The ingestion toxicity
of CANDU nuclear wastes
over a period of 10 Million Years

[ pour la version française ]

This graph, published in 1978 by the Ontario Royal Commission on Electric Power Planning, shows (over a period of 10 million years) the toxicity of radioactive wastes created in one year by the operation of a (hypothetical) 1000 megawatt CANDU nuclear reactor.

The ''high-level wastes'' consist mainly of fission products and actinides contained in the spent reactor fuel.

The ''uranium mill tailings'' are the sandy radioactive residues left over from mining and milling uranium ore to produce CANDU reactor fuel.

The vertical axis indicates the "ingestion toxicity": it is the volume of water required to dilute the nuclear wastes to public drinking water standards.

Although this hazard index is only a crude measure of of the potential danger of the radioactivity, because many environmental factors are involved, it nevertheless gives an idea of the serious nature of the danger.

The horizontal scale indicates the storage time in years -- starting at 1 year and extending out to 10 million years [10 to the seventh power = a "1" followed by seven zeros].

For the first 600 years the radiotoxicity is due, almost exclusively, to the fission products, and for the following 100,000 years the main radiotoxic isotopes are the "actinides" plutonium and americium.

For comparison purposes, the relative ingestion hazards of uranium tailings [from uranium mining and milling] and residual uranium within the spent fuel is also shown, as well as the total radiotoxicity of the high-level waste [i.e. the irradiated nuclear fuel].

from A Race Against Time, pp. 91-93
Royal Commission on Electric Power Planning
Ontario, 1978.

[Findings on Uranium Tailings]

[Findings on High-Level Waste]


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