Nuclear lessons to learn

 
 

While an extreme case, those in Fukushima would do well to learn from the lessons of Chernobyl, writes Katie Hughes

The International Nuclear Event Scale (INES) is a meter used to rate the severity of a nuclear disaster, with levels ranging from zero – a deviation, to seven – a major accident.

The nuclear crisis, which occurred at the Fukushima I Nuclear Power Plant in Japan on March 11th, was rated at Level 5 due to a small amount of radioactive material being released despite severe damage to the core of the reactor. However, this rating may change as the situation unfolds – with final ratings commonly being assigned after the resolution of the crisis in question.

The accident was triggered following the failure of reactor cooling systems due to the earthquake and tsunami that had hit Japan that day. A power-cut caused by the flooding of the plant by seawater caused the failure that meant that the cores’ temperatures could not be brought down, leading to explosions and melting of the fuel rods.

The 1986 Chernobyl disaster is the only disaster of its kind classified as level 7 under the INES. Due to a failed testing of a new safety protocol, there was an explosion in one of the reactors, which led to the dispersion of massive quantities of radioactive material into the atmosphere, the after-effects of which can be seen to this day.

The difference between Fukushima and Chernobyl is that Chernobyl did not have any containment vessels in place, meaning that as soon as the external building exploded, radioactivity blasted out into the atmosphere with no constraining structure.

The main reason why the area around Chernobyl is still considered a health hazard, despite being shrouded in tons of concrete with a 30km exclusion zone around the site of the accident still in place to this day, is due to the radioactive elements still present in the area – something Fukushima will undoubtedly face in the years to come.

The half-life of an element is the time it takes for half of the sample to decay: the half life of certain isotopes of caesium and strontium, which are still found in the Chernobyl area, is over thirty years – this means that after thirty years of the substance being present, half of it will decay to a different element. However, it will be another thirty years before half of what remains decays again – and so the cycle continues.

There are two main effects of radiation on the body – it can kill cells and it can mutate DNA. It is because of their ability to kill cells that elements such as radium were used 60 years ago as a direct treatment of cancer – thick lead, which cannot be penetrated by radioactive alpha, beta and gamma particles, was placed around the cancerous tissue to prevent the radium having a mutant effect on other parts of the body.

A radioisotope of iodine, iodine-131 (radioiodine), is a product of the nuclear fission of uranium and plutonium and was emitted from the damaged reactor core in Fukushima I. Iodine, in an non-radioactive form, generally accumulates in the thyroid; radioiodine follows the same pattern of behaviour which is why, by accumulating in the thyroid, it causes thyroid cancer.

This will have long term effects on those who have consumed radioactive food, as can be seen from the after-effects of Chernobyl – the number of incidents of thyroid cancer in children under the age of five greatly increased after the explosion, the increase was in children as they would have been consuming a similar amount of iodine as adults, but due to having a smaller thyroid gland, would have retained a higher concentration.

The way in which the emitted and remaining radioactive substances are treated is paramount to the safety of the affected area. In the case of the 1979 Three Mile Island incident, also classified as level five on the INES, the majority of the reactor core debris was shipped off site to the Department of Energy’s National Engineering Laboratory.

In the case of Chernobyl, the majority of the radioactive debris was gathered in the remains of the reactor that was in turn covered with bags of sand and lead and eventually enclosed in a concrete ‘sarcophagus’ by December 1986, months after the original accident.

What will ultimately happen to the Fukushima Dai-ichi plant is yet unknown, the worst possible scenario is the complete meltdown of the fuel rods, which could ultimately burn through the ground and contaminate the ground below. Already radioactive water has leaked out into the ocean, contaminating it with plutonium.

The treatment of the Fukushima Dai-ichi Plant has not yet been finalised with several obstacles standing in the way – there is great difficulty in removing the radioactive water in basements as well as there being a large build-up of salt caused by seawater being used to bring down the temperature of the core.

The flooding and consequent destruction of the Fukushima I Power Plant is the biggest nuclear disaster to occur in recent years. The outcome of the event cannot yet be seen due to the plant remaining in an unstable condition, leaving the future of the surrounding area and its remaining inhabitants hanging in the balance.

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