Radiation Flashcards
What is radiation?
Energy in motion/ energy in the form of particles or electromagnetic waves
What is radioactivity?
The spontaneous emission of radiation from the nucleus of atom
What is an isotope?
Atoms with the same number of protons but different number of neutrons
What is a radioisotope?
Unstable isotope of an element that decays or disintegrates spontaneously emitting radiation.
What is non-ionising radiation?
Radiation that does not have sufficient energy to dislodge orbital electrons
Give examples of non-ionising radiation
Microwaves, ultraviolet light
What is ionising radiation?
Radiation with sufficient energy to remove an electron from an atom or molecule
Give examples of ionising radiation
Alpha and beta particles, neutrons, x rays
What is the process of radioactivity?
The process by which unstable atoms spontaneously transform to new atoms and in the process emit radiation
Give some examples of radioactive sources.
- Solar Radiation
- Terrestrial radiation
- Each other
- Food and drink
What are the common units of radioactivity?
The Curie - 1 gram of radium disintegrates
Alternatively the becquerel - 1 disintegration per second
What is the half life?
It is the amount of time needed for the activity to reach one half of its initial amount.
What is the common units of exposure?
Roentgens
What is the Roentgen?
Charge produced in air from ionisation by gamma and x-rays. Only for photons in air.
What is the absorbed dose?
The energy deposited by any form of ionising radiation in a unit mass of material.
What are the common units of absorbed dose?
- Roentgen Absorbed Does (rad)
- Gray 1 Gy = 100 rad
What is the dose equivalent?
Risk adjusted absorbed dose. The absorbed dose is weighted by the radiation type and tissue susceptibility to biological damage.
What are the units for damage in tissue measured?
Rem
How are Q, rad and rem related?
rem = Q * rad
where Q is the risk of biological injury
What is the conversion between rem and Sv?
1 Sv = 100 rem
For which radiation is it applicable that 1 rad = 1 rem? And for which radiation is this not applicable?
- For whole body gamma and beta ray exposure, this is applicable
- For alphas, neutrons and protons it is not applicable
Where does terrestrial radiation originate from?
When the earth was created
What is the greatest contributor to terrestrial radiation?
226 Radium
In which rock is terrestrial radiation principally found?
Igneous rock
Also fly ash from coal burning plants
What is the relationship between cosmic radiation and altitude?
As the altitude increases, the amount of cosmic radiation also increases.
Give some common consumer products that emit radiation.
- television sets emit low energy x rays
- smoke detectors
- watches
What does the anatomy of an atom consist of?
- electron
- neutron
- proton
- nucleus
What is ionisation?
Formation of a charged and reactive atom. It occurs from the addition or removal of electrons from neutral atoms.
How does ionisation come about?
Beta particle approaches an atom. The coulombic field of the beta particle and electron collide. The electron is then ejected from the atom.
What are the four types of ionising radiation?
- Alpha
- Beta
- Gamma
- Neutron
What is alpha decay?
Emission of a helium nucleus. Doubly ionised
How hazardous is alpha decay?
Only hazardous for the ingestion or inhalation of an alpha emitter. It is not usually an external radiation hazard.
How can alpha radiation be stopped?
By paper or a dead layer of skin.
Give examples of alpha emitters
Uranium, radon
What is beta decay?
Emission of energetic electron. Singly ionised.
How hazardous is beta decay?
External hazard to eyes and skin. Internal hazard via ingestion or inhalation of beta emitter.
How can beta radiation be stopped?
By plastic. Can travel 12 feet in air.
Give examples of beta emitters
Phosphorus, Carbon, Sulphur
What is gamma decay?
X rays and gamma rays are photons - no charge.
How hazardous Is gamma decay?
External radiation hazard to deep organs and tissues. Internal hazard via ingestion or inhalation of gamma emitter.
How can gamma radiation be stopped?
By lead.
Give an example of gamma emitter
Iodine 125
What materials can stop each radiation?
- Alpha = paper
- Beta = plastic
- Gamma = lead
What are Bremsstrahlung x-rays?
It is the radiation given off by a charged particle due to its acceleration caused by an electric field of another charged particle. Emitted as x-rays.
What is Bremmstrahlung x-ray intensity and energy dependent on?
- x - ray intensity = increasing atomic number
- energy = increasing electron energy
What does ALARA stand for?
As Low As Reasonably Achievable
Give three examples of radiation safety under ALARA?
- Time
- Distance
- Shielding
Why do we implement ALARA?
To minimise the dose
How does ALARA depict the time for radiation safety?
- The smaller the time = the less radiation exposure
- Use Radioactive material only when necessary
- Do dry runs without the radioactive material
- Shorten time when near RAM
How does the radiation dose relate to the distance?
- Doubling the distance from the source, decrease the dose by four
- More distance = less radiation exposure
- Effective and easy
Give examples of equipment which gives distance from radiation?
