Nuclear power is an important source of non-fossil base load electricity in 30 countries, and is often cited as a necessary component of a diverse, reliable electricity sector. Globally, the nuclear power sector continues to expand, although in recent years nuclear power has faced significant challenges. These challenges include the high cost of building new nuclear facilities, the economics of operating nuclear facilities in liberalized electricity markets, where nuclear power has had trouble competing in recent years, safety (as highlighted by the 2011 Fukushima Daiichi accident in Japan), waste storage, and proliferation.
