Japanese engineers work to contain nuclear reactor damage
Engineers are now pumping seawater laced with boron into two
nuclear reactors at Japan's Fukushima No. 1 (Daiichi) power
plant 150 miles north of Tokyo and are considering doing it at a
third reactor in a last-ditch effort to stave off a meltdown
that could release dangerous amounts of radioactivity into the
environment. Hydrogen explosions have now occurred at two
reactors at the facility. Here's a look at the engineers'
efforts and what the potential consequences are, according to
various experts.  Why do the reactors have to be cooled?
Nuclear reactors operate through the chain-reaction splitting,
or fissioning, of uranium atoms. The process creates heat used
to turn water into steam. When an earthquake occurs, a safety
mechanism inserts control rods into the core of the reactor to
halt the chain reaction. But the fuel rods continue to produce
excess amounts of heat for several days and must be cooled. If
they are not cooled, they could melt, with