Nuke waste
Nuke wasteRadioactive wastes, must for the protection of mankind be
stored or disposed in such a manner that isolation from the
biosphere is assured until they have decayed to innocuous
levels. If this is not done, the world could face severe
physical problems to living species living on this planet.
Some atoms can disintegrate spontaneously. As they do,
they emit ionizing radiation. Atoms having this property are
called radioactive. By far the greatest number of uses for
radioactivity in Canada relate not to the fission, but to
the decay of radioactive materials - radioisotopes. These
are unstable atoms that emit energy for a period of time
that varies with the isotope. During this active period,
while the atoms are 'decaying' to a stable state their
energies can be used according to the kind of energy they
emit.
Since the mid 1900's radioactive wastes have been
stored in different manners, but since several years new
ways of disposing and storing these wastes have been
developed so they may no longer be harmful. A very
advantageous way of storing radioactive wastes is by a
process called 'vitrification'.
Vitrification is a semi-continuous process that
enables the following operations to be carried out with the
same equipment: evaporation of the waste solution mixed with
the
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1) borosilicate: any of several salts derived from both
boric acid and silicic acid and found in certain minerals
such as tourmaline.
additives necesary for the production of borosilicate glass,
calcination and elaboration of the glass. These operations
are
carried out in a metallic pot that is heated in an induction
furnace. The vitrification of one load of wastes comprises
of the following stages. The first step is 'Feeding'. In
this step the vitrification receives a constant flow of
mixture of wastes and of additives until it is 80% full of
calcine. The feeding rate and heating power are adjusted so
that an aqueous phase of several litres is permanently
maintained at the surface of the pot. The second step is the
'Calcination and glass evaporation'. In this step when the
pot is practically full of calcine, the temperature is
progressively increased up to 1100 to 1500 C and then is
maintained for several hours so to allow the glass to
elaborate. The third step is 'Glass casting'. The glass is
cast in a special container. The heating of the output of
the vitrification pot causes the glass plug to melt, thus
allowing the glass to flow into containers which are then
transferred into the storage. Although part of the waste is
transformed into a solid product there is still treatment of
gaseous and liquid wastes. The gases that escape from the
pot during feeding and calcination are collected and sent to
ruthenium filters, condensers and scrubbing columns. The
ruthenium filters consist of a bed of
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2) condensacate: product of condensation.
glass pellets coated with ferrous oxide and maintained at a
temperature...
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