Atomic Structure Flashcards
Activity
the number of unstable atoms that decay per second in a radioactive source
Bacquerei
the unit used to measure activity in radioactive substances
Alpha
the same as a helium nucleus, with two neutrons and two protons, very high ionising ability but stopped by a sheet of paper, very slow but has positive charge
Atom
has a nucleus of approximately 1x10^-1, has a positively charged nucleus surrounded by negatively charged electrons
Background Radiation
a type of radiation that is always present around us but in very low doses (e.g. 0.1-0.2 microsieverts), which is safe. Sources include:
* Underground rocks
* Food
* Drink
* Cosmic rays from space
* Medical uses (artificial source)
* Industrial uses (artificial source)
* The ground
* Buildings
* Nuclear power (artificial source)
* Nuclear weapons test (artificial source)
Radioactive Tracers
used to race the flow of a substance through an organ. The tracer contains a radioactive isotope that omits gamma radiation as it can be detected outside of the system. For example, doctors can use radioactive tracers to see if a patient’s kidney is blocked.
Radioactive Implants
radioactive implants are used to destroy cancer cells in some tumours. Beta or gamma emitting isotopes are used in the form of small seeds or rods. Permanent implants use isotopes with implants long enough to eradicate the tumour over a given time, but short enough so that most of the unstable nuclei will have decayed soon afterwards.
Gamma Knives
gamma knives are used to treat cancer. They work by targeting small doses at the tumour from a moveable box. Small doses pass through the healthy brain while the doses are all concentrated on the tumour. This irradiates the person.
Barium Meal
used to track movement through organs, as barium shows up on x-rays
Beta
the same as a high-energy electron, with medium ionising ability, stopped by 5mm aluminum, negative charge, fast
Energy Levels
electrons are arranged at different distances from the nucleus in energy levels which are sometimes called shells. The electron arrangement may change when electromagnetic radiation is absorbed, causing electrons to move further from the nucleus to a higher energy level. If electromagnetic radiation is omitted, electrons move closer to the nucleus to a lower energy level.
Fission
The splitting of an atom’s nucleus into two smaller nuclei and the release of two or three neutrons and energy. The energy comes from fission neutrons and fragment nuclei.
Chain Reaction
occurs in a nuclear reactor when each fission events causes further fission events. On average, in a nuclear reactor, one fission event goes on to cause one more fission event. This makes sure energy is released at a steady rate. Chain reactions are kept under control using control rods.
Fissionable Isotopes
the fuel in nuclear reactors, such as U-238 (as opposed to non-fissionable U-235) and Pu-239. Different elements need different reactors.
Food Irradiation
the application of ionising radiation to food to extend shelf life and improve safety by killing bacteria
Nuclear Reactor
used to generate nuclear power
Control Rods
are evenly spread and are used to control the amount of reactions. These absorb surplus neutrons and can be adjusted to maintain steady chain reactions.
Generator
generates heat which creates steam
Heat Exchanger
where the water from the turbines is turned to steam to power them
Pump
supplies water to maintain the volume when the primary reactor coolant has contracted due to decreased load
Turbines
these create the energy as they are driven by steam that is produced in the heat exchanger of the reactor. The energy used to heat the water comes from the nuclear generator.
Reactor Core
is made of thick steel to withstand the very high pressure and temperature in the core. This is where the reactions happen.
Fuel Rods
must be made of fissionable isotopes, often U-235 or Pu-239. These must be disposed of safely (often by burial) after they have been used as they are still radioactive
Pressuriser
increases pressure
Steel Vessels
are made of steel to withstand the high temperatures and to enclose the radiation. They enclose the heat exchanger and the reactor core
Concrete Sheild
both vessels are enclosed by thick concrete walls. These absorb ionising radiation that escapes through the walls of the steel vessel.
Fusion
happens in the Sun and other stars. During fission, small nuclei join together to form a larger nuclei and energy is released. Particles must be under huge pressure to create fusion. Temperatures of 15million degrees Celsius may be needed. The hydrogen fuse to form helium nuclei, releasing vast amounts of energy. However, it is difficult to force protons together because of their repulsive electrostatic forces, so it only occurs at very high pressures and temperatures. These are the conditions where it occurs in starts but it is very hard to replicate those conditions on earth.
Gamma
electromagnetic wave, least ionising, stopped by thick concrete, no charge, travels at the speed of light
Geiger Counter
used to measure the amount of radioactivity in the air
Half Life
the time taken for half of the radioisotopes in a substance to decay, or for the count rate to halve
Induced Nuclear Fission
occurs when a stable isotope is struck by a neutron. The isotope absorbs the neutron, becomes unstable and then splits into two smaller fragments, releasing neutrons and energy. Induced fission is under control and deliberate.
Ionisation
any process by which atoms become charged
Irradiation
when an object is exposed to ionising radiation but does not become radioactive. It happens when there is radioactive material outside your body that can reach you as waves. X-rays are a form of irradiation. A person is unlikely to develop cancer through irradiation.
Isotope
has the same number of protons, but a different number of neutrons
Net Decline
the overall amount that the activity of a source has fallen in a period of time.
Neutrino
a particle able to travel faster than the speed of light
Nuclear Bombs
unctrolled fission reactions
Nucleus
made out of protons and neutrons and is positively charged and makes up most of the mass of the atom
Particle Physicist
someone who studies the part of physics relating to particles
Radioactive
substances that emit nuclear radiation
Radiation
the word for alpha and beta particles and gamma rays that are being emitted from a substance
Radiation Dose
a measure of the risk of harm resulting from an exposure of the body to the radiation depends on the type of radiation used, how long the body is exposed to it and the energy per second absorbed by the body from the radiation
Speed of light
3x10^8
Spontaneous Fission
is roughly the same as induced fission, as it releases neutrons and energy. Occurs without a neutron being absorbed
Unstable
an element becomes unstable if it has too many protons or neutrons. In an attempt to stabilise itself, it omits radioactivity, decaying
