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Perilous ray of hope

ANTOINE HENRI BECQUEREL 1852 - 1908 FRENCH PHYSICIST. Ten years after the Chernobyl disaster, James Williams investigates the man who first discovered radioactivity, the 'miracle cure'. Just over 100 years ago the world was blissfully unaware of the existence of radioactivity.

Since then it has been proclaimed as both mankind's saviour and destroyer. 1996 sees two anniversaries: the discovery of radioactivity by the French physicist Henri Becquerel and, more ominously, the 10th anniversary of the Chernobyl disaster, the consequences of which are still not fully unveiled, nor will they be for many years to come. Yet, at the advent of the discovery of radioactivity it was being billed as a potential miracle cure.

In the Twenties advertisements for radium therapy apparatus that deliberately produced radioactive drinking water were common. The apparatus produced water that had a high dosage of radioactivity which, it was claimed, could treat anything from arthritis to diabetes. Other treatments encouraged people to use radioactive cream on skin to remove wrinkles or to breath radioactive air.

Although the use of radioactivity in the treatment of various medical problems is still an important part of the arsenal of weapons doctors use to promote and save health, the potentially destructive nature of radioactivity needs to be carefully harnessed and controlled.

Exactly how radioactivity affects living cells is still not fully understood but it is known that some cells, in particular reproductive cells, are more sensitive to radiation than others, for example bone cells.

It was the earlier discovery of X-rays that led Becquerel to investigate whether naturally fluorescent materials emitted a similar type of ray.

Antoine Henri Becquerel was born in Paris in 1852 into a distinguished scientific family.

His grandfather was a physicist and his father was interested in naturally fluorescent materials, an interest passed to his son that ultimately led to the discovery of what we know today as gamma radiation. In addition to emitting light, Becquerel wondered whether a fluorescent mineral, potassium uranl sulphate, might also emit X-rays.

After exposing a sample to sunlight and wrapping it in foil he placed it close to a photographic plate. He reasoned that any X-rays would pass through the foil but the visible light of the fluorescent material would not. It worked, or so he thought. A series of cloudy days, however, prevented him from repeating his experiments. He decided to try once more to see if he could detect at least a weak reaction from an under-exposed sample.

Curiously, this produced just as heavy a fogging effect on the plate as the exposed sample. Further work showed that the fogging effect was independent of the fluorescent effect. The hunt was now on to find out what caused the fogging.

Soon it was obvious to Becquerel and other workers that they were dealing with a type of radiation that was made up of particles, not waves like X-rays. Being able to deflect the beam using magnets it was clear that there were two types of charged particles and a type of electromagnetic radiation that was similar to but stronger than X-rays.

Today these are known as alpha and beta particles and gamma radiation. The importance of this discovery lay in the fact that it gave clues to the structure of atoms. The emission of particles implied that atoms must have some kind of internal structure. This theoretical speculation was the first in a long line of discoveries that led to modern day scientists harnessing this potentially limitless energy in nuclear reactors, an energy that was sadly unleashed on April 26, 1986.

At 1.23am, reactor number 4 at the Chernobyl nuclear power station was in a hazardous condition. A design flaw made the working of the reactor at low power dangerous. A test to see just how long the reactor could last without power caused the most devastating nuclear accident yet. It took 3 seconds for the reactor to surge to 100 times the maximum working level. A fire resulted and a radioactive plume of gas was released causing problems as far afield as north Wales.

In the days after the explosion and fire 187 people fell ill with acute radiation sickness; 31 people died, mainly fire fighters. All told, some 260,000 square kilometres of land in the Ukraine, Russia and Belarus are contaminated and the consequences for the health of anything up to 2.6 million people are largely unknown.

For all these people who have been cured by radiotherapy or had the quality of their life enhanced or who have benefited from the internal diagnostic imaging offered by radionuclides, they have a lot to thank Becquerel and many other workers for. For the survivors and descendants of the workers and residents surrounding Chernobyl it was and still is a nuclear nightmare.

James Williams is head of the science faculty at The Beacon School, Banstead, Surrey

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