Radiation Safety TrainingBasic Radiation PhysicsWashington State UniversityRadiation Safety Office
Radiation Fundamentals Objectives: • Identify the three basic particles of an atom • Define radioactive material, radioactivity, radioactive half-life • Define ionization and ionizing radiation • Distinguish between ionizing radiation and non-ionizing radiation • Identify the four basic types of ionizing radiation • Physical characteristics • Range • Shielding • Biological hazards
Atomic Structure • The basic unit of matter is the atom. The three basic particles of the atom are: protons, neutrons, and electrons. The central portion of the atom is the nucleus. The nucleus consists of protons and neutrons. Electrons orbit the nucleus.
Notations AZX A = Atomic Mass (number of protons or electrons plus number of neutrons) Z= Atomic Number (number of Protons) or (number of Electrons in an electrically neutral atom) Number of Neutrons = A - Z
Tritium is designated as: 3 T or H-3 or H 1 Uranium (238) is designated as: 238 U-238 or U 92 Notations
What are Isotopes ? • They are not just a sports team on the Simpsons.
The Isotopes • Atoms which have the same number of protons but different numbers of neutrons are called isotopes. Isotopes of Carbon.
Tritium T Protium H Deuterium D n n n No neutrons 2 neutrons 1 neutron H D T The Isotopes. ISOTOPES of hydrogen The different isotopes of an atom are chemically identical. The above isotopes of hydrogen all act chemically the same.
What is Radioactivity ? • If there are too many or too few neutrons for a given number of protons, the nucleus will not be stable. • The unstable atom will try to become stable by giving off excess energy. This energy is in the form of particles or rays (radiation). These unstable atoms are known as radioactive atoms, or radioactive materials.
By Radioactive decay • Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting ionizing particles and radiation. This decay, or loss of energy, results in an atom of one type, called the parent nuclide transforming to an atom of a different type, called the daughter nuclide.
How long does Radioactive decay take? • Half life it’s more than just a game.
Radioactive half-life • The radioactive half-life for a given radioisotope is the time for half the radioactive nuclei in any sample to undergo radioactive decay. • After one half-life, there will be one half the activity of the original sample. After two half-lives, there will be one fourth the activity of the original sample, after three half-lives one eighth the activity of the original sample, and so forth.
Radioactive Decay is an Exponential Process • The activity at time (t) is related to the initial activity at time (0)
To determine the activity present after time (t) • You need to know 1. The initial activity of the isotope involved. (Activity at time “0” or Ao) 2. The half life of the radioactive isotope. (T1/2) 3. The time after the initial activity was determined. (DT after the determination at time “0”)
Example • You have 10 mCi of P-32 on January 1, 2008. • How much activity will you have on January 29, 2008? • Given: The half life of P-32 is 14.3 days.
Solution Example: Decay of 32P in time • Known: 1. Ao = 10 mCi 2. T1/2 = 14.3 days 3. Time after initial activity (t) = 28 days • Using A (t) = Ao e-lt = 10 e –(0.693/14.3)(28) = 2.57 mCi
Radioactivity may be defined as: Spontaneous nuclear transformation
Non-ionizing vs. Ionizing radiation • Non-ionizing radiationrefers to any type of electromagnetic radiation that does not carry enough energy per quantum to ionize atoms or molecules — that is, to completely remove an electron from an atom or molecule. • Examples of non-ionizing radiation: microwaves, ultraviolet light, lasers, radio waves, infrared light, and radar.
Ionizing radiationconsists of subatomic particles or electromagnetic waves that are energetic enough to detach electrons from atoms or molecules, ionizing them. • Examples of ionizing radiation: alpha particles, beta particles, neutrons, gamma rays, and x-rays.
Ionization • Ionization is the process of removing electrons from neutral atoms. • It is important to note that exposure to ionizing radiation, without exposure to radioactive material, will not result in contamination of the worker.
PARTICLES PHOTONS alpha X-ray neutron beta gamma ray Two general categories of ionizing radiation:
Radiation Fundamentals • The Four Basic Types of Ionizing Radiation • alpha particles, • beta particles, • gamma or X rays, • neutrons.
Alpha Particles • Physical Characteristics: Large mass, highly charged, helium nuclei (2 protons, 2 neutrons) • Range: 1-2 inches in air • Shielding: Dead layer of skin, paper. • Biological Hazards: Internal, it can deposit large amounts of energy in a small amount of body tissue.
Alpha particles are highly p+ energetic helium nuclei p+ internal cannot get hazard through skin stopped by paper soil, radon, and heavy man-made elements Alpha Particles
Beta Particles • Physical Characteristics: Small mass, electron size, • Range: Short distance (one inch to 20 feet). • Shielding: Plastic • Biological Hazard: Internal hazard. Externally, may be hazardous to skin and eyes.
Beta particle: an energetic electron from an unstable nucleus skin, eye, and internal hazard stopped by plastic natural food, water, air Beta Particles
Gamma Rays/X-Rays • Physical Characteristics: No mass. No charge.Electromagnetic wave or photon. • Range: Very far. It will easily go several hundred feet. Very high penetrating power. • Shielding: Concrete. Water. Lead. • Biological Hazard: Whole body exposure. The hazard may be external and/or internal. This depends on whether the source is inside or outside the body.
Gamma and X-rays are photons (massless electromagnetic energy) stopped by dense shielding naturally present in soil and in cosmic radiation medical, radioactive materials Gamma Rays/X-Rays
Neutrons • Physical Characteristics: Fairly large. No charge. Has mass. • Range: Range in air is very far. Easily can go several hundred feet. High penetrating power due to lack of charge (difficult to stop). • Shielding: Water. Concrete. Plastic (high hydrogen content). • Biological Hazard: External whole body exposure.
Review. • The three basic particles of an atom are, protons, neutrons, and electrons. • Radiationis energy in the form of particles or rays given off by unstable atoms. • The half-lifefor a given radioisotope is the time for half the radioactive nuclei in any sample to undergo radioactive decay.
Review cont. • Ionizing radiationconsists of radiation energetic enough to detach electrons from atoms or molecules, ionizing them. • Non-ionizing radiationrefers to any type of electromagnetic radiation that does not carry enough energy to completely remove an electron from an atom or molecule.
Review cont. • The four basic types of ionizing radiation are: alpha particles, beta particles, gamma or X rays, neutrons. • Alpha particles, Large mass, highly charged, • Range: 1-2 inches in air, • Shielding: Dead layer of skin, paper. • Biological Hazards: Internal • Beta particles, Small mass, • Range: one inch to 20 feet. • Shielding: Plastic. • Biological Hazard: Internal hazard. Externally, may be hazardous to skin and eyes.
Review cont. • The four basic types of ionizing radiation cont: • Gamma or X rays, No mass. No charge. • Range: It will easily go several hundred feet. Very high penetrating power. • Shielding: Concrete. Water. Lead. • Biological Hazard: External whole body exposure. • Neutrons, Fairly large. No charge. Has mass. • Range: Easily can go several hundred feet. High penetrating power due to lack of charge. • Shielding: Water. Concrete. Plastic (high hydrogen content). • Biological Hazard: External whole body exposure.
Test Time! • Follow this link to the test. https://myresearch.wsu.edu • Use your WSU user name and password to sign in. • Click on the training tab. • Then click on the available training tab • Find the basic radiation physics course, in the OR section, click on it and take the test.