Radiation True or False?

1. You are being bombarded with radiation right now.

2. You are giving off radiation right now

3. Your breakfast was irradiated with deadly radiation

4. You can see radioactivity

5. You can feel radioactivity

6. Radioactive substances are only harmful if you touch them

7. If you are irradiated then you become radioactive

8. Radioactivity is not very useful

9. We completely understand what causes radioactivity

10. Do you know the three types of radioactivity. Write them down..

True

True

True ??

False

False

FalseFalse

False

False

?

Let’s have a look at some radioactive samples

Think about how we may be able to use them!

Thin mica Thin aluminiumstops BETA

Thick leadreduces GAMMA

Skin or paper stops ALPHA

The penetration power of the three types of radiation.

So what exactly does cause this radiation? .

First we need to look at the structure of the atom

Draw diagrams to represent:

How did you go?

6 protons

7 neutrons

6 electrons

6 protons

8 neutrons

6 electrons

6 protons

6 neutrons

6 electrons

What do we call these?

6 protons

7 neutrons

6 electrons

6 protons

8 neutrons

8 electrons

6 protons

6 neutrons

6 electrons

Atoms of the same element with different numbers of neutrons

Isotopes

PM S5 K1: Distinguish between stable and radioactive isotopes and describe the conditions under which the nucleus is unstable.

Atoms of the same element with different numbers of neutrons

Isotopes

Because they have the same number of electrons there is NO difference to their chemical behaviour.

RadioisotopesAtoms with unstable nuclei which are radioactive.They emit radiation to become stable.

There are over 2000 different isotopes that have been discovered so far.

Only 279 are stable – they do not emit radiation.

The rest are unstable and are called radioisotopes

The nuclei rearrange to become more stable. As they do so they emit radiation.But which ones are unstable?Lets have a look at them

Stable and unstable Isotopes

This line is where the no. protons = no. neutrons

Stable and unstable Isotopes

• All atoms with atomic no > 83 are unstable

• Other nuclei are unstable because of the proton to neutron ratio.

For light elements, stable nuclei have a proton:neutron ration close to 1:1.

2412

For heavy elements the stable nuclei have a proton:neutron ratio closer to 1:1.5

20682

Why are some nuclei unstable

Mg is stable 12p, 12n

Pb is unstable 92 p, 114 n

There are four main types of radiation that can be given out by a nucleus of an atom:

Alpha radiation -

Description:

2 neutrons, 2 protons (like a helium nuclei)

Symbol 4

2

4 means mass = 4

2 means 2 protons

He

Beta radiation - -

high energy electron

Description:

High energy electron

Electric Charge:

Symbol 0 or 0

-1 -1

The 0 means mass = 0

How can the nucleus emit an electron?

Because a neutron turns into an electron and a proton!

The -1 means that the electron is the opposite of a proton.

e

Positron emission - +

positive electron

Description:

Positively charged electron

Electric Charge:

Symbol 0

+1

The 0 means mass = 0

How can this happen?

Because a proton an electron and a neutron.

The +1 means that the positron was made from a proton.

e

Gamma radiation -

Electromagnetic radiation

Description:

High energy electromagnetic radiation

Electric Charge:

0

Relative Atomic Mass:

0

This line is where

p = n

Can you tell why the different types of emitters are located together?

Radioactive half-life

What do we mean by half-life?

Radioactive half-life

The average time taken for half of the substance to decay is called the radioactive half-life.

Decay of carbon 15

02468

10

0 1 2 3 4 5 6 7 8 9 10

Time / s

Car

bo

n 1

5 / g

Radioactive half-life

Once an atom in a sample decays that atom is no longer radioactive.

Decay of carbon 15

02468

10

0 1 2 3 4 5 6 7 8 9 10

Time / s

Car

bo

n 1

5 / g

Uses of radiation

Hydraulicram

detector

Thickness Control Mill

Electronic instructions to adjust rollers.

Beta Source

A radioactive source is on one side of the material and a detector on the other.

If too much radioactivity is getting through, then the material is too thin and the rollers open up a bit to make the material thicker.

If not enough radioactivity is detected then the rollers compress to make the material thinner.

This method is used in the manufacture of lots of sheet materials: plastics, paper, sheet steel.

Leak detection in pipes

The radioactive isotope is injected into the pipe. Then the outside of the pipe is checked with a Geiger-Muller detector, to find areas of high radioactivity. These are the points where the pipe is leaking. This is useful for underground pipes that are hard to get near.

The radioactive isotope must be a gamma emitter so that it can be detected through the metal and the earth where the pipe leaks. Alpha and beta rays would be blocked by the metal and the earth.

The radioactive isotope must be a gamma emitter so that it can be detected through the metal and the earth where the pipe leaks. Alpha and beta rays would be blocked by the metal and the earth.

