of-coolant accident (LOCA), an uncontrolled power excursion or, in reactors without a pressure vessel, a fire within the reactor core. Failures in control systems may cause a series of events resulting in loss of cooling. Contemporary safety principles of defense in depth ensure that multiple layers of safety systems are always present to make such accidents unlikely.
  • The containment building is the last of several safeguards that prevent the release of radioactivity to the environment. Many commercial reactors are contained within a 1.2-to-2.4-metre (3.9 to 7.9 ft) thick pre-stressed, steel-reinforced, air-tight concrete structure that can withstand hurricane-force winds and severe earthquakes.
  • A core melt accident occurs when the heat generated by a nuclear reactor exceeds the heat removed by the cooling systems to the point where at least one nuclear fuel element exceeds its melting point. This differs from a fuel element failure, which is not caused by high temperatures. A meltdown may be caused by a loss of coolant, loss of coolant pressure, or low coolant flow rate or be the result of a criticality excursion in which the reactor is operated at a power level that exceeds its design limits. Alternately, in a reactor plant such as the RBMK-1000, an external fire may endanger the core, leading to a meltdown. Once the fuel elements of a reactor begin to melt, the fuel cladding has been breached, and the nuclear fuel (such as uranium, plutonium, or thorium) and fission products (such as cesium-137, krypton-85, or iodine-131) within the fuel elements can leach out into the coolant. Subsequent failures can permit these radioisotopes to breach further layers of containment. Superheated steam and hot metal inside the core can lead to fuel-coolant interactions, hydrogen explosions, or water hammer, any of which could destroy parts of the containment. A meltdown is considered very serious because of the potential for radioactive materials to breach all containment and escape (or be released) into the environment, resulting in radioactive contamination and fallout, and potentially leading to radiation poisoning of people and animals nearby.
  • In a loss-of-pressure-control accident, the pressure of the confined coolant falls below specification without the means to restore it. In some cases this may reduce the heat transfer efficiency (when using an inert gas as a coolant) and in others may form an insulating "bubble" of steam surrounding the fuel assemblies (for pressurized water reactors). In the latter case, due to localized heating of the "steam bubble" due to decay heat, the pressure required to collapse the "steam bubble" may exceed reactor design specifications until the reactor has had time to cool down. (This event is less likely to occur in boiling water reactors, where the core may be deliberately depressurized so that the Emergency Core Cooling System may be turned on). In a depressurization fault, a gas-cooled reactor loses gas pressure within the core, reducing heat transfer efficiency and posing a challenge to the cooling of fuel; however, as long as at least one gas circulator is available, the fuel will be kept cool.[6]
  • In an uncontrolled power excursion accident, a sudden power spike in the reactor exceeds reactor design specifications due to a sudden increase in reactor reactivity. An uncontrolled power excursion occurs due to significantly altering a parameter that affects the neutron multiplication rate of a chain reaction (examples include ejecting a control rod or significantly altering the nuclear characteristics of the moderator, such as by rapid cooling). In extreme cases the reactor may proceed to a condition known as prompt critical. This is especially a problem in reactors that have a positive void coefficient of reactivity, a positive temperature coefficient, are overmoderated, or can trap excess quantities of deleterious fission products within their fuel or moderators. Many of these characteristics are present in the RBMK design, and the Chernobyl disaster was caused by such deficiencies as well as by severe operator negligence. Western light water reactors are not subject to very large uncontrolled power excursions because loss of coolant decreases, rather than increases, core reactivity (a negative void coefficient of reactivity); "transients," as the minor power fluctuations within Western light water reactors are called, are limited to momentary increases in reactivity that will rapidly decrease with time (approximately 200% - 250% of maximum neutronic power for a few seconds in the event of a complete rapid shutdown failure combined with a transient).
  • Core-based fires endanger the core and can cause the fuel assemblies to melt. A fire may be caused by air entering a graphite moderated reactor, or a liquid-sodium cooled reactor. Graphite is also subject to accumulation of Wigner energy, which can overheat the graphite (as happened at the Windscale fire). Light water reactors do not have flammable cores or moderators and are not subject to core fires. Gas-cooled civilian reactors, such as the Magnox, UNGG, and AGCR type reactors, keep their cores blanketed with non reactive carbon dioxide gas, which cannot support a fire. Modern gas-cooled civilian reactors use helium, which cannot burn, and have fuel that can withstand high temperatures without melting (such as the High Temperature Gas Cooled Reactor and the Pebble Bed Modular Reactor).
  • Byzantine faults and cascading failures within instrumentation and control systems may cause severe problems in reactor operation, potentially leading to core damage if not mitigated. For example, the Browns Ferry fire damaged control cables and required the plant operators to manually activate cooling systems. The Three Mile Island accident was caused by a stuck-open pilot-operated pressure relief valve combined with a deceptive water level gauge that misled reactor operators, which resulted in core damage.
  • wizardbrown on 06 Jun 14
     
