Radioactivity - CCEA

Atomic Number letter

Z

Mass number letter

A

Radioactivity definition

the spontaneous disintegration of an unstable nucleus by alpha, beta, gamma decay

What is an Alpha Particle

a particle emitted in radioactive decay consisting of 2 neutrons and 2 protons,

• alpha particle is a helium nucleus

• positively charged

• alpha particles are big and move slowly

Why does alpha decay happen

when nuclei have too much mass to remain stable

Alpha Particle penetration

blocked by thick paper/ cardboard

Alpha Particles range in air

2-3 cm, as scattered by air particles

What is ionisation

the addition or removal of an electron from an atom

Ionisation ability of alpha

Highest as alpha particles are big they easilly dislodge electrons from nearby atoms, producing ions

What happens if atoms in humans are ionised

this disrupts their DNA structure, cause mutated cell.

What is a Beta Particle

A fast moving electron

• negatively charged

What does beta decay happen

when a nuclei has too many neutrons to remain stable

Beta particle penetrate

5mm Aluminum

Beta range in air

several meters

why does beta have medium ionisation ability

beta particles are very small and move very fast, therefore they interact less with matter and have a lower ionisation ability

What is gamma ray

High energy electromagnetic wave emitted in radioactive decay from an unstable nucleus

• no mass no charge

Gamma penetration

thick layered concrete

Gamma range in air

manny km

Background radiation definition

Background Radiation or Background Activity is the radioactive count rate still detected when no radioactive sources are present

Sources of background radiation

• cosmic rays from the sun

• leakage from radiotherapy and x-ray department

• radioactivity from rocks e.g granite

• radioactivty from smoke alarms

• radioactive waste from power stations

How to deal with background activity in an experiment

1. Before source is present record the background activity in the room e.g 15 counts per second

2. Introduce the source and record the countrate

3. Calculate corrected countrate = experimental value - background activity

How to prevent background radiation

Make homes well ventilated to prevent radon gas

How to minimise risk while using it

• wear protective clothing

• handle the source with long tong, especially for alpha

• minimise exposure time to source

• store source in led lined box

What is half life

Time taken for activity (number of decays in one second) to fall to half of its initial value

Nucleur Fission process

• Large Uranium Nucleus absorbs the slow moving neutron

• The Uranium Nucleus divides into smaller nuclei

• Extra fission neutrons are produced

• Each of these neutrons divides another uranium nucleus

• This sets up a chain reaction which all fuel available is use up

Positives Fission

• Jobs available in nuclear sector

• no CO2 produced

• large global reserves of Uranium are available

• fission produces 1 million times more energy than fossil fuels per kg of fuel

Negatives Fission

• Produces highly toxic radioactive waste with a long half-life, which is difficult, dangerous and expensive to store safely

• Nuclear accidents (Ukraine/ Japan) could destroy the planet for future generations

• Although Fission does not produce CO2 directly the mining and transport of uranium does

Nuclear Fusion occurs naturally where

stars e.g sun

Process of Nuclear Fusion

Two low mass hydrogen nuclei combine to form a more massive high mass ( and more stable nucleus)

Nucleur Fusion reaction

Deuterium + Tritium = Helium + neutron + energy

Advantages to Nuclear Fusion

• has potential to solve worlds energy crisis as it releases 4 million time more energy that fossil fuels and 4 times more energy than fusion per kg of fuel

• the fuel Deuterium and Tritum is abundant and available from sea water

• fusion does not produce any greenhouse gas, only helium which is non toxic

• fusion does not produce highly toxic radioactive waste

Difficulties to overcome with performing

• The hydrogen nuclei are both positive and repel each other, huge temperatures are required to provide the kinetic energy to overcome the repulsive force so that they can combine

• it is expensive and technically difficult to heat and contain the fuel for long enough for fusion to occur

• fusion reactors are very expensive and could spend money on hospitals or food