The Record 2006 - Keble College - University of Oxford

The Life of the College
to say that the risks of contracting radiation-induced cancer are not
known. [There always remains a statistical error, in this case at the
level of parts per thousand.]
In every situation there are special risks which require special
safety measures. In the case of nuclear accidents such a risk is the
inhalation of radioactive iodine which is rapidly absorbed by the
thyroid, especially in young children. This then causes cancer over
the following decades. The special measure requires the population
to take iodine tablets during the three weeks following an accidental
release. This dilutes the radioactive iodine to the point where its uptake
by the thyroid is negligible. This has been known for decades but was
ignored in the aftermath of Chernobyl. So far some 1100 children have
contracted cancer, of whom 3 have died (1998). The incidence peaked
in 1995 and is falling off. This was an entirely avoidable addition to the
accident.
A fresh estimate of safe levels of ionising radiation in an era of global
warming
The costs of nuclear power are predicated on safety levels. The
numbers above suggest that regulation levels for nuclear safety should
be relaxed by a factor 300 from 1mSv/yr to 25mSv/month for the
general public. Such a safety limit would still have a very conservative
ratio relative to a lethal dose (6000 mSv/25mSv = 240), compared for
example with tissue heating by ultrasound, (50ºC/1ºC = 50). Relative
to marginal damage levels the ratios would be 100mSv/25mSv = 4
and 2ºC/1ºC = 2, respectively. This change would significantly reduce
the supposed costs of nuclear power including decommissioning. A
combination of nuclear and renewable power in the next 50 years
would give time for the development of clean thermonuclear fusion
power whose feasibility can no longer be doubted.
This discussion has skipped many details and is debatable at the
level of factors of two. However the factors of ten are defensible, and
an adjustment by a factor 300 of nuclear safety levels should have
significant and immediate consequences for energy policy.
This article is based on a lecture given in College at the Reunion
weekend for 1957–62s in April this year and is the subject of
a book Fundamental Physics for Probing and Imaging
published in October. Available through bookshops, or direct from
OUP at:
http://www.oup.com/uk/catalogue/?ci=9780199203888
http://www.oup.co.uk/isbn/0-19-920389-X
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