[P6.2] hazards and uses of radioactive sources

contamination

occurs if the radioactive source is on or in the object
can occur INTERNALLY or EXTERNALLY

examples of internal contamination

eating
swallowing
injecting

examples of external contamination

on clothing
hair
when you touch radioactive source, radioactive atoms rub onto SKIN

irradiation

occurs when an object is exposed to a source of radiation outside the object
[radiation from radioactive source reaches an object]
CAN travel through body

examples of irradiation

xray scan

irradiation or contamination?
Doesn't cause the object to become radioactive.

irradiation

irradiation or contamination?
A contaminated object will be radioactive for as long as the source is on or in it.

contamination

irradiation or contamination?
Can be blocked with suitable shielding or moving away.

irradiation

irradiation or contamination?
Once an object is contaminated, the radiation cannot be blocked from it.

contamination

irradiation or contamination?
Stops as soon as the source is removed.

irradiation

irradiation or contamination?
It can be very difficult to remove all of the contamination.

contamination

how can risk of object getting irradiated decrease?

source is at a further distance so amount of radiation reaching a point decreases

how come risk of irradiation is lower with alpha radiation than gamma radiation?

alpha radiation has a shorter range compared to gamma

how can there be NO risk of contamination?

if radioactive source is solid and you do not touch it.

how can risk of contamination increase?

if radioactive source is gas then it could move and come into contact with object

RECAP:
irradiation is temporary because when source is taken away...

then any irradiation its causing stops

RECAP:
contamination lasts longer because when source is taken away...

the atoms causing the contamination are left behind

what type of radiation is MOST dangerous OUTSIDE body + why

beta and gamma because it can pass through skin and potentially into organs

what type of radiation is LESS dangerous OUTSIDE body + why

alpha because they cant penetrate skin

what type of radiation is MOST dangerous INSIDE the body + why?

alpha source most dangerous because they cant pass through skin and out of body
+ MOST IONISING

how are ionising radiations dangrous?

can enter cells and interact with them
they damage living cells by causing MUTATIONS IN DNA
causes cells to divide uncontrollably (this is cancer)

INCREASES RISK OF CANCER

what type of radiation is LESS dangerous INSIDE body + why?

beta and gamma because they are less ionising
+ GAMMA can pass STRAIGHT OUT of body

how can ionising radiation be useful though? (in terms of cells)

it can also kill cells completely ONLY AT HIGHER DOSAGES

define dosage

how much exposure
how long exposure

the atoms in a source with a LONG HALF LIFE will be MORE/LESS likely to decay?

less likely to decay
- bc activity is slower

two sources with DIFFERENT HALF LIVES start off with the SAME ACTIVITY.

which will be more dangerous overtime? the source with longer half life or shorter half life?

the source with longer half life because the activity will still be higher

how can radioactive sources be used as a tracer (in body)

when you inject or ingest radioactive isotope, it is absorbed by organs.
the isotope is detected by gamma camera
camera makes image of organs = help doctors diagnose disease

what do you need to consider about half life of isotopes? (in tracer)

CLUE: think of longevity of halflife

is half life of isotope is too SHORT then the tracer will decay before they can use the gamma camera

if half life of isotope is too LONG then the tracer will continue to emit radiation for a long time and increase risk of cancer

how can radioactive sources be used to treat cancer?

radiation of GAMMA RAYS can damage cancer cells to RESTRICT GROWTH or even kill them
doctors use a moveable source of gamma radiation [GAMMA KNIFE] to FOCUS gamma rays onto the one spot of the cancer tumour

why do you need a MOVEABLE source of gamma radiation to treat cancer?

to reduce the radiation dose to the healthy cells surrounding the cancer tumour and only concentrate the radiation to the tumour

how can beta radiation be used to determine thickness of aluminium?

place a sample that emits beta particles on one side of the aluminium and a Geiger counter on the other side that counts how much beta particle is passed through.

the rollers then control the gap between them accordingly

how can gamma radiation sterilise hospital equipment?

kills bacteria by breaking down bacterial DNA, stopping bacterial growth