From Wikipedia: http://en.wikipedia.org/wiki/Nuclear_power
There is a possible impediment to production of nuclear power plants, due to a backlog at Japan Steel Works, the only factory in the world able to manufacture the central part of a nuclear reactor’s containment vessel in a single piece[32], which reduces the risk of a radiation leak. The company can only make four per year of the steel forgings. It will double its capacity in the next two years, but still will not be able to meet current global demand alone. Utilities across the world are submitting orders years in advance of any actual need. Other manufacturers are examining various options, including making the component themselves, or finding ways to make a similar item using alternate methods.[33] Other solutions include using designs that do not require single piece forged pressure vessels such as Canada’s Advanced CANDU Reactors or Sodium-cooled Fast Reactors.