1. Lessons 7: Nuclear waste and half-life
What you need to know:
1. What is nuclear waste?
2. How we can deal with nuclear waste.
3. What is 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 Description
radioactivity
High level waste Very strong Spent fuels rods from a nuclear
(HLW) reactor. There is very little HLW as
it decays quickly.
Intermediate level Strong HLW decays to become ILW. Less
waste (ILW) 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.
© Studydoctor 2009

2. 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

3. 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.
© Studydoctor 2009