    "A core melt accident occurs when the heat generated by a nuclear reactor exceeds the heat removed by the cooling systems to the point where at least one nuclear fuel element exceeds its melting point. This differs from a fuel element failure, which is not caused by high temperatures. A meltdown may be caused by a loss of coolant, loss of coolant pressure, or low coolant flow rate or be the result of a criticality excursion in which the reactor is operated at a power level that exceeds its design limits."
gabb_03

Types of stem cell transplants for treating cancer - 0 views

www.cancer.org/...transplant-types-of-transplant

stemcell Medicine

shared by gabb_03 on 04 Jun 14 - No Cached
  • Types of stem cell transplants for treating cancer
  • In a typical stem cell transplant for cancer very high doses of chemo are used, often along with radiation therapy, to try to destroy all the cancer cells. This treatment also kills the stem cells in the bone marrow. Soon after treatment, stem cells are given to replace those that were destroyed. These stem cells are given into a vein, much like a blood transfusion. Over time they settle in the bone marrow and begin to grow and make healthy blood cells. This process is called engraftment
  • gabb_03 on 04 Jun 14
     
    stem cell transplant
laurenh468

Cellular Phones - 0 views

www.cancer.org/...cellular-phones

Exposure

shared by laurenh468 on 04 Jun 14 - No Cached
  • As noted above, the RF waves given off by cell phones don't have enough energy to damage DNA directly or to heat body tissues. Because of this, many scientists believe that cell phones aren't able to cause cancer. Most studies done in the lab have supported this theory, finding that RF waves do not cause DNA damage.
  • Some scientists have reported that the RF waves from cell phones produce effects in human cells (in lab dishes) that might possibly help tumors grow. However, several studies in rats and mice have looked at whether RF energy might promote the development of tumors caused by other known carcinogens (cancer-causing agents). These studies did not find evidence of tumor promotion.
  • Cell phones work by sending signals to (and receiving them from) nearby cell towers (base stations) using RF waves. This is a form of electromagnetic energy that falls between FM radio waves and microwaves. Like FM radio waves, microwaves, visible light, and heat, RF waves are a form of non-ionizing radiation. They don't have enough energy to cause cancer by directly damaging the DNA inside cells. RF waves are different from stronger (ionizing) types of radiation such as x-rays, gamma rays, and ultraviolet (UV) light, which can break the chemical bonds in DNA. At very high levels, RF waves can heat up body tissues. (This is the basis for how microwave ovens work.) But the levels of energy given off by cell phones are much lower, and are not enough to raise temperatures in the body.
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  • According to the Food and Drug Administration (FDA), which regulates the safety of radiation-emitting devices such as cell phones in the United States: "The majority of studies published have failed to show an association between exposure to radiofrequency from a cell phone and health problems."
  • According to the Federal Communications Commission (FCC): "There is no scientific evidence that proves that wireless phone usage can lead to cancer or a variety of other problems, including headaches, dizziness or memory loss. However, organizations in the United States and overseas are sponsoring research and investigating claims of possible health effects related to the use of wireless telephones." According to the Centers for Disease Control and Prevention (CDC): "Some… studies have suggested the possibility that long-term, high cell phone use may be linked to certain types of brain cancer. These studies do not establish this link definitively. Scientists will need to conduct more studies to learn more about this possible risk."  According to the National Institute of Environmental Health Sciences (NIEHS), which is currently conducting studies of the possible health effects of cell phones: "The weight of the current scientific evidence has not conclusively linked cell phones with any adverse health problems, but more research is needed." According to the National Cancer Institute (NCI): "Studies thus far have not shown a consistent link between cell phone use and cancers of the brain, nerves, or other tissues of the head or neck. More research is needed because cell phone technology and how people use cell phones have been changing rapidly."
daym2015

