From Jonathan Cardy
Teddington, Middlesex
May I suggest a couple of technical difficulties with the proposal to store
nuclear waste in exhausted oilfields
(Letters, 16 August, p 47).
Past performance being no guarantee of future results, we would need some way
of calculating the impact of erosion until the waste decayed to inert levels.
Just because an oilfield has been leakproof for millions of years doesn’t mean
it will be for the next few hundred thousand, especially since the very
extraction of this oil has disrupted the strata and may cause subsidence.
Oilfields trap light molecules such as water and hydrocarbons. Many
radioactive elements are heavy and might sink out of the trap and away, so only
oilfields that are sealed in every direction could be used.
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Liquefied waste pumped into oilfield strata would be subject to separation by
both gravity and rock filtration, which could lead to a critical mass of fissile
material being concentrated in one part of the strata with unfortunate
results.
Today’s exhausted oilfields still contain large quantities of oil—the
technology for extracting oil has improved greatly this century. In future, we
might regret the radioactive contamination of this oil. Worse still, in a
thousand or a hundred thousand years’ time people might extract irradiated oil
without knowing the dangers of radiation.
Even if we close the whole nuclear industry tomorrow we still need to find a
way of ensuring that the nuclear waste we have already created is kept separate
from the biosphere until it’s safe. Pumping waste into oilfields is better than
pouring it into our seas and rivers, but it is still not acceptable.
