"How great a matter a little fire kindleth," observed St James, by way of obiter dictum in the course of his Epistle. And, indeed, the ramifications of one minor conflagration which started 40 years ago today are still the subject of much emotive verbal cut and thrust - quite out proportion to the little fire itself. It was on October 7th, 1957, that a number of uranium rods overheated at the Windscale nuclear plant in Cumbria, and the ensuing fire resulted some days later in a significant quantity of radioactive material being released into the atmosphere.
The danger at the time was somewhat understated, the radioactive material being described as having been "carried out to sea and therefore not a danger to the public". Nowadays, however, nobody would deny the potential hazards of an accident at a place like Windscale - or Sellafield as it is known today. But "radioactive" is a very emotive word. It is worth remembering that radioactivity is a natural process that happens constantly around us; it is a consequence of the physical composition of our planet, and exposure to radiation is a natural hazard that all of us, willynilly, must endure.
The unit used by scientists to quantify the potential of radiation to cause damage to living cells - and ultimately to kill - is called the sievert, abbreviated to Sv. A person living in Ireland typically receives an annual dose of radiation amounting to slightly over 2 millisieverts. Of this, only about 13 per cent can be identified as being of human origin; it results from accidents such as those at Sellafield or at Chernobyl, from the testing of nuclear weapons in the atmosphere as used to happen during the 1950s, or most importantly of all, from exposure to X-rays for medical diagnostic purposes. About 1.8 mSv, however , or 87 per cent of the total, comes from natural sources.
The sources of natural radiation comprise a lengthy list. Cosmic radiation reaching us from outer space is one; terrestrial radiation, emanating mainly from the igneous rocks, like granite, is another. But perhaps the most significant source is a radioactive gas called radon, emitted by the small amounts of uranium and thorium contained in rocks and soils. It has no taste, no smell or colour, and requires special equipment to detect its presence.
Normally radon is exuded in the open air, and quickly diluted to a low and harmless concentration in the atmosphere. But when confined, it may well accumulate. Much attention nowadays is paid to monitoring radon levels inside buildings in parts of the country where the composition of the local rock may make it a potential danger.