02-08-2013, 12:38 PM
ATOMIC BATTERY
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INTRODUCTION
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 communication satellites and especially high technology weapon platforms will require much larger power source than today’s power systems can deliver. For the very high power applications, nuclear reactors appear to be the answer. However, for intermediate power range, 10 to 100 kilowatts (kW), the nuclear reactor presents formidable technical problems.
Because of the short and unpredictable 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 cells and solar cells require little maintenance, and the latter need plenty of sun.
Thus the demand to exploit the radioactive energy has become inevitably high. Several methods have been developed for conversion of radioactive energy released during the decay of natural radioactive elements into electrical energy. A grapefruit-sized radioisotope thermo- electric generator that utilized heat produced from alpha particles emitted as plutonium-238 decay was developed during the early 1950’s.
HISTORICAL DEVELOPMENTS
The idea of nuclear battery was introduced in the beginning of 1950, and was patented on March 3rd, 1959 to tracer lab. Even though the idea was given more than 30 years before, no significant progress was made on the subject because the yield was very less.
A radio isotope electric power system developed by inventor Paul Brown was a scientific break through in nuclear power. Brown’s first prototype power cell produced 100,000 times as much energy per gram of strontium -90(the energy source) than the most powerful thermal battery yet in existence. The magnetic energy emitted by the alpha and beta particles inherent in nuclear material. Alpha and beta particles are produced by the radio active decay of certain naturally occurring and man –made nuclear material (radio nuclides). The electric charges of the alpha and beta particles have been captured and converted to electricity for existing nuclear batteries, but the amount of power generated from such batteries has been very small.
Alpha and beta particles also posses kinetic energy, by successive collisions of the particles with air molecules or other molecules. The bulk of the R &D of nuclear batteries in the past has been concerned with this heat energy which is readily observable and measurable. The magnetic energy given off by alpha and beta particles is several orders of magnitude grater than the kinetic energy or the direct electric energy produced by these same particles. However, the myriads of tiny magnetic fields existing at any time cannot be individually recognized or measured. This energy is not captured locally in nature to produce heat or mechanical effects, but instead the energy escapes undetected.
ENERGY PRODUCTION MECHANISM
Betavoltaics
Betavoltacis is an alternative energy technology that promises vastly extended battery life and power density over current technologies. Betavoltaics are generators of electrical current, ineffect a form of a battery, which use energy from a radioactive source emitting beta particles (electrons). The functioning of a betavoltaics device is somewhat similar to a solar panel, which converts photons (light) into electric current.
Betavoltaic technique uses a silicon wafer to capture electrons emitted by a radioactive gas, such as tritium. It is similar to the mechanics of converting sunlight into electricity in a solar panel. The flat silicon wafer is coated with a diode material to create a potential barrier. The radition absorbed in the vicinity of and potiential barrier like a p-n junction or a metal-semiconductor contact would generate separate electron-hole pairs which inturn flow in an electric circuit due to the voltaic effect. Of course, this occurs to a varying degree in different materials and geometries.
A pictorial representation of a basic Betavoltaic conversion as shown in figure 1. Electrode A (P-region) has a positive potential while electrode B (N-region) is negative with the potential difference provided by me conventional means.
Direct charging generators
In this type, the primary generator consists of a high –Q LC tank circuit. The energy imparted to radioactive decay products during the spontaneous disintegrations of radioactive material is utilized to sustain and amplify the oscillations in the high-Q LC tank circuit the circuit inductance comprises a coil wound on a core composed of radioactive nuclides connected in series with the primary winding of a power transformer. The core is fabricated from a mixture of three radioactive materials which decay primarily by alpha emission and provides a greater flux of radioactive decay products than the equivalent amount of single radioactive nuclei.
Optoelectrics
An optoelectric nuclear battery has been proposed by researchers of the kurchatov institute in Moscow. A beta emitter such as technetium-99 are strontium-90 is suspended in a gas or liquid containing luminescent gas molecules of the exciter type, constituting “dust plasma”. This permits a nearly lossless emission of beta electrons from the emitting dust particles for excitation of the gases whose exciter line is selected for the conversion of the radioactivity into a surrounding photovoltaic layer such that a comparably light weight low pressure, high efficiency battery can be realized. These nuclides are low cost radioactive of nuclear power reactors. The diameter of the dust particles is so small (few micrometers) that the electrons from the beta decay leave the dust particles nearly without loss. The surrounding weakly ionized plasma consists of gases or gas mixtures (e.g. krypton, argon, xenon) with exciter lines, such that a considerable amount of the energy of the beta electrons is converted into this light the surrounding walls contain photovoltaic layers with wide forbidden zones as egg. Diamond which converts the optical energy generated from the radiation into electric energy.
