Lesson 4 (PRELIMS) Flashcards
(35 cards)
- Atoms found in nature are either _____ or _____.
- An atom is _____ if the forces among the particles that makeup the nucleus are balanced.
- An atom is _____ (radioactive) if these forces are unbalanced; if the nucleus has an excess of internal energy.
stable or unstable
stable
unstable (radioactive)
- As the nucleus emits radiation or disintegrates, the radioactive atom (radionuclide) transforms to a different nuclide. This process is called _____. It will continue until the forces in the nucleus are balanced.
- For example, as a radionuclide decays, it will become a different isotope of the same element if it gives off neutrons or a different element altogether if it gives off protons.
radioactive decay
_____ refers to the particles which are emitted from nuclei as a result of nuclear instability. Because the nucleus experiences the intense conflict between the two strongest forces in nature, it should not be surprising that there are many nuclear isotopes which are unstable and emit some kind of radiation.
Radioactivity
- Instability of an atom’s nucleus may result from an _____ of either neutrons or protons. A radioactive atom will attempt to reach stability by ejecting nucleons (protons or neutrons), as well as other particles, or by releasing energy in other forms.
excess
As its name implies, _____ is the act of emitting radiation spontaneously. This is done by an atomic nucleus that, for some reason, is unstable; it “wants” to give up some energy in order to shift to a more stable configuration.
radioactivity
- _____ is the spontaneous breakdown of an atomic nucleus resulting in the release of energy and matter from the nucleus. Remember that a _____ has unstable nuclei that does not have enough binding energy to hold the nucleus together.
Radioactive decay
radioisotope
- It is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive. Three of the most common types of decay are _____, _____ and ______, all of which involve emitting one or more particles or photons.
alpha decay, beta decay, and gamma decay
- _____ is the energy or particles that are released during radioactive decay.
Radiation
- The ______ of a material refers to the rate at which it emits radiation.
radioactivity
- The activity of a sample of radioactive material is determined by measuring the number of _____. A disintegration occurs each time a nucleus ejects particles or energy. Activity is measured in a unit called the Becquerel (Bq) 1 Bequerel is equivalent to ___ disintegration per second (1 Bq = 1dps)
disintegrations per unit of time
1
Are all nuclear radiation the same? - The radiation that emanates spontaneously from the nuclei of unstable isotopes (radionuclides) as the nuclei undergo radioactive decay is generally alpha, beta, or gamma, neutron radiation. These are the types of particles or energy emitted in radiation:
- Alpha radiation
- Beta Radiation
- Gamma radiation
- Neutron
a positively charged helium nuclei.
- Alpha radiation
is either electron or subatomic particles called positron.
- Beta Radiation
occupy the highest level in electromagnetic radiation emitted by the sun (solar radiation).
- Gamma radiation
is also encountered in nuclear power plants and high altitude flight and emitted from some industrial radioactive sources.
- Neutron
- Alpha radiation is a heavy, very short-range particle and is actually an ejected helium nucleus.
Some characteristics of alpha radiation are:
- Most alpha radiation is not able to penetrate human skin.
- Alpha-emitting materials can be harmful to humans if the materials are inhaled, swallowed, or absorbed through open wounds.
- A variety of instruments has been designed to measure alpha radiation. Special training in the use of these instruments in essential for making accurate measurements.
- A thin-window Geiger-Muller ( GM ) probe can detect the presence of alpha radiation.
- Instruments cannot detect alpha radiation through even a thin layer of water, dust, paper or other materials because alpha radiation is not penetrating.
- Alpha radiation travels only short distance ( a few inches ) in air but is not an external hazard.
- Alpha radiation is not able to penetrate clothing.
● Example of some Alpha Emitters : Radium, Radon, Uranium and Thorium
Alpha Radiation
- Beta radiation is a light, short-range particle and is actually an ejected electron.
Some characteristics of beta radiation are:
- Beta radiation may travel several feet in air and is moderately penetrating.
- Beta radiation can penetrate human skin to the “germinal layer,” where new skin cells are produced. If high levels of beta-emitting contaminants are allowed to remain on the skin for a prolonged period of time, they may cause skin injury.
- Beta-emitting contaminants may be harmful if deposited internally.
- Most beta emitters can be detected with a survey instrument and a thin-window GM probe (e.g., “pancake” type). Some beta emitters, however, produce very lowenergy, poorly penetrating radiation that may be difficult or impossible to detect. Examples of these difficult-todetect beta emitters are hydrogen-3 (tritium), carbon-14, and sulfur-35.
- clothing provides some protection against beta radiation
● Examples of beta pure beta emitters: Strontium-90 Carbon-14, tritium and sulfur-35
Beta Radiation
- Gamma radiation and x-rays are highly penetrating electromagnetic radiation ( EMR )
Some characteristics of these radiation are:
- Gamma radiation or x-rays are able to travel many feet in air and many inches in human tissue. They readily penetrate most materials and sometimes called “ Penetrating Radiation “
- X-rays are like gamma rays. X-rays, too, are penetrating radiation. Sealed radioactive sources and machine that emit gamma radiation and x-rays respectively constitute mainly an external hazard to humans.
- Gamma radiation and x-rays are electromagnetic radiation like visible light, radio waves, and ultraviolet light. These electromagnetic radiations differ only in the amount of energy they have. Gamma rays and x-rays are the most energenic of these.
- Lead materials are needed for shielding from gamma radiation. Clothing provides little shielding from penetrating radiation but will prevent-contamination of the skin by gamma-emitting radioactive materials.
- Gamma radiation is easily detected by survey meters with a sodium lodide detector probe.
- Gamma radiation and/or characteristic x rays frequently accompany the emission of alpha and beta radiation during radioactive decay.
● Examples of some gamma emitters: Iodine-131, Cesium-137, Cobalt 60, Radium-226, and Technitium-99m.
Gamma And X Radiation
- The _____ of a radioactive substance is the time interval required for a quantity Original substance of material to decay to half its original value.
half-life
- When radioactive elements decay, they decay mathematically via the concept of a _____. That means that in a certain amount of time specific to that element, half of the element will decay. The element will always decay by half, so it will never truly _____.
half-life
disappear
Half life is denoted by ___
T1/2
- The rate at which a radioactive isotope decays is measured in _____. The term _____ is defined as the time it takes for one-half of the atoms of a radioactive material to disintegrate. _____ for various radioisotopes can range from a few microseconds to billions of years.
half-life
- Knowing about half-lives is important because it enables you to determine when a sample of radioactive material is safe to handle. They need to be active _____ to treat the condition, but they should also have a short enough half-life so that they don’t injure healthy cell.
long enough
There are four different but interrelated units for measuring radioactivity: exposure, absorbed dose, and dose equivalent. These can be remembered by the mnemonic R-E-A-D, as follows:
Radioactivity
Exposure
Absorbed dose
Dose equivalent (Effective dose)
