P3 – Radioactive Materials

Radioactive Elements• Some elements emit ionising radiation all the time

and are called radioactive • Radioactive elements are naturally found in the

environment, emitting background radiation

The Atom• Electrons, Protons, Neutrons and the Nucleus

are all parts of an atom• The Nucleus, made of Protons and Neutrons

Isotopes• Every atom of any element has the same number

of protons but the number of neutrons may differ• The same element with different numbers of

neutrons is called an isotope• These 3 atoms are all isotopes of Hydrogen:

The Nucleus is the only thing involved in Radioactive Substances

• Radioactive Materials are unchanged by:– Chemical reactions (only electrons involved in these)– Changes of state (Solid, Liquid, Gas)– Passing electricity through them (only electrons involved)– Crushing

3 Types of Radiation

• Alpha: – 2 Protons + 2

Neutrons

• Beta:– 1 Electron

• Gamma:– High energy wave

An unstable nucleus will emit radiation to become more a more stable nucleus

Half-Life• Overtime, the

Activity of Radioactive Sources Decrease

• Half-Life: The time it takes for the number of unstable atoms in a sample to halve.

• Carry out simple calculations

Ionising Radiation• Ionising Radiation removes electrons from

atoms creating Ions (Charged atoms). These can then take part in other chemical reactions

When ionising radiation strikes living cells these may be

killed or may become cancerous

Helpful Ionising Radiation• Ionising Radiation can be used to: – sterilise surgical instruments– sterilise food– treat cancer

Radiation Dose• Sieverts: A

measure of the possible harm done to your body

• Based on the amount and type of radiation

Irradiation: body exposed to radiation from an external source Contamination: can affect the body internally if it gets into the body through lungs, stomach or a wound

Safe Radioactive Substances• All radioactive substances become less radioactive as time

passes• A substance is only considered safe once its activity had

dropped to the same level as background radiation• Substances with a long half-life remain harmful for

thousands of years

Electricity• Electricity is a secondary energy source. • This means that we get electricity from the

conversion of other sources of energy, such as coal, nuclear, wind or solar energy.

• These are called primary sources.

Electricity = Convenient• Electricity is convenient because it is easily

transmitted over distances and can be used in many ways

Making Electricity1. Coal is burnt to heat water to make steam2. The steam turns the turbine3. Turbine turns a generator which produces electricity4. Electricity goes to the transformers to produce the

correct voltage

Efficiency• Light bulbs are only 10% efficient. 90% of the

energy provided to them is lost as heat

You need to know how to read these diagrams

Renewable Energy• Recall two examples:

1. Solar panels2. Wind turbines3. Geothermal4. Hydroelectricity

Power stations which burn carbon fuels (fossil fuels) produce carbon dioxide

Nuclear Fuel / Nuclear Fission• Changes in the nucleus creates lots of energy• Nuclear Fission: a neutron splits a large and

unstable nucleus (Uranium) into two smaller parts, roughly equal in size, releasing more neutrons

Nuclear Energy• The amount of energy contained in nuclear fuel is

millions of times the amount of energy contained in a similar mass of chemical fuel such as coal, making nuclear fission a very tempting source of energy.

• Nuclear Fission creates a chain reaction and these can be dangerous unless they are controlled

Controlling Fission

• Fission heats the coolant which is used to heat water for steam

• Control rods absorb neutrons

• These can be moved up and down to control the amount of neutrons escaping the fuel rods

Radioactive Waste• Is categorised into 3 parts and this relates to it’s

disposal methods– high – intermediate – low

Health Risks of Background Radiaton• Most background radiation is harmless, but it’s not possible

to state that it’s “completely safe”.• The actual risk is very low because it has low energy• If you mentioned to people that some background

radiation comes from nuclear power stations they might become quite frightened. This is their perceived risk which they believe to be true.

Precautionary Principle• Better Safe than Sorry• To the people who believe a new technology is not safe, it

is up to them to prove that it is. Otherwise society / individual will continue to believe that there is a danger.

• Examples:– Mobile Phones– Microwaves– Tourists in Space

ALARA: As Low As Reasonably Achievable• A radiation dose, no matter how small, may have

harmful effects. So every reasonable measure should be used to lower it.

1. Time – short exposure2. Distance – double distance = exposure decreases by a

factor of four3. Shielding - protection

Benefits and Risks• Can suggest benefits to a known risk and offer

reasons for people’s willingness/reluctance to accept the risk of a given activity.

Regulations and the Future

• Scientific research and applications are subject to official regulations and laws (government)

• Technically feasible: what can be done• Values: what should be done

• Sustainable development: aims to meet human needs while preserving the environment so that these needs can be met not only in the present, but also for future generations