Neutron radiation - Wikipedia, the free encyclopedia - 0 views

en.wikipedia.org/...Neutron_radiation

neutron

shared by daym2015 on 08 Jun 14 - No Cached
  • Neutrons readily pass through most material, but interact enough to cause biological damage. The most effective shielding materials are hydrocarbons, e.g. polyethylene, paraffin wax or water. Concrete (where a considerable amount of water molecules are chemically bound to the cement) and gravel are used as cheap and effective biological shields due to their combined shielding of both gamma rays and neutrons.
  • the ability of neutron radiation to induce radioactivity in most substances it encounters, including the body tissues of the workers themselves.
erlaskaris

Spent Nuclear Fuel and High-Level Radioactive Waste | Radiation Protection Program: | U... - 0 views

www.epa.gov/...402-k-94-001-snf_hlw.html

environmental

shared by erlaskaris on 12 Jun 14 - No Cached
    • erlaskaris
      erlaskaris on 12 Jun 14
       
      This page talks about the literal process of nuclear waste and energy. 
  • In addition to being used to generate commercial electricity, nuclear reactors are used in government-sponsored research and development programs, universities and industry; in science and engineering experimental programs; at nuclear weapons production facilities; and by the U.S. Navy and military services. The operation of nuclear reactors results in spent reactor fuel. The reprocessing of that spent fuel produces high-level radioactive waste (HLW).
  • The fuel for most nuclear reactors consists of pellets of ceramic uranium dioxide that are sealed in hundreds of metal rods
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  • As the nuclear reactor operates, uranium atoms fission (split apart) and release energy. When most of the usable uranium has fissioned, the "spent" fuel assembly is removed from the reactor.
  • Until a disposal or long-term storage facility is operational, most spent fuel is stored in water pools at the reactor site where it was produced.
erlaskaris

Radioactive Waste Disposal: An Environmental Perspective | Radiation Protection | US EPA - 0 views

www.epa.gov/...radwaste

environmental

shared by erlaskaris on 03 Jun 14 - No Cached
    • erlaskaris
      erlaskaris on 03 Jun 14
       
      Introduction to the Nuclear Waste topic
  • Any activity that produces or uses radioactive materials generates radioactive waste. Mining, nuclear power generation, and various processes in industry, defense, medicine, and scientific research produce byproducts that include radioactive waste
  • Radioactive waste can be in gas, liquid or solid form, and its level of radioactivity can vary. The waste can remain radioactive for a few hours or several months or even hundreds of thousands of years.
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  • Designs for new disposal facilities and disposal methods must meet environmental protection and pollution prevention standards that are more strict than were foreseen at the beginning of the atomic age.
  • Disposal of radioactive waste is a complex issue, not only because of the nature of the waste, but also because of the complicated regulatory structure for dealing with radioactive waste.
ferriska2015

Nuclear Ventriculography: Purpose, Procedure & Risks - 1 views

www.healthline.com/...nuclear-ventriculography

Nuclear Ventriculogy

shared by ferriska2015 on 03 Jun 14 - No Cached
  • You will be asked to walk or run on a treadmill until a target heart rate has been reached.
  • sive test with very low risk. The test exposes you to a small amount of radiation from th
  • noninvasive test with very low risk
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  • lower dose of radiation than an occurs from an X-ray
  • electrocardiogram
  • (ECG), a test that detects electrical activity in the heart
  • different intervals in the heart’s cycle
  • an (MUGA) or radionuclide ventriculography (RNV).
  • , which shows the strength of the heart’s contraction
  • determine the location of a pumping problem in your heart chambers.
  • gain information about or diagnose other conditions.
  • avoid caffeine for 48 hours before the test.
  • The nuclear substance used during the test may be passed to the fetus or excreted in breast milk.
  • metal plate or screw in your body, inform your doctor and the technician.
  • remove all metal from your body
  • hospital gown so the technican has access to your ches
  • metal plate or screw in your body
  • It is normal to feel flushed or chilled as the radioactive tracer makes its way into your body
  • The technician will apply electrodes to different areas on your chest for the electrocardiogram.
  • special type of camera and begin taking pictures.
  • change positions in order to get certain images
  • exercise stress test in
  • heart performs during activity
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