Environmental Engineering Reference
In-Depth Information
Chernobyl type have never been used for energy produc-
tion outside the old Soviet bloc because of their potential
to become unstable under certain conditions. In this type
of reactor under unusual conditions the chain reaction can
build up very fast, leaving no time for the reactor
s control
rods to move in to stop an ultra-fast power excursion.
Even for reactors of this type, the accident would not
have happened had not the operators, for reasons that
are still unclear, systematically disabled all of the reactor
'
s
safety systems. We know what they were doing because
the control room log books survived. When the last safety
system was disabled, the reactor ran away, blew off its own
top along with the roof of the building, and spread radio-
activity far and wide (the explosion was caused by super-
heated steam from the reactor
'
s power build-up; it was
not a nuclear explosion). The Chernobyl building
was a light structure designed to keep out the weather
rather than to keep in radioactivity from an accident. The
European Union and the United States have cooperated
in a program to have all such reactors modi
'
ed to
improve the safety systems or shut them down.
Fukushima: All nuclear power plants are designed to
cope with natural disasters that can isolate the plant from
external sources of power. Fukushima was no exception in
principle, although it turned out, according to the Com-
mission set up by the Japanese Diet, to be one in practice.
One of the design features of all plants is a system to cope
with the loss of all external electrical power sources, called
“
On-site generators are turned on in
emergencies, and enough fuel for the generators is stored
on site to last for many days. The earthquake that struck
on March
station blackout.
”
,
was one of the most powerful ever to
