SCIENCE IN ACTION
By MICHAEL JOHN UGLO
THIS is the 10th lecture in the Science in Action series.
Welcome all to the topic of Radioactivity and Nuclear Energy. From a distance, the topic is very complex and it may be an opportune time for you to learn what it is all about if you have thought hard about it.
Firstly, let’s isolate the topics and learn them in sequence. The word radioactivity is something known and studied in physics. It talks about an atom with a nucleus which is unstable. Every element we have on earth is made up of a similar kind of atoms. Atoms of one element are different from atoms of another element. That difference is caused by different number of protons (with electrons) and neutrons found in a nucleus. So the nucleus is made of protons and electrons with the lighter electrons orbiting in shells known as energy levels around the nucleus.
When the nucleus become unstable, it begins to disintegrate or try to come apart. When it does that, it emits energy called radiation. Radiations are of three types. The three radiation and energy types are namely, alpha (α) radiations, beta (β) radiations and gamma (γ) radiations. The alpha radiation is not really energetic and can be stopped by a sheet of paper. The beta radiation is a bit energetic so it can penetrate the paper but can be stopped by an aluminium foil. The third and the most energetic is the gamma radiation and can travel through the aluminium but can be stopped by a very thick layer of a very dense and heavy element like lead. That is why highly radioactive wastes with very high penetrating powers are stored away in lead containers.
Weak nuclear force
Beta radiations come from the very weak nuclear force that bind them. The alpha and the gamma rays come from the very strong nuclear forces that bind them in a nucleus.
The alpha nucleus is the emission of a helium nucleus that consist of two protons and two neutrons. The alpha and the beta radiations are emitted as photons of energies in the nuclear decay process. The alpha radiation is positively charged and the beta radiation is negatively charged.
The gamma radiation is not charged. The gamma radiation is emitted after the alpha and the beta radiations. The gamma radiation is emitted when the nucleus is decaying to a daughter nuclides.
There can also be gamma radiations when isotopes of the same elements are formed when neutrons are emitted.
In electron captures, reactions by protons in a nucleus, which will cause a proton to change to a neutron from its electron orbit. A gamma ray is emitted with a neutrino. A neutrino and a positron are emitted in a beta plus decay. This will change a neutron into a proton and this process is also known as positron emission. In a negative or minus-beta emission, the nucleus will emit an electron and an antineutrino and that will convert a neutron to a proton.
Also known as radioactive decays
Radioactivity also known as radioactive decays. Nuclear decays and nuclear disintegration are very similar terms used to mean the breakup of unstable nucleus of elements.
After the break up from parent nucleus to daughter nuclides, chemically very different chemical elements can be formed. These different chemical elements will have very different mass numbers which include the number of protons together with the number of neutrons.
Also, different atomic numbers which include the different number of protons.
There are atoms which date back to antiquity. They were present at the time the universe and the earth were formed. These elements are known as primordial nuclides. These elements would include the highly fissionable elements called the uranium and thorium. The other elements are formed from the decay of those primordial nuclides into the respective types of elements and their isotopes we have in their relative abundances in nature today.
A random event
The radioactive decay process is a random event. That is the reason that a radioactive state of an atom cannot be determined by any means regardless of its age.
It is therefore a stochastic or more simply an event that happens in a time series which is a rare event. The clusters of the radioactive daughter nuclides can be identified and measured as half-lives. That is the time taken for a particular nucleus to disintegrate by half of its mass.
Some isotopes and nuclides as radon and radium can take only brief periods to decay while others like uranium and thorium can take the whole age since the formation of the entire universe.
Energy can be derived from nuclear power. The fissionable elements with a critical mass can disintegrate and in so doing release the atomic energy the form of the three radiation types. In nuclear power plants, the nuclear energy harnessed is very clean and does not produce air pollution like the burning of fossil fuels and coals. They can be carefully treated to emit less harmful levels of emissions and discarded.
The only problem to consider are the natural disasters that affect those nuclear facility sites as well as treatment facilities. There are also possible dangers of development of nuclear weapons when it gets into the hands of terrorists.
Countries around the world that use nuclear power energies are USA, France, Germany, Japan to name a few. Some disasters that happened with the use of nuclear energy include the bombing of Hiroshima and Nagasaki in Japan during World War 2.
My prayer for PNG today is; “Thy word, is a lamp unto my feet, and a light unto my path. When I feel afraid, think I’ve lost my way, still You’re there right beside me. Nothing will I fear as long as you are near, please be near me to the end”.
Next week: Sciences of the Electricity Principles and Technology
Michael Uglo is the author of the science textbook “Science in PNG, Pacific, Asia and Caribbean, and a lecturer in avionics, auto-piloting and aircraft engineering. Please send comments to: [email protected]