Accidents - Radioactivity - Safety and Measurement
Why Accidents Occur (explained by Peter Bunyard)
Already the nuclear industry, in its relatively brief history, has had serious accidents which have led to the release of large quantities of radioactive materials into the environment. These are a British reactor fire at Windscale, where the graphite moderator overheated, and the disaster [previously explained] at Kyshtym in the Urals.
The British accident sent a plume of radioactive contaminants across
Britian to Denmark and over the European continent. Part of it passed
across the Irish Sea into Ireland... the greatest contamination occured
close to the reactor itself.. thousands of gallons of milk had to be poured
out because it contained high levels of iodine-131.
Every attempt was made to cover up the implications of the Windscale Fire
... no advice was given to the public in the vicinity or indeed in the path of the
plume to take simple precautions - such as staying indoors when the
radiation in the air had reached its peak.
By the time of Chernobyl in 1986, all European countries had networks
of radiation-monitoring stations, particularly in sensitive areas such as
those close to nuclear power plants.
It was therefore no coincidence that the first indication in the West of a
nuclear disaster somewhere in the Soviet Union, and very quickly pinned
down to the Ukraine, was from abnormally high level readings of
radioactivity in the air at Forsmark nuclear power station on the
Eastern side of Sweden.
Indeed, when workers arrived at the Swedish station on the morning
of the 28th April 1986, they were stopped from entering the plant
because of contamination on their faces, hands and clothing.
Activity was also found on cars in the car park, on the ground,
and in puddles of water. Workers were therefore sent away and
both local and central authorities were notified to put them in a
state of readiness for carrying out routine emergency action
and establishing countermeasures.
Within an hour of the notification, an emergency organization was
already set up at the Swedish National Institute of Radiation Protction,
growing in numbers to some 100 people and remaining active for
24 hours a day over the first months following the accident at Chernobyl.
Within the first day, the emergency task force had concluded that evacuation
of any of the Swedish population, sheltering them or advising them to take
iodine tablets to counter the fallout of radioactive iodine would not be justified.
Similar conclusions were reached throughout Western Europe, although
more careful analysis of the situation in hot-spot areas revealed later that
a more judicious approach might well have been followed.
What is a Tritium Measurement Facility? - What is Tritium ?
The Nuclear Industry Worldwide
The Nuclear Industry worldwide is generating an appalling legacy of
radioactive wastes. The properties of those wastes vary enormously,
but many are highly radioactive and toxic, and many will remain
radioactive for hundreds of thousands of years.
Nuclear waste embraces a great range of material, from lightly
contaminated overalls, to uranium mill tailings, to the fiercely
radioactive liquid high level waste that is produced by reprocessing.
By the turn of the century, the worldwide inventory of high-level wastes
is projected to reach 150,000 million curies.
The production wastes starts at the first stage of the nuclear fuel cycle
- with the mining of uranium. In the USA it has been calculated that
radon emissions from mill tailings could cause 4,000 cancer deaths a year.
Mill tailings apart, the amount of radioactive wastes produced by a
nuclear power programme depends critically on whether reprocessing
or long term storage is practiced.
A large pressurized water reactor (PWR) produced 11 cubic metres of
irradiated fuel per gigawatt per year. If stored, this is the only volume to
be dealt with. If reprocessed, 6.25 cubic metres high-level waste,
40 metres of intermediate-level waste and 600 cubic metres of lowlevel
waste are produced from the original 11 cubic metres of spent fuel.
At the end of the first year after extraction from the reactor, the irradiated
fuel still contains, in highly concentrated form, 270,000 times more
radioactivity than the ore from which it was derived. Even after 10,000 years,
one kilogram would contain, gram for gram, 18 million times more
radioactivity than the lambs that Britons were forbidden to eat as a result of Chernoybl.
High-level wastes are generally stored in stainless steel tanks,
constantly cooled. In the USA the main storage center is Hanford,
a site that has a notorious record for accidents involving waste.
Between 1945 and 1973, some 422,000 gallons liquid waste
containing 500,000 curies of radioactivity had leaked out of the tanks.
Tritium and ruthenium have been detected in the groundwater;
strontium-90 and iodine-131 in the Columbia River; and plutonium-239
in the soil. The levels of plutonum were 5,000 times the permissible level.
In the UK, high level wastes are stored at Sellafield. Ultimately, the aim
is to solidify the waste in glass through a process known as vitrification.
The process is intended to reduce the volume of waste and to make
it easier to handle.
A pilot vitrification plant is now in operation at Marcoule in France,
but it has only vitrified waste with a radioactivity no higher than
10 curies per cubic metre: once fully operational, it must contend
with wastes with a radioactivity up to 300 curies per cubic metre.
Several US and Austrailian researchers are strongly critical of vitrification.
The danger is that the glass blocks will disintegrate at some time in the future.
Even assuming vitrification works, the problem of a long-term repository
for high-level wastes remains unresolved - and, many would claim, insoluable.
In both Europe and the USA, the nuclear industry talks of burying waste
in deep underground sites, but the search for stable geological sites
has proved fruitless. Indeed, uncertainities of geological faults,
the ability to predict future geological movement, and the possibility
of earthquakes, make it possible to guarantee the integrity of any
site for the length of time that the waste must be kept isolated.
In the USA, three out of six sites have been closed down due to
contamination problems or breeches in transportation regulations.
The West Valley Site in New York State was closed after tritium
contaminated local ground water, and the Maxley Flats dump in
Kentucky after plutonium was fond to have migrated three-forths
of a mile off site within three years of the site opening. At Bernwell,
South Dakota - one of the three sites still operating - movement of
both cobalt-60 and tritium have been detected.
The only available dump site in Britian for disposing of solid low-level
waste is at Drigg, adjacent to Sellafield. The site, which is almost full,
is designed to allow its wastes to drain into the Irish Sea, on the
grounds that they will be rendered harmless through "dilution and dispersal."
...Discharges of low-level nuclear waste into the sea from land
(as opposed to dumping from ships) escape the LDC moratorium,
and such waste is still discharged by both Sellafield and Cap de la Hague.
The failure to find a suitable land-disposal site for intermediate and
low-level wastes in Britian has again focused on the sea, one proposal
being to bury the waste under the seabed, with access via tunnels from the land...
WestGermany's nuclear industry seeks to dispose of waste in
China's Gobi Desert. Germany's biggest nuclear company - Kraftwerke Union -
announced that deal with China would be taken in exchange for nuclear technology.
If 12,000 reactors power the world of tomorrow,
how much waste will result if there are no accidents?
In the event of an ACCIDENT,
Escaped fuel in process
is 200 million more times radioactive than when first mined.
In the event of an accident,
the amount of fuel continually generating would extend
from the earth to the moon and back within three seconds.
Because of the immense amount of waste,
it is important that someone must shut down a nuclear reactor
with control rods and moderators: steel beams, boron carbide, cadmium
inserted into the reactor core
as soon as possible.
Where "Plutonium-239 chinasyndrome" emerges from fissures,
control moderators may be inserted and finally dolomite
in an effort to re-route the plumes.
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