130 / Basics of Environmental Science
Coolant water then came into contact with hot fuel, producing steam that reacted
with the graphite moderator. This caused the second, very much bigger
explosion that blew away the top of the reactor, allowing radioactive material
to escape.
More than 30 fires began. The station fire brigade arrived within five minutes
and the brigade from Chernobyl a few minutes later. Helicopters were used to
drop boron through the hole in the roof to capture neutrons. When the fires
had been extinguished, the reactor was sealed inside a concrete casing, called
a ‘sarcophagus’. Some years later, fears were expressed about the condition
of the sarcophagus.
A total of 31 workers were killed by burns, falling masonry, and radiation, and
about 150 people on the site suffered from radiation sickness. The radioactive
plume was detected in Sweden.
Within 24 hours 47000 local residents had been evacuated and by May 7
everyone living within a radius of 30 km had been removed. In all, 116000
people from 186 settlements were evacuated. In subsequent years still more
people were moved out of the affected area. Although radiation was detected
further afield, outside the 30 km zone its effect on human health was predicted
to be too small to be statistically detectable.
In the following years the health of exposed people was monitored closely
under the leadership of the World Health Organization. Soon after the event,
the most serious problem was caused by the psychological and social trauma
of the accident and its aftermath of compulsory evacuation. Later there was an
increase in thyroid cancer among children in Belarus.Our production and use of fuels raises many environmental and economic questions. Posing those
questions is not difficult, but finding answers to them is.
31. Mining and processing of minerals
A ‘mineral’ is a naturally occurring inorganic substance with a crystalline structure and characteristic
chemical composition. Rocks are composed of minerals.
Whole rock is obtained by quarrying. Blocks of suitable rock are used for construction, in the case of
slate after being split into thin sheets for roofing and cladding. Sand and gravel is also used for building,
mainly of roads. Clay, won by a type of open-cast mining, is used for brick-making. High-pressure
hoses (called ‘monitors’) are used to wash kaolin, or china clay, from the granite matrix in which it
occurs, and it is removed as a slurry for purifying and drying. It was used originally to make fine
ceramics (porcelain) but its principal use now is as a filler and whitener in paper and other materials.
Rock and building stone are quarried on a huge scale. Each year, over the world as a whole, rivers
deliver to the sea about 24 billion tonnes of naturally weathered rock. Humans remove about 3
billion tonnes a year (ALLABY, 1993a, p. 150). This means we are now quarrying amounts comparable
to those removed by natural processes.