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 Batteries/Nuclear 070215
Russia and Norway will  replace nuclear batteries in Barents Sea Region. Solar panels will replace the batteries. The nuclear batteries have been used to power lighthouses, but recently, there have been attempts to steal the batteries.   Thieves  want the batteries for the isotope strontium-90 which can be used to make” dirty bombs”.  The Norway Post  states that if the batteries fall into the hands of terrorists, the radioactive element could be used to make such devices. (“Norway and Russia to replace nuclear batteries,” dated 02/19/2005)  Eleven nations, including 80 experts, met in Oslo in February to discuss the problem.
The Daintiest Dynamos
 While the steady progression of electrochemical batteries to increase energy density approaches the physical limit, alternatives must be found to power the technologies of the future. Fuel cells with methanol offer a ten times increase in energy, but nuclear batteries can offer 300 to 20,000 times greater energy density, even with single digit conversion efficiencies.

There are three proven ways to convert radioactivity to electrical current. The most noted method is to use the heat generated to activate  Seebeck effect materials. The method is used in deep space probes, from Pioneer 10 (see BD # 63, pp. 2 - 3 ) to the  more recent Cassini probe.

Another direct way is to irradiate a semiconductor junction with radiation resulting in an electrical current just as photodiodes produce electric in our ubiquitous photovoltaic arrays in both space and terrestrial applications.

Taking advantage of the unique abilities of micromelectromechanical systems (MEMS), the attractive forces bending a microbeam with an attached piezoelectric material generate electricity. The beam attraction is caused by absorption of high speed electrons from the nuclear source.

Although small in size and energy output, the small size may work toward the practical acceptance of nuclear batteries by keeping the nuclear material quantity small, and allowing multiple devices to have their own power source rather than start with a high power ‘bus.’

Still in the research phase, the devices have efficiencies in the 4% region, but 20% is a targeted goal.

For all who are interested in a detailed, but easily readable summary of the state of these batteries, this is a ‘must read’ article.

IEEE Spectrum, September 2004, pp36-41