The main subject emphasized in the passage is ----.

In the years following the Chernobyl reactor disaster
in 1986, nuclear power was seen as a dying industry.
Public support had lessened because of safety fears,
and many countries decided to put a halt to new
reactor construction. But there has recently been a
dramatic revival of interest in nuclear energy, thanks
to the twin threats of climate change and energy
insecurity. Nuclear reactors do not emit CO2 when
they generate electricity, so governments are
increasingly seeing the construction of such reactors
as a way to bring down carbon emissions and
generate stable supplies of electricity.