ACS Distance Education UK
While much is discussed in the media regarding the dangers of nuclear energy, it is worth actually understanding a little about what radioactivity is and why it is dangerous.
An atom has at its core the nucleus.
The nucleus is made up of protons (positively (+ve) charged) and neutrons (electrically neutral – no charge).
Around the nucleus is a cloud of electrons (negatively (-ve) charged).
Normally the number of electrons will equal the number of protons plus neutrons, thus balancing the charges and creating a neutrally charged atom.
An isotope however is an atom that has the same number of protons but a different number of neutrons.
The isotope therefore has an unbalanced charge and an unstable nucleus.
Due to this instability the nucleus can ‘decay’ spontaneously.
This is called radioactivity. When a nucleus decays, it breaks apart and emits radiation and particles (parts of an atom).
Below three types of radioactivity are outlines, note that there are actually more than this;
Alpha particles are emitted from the nucleus.
Alpha particles consist of two protons and two neutrons bound together into a particle. This type of particle radiation has low penetration.
An electron is emitted.
This is a high speed and high energy particle with medium penetration.
: This occurs when there are too many protons in the nucleus and one of the electrons is captured by a proton to form an extra neutron in the nucleus.
As mentioned above, a half life of an isotope is the amount of time it takes for one half of the nuclei in the sample to day.
This is the common way of expressing the time for radioactive decay.
Half lives of known radionuclides vary widely, with highly radioactive substances decaying much faster than those that are weak.
Additionally rates of decay can and are measured precisely nor does the rate of decay vary in differing conditions.
This means that it is an excellent technique for determining geological ages.
If the half life is known, the parent/daughter ratio can be measured.
It is this ratio that allows the calculation of the samples age.
Note that the ratio refers to the percentage of atoms that decay during a half life (50%).
However the actual numbers of parent isotopes will decline continuously while the number of daughter atoms will rise in proportion. For example:
If there are 100 parent isotopes and 0 daughter atoms the half life will be equal to zero. If there are 50 parent isotopes and 50 daughter atoms the half-life is 1.
If there are 25 parent atoms and 75 daughter atoms, then the half life is equal to 2.
Daughter atom (stable)
Half Life Value
50 billion years (error of 30-50 million years)
700 million years
4.5 billion years
1.3 billion years
Half life of some common isotopes
Radioactive Waste Disposal
Despite the horrors of a nuclear accident the disposal of spend radioactive material is possibly one of the greatest problems with this type of energy production.
This is due to the extremely long half life of the materials used (table 2).
It is estimated that one reactor can produce up to 30-40 tonnes annually of waste.
Currently technology has not found a way to safely store waste nuclear material. Generally, it is stockpiled in repository sites around the world.
Accidents & Safety
Nuclear fuels have been adopted in some countries however there remains a question of safety associated with that energy source. For example, storage of nuclear waste and it’s very long half-life, and risks of nuclear accidents and spills causing catastrophic damage. One very well-known nuclear disaster was
nuclear power station disaster in the
It happened largely because normal reactor operations were suspended; an experiment was to take place in the reactor. Normal safety guidelines were disregarded, and the accident occurred.
Several fuel rods within the reactor shattered and two explosions occurred as a result of liquid uranium reacting with steam. A fire within the plant emitted extremely radioactive smoke into the area surrounding the reactor. The effects of the disaster at
were very widespread. The World Health Organization (WHO) found that the radiation release from the
accident was 200 times that of the
nuclear bombs combined. The fallout was also far-reaching travelling as far as
. Thirty lives were directly lost during the accident or within a few months after it. Many of these lives were those of the workers trying to put out the graphite fire and were lost from radiation poisoning. The radiation released has also had long-term effects on the cancer incidence rate of the surrounding population. According to the Ukrainian Radiological Institute over 2500 deaths resulted from the
incident. The rate of thyroid cancer is particularly high after the
accident because much of the radiation was emitted in the form iodine-131, which collects in the thyroid gland, especially in young children.
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