© Studydoctor 2009

Lessons 7: Nuclear waste and half-life

Nuclear waste is the products created during fission reactions as well as

contaminated equipment used to handle nuclear material. Most nuclear waste in

the UK comes from nuclear power stations and is very hazardous.

This means that it needs to be disposed of safely so that it does not harm

anyone. If nuclear waste was simply dumped into a sewer or a landfill site then

it could get into the food chain and cause lots of people to become ill.

Nuclear waste was once simply dumped at sea and pretty much forgotten about,

but environmentalists campaigned that this practice was polluting the seas, and

could cause long-term damage which was unacceptable. Therefore another

method of disposing or nuclear waste was needed. Currently nuclear waste is

stored within containers and buried in deep rock, but a permanent solution is

still needed.

There are three categories of nuclear waste:

Type of waste Strength of

radioactivity

Description

High level waste

(HLW)

Very strong Spent fuels rods from a nuclear

reactor. There is very little HLW as

it decays quickly.

Intermediate level

waste (ILW)

Strong HLW decays to become ILW. Less

radioactive than HLW, but there is

lots of it.

Low level waste (LLW) Weak Protective equipment and clothing

used by staff at nuclear power

stations can be slightly

radioactive.

In your exam you may be asked what nuclear waste is.

What you need to know:

1. What is nuclear waste?

2. How we can deal with nuclear waste.

3. What is half-life?

© Studydoctor 2009

The amount of radiation that a radioactive source emits every second is called its

activity. This can be heard as clicks on a detector.

The activity of a radioactive source decreases with time. This is because every

time a radioactive atom decays, it becomes more stable, meaning that there are

less radioactive atoms. This means that over time fewer and fewer radioactive

atoms exist. The half-life of a radioactive material is the time it takes for

the activity (or the amount of radioactive atoms) to decrease by half.

Different radioactive elements have different half-lives.

For example, looking at the graph above, a source of radiation has an activity of

16,000 counts at the start but after 5 minutes the activity has dropped to 8,000

counts. Its activity has halved, meaning that its half-life must be 5 minutes. In

another half-life the activity of the source will drop to 4,000 counts.

In your exam you may be asked to describe what half-life is. You may also need

to use data contained in graphs or draw a graph to calculate a radioactive

source’s half-life.

© Studydoctor 2009

Recap:

1. Radioactive waste is the radioactive products created in places that use radioactive

materials.

2. Radioactive waste is very hard to get rid of and at the moment governments are still

trying to find a permanent solution.

3. Half-life is the time it takes for the count rate (or the number of radioactive atoms)

from a radioactive source to decrease by half.