Tongs, Tweezers, Pipettes
Why is shielding effective to reducing the radioactive dose?
Materials absorb radiation.
- Proper shielding = less radiation exposure
Which materials are effective in shielding?
Lead and plexiglass
When working with radioactive materials in the lab what safety should you use as a precaution?
- Wear safety glasses
- Wear gloves
- Wash hands
- No food or drink near radioactive materials
What are the two types of somatic effects for radiation?
- Prompt - skin burns and cataracts
- Delayed - cancer
What are the other biological effects of radiation?
- Genetic effects
- Teratogenetic effects
What are the two ways in which radiation can damage cells?
- Production of free radicals
- Direct damage to the DNA
What is the risk factor of cancer for radiation dose?
- 4 % increase in risk of dying of cancer for each 100 rem of dose
What are the two aims in occupational exposure limits?
- eliminate the ability of non-stochastic effects (acute) to occur e.g. skin reddening
- reduce the probability of the occurrence of stochastic effects (chronic) to the same level as other occupations e.g. leukemia
What is the total effective dose equivalent and what is its limit?
TEDE = internal + external
We assume that the internal is zero unless there is absorption or inhalation
The limit is 5 rem/year
Which three classes of people should wear radiation dosimeters or badges?
- Those who are likely to exceed 10 % of their annual limit are required.
- Those who would like a badge
- Minors or pregnant workers
What are the three general classes of detectors?
- Gas-Filled Detectors
- Solid Detectors
- Liquid Detectors
Give an example of gas filled detector.
Gieger-Mueller Counters
What is the summary of the biological effects of radiation?
- Deposit energy in body
- Cause DNA damage
- Create ionisations in body leading to free radicals
These may all lead to biological damage
What makes cells radiosensitive?
- High division rate
- Long dividing future
- Unspecialised type
What are acute or nonstochastic effects?
Occur when the radiation dose is large enough to cause extensive biological damage to cells so that large numbers of cells die off. Evident hours to a few months after exposure.
What are late or stochastic effects?
Exhibit themselves over years after acute exposure. (delayed).
- Genetic
- Somatic
- Teratogenic
What are the medical treatments for external decontamination?
- Mild cleaning solution applied to intact skin.
Never use harsh abrasive or steel wool. Use soap.
What is the medical treatment for internal decontamination?
- Treatment which enhances excretion of radionuclides.
How did Chernobyl occur?
There was a reactor vessel rupture whilst running a test in reactor 4. This then led to a series of steam explosions and resulted in the graphite moderator of reactor 4 being exposed to air. This cause a fire and led to a large amount of radioactive material in the air.
What were the most severly contaminated areas?
- Belarus
- Russia
- Ukraine
Where did radioactive material fall and what was the effect on food production?
It fell all over Europe and it meant that much land in Europe was unsuitable for food production.
What is the purpose of graphite moderators in a nuclear reactor?
To reduce the speed of fast neutrons and convert them to thermal neutrons which are capable of sustaining the nuclear reaction.
What was the main cause for injury, death and illness?
- Acute radiation poisoning leading to immediate deaths.
- Mutations and birth defects
- Thyroid cancer is particularly prevalent in children born in the region.
What was the cause relating to the RBMK reactor?
- Positive void coefficient. This causes the power to increase when more steam is produced which is an unstable configuration.
- Design of control rods was also bad. Bottom was graphite so when rods inserted into reactor from fully raised position, the graphite part displaces water which can absorb neutrons and thus raises the power rather than lowers it.
What was the causes relating to the testing of the reactor at the time?
Some automatic safety systems and alarms were disarmed during the test and the competence of the operators chosen to do the test.
What was the causes relating to the operation of the plant during the test?
There was insufficient communication between the safety officers and the operators in charge of the experiment before the run that night. The reactor operators disabled safety systems and shut down a computer controlling the unit so all systems were human operated rather than computer controlled.
What was the causes relating to the safety management?
Management of the plant and in particular, safety management was poor.
What was the cause relating to the authorities?
Due to lack of information flow, the Soviet government was not fully aware of the seriousness of the incident which meant evacuations occurred too late. It was only 2-3 days after the accident that the Soviet government informed other countries.
What was the change in practice and law after Chernobyl?
- Nuclear power became less popular around the world
- RBMK reactors being planned or constructed were cancelled. Safety modifications made to RBMK reactors in Russia. Positive void coefficient reduced. Ability to operate during loss of cooling incidents has improved.
- Establishment of competent and independent licensing authorities has been set up.
Why was the test being carried out?
In the event of power grid failure, Chernobyl had three back up diesel generators. It took 15 seconds to start up and 60 seconds to attain full speed. The test was to check if residual energy in the turbine could be used to make the water pump start more quickly.
Would the test have been safe if the operators had followed the approved procedure?
Yes. If the test was carried out as planned the procedure would have been carried out safely. Operators tried to boost the reactor output once the experiment had started.
