Topic 6 - Using radioactive materials Flashcards
What is background radiation
low-level radiation thats around all the time
Where does background radiation come from
naturally occurring unstable isotopes found in air, food, boiling materials, rocks etc
Space
Why does the level of background radiation depend on where you live
certain underground rocks (e.g granite) can cause higher levels of background radiation at surface especially if they release radioactive radon gas.
What is half life
time taken for half the un-decayed nuclei to decay
What is radioactive activity measure in
becquerels (Bq)
how do you calculate half life
step by step, keep halving until you get the answer
What is a use of alpha radiation
fire alarms
weak source of alpha radiation is placed in a smoke detector close to two electrodes.
source causes ionisation which allows a current to flow
smoke absorbs radiation so current stops and alarm sounds
How are gamma rays used to sterilise food and equipment
food can be irradiated with high dose of gamma rays which will kill all microbes so food won’t go bad as quick. Medically equipment treated the same.
need a strong emitter of gamma rays with reasonably long half life so doesn’t need replacing that often
Why is irradiation better than boiling for sterilising
doesn’t involve high temperatures so fresh fruit or plastic instruments won’t be damaged.
how are gamma and beta used as tracers
injected or swallowed into patient and progress through the body is followed by detector. Computer uses reading from detector to produce an image. can be used to diagnose medical conditions e.g cancer
why must tracers be beta or gamma
so it passes out of the body
should have short half life
How is gamma used to detect leaks in pipes
place tracer in pipe, where largest amount detected the leak is
how is beta radiation used in thickness control
direct radiation through the thing being made (e.g paper) and put detecter on the other side, when amount detected changes it means thickness has changed so the control unit adjusts rollers, needs to have short half life and be beta so paper will partly block radiation, if all go through reading won’t change
How are gamma rays used to treat cancer
high doses kill all living cells, have to be careful and direct gamma rays right at cancer to minimise damage to healthy cells.
What do lower doses of ionisation do to cells
cause minor damage without killing cell
can give rise to mutant cells which divide uncontrollably (cancer)
What do high doses of ionisation do
kills cell completely which causes radiation sickness if a lot of cells get killed at once
Which radioactive sources are more dangerous outside body
beta and gamma
can penetrate body and harm organs
Which radioactive sources are more dangerous inside body
alpha
highly ionising, others pass out of body alpha cant
How do you minis risk in a lab with radioactive materials
avoid skin contact with source
keep as far away from the body as possible
point away from body and don’t look directly at it
always put back in labelled lead box as soon as experiment is over.
How do people who work with nuclear radiation stay safe
full protective suits to prevent inhaling radioactive particles or landing on skin
lead lined suits/lead or concrete barriers/lead screens to prevent exposure to gamma rays
remote control robot arms to carry out tasks in highly radioactive areas
What are the problems with waste from fission reactions
can’t be recycled
have long half lives
needs to be put far away from people
What are the two ways to deal with nuclear waste
vitrification - melt waste products into a type of glass which is sealed in steel canisters and buried deep underground
Put in thick metal containers and/or bury the waste in a deep hole and fill with concrete
What are the negatives of nuclear power
seen to be dangerous
people worry it can’t be disposed of safely (there have been serious accidents in the past)
not worth the risk of nuclear disasters like chernobyl
overall cost is high due to initial cost and final decommissioning
What are the positives of nuclear power
not as risky as people think
very reliable
reduces need for fossil fuels
doesn’t release harmful gases, clean source of energy
huge amounts of energy can be generated from small amount of material
fuel is cheap and readily available
