A burgeoning need exists today for small, compact, reliable, lightweight and self-contained rugged power supplies to provide electrical power in such applications as electric automobiles, homes, industrial, agricultural, recreational, remote monitoring systems, spacecraft and deep-sea probes. Radar, advanced communications satellites and, especially, high-technology weapons platforms will require much larger power sources than today's space power systems can deliver. For the very high power applications, nuclear reactors appear to be the answer.

However, for the intermediate power range, 10 to 100 kilowatts (KW), the nuclear reactor presents formidable technical problems. Because of the short andunpredictable lifespan of chemical batteries, however, regular replacements would be required to keep these devices humming. Also,enough chemical fuel to provide 100 KW for any significant period of time would be too heavy and bulky for practical use.

Fuel cellsand solar cells require little maintenance, but the former are too expensive for such modest, low-power applications, and the latter need plenty of sun. Thus the demand to exploit the radioactive energy has become inevitable high. Several methods have been developed for conversion of radioactive energy released during the decay of natural radioactive elements into electrical energy. A grapefr uit-sized radioisotope thermo-electric generator that utilized the heat produced from alpha particles emitted as plutonium-238 decays was developed during the early 1950's.

Since then the nuclear power has taken a significant consideration in the energy source of future. Also, with the advancement of the technology the requirement for lasting energy sources has been increased to a great extent. The solution to the long term energy source is, of course, the nuclear batteries with a lifespan measured in decades and has the potential to be nearly 200 times more efficient than the currently used ordinary batteries. These incredibly long-lasting batteries are still in the theoretical and developmental stage of existence, but they promise to provide clean, safe, almost endless energy.