Radioactivity and Particles Flashcards
What are the components of an atom?
A positively charged nucleus made of:
* Positive protons
* Neutral neutrons
Surrounded by negatively charged electrons which orbit the nucleus.
Where is most of the mass of atoms located?
Almost all the mass of the atoms lies in the nucleus.
What is the relative mass and charge of a proton?
Relative Mass: 1
Relative Charge: +1
What is the relative mass and charge of a neutron?
Relative Mass: 1
Relative Charge: 0
What is the relative mass and charge of an electron?
Relative Mass: 0.0005
Relative Charge: -1
What defines isotopes of an element?
Atoms of the same element with the same number of protons but a different number of neutrons.
In a nuclide, what does the symbol X represent?
X is the symbol of the element.
In a nuclide, what does the mass number A represent?
A is the mass (nucleon) number (number of neutrons and protons).
In a nuclide, what does the atomic number Z represent?
Z is the atomic (proton) number (number of protons).
What is radioactive decay?
The spontaneous transformation of an unstable nucleus into a more stable one by the release of radiation.
Is radioactive decay a random process?
Yes, it is a random process.
What occurs during alpha decay?
A heavy nucleus emits an alpha particle (helium nucleus - 2A, 4X) and changes to that of a different element.
What is the equation for alpha decay?
ZAX → (X - 4A - 2Z) + α
How penetrating are alpha particles?
They are highly ionising and weakly penetrating, stopped by a sheet of paper.
What occurs during beta decay?
A neutron turns into a proton and emits a beta particle (electron), changing to a different element.
What is the equation for beta decay?
ZAX → (X - A - Z) + β
How penetrating are beta particles?
They are moderately ionising and moderately penetrating, stopped by a thin sheet of aluminium.
What occurs during gamma decay?
A nucleus with excess energy emits a gamma particle after a previous decay.
How penetrating are gamma particles?
They are lowly ionising and highly penetrating, stopped by many centimetres of lead.
What is neutron radiation?
Occasionally one or more neutrons are ejected from neutron-rich nuclides, also emitted during nuclear fission.
What is the equation for neutron emission?
ZAX → (X - A) + 1n
What happens to photographic film when it absorbs radiation?
The film gets darker as it absorbs more radiation
The film is initially white and darkens with exposure.
What is the purpose of wearing photographic film badges?
To check how much radiation exposure a person has had
These badges are commonly used by workers in radiation environments.
What is a Geiger-Muller tube?
A tube that detects radiation by transmitting electrical pulses
Each pulse corresponds to a detected radiation event, producing a clicking sound.
What does a higher frequency of clicks from a Geiger-Muller tube indicate?
More radiation is present
The clicking sound increases with the amount of radiation detected.
What is background radiation?
Weak radiation detectable from external sources
It is a normal part of the environment.
List three sources of background radiation.
- Cosmic rays
- Radioactive rocks
- Food and drink containing radioactive isotopes
Additional sources include fallout from nuclear testing and medical sources like x-rays.
How is the activity of a radioactive source measured?
In becquerels (Bq)
1 Bq equals 1 decay per second.
What does the half-life of an isotope represent?
The time taken for half the nuclei to decay or for the activity to halve
It varies for different radioactive isotopes.
If the count rate drops from 80 to 40 counts per minute in 2 days, what is the half-life?
Around 2 days
This pattern continues with subsequent halving over equal time intervals.
Why must background radiation be subtracted in half-life calculations?
To obtain accurate measurements of the radioactive source’s activity
Background radiation can interfere with the results.
What is one use of long half-life alpha emitters in industry?
In smoke detectors
Alpha particles create a current that triggers an alarm when smoke is detected.
How are long half-life beta emitters used in thickness monitoring?
They detect changes in the thickness of metal sheets during production
A source and receiver are placed on either side of the sheet to monitor beta particle detection.
What is the purpose of gamma emitters in sterilisation?
To kill bacteria or parasites on equipment so it is safe for operations
Gamma emitters can sterilise through their protective packaging, eliminating contamination risk.
What is the role of technetium-99m in medicine?
Used as tracers in diagnostic procedures due to its short half-life
It concentrates in certain parts of the body, allowing for effective imaging.
What is the significance of the half-life of gamma emitters in diagnostics?
Must be long enough for procedures but short enough to not remain radioactive for too long
What is the application of cobalt-60 in medicine?
Used to destroy tumours with a high dose of radiation
Define contamination in the context of radioactive materials.
Occurs when a radioactive source has been introduced into or onto an object
What is irradiation?
When an object is exposed to a radioactive source outside the object
The irradiated object does not become radioactive.
How can exposure to radiation affect living cells?
Can destroy cell membranes by ionisation or damage DNA, leading to mutations and cancer
List three safety measures for radiation exposure.
- Minimising time of exposure
- Keeping a large distance from the source
- Using shielding against radiation
How should radioactive waste from nuclear reactors be disposed of?
Usually by burying it in sealed drums deep underground and remotely handling it after cooling
What is nuclear fission?
The process of splitting a nucleus
What happens when a uranium-235 nucleus absorbs a thermal neutron?
It splits into two daughter nuclei and releases energy along with 2 or 3 neutrons
What is a chain reaction in nuclear fission?
When neutrons released from one fission event induce further fission events in other uranium-235 nuclei
What is the function of control rods in a nuclear reactor?
To absorb neutrons and regulate the fission process
Usually made of boron.
What is the role of the moderator in a nuclear reactor?
Slows down neutrons to make them suitable for absorption by uranium-235 nuclei
Usually water is used as a moderator.
What is the purpose of a coolant in a nuclear reactor?
To prevent the reactor system from overheating
Describe the reactor core.
A thick steel vessel that withstands high pressures and temperatures and absorbs some radiation
What is the function of the building surrounding the reactor core?
Acts as a radiation shield to absorb radiation escaping the reactor core
Made of thick reinforced concrete.
What is the process of fusing two nuclei to form a larger nucleus called?
Nuclear fusion
What is the result of the nuclear fusion process in terms of mass?
There is a very small loss of mass
What accompanies the small loss of mass during nuclear fusion?
A release of energy
How do the sun and other stars release energy?
Through nuclear fusion
True or False: Nuclear fusion occurs at low temperatures and pressures.
False
What prevents nuclear fusion from happening at low temperatures and pressures?
The electrostatic repulsion of the protons is too great
Fill in the blank: The nuclei that collide and fuse together in nuclear fusion include _______ and hydrogen-2.
hydrogen-1
What is one of the products formed from the fusion of hydrogen-1 and hydrogen-2?
Helium-3