The isotope must have a short half life so the material does not become a long term problem.

The isotope must have a short half life so the material does not become a long term problem.

GM tube

PM S5 K5. Identify one use of a named radioisotope:

- in industry

- in medicine

PM S5 K6. Describe the way in which the above named industrial and medical radioisotopes are used and explain their use in terms of their properties.

PM S5 K5. Identify one use of a named radioisotope:

- in industry

- in medicine

PM S5 K6. Describe the way in which the above named industrial and medical radioisotopes are used and explain their use in terms of their properties.

Cobalt-60 Sterilisation

Gamma rays are used to kill bacteria, mould and insects in food. Also used to kill bacteria on hospital equipment.

This is useful particularly on packaged food or on plastic items which would be damaged by heat sterilisation.

It can affect the taste and the vitamin content, but it lengthens the shelf life.

Gamma rays are used to kill bacteria, mould and insects in food. Also used to kill bacteria on hospital equipment.

This is useful particularly on packaged food or on plastic items which would be damaged by heat sterilisation.

It can affect the taste and the vitamin content, but it lengthens the shelf life.

Gamma Sourceunsterilised sterilised

Sterilisation

Cobalt-60 is used as it is a gamma emitter – very penetrating.

It has a half life of 5.3 years so the machines can run cheaply without regular maintenance.

You don’t need external power to produce the gamma rays as you do with x-rays

Cobalt-60 is held in a chemically inert form in a sealed container.

When the cobalt-60 is exhausted it can easily be replaced.

Cobalt-60 is used as it is a gamma emitter – very penetrating.

It has a half life of 5.3 years so the machines can run cheaply without regular maintenance.

You don’t need external power to produce the gamma rays as you do with x-rays

Cobalt-60 is held in a chemically inert form in a sealed container.

When the cobalt-60 is exhausted it can easily be replaced.

Gamma Sourceunsterilised sterilised

Cobalt-60 production.1. Iron-58 placed in a nuclear reactor and

bombarded with neutrons. One neutron is absorbed and iron-59 is formed

2. Iron-59 is formed which decays into cobalt-59 plus a beta particle

3. Cobalt-59 is then placed in a nuclear reactor and bombarded with neutrons. One neutron is absorbed and cobalt-60 is formed.

Can you write equations for these nuclear processes?

Use of Technetium 99m in medicine

Tc-99m is bound to a carrier molecule

Tc-99m

Technitium is useful because it is a transition metal and therefore chemically binds easily with atoms (such as N) in biological molecules.

It also has a half life of 6 hours so it does not expose the patient to radiation for any significant length of time.

In all other respects the carrier molecule is identical to normal biological equivalent

Tc-99m

The biological molecule is introduced into the body

The Tc-99m is carried to the specific organ (depends on the molecule)

Special gamma cameras then take pictures of the gamma rays emitted by the technetium-99m

The benefits: surgeons and doctors can make an accurate diagnosis without performing surgery

•The problems: Tissue damage – leading to sickness and ultimately death for high exposureCan cause cancer – leukemia/lung – up to 20 years after treatmentGenetic damage causes deformities in offspring.

Production of technetium-99m

Molybdenum-98 absorbs a neutron to make molybdenum-99.

Molybdenum-99 decays to make technetium99-m

Mo-99 is delivered to hospitals in a “generator”Over time this produces Tc-99m which the hospitals extract when they need it.

Please make a note to find more out about this when we go to ANSTO.

PM S5 P2 – Use available evidence to analyse benefits and problems with the use of radioactive isotopes in industries and medicine

Read p 101 and from what you have learnt today make a list of problems.Read p 101 and from what you have learnt today make a list of problems.

Read p98 and from what you have learnt today make a list of benefits.Read p98 and from what you have learnt today make a list of benefits.

PM S5 P2 – Use available evidence to analyse benefits and problems with the use of radioactive isotopes in identified industries and machines.

Benefits:Benefits: Problems:Problems:

PM S5 P2 – Use available evidence to analyse benefits and problems with the use of radioactive isotopes in identified industries and machines.

Benefits:

•Non-invasive diagnostic procedures

•Treatment of cancers

•Sensitive monitoring of industrial processes

•Sterilisation

•Non-invasive examination of pipes / aircraft etc.

Benefits:

•Non-invasive diagnostic procedures

•Treatment of cancers

•Sensitive monitoring of industrial processes

•Sterilisation

•Non-invasive examination of pipes / aircraft etc.

Problems:

•Tissue damage for people exposed

•Risk of cancer if exposed

•Genetic damages to people exposed

•Hard to dispose of some isotopes (long half-life)

Problems:

•Tissue damage for people exposed

•Risk of cancer if exposed

•Genetic damages to people exposed

•Hard to dispose of some isotopes (long half-life)