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radioactivity and particles - Coggle Diagram
radioactivity and particles
units
Becquerel
count rate
centimetre
distance
hour
time (half-life)
minute
time (half-life)
second
time
structure of an atom
the mass number is the total number of protons and neutrons
the atomic number is the number of protons or electrons
the atom has a symbol as well
isotope
an atom of the same element with the same number of protons but different number of neutrons
types of ionising radiations
alpha
helium nucleus
decreases mass number by 4 and atomic by 2
low penetrating power
highly ionising
beta
electron
increases atomic number by 1
medium penetration power
medium ionisation
gamma
doesn't change mass or atomic number
high penetrating power
low ionising
penetrating power practical
variables
IV: absorber material
DV: count rate
CV:
radioactive sources
distance of GM tube to source
location/background radiation
connect GM tube to counter. in the presence of no sources, measure background radiation. repeat and average. then place source a fixed distance away from tube and take another reading. then take absorbing materials and place them between the source and tube. then take readings, repeat and average. if count rate decreases you can determine the type of radiation emitted
Geiger-muller tubes detect ionising radiation
background radiation
natural sources
radon from rocks and soil
heavy elements such as uranium radiate naturally
cosmic rays from space
man-made sources
medical sources
fallout
the activity of radioactive sources decrease over a period of time, measured in Becquerels
half-life
the time taken for the number of radiactive nucleiand activity to halve
uses of radioactivity
nuclear fusion and fission in power plants
medicine, steralising equipment and treating cancer
contamination vs irridation
contamination
unwanted presence of materials containing radioactive atoms on other materials (physical contact)
irradiation
the process of expanding a material to alpha, beta or gamma radiation (exposure)
dangers of ionisation
causes mutations in living organisms
can damage cells and tissue
problems arising from he disposal of radioactive waste and how the associated risks can be reduced
nuclear reactions, including fission, fusion and radioactive decay, can be a source of energy
fission
the fission of U-235 produces two radioactive daughter nuclei and a small number of neutrons
a nucleus of U-235 can be split (the process of fission) by collision with a neutron, and that this process releases energy as kinetic energy of the fission products
chain reactions
Only one extra neutron is required to induce a uranium-235 nucleus to split by fission. During the fission, it produces two or three neutrons which move away at high speed. Each of these new neutrons can start another fission reaction, which again creates further excess neutrons. This process is called a chain reaction
control rods and moderator
control rods
absorb nutrients, by rising them, the rate of fission increases.
moderator
to slow down neutrons so they are in thermal equilibrium with the moderator, so an efficient reaction occurs
shielding around a nuclear reactor
absorbs hazardous radiation, made of steel and concrete nearly 2m thick , ensuring the surrounding environment is safe
fission vs fusion
fission
the splitting of large, unstable nucleus into two smaller nuclei and neutrons
fusion
the joining of two light nuclei to form a heavier nucleus
nuclear fusion is the creation of larger nuclei resulting in a loss of mass from smaller nuclei, accompanied by a release of energy
fusion is the energy source for stars
disposal of radioactive waste
these containers can be expensive and difficult to manufacture
you also have to confirm that there is no risk of leaking into the sea or water table
use a strong container that cannot rust
fusion conditions
nuclear fusion does not happen at low temperatures and pressures because the electrostatic repulsion of the protons in the nucleus is too great