Presentation is loading. Please wait.

Presentation is loading. Please wait.

Basic of radiation Prof. Dr. Moustafa. M. Mohamed Vice Dean Faculty of Allied Medical Science Pharos University Alexandria Dr. Yasser khedr Department.

Similar presentations


Presentation on theme: "Basic of radiation Prof. Dr. Moustafa. M. Mohamed Vice Dean Faculty of Allied Medical Science Pharos University Alexandria Dr. Yasser khedr Department."— Presentation transcript:

1 Basic of radiation Prof. Dr. Moustafa. M. Mohamed Vice Dean Faculty of Allied Medical Science Pharos University Alexandria Dr. Yasser khedr Department of Medical Biophysics Pharos University

2 Operating Engineers National Hazmat Program2 The New Understanding n In 1913 several scientists published the theory that an atom is made of u a positively-charged central nucleus u orbited by negatively-charged particles

3 Bohr Model

4 Atomic Structure

5 Nucleus n Contains positively-charged protons n Non-charged neutrons

6 Electrons n Orbit nucleus n An atom can have as many electrons as it has protons

7 How big is an atom? n An atom is the same size compared to a golf ball n As a golf ball is compared to the earth

8 Radioactivity: Elements & Atoms Atoms are composed of smaller particles referred to as: –Protons –Neutrons –Electrons Atoms are composed of smaller particles referred to as: –Protons –Neutrons –Electrons

9 Basic Model of a Neutral Atom. n Electrons (-) orbiting nucleus is the same number of protons; net charge = 0. n Atomic number (number of protons) determines element. n Mass number (protons + neutrons)

10

11 Definition of Radiation n “Radiation is an energy in the form of electro- magnetic waves or particulate matter, traveling in the air.”

12 What is Radiation? n Form of energy n Emitted by nucleus of atom or orbital electron n Released in form of electromagnetic waves or particles 12

13 Operating Engineers National Hazmat Program13 What is Radiation? n As either particles or rays n Two kinds: ionizing and non- ionizing

14 Operating Engineers National Hazmat Program14 Fission u Fission is the process by which a large, unstable nucleus splits into two nuclei u It rarely occurs naturally

15 Fission n When the atom splits, “fission fragments” are released

16 Operating Engineers National Hazmat Program16 The Search for Stability n An atom is stable based on it’s proton to neutron ratio n If there are too many or too few neutrons or protons, the atom will give off excess energy as u rays u particles n This process is called radioactive decay

17 Operating Engineers National Hazmat Program17 Radioactive Decay n When an atom’s nucleus gives off excess energy, the process is called radioactive decay n Radioactive half-life is the time it takes half the radioactive atoms present to decay

18 Half-Life n The time it takes half the radioactive atoms present to decay BeforeAfter one half-life

19 Operating Engineers National Hazmat Program19 Half-Life n The time it takes half the radioactive atoms present to decay BeforeAfter one half-life

20 Types of Radiation n Radiation is classified into: u Ionizing radiation u Non-ionizing radiation

21 21 The Electromagnetic Spectrum Waveform of Radiation

22 Operating Engineers National Hazmat Program22 Ionizing Radiation n The energy given off by the nucleus is called ionizing radiation n It is strong enough to detach an electron from an atom u When an atom loses an electron, it has a positive charge and is called an ion u The ion and its lost electron are called an ion pair

23 IonizationIonization Ionizing radiation is produced by unstable atoms. Unstable atoms differ from stable atoms because they have an excess of energy or mass or both. Unstable atoms are said to be radioactive. In order to reach stability, these atoms give off, or emit, the excess energy or mass. These emissions are called radiation. Ionizing radiation is produced by unstable atoms. Unstable atoms differ from stable atoms because they have an excess of energy or mass or both. Unstable atoms are said to be radioactive. In order to reach stability, these atoms give off, or emit, the excess energy or mass. These emissions are called radiation.

24 TYPES OF IONIZING RADIATION

25 Alpha Particle n Large mass n Consists of 2 protons and 2 neutrons n Electrical charge of +2 n Range in air 1 to 2 inches +1

26 Alpha shielding n A sheet of paper n Outer layer of skin

27 Operating Engineers National Hazmat Program27 Biological Hazard n Alpha radiation is not an external hazard, because it can be stopped so easily n If inhaled or swallowed, the alphas emitted from an alpha emitter, can deposit large amount of energy in a small area of body tissue

28 Operating Engineers National Hazmat Program28 Sources of Alpha Radiation n Plutonium 238 and 239 n Uranium 238 and 235

29 Beta Particle - ß n Small mass n Electrical charge of -1 n Emitted from nucleus n Range in air about 10 feet

30 Beta Shielding n Beta has a limited penetrating ability because of its negative charge n Most beta particles can be shielded by plastic, glass, metal foil, or safety glasses

31 Operating Engineers National Hazmat Program31 Biological Hazard n If ingested or inhaled, a beta- emitter can be an internal hazard n Externally, beta particles are potentially hazardous to the eyes and skin

32 Operating Engineers National Hazmat Program32 Beta Sources n Uranium decay products n Decay of some radioactive substances (Tritium) n Products of the fission process

33 Gamma and X-Rays n An electromagnetic wave or photon, which has no electrical charge n Great penetrating power n Range in air easily several hundred feet

34 Gamma and X-Ray Shielding n Concrete n Lead n Steel

35 Neutron n A neutron is ejected from the nucleus n No electrical charge n Range in air easily several hundred feet

36 Operating Engineers National Hazmat Program36 Neutron Radiation Shielding n Best shielded by material with a high hydrogen content u Water u Plastic

37 Types or Products of Ionizing Radiation    or X-ray  neutron

38 Ionizing Radiation alpha particle beta particle Radioactive Atom X-ray gamma ray

39 Non-Ionizing Radiation n Energy in transit that is too weak to detach an electron from another atom n Examples u Light u Radio and television waves u Microwaves

40 RADIATION MEASUREMENT

41 Operating Engineers National Hazmat Program41 Roentgen (R) n A unit for measuring exposure n Defined for effect in air only n Applies only to gamma and x-rays n Does not relate radiation to the effect on the human body

42 Operating Engineers National Hazmat Program42 Roentgen (R) n A unit for measuring exposure n Defined for effect in air only n Applies only to gamma and x-rays n Does not relate radiation to the effect on the human body 1 R = 1000 milliRoentgen (mR)

43 Operating Engineers National Hazmat Program43 Radiation Absorbed Dose (rad) is the absorption of one joule of ionizing radiation by one kilogram (1 J/kg) of matter n Unit for measuring the absorbed dose in any material n Applies to all types of radiation n 1 rad = 1000 millirad (mrad) 1 rad= 1000 millirad (mrad)

44 44 Roentgen Equivalent Man (rem) equal to an effective dose of a joule of energy per kilogram of recipient mass n Unit for measuring radiation dose equivalence n Most commonly used unit n Takes into account the energy absorbed (dose) and effect on the body of different types of radiation 1 rem = 1000 millirem (mrem)


Download ppt "Basic of radiation Prof. Dr. Moustafa. M. Mohamed Vice Dean Faculty of Allied Medical Science Pharos University Alexandria Dr. Yasser khedr Department."

Similar presentations


Ads by Google