Sunday, October 10, 2010

Small modular reactors: The shape of things to come?

   The World Nuclear Association and other groups involved in energy policy are reporting a spike in interest in what are termed small modular reactors (SMR). There are a number of reasons, a recent report from the WNA explains, including economics, the practicality in providing power to remote locations, and the overall need to reduce the world's dependence on larger grid systems.
   In a report at http://www.world-nuclear.org/info/inf33.html  (See also: http://en.wikipedia.org/wiki/World_Nuclear_Association), updated in October, 2010, the association cites the following:
  • Modern small reactors are simpler in design than older ones and are easier to mass produce.
  • Inherent safety features are incorporated into many SMRs in the event of a malfunction.
  • Four 62 MWt (thermal) units at the Bilbino plant in remote Siberia have been in operation since 1976 and generate electricity more efficiently than would fossil fuels.
  • Construction of the world's first floating nuclear power plant (Akademik Lomonosov) in Vilyuchinsk, Russia, began in 2007 and is expected to be completed next year.
   "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," notes the report at http://www.world-nuclear.org/info/inf33.html. "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, yielding enormous expertise in the engineering of small units."
   The IAEA defines small as "under 300 MWe, though 500 MWe is a considered a limit elsewhere.
   A nuclear-powered battery system under development in Japan, described as "4S" -- for super safe, small and simple, would have built-in safety features and power a steam cycle from an underground location for as long as 30 years. Some versions of the system produce an outlet coolant temperature of 550 degrees Celsius, the report says, "suitable for power generation with high temperature electrolytic hydrogen production."
   Traveling wave reactor (TWR) technology being developed by TerraPower and with funding from Bill Gates is another promising future nuclear power source in which a slow-burning reactor actually makes its own fuel in the process of burning.
   As noted in the WNA report:
   "The reactor uses natural or depleted uranium packed inside hundreds of hexagonal pillars. In a 'wave' that moves through the core at only one centimeter per year, the U-238 is bred progressively into Pu-239, which is the actual fuel that undergoes fission. The reaction requires a small amount of enriched uranium to get started and could run for decades without refueling."
   As the world's population grows larger and its energy needs accordingly, expect to hear a lot more about these and other alternative sources. We're also certain to here plenty of debate. Among the critics is the Institute for Energy and Environmental Research, which states in a recent fact sheet.
   “Efficiency and most renewable technologies are already cheaper than new large reactors.  The long time — a decade or more — that it will take to certify SMRs will do little or nothing to help with the global warming problem and will actually complicate current efforts underway."