Categorisation can sometimes have a dramatic effect on how we
perceive the world, and to learn yesterday that the nuclear
debacle at Fukushima now officially ranks alongside that of
Chernobyl in terms of seriousness appears to be an ominous
worsening of the situation in Japan. The move will certainly
have political ramifications, with neighbouring countries
perceiving the threat to them as being that much greater. But in
reality, as Japanese officials were at pain to stress, nothing
fundamental has changed; listing Fukushima as a "level seven"
nuclear accident alongside the 1986 disaster in the Ukraine, was
merely an overdue recognition of what has happened so far at the
tsunami-stricken plant, combined with what may happen in the
future. How do the two incidents compare? Although Fukushima has
spilt a lot of radioactivity into the environment, the full
amount is still thought to be far below the amount released in
the accident at Chernobyl 25 years ago. Using the common measure
of "terabecquerels", it is tho