2: Radiation/Radioactivity Flashcards
How fast is electromagnetic radiation?
The speed of light
How do you determine atomic number?
Number of protons
How do you determine atomic mass?
Number of neutrons + number of protons
How does a metallic bond occur?
Between electrically conductive elements.
What does “fissile” refer too?
Nucleus being split by a high speed particle (ex. neutron)
How do thermal neutrons move?
Slow
What is radioactivity?
Dispersal of high energy radiation from an unstable atom while changing into a lighter, stable atom.
What is radioactive decay?
Energy released through the loss of atomic particles.
What does particulate radiation consist of?
Particles that have mass AND energy but may/may not have an electric charge.
What does electromagnetic radiation consist of?
Photons that have energy but no mass or charge.
What are the 4 types of radioactive decay/disintegration?
- Spontaneous fission
- Alpha decay
- Beta decay
- K-electron capture
Spontaneous fission happens with what masses?
Greater than 200
What is the result of alpha decay?
A 2 proton 2 neutron particle.
What is the result of beta decay?
A neutron is converted to a proton then to an electron. The free neutron consists of a proton, beta particle and a neutrino.
What is Q represented by?
Energy released in the disintegration process.
For every Beta emission…
A include loses a neutron, gains a proton and atomic number increases by one.
What is an alpha particles speed compared to light?
5% of the speed of light
It’s heavier so it’s slower
What is an alpha particles usual value of energy?
4-9 MeV (mega electron volt)
Alpha particles have low penetration and can be absorbed by a few centimetres of what?
Air or thin piece of paper.
When are alpha particles harmful?
When inhaled/injected they cause damage to the body tissues.
What is the mass of a Beta particle?
Same as a electron (-1) and negatively charged.
How fast is a Beta particle compared to the speed of light?
99.95% the speed of light.
What is a Beta particles energy level?
0 - max
A Beta particle can penetrate a few centimetres of what?
Human tissue
A Beta particle can be absorbed by a few millimetres of what?
A few millimetres of aluminum or metres of air.
A Beta particle is a decay product of what industrial radiography sources?
Iridium-192 and Cobalt-60
What are neutrons?
High energy particles released from nucleus of an atom during fission reactions.
OR
Knocking out of nucleus by energizing a nuclide using gamma radiation OR bombarding it with suitable projectiles.
What are some characteristics of neutrons?
NO charge - not affected by electrical/magnetic fields.
Pass with ease through lead/steel.
Absorbed by water/graphite.
What happens when a neutron hits water?
Water contains 1 proton and 0 electrons so when a neutron hits an H atom, it loses all energy in one collision.
Gamma radiation is what stage of nuclear transformation?
Secondary effect
How fast is gamma radiation and how does it travel?
Travels at speed of light - no mass
Travels in straight lines - no charge
What type of wavelengths make it highly penetrating?
Short wavelengths
How is the radioactivity of a material measured?
The number of atoms that disintegrate in a given time.
What is the main type of radiation that is used in isotope radiography?
Gamma radiation
A Curie was initially made to represent what?
1 gram of radium-226
3.7 x 10^10/37 billion disintegration’s per second
With each disintegration, what is released?
Gamma radiation.
Higher the activity, the more radiation
What is meant by “half-life?”
Time required for half of the atoms to decay.
Energy is expressed in what?
KeV or MeV
How is intensity measured?
Per hour at a distance of one meter from source.
What part of radiation that is produced by an isotope cannot be changed?
Energy and intensity
What are X-rays?
A transfer of energy between high speed interaction of electrons and a dense target material (usually tungsten)
3 requirements to generate X-rays are:
- Electrons
- Means to accelerate electrons to a high velocity (voltage)
- High density material to receive impact of electrons
What percentage of electrical energy produces X-rays?
2% and remaining energy is heat
What are the 3 principle controls of an X-ray tube?
- Milliamperage (Ma) control
- Kilo voltage (Kv) control
- Timer control
What does Ma (milliamperage) govern?
Amount of electricity going to negative cathode
What does Kv (kilo voltage) govern?
Electrical potential/pressure (energy) between negative cathode and positive anode
What 2 atomic processes can produce X-ray photons?
- Characteristic X-rays
2. Bremsstrauhlung X-rays
When are characteristic X-rays produced?
When a striking electron actually hit an orbiting electron in atom of target.
(The energies produced are the difference between energies of two consecutive shells.)
What is bremsstrahlung in German?
Braking
What happens when bremmstrahlung X-rays are produced?
An active electron passes between orbiting electrons in tungsten atom then is SLOWED DOWN - must give off some kinetic energy so it produces an X-ray photon and heat
Describe the energy produced in bremsstrahlung rays:
Most produced energy is random and depends on difference of kinetic energy between original velocity and final one (most X-rays produce like this).
Type I film is used for?
Critical inspections
Type II film is used for?
Light metal/heavier steel
Type III film is used for?
Steel/brass alloys
Type IV film is used for?
Highest speed available
What is a ion pair?
Atom missing an electron = positive ion, atom with an extra electron = negative ion.
How is an isotope made?
- Fission - large unstable nucleus bombarded by neutrons
2. Alter neutron to proton ratio (N/Z) of stable element - my life absorbs a neutron
2 main isotopes in industrial radiography?
Cobalt-60 and iridium-192
Define becquerel:
Unity of activity = 1 Bcq = 1 disintegration per second
What is a specific activity?
Concentration of radioactive material within a radioactive source.
What is characteristic intensity?
Measure of ionizing air an isotope produces.
Each isotope is different, based on disintegration process
What’s the difference between the generation of X-rays and gamma rays?
X-rays are electrical and gamma rays are a decay of radioactive material.
What’s the difference between the intensity of X-rays and gamma rays?
X-ray intensity can be adjusted by changing amperage, gamma intensity depends on disintegration rate and cannot be changed.
What is the difference in energy between X-rays and gamma rays?
X-rays are adjusted by changing amperage, gamma is determined by radionuclide and can’t be changed.
What’s the difference between radiographic quality and radiation quality?
Radiographic is the quality of image (ex. Contrast, definition, sensitivity, etc.) and radiation quality is based off wavelength (ex. Higher energy = shorter wavelength = greater penetration).
