Small Nuclear Power Reactors

(Updated 22 March 2012)

• There is revival of interest in small and simpler units for generating electricity from nuclear power, and for process heat. 
• This interest in small and medium nuclear power reactors is driven both by a desire to reduce capital costs and to provide power away from large grid systems. 
• The technologies involved are very diverse. 

As nuclear power generation has become established since the 1950s, the size of reactor units has grown from 60 MWe to more than 1600 MWe, with corresponding economies of scale in operation. At the same time there have been many hundreds of smaller power reactors built both for naval use (up to 190 MW thermal) and as neutron sources^a, yielding enormous expertise in the engineering of small units. The International Atomic Energy Agency (IAEA) defines 'small' as under 300 MWe, and up to 700 MWe as 'medium' – including many operational units from 20th century. Together they are now referred to by IAEA as small and medium reactors (SMRs).  However, 'SMR' is used more commonly as acronym for Small Modular Reactors.

Advanced Nuclear Power Reactors

(Updated 13 February 2012)

• Improved designs of nuclear power reactors are currently being developed in several countries. 
• The first so-called 3rd generation advanced reactors have been operating in Japan since 1996.   
• Newer advanced reactors now being built have simpler designs which reduce capital cost.  They are more fuel efficient and are inherently safer. 

The nuclear power industry has been developing and improving reactor technology for more than five decades and is starting to build the next generation of nuclear power reactors to fill new orders.

Several generations of reactors are commonly distinguished.  Generation I reactors were developed in 1950-60s, and outside the UK none are still running today.  Generation II reactors are typified by the present US and French fleets and most in operation elsewhere.  So-called Generation III (and 3+) are the Advanced Reactors discussed in this paper, though the distinction from Generation II is arbitrary.  The first are in operation in Japan and others are under construction or ready to be ordered.  Generation IV designs are still on the drawing board and will not be operational before 2020 at the earliest.

About 85% of the world's nuclear electricity is generated by reactors derived from designs originally developed for naval use.  These and other nuclear power units now operating have been found to be safe and reliable, but they are being superseded by better designs.

Reactor suppliers in North America, Japan, Europe, Russia and elsewhere have a dozen new nuclear reactor designs at advanced stages of planning, while others are at a research and development stage.  Fourth-generation reactors are at concept stage.