The Chernobyl (Ukraine, 1986) and
the Fukushima (Japan, 2011) accidents have been rated on the International
Atomic Energy Agency (IAEA) International Nuclear andRadiological Event Scale
(INES) as a “Major Accident” as INES 7.However, are the
accidents as comparable as suggested by this rating?
The nuclear accidents of Chernobyl
and Fukushima exhibit someinteresting similarities and differences, which
The Chernobyl nuclear
accident was as a result of a technical test in Unit 4 of the Chernobyl NPP.
Inappropriate reactor operation at low power level led to “xenon-poisoning” of the
reactor, which was not
recognized properly by the reactor staff and caused improper operation of the
reactor’s control rods (Grishanin,2010; Smith
and Beresford, 2005).This operating error led to thermal
destruction of the RBMK-1000 reactor by a sudden power excursion, which
ultimately caused at least one (steam) explosion and ignition of the graphite
moderators (Michel, 2006).The Fukushima was caused by the earth quake
that hit Japan. The tsunami, however reached as high as 14m at the plant site.
Three of the six reactors (Units 1, 2, and 3) were in operation at the time of
theearthquake, but the first
seismic signals of the earthquake triggered an automatic shutdown of the
zone” initially encompassed a 30 km radius(2800 km2) around the NPP.
Approximately 116000 people within the”exclusion zone” were
evacuated to less contaminated areas in the months following the accident.
Evacuation began 3–11 days after theaccident, which was already late for parts of the
affected population(Pröhl et al., 2002). Later, the exclusion zone was extended and
covered 4300 km2 in 1996, in order to contain the areas with the highest radiation
levels (IAEA, 1996).
Whereas , more than 80%
of the atmospherically-releasedradionuclides are estimated to have gone
offshore from Fukushima,followed by deposition in the Pacific Ocean (Kawamura et
al., 2011;Morino et al., 2011).Both the Chernobyl and Fukushima accidents caused
radionuclidecontamination of the atmosphere, hydrosphere, biosphere
andpedosphere over the entire northern hemisphere.