EQUIVALENCE AND PROPORTIONALITY
Two key concepts in nuclear accountancy and the management of the safeguards
system are equivalence and proportionality. Atoms of uranium,
as with atoms of many other commodities, are indistinguishable from one
another. As described by DFAT/ASO:
II.13 The large scale physical and chemical processes which nuclear
material from a variety of sources must undergo at a limited number
of processing facilities mean that it is impossible to track the identity
of individual atoms or quantities of nuclear material. This circumstance
has led to the development of two principles used universally in the
industry and in the application of safeguards: equivalence and proportionality.
All safeguards, both bilateral and multilateral, are applied on the
basis of the equivalence of similar quantities of the same type of nuclear
material.
II.14 The equivalence principle provides that where AONM loses
its separate identity because of process characteristics, e.g., mixing,
an equivalent quantity is designated as AONM, based on the fact that
atoms or molecules of the same substance are indistinguishable, any
one atom or molecule being identical to any other of the same substance.
In such circumstances, equivalent quantities of the products of such
nuclear material may be derived by calculation or from operating plant
parameters. However, equivalence does not permit substitution of batches
of nuclear material of a different category, e.g., enriched uranium
cannot be replaced by natural or depleted uranium, and cannot be used
to circumvent safeguards designed to ensure exclusively peaceful uses
of AONM.
II.15 The proportionality principle provides that where AONM
is mixed with other nuclear material, and is processed or irradiated,
a proportion of the resulting material will be regarded as AONM corresponding
to the same proportion as was AONM initially.
II.16 A simple banking analogy illustrates these principles.
Individual depositors use an accounting system to be sure that they
are correctly credited with their share of a bank's assets, but they
do not expect to withdraw the exact notes and coins they originally
deposited. Nuclear materials accountancy tracks exports of Australian
uranium in the same way.
II.17 The application of the equivalence and proportionality
principles provides Australia with the assurance that at all times a
quantity of nuclear material precisely equivalent to the quantity exported
is identified as being subject to Australian safeguards obligations
and treated and accounted for as AONM. (S 60, II.13-17, 8)
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