nuclear radiation Flashcards
describe the nature of alpha
a helium nucleus
most ionising
most dangerous form of radiation
describe the nature of beta
negatively charged
a very high speed electron that is ejected from the nucleus when a neutron changes into a proton
mildly ionising
describe the nature of gamma
a very high energy light wave
very short wavelength
very high frequency
weakly ionising
member of the EM spectrum
define activity
the number of nuclear disintegrations per second
define half-life
the time it takes for the activity in a radioactive source to fall to half its original value.
what units are used to measure activity
Bq - becquerels
what units are used to measure half life
time eg: - seconds, years, days etc
how would you measure half life in an experiment
First measure the background radiation (no source present) using the Geiger-Müller tube and counter
Place a radioactive source a set distance from the GM tube and measure the count rate at set time intervals for a suitable time period
Deduct the background count rate from the source count rate, to get the corrected count rate
Plot a graph of corrected count rate vs. time and read the half-life from the graph.
what are the dangers of ionising radiation to living things
Cells can be altered by ionising radiation and change their function.
Cells can be destroyed by ionising radiations.
This can lead to the creation of cancer cells.
formula to calculate activity
A = N/t (activity = number of nuclear disintegrations/time in SECONDS
define absorbed dose
the energy absorbed per unit mass of the absorbing material
formula to calculate Absorbed dose (D)
D=E/m (absorbed dose = energy in joules/mass in KG
units for absorbed dose?
Gy ( grays ) or J/kg, J kg-1 ( joules per kilogram )
ionising ability of gamma?
low
ionising ability of beta?
moderate
ionising ability of alpha?
high
penetration of alpha?
low
stopped by paper
penetration of beta?
moderate
stopped by aluminium
penetration of gamma?
high
stopped by lead/few metres of concrete
define equivalent dose?
a more accurate estimation of damage done by radiation than absorbed dose
units for Equivalent dose
sv (sieverts)
relationship for equivalent dose
H=DWr (equivalent dose=absorbed doseweighting factor)
define equivalent dose rate
how rapidly the equivalent dose was absorbed.
formula for equivalent dose rate
H(with a dot on top)=H/t (eq dose rate=eq dose/time)
what is the radiation weighting factor
because diff radioisotopes do diff amounts of damage, we use a table to factor that into the equivalent dose.
describe nuclear fusion process
when two light nuclei join/fuse together to form one single, larger nucleus. This process creates LOTS of energy
describe nuclear fission process
the splitting of large, unstable nuclei into smaller nuclei, by hitting the large nucleus with a slow neutron causing it to split into ‘daughter nuclei’, and also releasing 2 or 3 more neutrons, which can be used to continue the process in a chain reaction.
challenges of nuclear FUSION?
-can’t be done on earth, needs high VERY temps and pressures
