Radiation

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Nuclear Radiation

Nuclear Decay and Radiation

- Some atomic nuclei are unstable and give out radiation in order to become more stable

- The type of radiation emitted depends on why the nucleus is unstable and is a random process

- The activity of a radioactive source is the rate at which it decays

- Its measured in becquerels (Bq)

- 1 Bq is equivalent to 1 decay per second

- Count-rate is the number of decays recorded each second by a Geiger Counter

- 1 Bq = 1 count per second

Alpha, Beta and Gamma Decay

- Each type of radiation consists of different particles

- All 3 are ionising - can knock electrons from atoms

- Alpha most ionising, gamma least

Radiation Type Components Hazards

- 2 neutrons + 2 protons - High chance of being absorbed and cause

Alpha - Ejected from nucleus damage if passing through living cells

- A high-speed electron - Likely to cause damage if absorbed by living cells

Beta - Ejected from nucleus as a neutron - Can penetrate the body to inner organs

turns into a proton

- Electromagnetic radiation - Likely to pass through living cells without being

Gamma - Emitted from nucleus absorbed and causing ionisation

Radioactive Contamination

- The unwanted presence of materials containing radioactive atoms

- Hazard from contamination due to decay of contaminating atoms

- Type of radiation emitted affects the hazard

- Irradiation

- process of exposing an object to nuclear radiation

- deliberate or accidental

- doesn't cause object to become radioactive

- Important to protect against irradiation, by:

- use sources of lowest activity possible, for shortest time

- Wear appropriate protection e.g. lead apron

- Don't handle source with bare hands

Using Radioactive Source:

Half-Life

- Radioactive decay has a random nature, which makes it impossible to predict which nucleus will decay

- With enough nuclei it is possible to predict how many will decay in a certain time period

- The half-life of a radioactive isotope is:

- the average time it takes for half of the nuclei to decay

- The half-life of a particular isotope doesn't change

- Half-life can vary from seconds to millions of years

- Isotopes with a short half-life:

- very unstable and emit radiation quickly, so exposure is hazardous

- do not remain radioactive for long

Isotopes with a long half-life:

- more stable and remain radioactive for a very long time

- emit radiation slowly, exposure is less hazardous

Uses of Nuclear Radiation

- Medical tracers are used to look at internal organs:

- A radioactive is ingested or injected into the body

- As it travels around the body, it can be detected on the outside

- One use is to monitor kidney function:

- An isotope that will pass through the kidney is used

- If it builds up in one kidney and not the other, one kidney may not be working

- Nuclear radiation also be used for treatment of tumours:

- A tumour in the thyroid gland could be treated with radioactive iodine, which destroys nearby cells.

- A focussed beam of gamma rays can destroy some tumours

- When chosing an isotope to use for a specific job its important to consider the half-life, activity and type of radiation