Half life and radioactive safety

Question 1

What is the unit for measuring radioactivity?

What does one … mean?

Answer 1

Becquerel Bq

One nucleus decaying per second

Question 2

What happens every time a nucleus decays?

This means what?

Answer 2

Alpha beta or gamma radiation is given off

One more radioactive nucleus has disappeared

Question 3

As …. nuclei decay the …. of the solid will ….

So the …. samples become the … ….. they will ….

Answer 3

Unstable
Radioactivity
decrease
older, less radiation, emit

Question 4

What is the time frame for the activity of radioactive material dropping?

Answer 4

A few microseconds to millions of years for most of the unstable nuclei have decayed, activity never stops

Question 5

What is half-life?

Answer 5

The average time it takes for the number of nuclei in a radioactive isotope sample to halve.

Question 6

What does a short half life mean?

Answer 6

Activity falls quickly because lots of nuclei decay quickly

Question 7

What does a long half life mean?

Answer 7

Activity falls more slowly because most of the nuclei don’t decay for a long time they just remain unstable.

Question 8

How do you find the half-life of a sample when it’s said that the activity count used to be 640cpm then went to 80cpm?

Answer 8

You just keep dividing the first number by two until you reach the second. Every time divided is one half-life.

Question 9

What is half-life measured inside?
What does the graph of the results of decay look like?
What are the axes?
How is the half life found on the graph?

Answer 9

A G-M tube and counter.
A negative curve not going blow a couple of Bequerels
Activity - y, x - time in hours
Finding where the activity halves, and finding where that falls on the time axis and so on, halving an halving.

Question 10

what uses a radioactive source in the home?

Answer 10

Smoke detectors

Question 11

How do smoke detectors work?

Answer 11

A weak source of alpha radiation is placed in the detector close to two electrodes.
The source causes ionisation and current flows between the electrodes.
When there is smoke the radiation will be absorbed by it and so the current stops and the alarm sounds.

Question 12

How do radioactive tracers work in people? (2)

Answer 12

Radioactive isotopes can be injected or swallowed, and their progress around the body can be followed by an external detector.
A computer coverts the reading into a display showing where the strongest reading is coming from.

Question 13

What radioactive substance is commonly used in medical tracing?
What happens to this?

Answer 13

Iodine -131
Absorbed by the thyroid gland like normal iodine -127, but gives out radiation detected to indicate whether the gland is taking in iodine

Question 14

What types of isotopes should be used inside the body and why?

Answer 14

Gamma abd Beta emitters instead if alpha as the radiation passes through the body quickLy - they should onLy last a couple of hours so that the radiation quickly disappears - they have a short half life

Question 15

Why is radiotherapy used?

Answer 15

High doses of gamma rays will kill all living cells so good for treating cancers

Question 16

How is radiotherapy done? (simple) ……. so that?: …..
What is inevitable?
Yet:

Answer 16

The gamma rays have to be directed carefully at just the right dosage to kill the cancer cells without killing to many normal healthy cells
Damage will be done to normal cells which makes the patient very ill.
If the cancer is successfully killed off it’s worth it

Question 17

Why is food exposed to high doses of gamma rays?
What is the advantage to doing this?
and the food is…

Answer 17

To kill all the microbes keeping the food fresh for longer
No hot temperatures are needed to kill the microbes.
…safe, it’s not radioactive

Question 18

What can be done to sterilise medical instruments instead of boiling them in water?
What is the advantage to doing this over boiling them?

Answer 18

Expose them to a high dose of gamma rays

Irradiation doesn’t involve high temperatures so the equipment isn’t damaged

Question 19

What type of isotope should be use for sterilising equipment? and why?

Answer 19

A very strong gamma ray emitter, with a reasonably long half life, so that it doesn’t require replacing very often.

Question 20

What happens inside a cell when it is ionised?
What do lower doses do? What can this cause?
What do higher doses do and cause?

Answer 20

Alpha beta or gamma radiation enters a living cell and collides with molecules, damaging or destroying them.

Causes minor damage instead of killing the cell…. mutant cells, as they aren’t dead, which divide uncontrollably, this is cancer.
They kill cells completely, radiation sickness if a lot of cells get hit at once

Question 21

What does the extent of harmful effects due to radiation depend on?

Answer 21

How much exposure you have from the radiation

The energy and the penetration of the radiation since some types are more hazardous.

Question 22

Outside the body which types of radiation sources are more dangerous?
Why?
Where as … is much less dangerous outside the body because ..

Answer 22

Beta and gamma
They can get inside the body to delicate organs and damage them
alpha, it can’t penetrate the skin

Question 23

Inside the body what type of radiation source is more dangerous?
Why?
Where as …. and …. are much less dangerous inside the body because ..

Answer 23

Alpha, they do all their damage in a very localised area

beta and gamma because they tend to pass straight outside the body without ionising much

Question 24

How can you be safe around radioactive sources when doing an experiment? 
1. ...... and what does this do for you?
2.
3.... what does this do for you?
4. Two smaller things...

Answer 24

Use the source for as shorter time as possible to keep your exposure to a minimum
Never allow skin to touch the source so always handle with tongs
Hold it at arm’s length to keep it away from the body, decreases the amount of radiation that hits you especially as alpha particles don’t travel far.
Keep the source pointed away from you and avoid looking directly at it

Question 25

What does lead do that is useful?

What should you do with this in an experiment?

Answer 25

Absorbs all 3 types of radiation, but a lot is needed to stop gamma completely
Store your source in it as soon as the experiment is over

Question 26

What do medical professionals and radiographers who work with radiation every day stand behind? What do they wear?

Answer 26

Lead screens

Lead aprons

Question 27

When you get an x-ray how do they reduce your dose?

Answer 27

Only expose the area that needs treatment

The rest of the body is protected by a lead or radiation-absorbing material.