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Radioactive Wastes

Radioactive Wastes


        Radioactive 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 additives necessary
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...