What happened at Chernobyl? Understanding radioactivity!

Chernobyl served as a nuclear power plant, where during a test in the early hours of April 26, 1986, an explosion blew the roof off of reactor 4.

Blocks of super-heated graphite rained down on the site and huge amounts of radioactive particles were released into the air. The explosion at the power plant contaminated a wide area and sent radiation clouds across the globe.

Thousands of people lived in a town called Pripyat near the power plant. During the catastrophe, two people died immediately, while 29 more died within weeks.

It is estimated thousands more have died from cancers and other illnesses in the ensuing years. Vast areas of the country have not seen any animal life for over thirty years.

But it doesn’t end there – more than 200 tons of uranium are still inside the reactor site, fueling fears that new radiation leaks could occur in the area, which is already considered to be unsafe for at least the next century, and will remain uninhabitable for the next tens of thousand of years, at the best.

So, what was it that makes this accident so catastrophic? We have seen and read about volcanic explosions, earthquakes, tsunamis, which kill thousands of people, but none of them have had such a serious impact in history – what is it that makes the area uninhabitable even after the accident has ended?

Why can’t the people of Pripyat go back to their city even after more than 30 years of this accident?

The answer is radioactivity.

To understand radioactivity, first we have to understand what makes everything around us – the atoms and their structure!

According to one of the simplest models, each atom consists of a nucleus in the centre containing protons and neutrons and electrons revolving around it. Different types of atoms have different number of electrons, protons and neutrons, which makes them unique. The defining character of an element is the number of protons in the nucleus of its atoms.

Now in most atoms around us, this structure is stable. Which means all particles stay the way they are – and matter exists around us as we know it, without changing abruptly.

But in some special cases, the nucleus of the atom becomes unstable – major reason for this is an unusual number of neutrons and protons – they just can’t stay together bound up in a nucleus!

Most elements have isotopes found in traces in nature, that have very unstable nuclei.
Such unstable nuclei lose neutrons and protons as they attempt to become stable. The division or fission of the nucleus is accompanied by release of energy.

This release of energy in the form of moving waves or streams of particles is known as radiation. And the process of an unstable atom giving off its particles is called radioactive decay.

Now, what happens to this radiation energy? Some kinds of radiation (called ionizing radiation) can hit other atoms and ionize them, removing electrons – and this is where the problem begins! In the body of humans, or other living things, this can break the bonds within the DNA.

It can ruin the complex structure of proteins. In small doses, the cell has enough mechanisms to repair itself.

But when exposed to a large amount of radiation, the cell’s defenses are overwhelmed. And eventually, the cell commits suicide.

The death of a few cells can be tolerated, but the death of many can lead to necrosis. Severe radiation exposure can damage or destroy the central nervous system, and at such levels, the result is a very painful death.

Ionizing radiation can also cause cells to stick together improperly, leading to risk of cancer.

But radioactivity can be useful if dealt with care. Today, radiation is used in medicine, academics, and industry, as well as for generating electricity.

In addition, radiation has useful applications in areas such as agriculture, archaeology (carbon dating), space exploration, law enforcement, geology (including mining), and many others.

In the case of chernobyl, just like any other nuclear plant, radioactive isotopes were used to generate electricity. How exactly – a radioactive material gives out energy, which is used as a fuel to heat water, creating steam that drives the reactors’ turbines and generates electricity.

After the explosion, a huge amount of radioactive matter was released in the atmosphere. Most of the radiation released from the failed nuclear reactor was from iodine-131, cesium-134 and cesium-137. Iodine-131 is rapidly ingested through the air and tends to concentrate in the thyroid gland. Cesium isotopes are the ones that don’t disintegrate rapidly, but this makes them a matter of concern for years after their release into the environment.

A committee was created soon after the explosion to see why it happened and a lot of problems were found in how chernobyl nuclear plant was functioning. It was soon shut-down too and people were evacuated, but more pressing question was – what to do now, with all the radioactive matter just floating around free in the atmosphere?

Numerous measures have been taken since then to control the matter inside the plant perimeter, including building a confinement area around the power plant to stop anymore harmful material from leaking.

But the more important question is – what will prevent another chernobyl? You can read about this more online, and also about preventive measures that we learned from chernobyl.