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What Types of Radiation Are There?

The radiation one typically encounters is one of four types: alpha radiation, beta radiation,

gamma radiation, and x radiation. Neutron radiation is also encountered in nuclear power plants

and high-altitude flight and emitted from some industrial radioactive sources.

1.  Alpha Radiation 

Alpha radiation is a heavy, very short-range particle and is actually an ejected helium

nucleus. Some characteristics of alpha radiation are:

o  Most alpha radiation is not able to penetrate human skin.

o  Alpha-emitting materials can be harmful to humans if the materials areinhaled, swallowed, or absorbed through open wounds.

o  A variety of instruments has been designed to measure alpha radiation.

Special training in the use of these instruments is essential for makingaccurate measurements.

o  A thin-window Geiger-Mueller (GM) probe can detect the presence of alpha

radiation.

o  Instruments cannot detect alpha radiation through even a thin layer of water,

dust, paper, or other material, because alpha radiation is not penetrating.

o  Alpha radiation travels only a short distance (a few inches) in air, but is not an

external hazard.

o  Alpha radiation is not able to penetrate clothing.

 Examples of some alpha emitters: radium, radon, uranium, thorium.

2.  Beta Radiation Beta radiation is a light, short-range particle and is actually an ejected electron.

Some characteristics of beta radiation are:

o  Beta radiation may travel several feet in air and is moderately penetrating.

o  Beta radiation can penetrate human skin to the "germinal layer," where new

skin cells are produced. If high levels of beta-emitting contaminants areallowed to remain on the skin for a prolonged period of time, they may cause

skin injury.

o  Beta-emitting contaminants may be harmful if deposited internally.

o  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 low-energy, poorly penetrating radiation that may be difficult or

impossible to detect. Examples of these difficult-to-detect beta emitters are

hydrogen-3 (tritium), carbon-14, and sulfur-35.

o  Clothing provides some protection against beta radiation.

 Examples of some pure beta emitters: strontium-90, carbon-14, tritium, and sulfur-35.

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3.  Gamma and X Radiation 

Gamma radiation and x rays are highly penetrating electromagnetic radiation. Some

characteristics of these radiations are:

o  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 are sometimescalled "penetrating" radiation.

o  X rays are like gamma rays. X rays, too, are penetrating radiation. Sealed

radioactive sources and machines that emit gamma radiation and x raysrespectively constitute mainly an external hazard to humans.

o  Gamma radiation and x rays are electromagnetic radiation like visible light,

radiowaves, and ultraviolet light. These electromagnetic radiations differ onlyin the amount of energy they have. Gamma rays and x rays are the most

energetic of these.

o  Dense 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.o  Gamma radiation is easily detected by survey meters with a sodium iodide

detector probe.

o  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 

 technetium-99m.

USES OF RADIATIONS

In public health care, radiation can be used to examine and treat patients. Examinations

are X-ray or isotope examinations. In examinations or procedures that use radiation, care is taken

to ensure that radiation exposure to the patient is kept to a minimum. In treating cancer, largedoses of radiation are used to destroy diseased tissue.

In industry, radiation is beneficial in quality control of materials, measuring the level of 

containers, or monitoring the thickness or consistency of paper, for example. Devices which

monitor industrial processes consist of radiation sources and detectors. When the material

between the radioactive source and the detector changes thickness or density, the level of 

radiation detected also changes. The process can be controlled by weakening or strengthening thesignal from the detector.

Industrial radiography is a method of non-destructive testing, used to check for flaws in

metal structures and welding seals, among others. The principle is the same as in medical

imaging: radiation passes through the object to be tested and exposes the X-ray film placedbehind it. Dark patches in the developed film reveal flaws. Radiography devices create radiation

using either X-ray machines, or for thicker material, a gamma source or linear accelerator.

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Radioactive isotopes are used as tracers in many biochemical and physiological

examinations. The path of material marked with tracers is monitored with an activitydetermination. Radioactive isotopes of carbon and hydrogen can be used to examine the path of 

nutrients into plants, for example.

Practical applications for non-ionising radiation are, among others, lasers, microwaveovens, solariums, mobile telephones, MRI devices in the medical field, and industrial heaters.

Uses of radiation and their comparative portions.

Radiation is used in about 1500 locations and 9000 individual radiation sources ordevices are in use. Dental X-ray machines are not included in these figures. There are about 5000

of these used in 2000 locations.

The field in which the subatomic fragments emitted in radioactive decay (alpha-, beta-,

gamma-rays) or produced by high-voltage accelerators (electrons, protons, x-rays) are applied tothe problems of science, engineering, industry, and medicine. The techniques are extraordinarily

versatile and sensitive and are basically inexpensive. A disadvantage that limits the range and

extent of these applications is the health hazard that may be involved.

Tracer applications are based on two principles. First is the chemical similarity of 

radioactive atoms and other atoms of the same element. Periodically a few of the radioactiveatoms decay, emitting some penetrating subatomic fragments that can be detected one by one,usually through their ability to cause ionization. Thus the movement of a particular element can

be followed through various chemical, physical, and biological steps. The second principle

involves the characteristic half-life and nature of the emitted fragments. This makes a radioactive

species unique and thereby detectable above a background of radioactive emitters associatedwith elements. For discussions of radioisotope techniques relating to tracer methodology.

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Penetration and scattering applications arise from the fact that subatomic fragments can

penetrate a thick section of a material, and yet a small fraction of the incident particles can bebackscattered by a relatively thin section. The oldest application of the penetrating properties of 

energetic ionizing photons is radiography. An extension of this technique is autoradiography. 

Since World War II the penetration and scattering properties of beta- and gamma-rays have been

applied in industry in the form of thickness gages. See also

Autoradiography; Radiography. 

The absorption of small amounts of energy from ionizing particles and ionizing photonshas chemical effects that have been the basis of several practical applications. The oldest

application of this principle is radiation therapy. For example, in cancer therapy the local

affected areas are irradiated by external beams of gammas from cobalt-60 or of radiation fromaccelerators. Radioactive sources have also been administered internally to induce beneficial

biochemical reactions in patients afflicted with various ailments. See also  Isotopic irradiation; 

Radiology. 

A related area is the radiation sterilization of biomedical supplies. The advantages to this

method of biochemical destruction of microscopic life are that (1) unlike steam sterilization, itcan be performed at low temperatures on plastics and other thermally unstable materials, and (2)unlike germicidal gases, ionizing radiation can reach every point in the treated product.

Radiation-sterilized objects are not radioactive.

The radiation preservation of food is an area of considerable promise. Small doses can

inhibit sprouting in potatoes, kill insects in wheat, and sterilize pork products but practical

applications have been sharply limited due to a cautious role by regulatory authorities inapproving such procedures.

Kinetic energy of emissions in radioactive decay can be converted to useful forms of 

light, heat, and electricity.See also

Luminous paint; Nuclear battery. 

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 SUBMITTED BY:

 Mr. Rodolfo A. FRigillana

 Submitted to: Mr.