Nuclear Energy

The biggest deficiency in the Rajasthan and Madras reactors is the absence of a high-
pressure emergency-core cooling system (ECCS) for avoiding core meltdown in the case of a loss-
of-coolant accident. No pressurized heavy water reactor anywhere in the world currently operates
with such an obsolete and unsafe ECCS, according to Gopalakrishnan. dxxiv
iv) NAPS
The two reactors of Narora Atomic Power Station (NAPS) in Uttar Pradesh are also of 220
MW each. The first went critical in 1989 and the second in 1991.
The most serious accident that has occurred at an Indian nuclear reactor took place at this
plant on March 31, 1993. We discuss it in slightly greater detail to again illustrate the point made in
Chapter 3 that because of the inherently complex nature of nuclear reactor technology, even minor
failures or human errors can lead to a cascading chain of events culminating in a major accident.
Early that morning, two blades of the turbine at the first unit broke off due to fatigue. These
sliced through other blades, destabilizing the turbine and making it vibrate excessively. The
vibrations caused pipes carrying hydrogen gas that cooled the turbine to break, releasing the
hydrogen which soon caught fire. Around the same time, lubricant oil also leaked. The fire spread
to the oil and through the entire turbine building. Among the systems affected by the fire were four
sets of cables that carried electricity, which led to a general blackout in the plant. One set of cables
supplied power to the secondary cooling systems, which were consequently rendered inoperable. In
addition, the control room became filled with smoke and the staff were forced to leave it within just
10 minutes after the blade failure.
The operators responded by manually actuating the primary shutdown system of the reactor
39 seconds into the accident. Although the reactor was shut down, since the fuel rods would
continue to undergo radioactive decay even after the reactor was shut down, thereby generating
heat which could cause a meltdown, some operators climbed onto the top of the building and,
under battery-operated portable lighting, manually opened valves to release liquid boron into the
core to slow down the reaction. That instinctive action by the technicians was the fourth and last
level of safety protection, and it prevented what would most certainly have led to a partial core
meltdown.
It took 17 hours from the time the fire started for power to be restored to the reactor and its
safety systems. Operators who were forced to leave the control room because of smoke could not
re-enter for close to 13 hours. An attempt was made to take control of the plant from the emergency
control room; but, since there was no power available, even this was not possible. Thus, Narora
was almost unique in that for many hours, the operators had no indication of the condition of the
reactor! dxxv
v) Kaiga
Unit-1 of the Kaiga Atomic Power Station located in Karnataka was supposed to achieve
criticality in 1996. However, the concrete containment dome collapsed on May 13, 1994 during the
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