FUEL CONSIDERATIONS
The major criterions considered in the selection of fuels are:
Avoidance of gamma in the decay chain
Half life
Particle range
Watch out for (alpha, n)reactions
Any radioisotope in the form of a solid that gives off alpha or beta particles can be utilized in the nuclear battery. The first cell constructed (that melted the wire components) employed the most powerful source known, radium-226, as the energy source. However, radium-226 gives rise through decay to the daughter product bismuth-214, which gives off strong gamma radiation that requires shielding for safety. This adds a weight penalty in mobile applications.
Radium-226 is a naturally occurring isotope which is formed very slowly by the decay of uranium-238. Radium-226 in equilibrium is present at about 1 gram per 3 million grams of uranium in the earths crust. Uranium mill wastes are readily available source of radium-226 in very abundant quantities. Uranium mill wastes contain far more energy in the radium-226 than is represented by the fission energy derived form the produced uranium.
DRAWBACKS
First and foremost, as is the case with most breathtaking technologies, the high initial cost of production involved is a drawback but as the product goes operational and gets into bulk production, the price is sure to drop. The size of nuclear batteries for certain specific applications may cause problems, but can be done away with as time goes by. For example, size of Xcell used for laptop battery is much more than the conventional battery used in the laptops.
Though radioactive materials sport high efficiency, the conversion methodologies used presently are not much of any wonder and at the best matches conventional energy sources. However, laboratory results have yielded much higher efficiencies, but are yet to be released into the alpha stage.
A minor blow may come in the way of existing regional and country specific laws regarding the use and disposal of radioactive materials. As these are not unique worldwide and are subject to political horrors and ideology prevalent in the country. The introduction legally requires these to be scrapped or amended. It can be however be hoped that, given the revolutionary importance of this substance, things would come in favor gradually.
Medical Applications
The medical field finds a lot of applications with the nuclear battery due to their increased longevity and better reliability. It would be suited for medical devices like pacemakers, implanted deep fibrillators or other implanted devices that would otherwise require surgery to replace or repair the best out of the box is use in ‘cardiac pacemakers’. Batteries used in implantable cardiac pace makers-present unique challenges to their developers and manufacturers in terms of high levels of safety and reliability and it often poses threat to the end-customer. In addition, the batteries must have longevity to avoid frequent replacement. The technological advances in leads/electrodes have reduced energy requirements by two orders of magnitude. Microelectronics advances sharply reduce internal current drain, concurrently decreasing size and increasing functionality, reliability and longevity. It is reported that about 600,000 pacemakers are implanted each year worldwide and the total number of people with various types of implanted pacemaker has already crossed 3,000,000. A cardiac pacemaker uses half of its battery power for cardiac stimulation and the other half for house keeping tasks such as monitoring and data logging.
Mobile devices
Xcell-N is a nuclear powered laptop battery that can provide between seven and eight thousand times the life of a normal laptop battery-that is more than five years worth of continuous power.
Nuclear batteries are about forgetting things around the usual charging, battery replacing and such bottlenecks. Since chemical batteries are just near the end of their life, we can’t expect much more from them, in its lowest accounts, a nuclear battery can endure at least upto five years. The Xcell-N is in continuous working for the last eight months and has not been turned off and has never been plugged into electrical power since. Nuclear batteries are going to replace the conventional batteries and adaptors, so the future will be of exciting innovative new approach to powering portable devices.
CONCLUSION
The world of tomorrow that science fiction dreams of and technology manifests might be a very small one. It would reason that small devices would need small batteries to power them. The use of power as heat and electricity from radioisotope will continue to be indispensible. As the technology grows, the need for more power and more heat will undoubtedly grow along with it.
Clearly the current research of nuclear batteries shows promise in future applications for sure. With implementation of this new technology credibility and feasibility of the device will be heightened. The principal concern of nuclear batteries comes from the fact that it involves the use of radioactive materials. This means through out the process of making a nuclear battery to final disposal, all radiation protection standards must be met. The economic feasibility of the nuclear batteries will be determined by its applications and advantages. With several features being added to this little wonder and other parallel laboratory works going on, nuclear cells are going to be the next best thing ever invented in the human history.