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Report on nuclear batteries Document Transcript

  • 1. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 1 CONTENTS 1. Introduction 3 2. What are nuclear power batteries? 5 3. Types of nuclear batteries 6 a. Thermal converters 6 i. Thermionic Converters 6 ii. Radioisotope thermoelectric generator 7 iii. Thermo photovoltaic cells 9 iv. Alkali-metal thermal to electric converter 10 b. Non-thermal converter 13 i. Direct charging generators 13 ii. Betavotaic 13 iii. Alphavoltaics 15 iv. Optoelectric 15 v. Reciprocating electromechanical battery 16 4. Fuel consideration 17 5. Advantages 20 6. Drawbacks 21 7. Applications 22 8. Conclusion 26
  • 2. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 2 LIST OF FIGURE SR. NO. NAME PG. NO. 1. THERMIONIC CONVERTER 7 2. RADIOISOTOPE THERMOELECTRIC GENERATOR 8 3. THERMOPHOTOVOLTAIC CELLS 10 4. AMTEC Direct Energy Conversion 12 5. BETAVOLTAIC CELL 14 6. Radioisotope piezoelectric generator 16 7. Power Density 19
  • 3. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 3 CHAPTER 1 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. Since then the nuclear has taken a significant consideration in the energy source of future. Also, with the advancement of the technology the requirement for the 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 life span 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. Unlike conventional nuclear power generating devices, these power cells do not rely on a nuclear reaction or chemical process do not produce radioactive waste products. The nuclear battery
  • 4. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 4 technology is geared towards applications where power is needed in inaccessible places or under extreme conditions. The researchers envision its uses in pacemakers and other medical devices that would otherwise require surgery to repair or replace. Additionally, deep-space probes and deep-sea sensors, which are beyond the reach of repair, would benefit from such technology. In the near future this technology is said to make its way into commonly used day to day products like mobile and laptops and even the smallest of the devices used at home. Surely these are the batteries of the near future.
  • 5. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 5 CHAPTER 2 WHAT ARE NUCLEAR POWER BATTERIES? The terms atomic battery, nuclear battery, tritium battery and radioisotope generator are used to describe a device which uses energy from the decay of a radioactive isotope to generate electricity. Like nuclear reactors they generate electricity from atomic energy, but differ in that they do not use a chain reaction. Compared to other batteries they are very costly, but have extremely long life and high energy density, and so they are mainly used as power sources for equipment that must operate unattended for long periods of time, such as spacecraft, pacemakers, underwater systems and automated scientific stations in remote parts of the world. Nuclear battery technology began in 1913, when Henry Moseley first demonstrated the beta cell. The field received considerable in-depth research attention for applications requiring long-life power sources for space needs during the 50s and 60s. In 1954 RCA researched a small atomic battery for small radio receivers and hearing aids. After RCA development, over the years after many types and methods has been developed. The scientific principles are well known, but modern nano-scale technology and new wide band gap semiconductors have created new devices and interesting material properties not previously available. Batteries using the energy of radioisotope decay to provide long-lived power (10–20 years) are being developed internationally. Conversion techniques can be grouped into two types: thermal and non-thermal. The thermal converters (whose output power is a function of a temperature differential) include thermoelectric and thermionic generators. The non-thermal converters (whose output power is not a function of a temperature difference) extract a fraction of the incident energy as it is being degraded into heat rather than using thermal energy to run electrons in a cycle. Atomic batteries usually have an efficiency of 0.1–5%. High efficiency betavoltaics have 6–8%.
  • 6. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 6 CHAPTER 3 TYPES OF NUCLEAR BATTERIES Nuclear batteries are mainly classified into two main categories: I. THERMAL CONVERTERS The thermal converters are the devices which convert heat energy to electrical energy i.e. whose output power is a function of a temperature differential. Thermal converters are also classified into four types. 1. THERMIONIC CONVERTER A thermionic converter consists of a hot electrode which thermionically emits electrons over a potential energy barrier to a cooler electrode, producing a useful electric power output. Caesium vapor is used to optimize the electrode work functions and provide an ion supply (by surface contact ionization or electron impact ionization in a plasma) to neutralize the electron space charge. The scientific aspects of thermionic energy conversion primarily concern the fields of surface physics and plasma physics. The electrode surface properties determine the magnitude of electron emission current and electric potential at the electrode surfaces and the plasma properties determine the transport of electron current from the emitter to the collector. All practical thermionic converters to date employ caesium vapor between the electrodes, which determines both the surface and plasma properties. Caesium is employed because it is the most easily ionized of all stable elements. The surface property of primary interest is the work function, which is the barrier that limits electron emission current from the surface and essentially is the heat of vaporization of electrons from the surface. The work function is determined primarily by a layer of caesium atoms adsorbed on the electrode surfaces. The properties of the interelectrode plasma are determined by the mode of operation of the thermionic converter. In the ignited (or “arc”) mode the plasma is
  • 7. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 7 maintained via ionization internally by hot plasma electrons (~ 3300 K); in the unignited mode the plasma is maintained via injection of externally-produced positive ions into a cold plasma; in the hybrid mode the plasma is maintained by ions from a hot-plasma interelectrode region transferred into a cold-plasma interelectrode region. Fig. 1 THERMIONIC CONVERTER 2. RADIOISOTOPE THERMOELECTRIC GENERATOR A radioisotope thermoelectric generator (RTG, RITEG) is an electrical generator that obtains its power from radioactive decay. In such a device, the heat released by the decay of a suitable radioactive material is converted into electricity by the See beck effect using an array of thermocouples. RTGs have been used as power sources in satellites, space probes and unmanned remote facilities, such as a series of lighthouses built by the former Soviet Union inside the Arctic Circle. RTGs are usually the most desirable power source for robotic or unmaintained situations needing a few hundred watts (or less) of power for durations too long for fuel cells, batteries, or generators to provide economically, and in places where solar cells are not practical.
  • 8. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 8 Safe use of RTGs requires containment of the radioisotopes long after the productive life of the unit. RTGs were developed in the US during the late 1950s by Mound Laboratories in Miamisburg, Ohio under contract with the United States Atomic Energy Commission. Critics argue that they could cause environmental and security problems as leakage or theft of the radioactive material could pass unnoticed for years, particularly as the locations of some of these lighthouses are no longer known due to poor record keeping. In one instance, the radioactive compartments were opened by a thief. In another case, three woodsmen in Georgia came across two ceramic RTG heat sources that had been stripped of their shielding. Two of the three were later hospitalized with severe radiation burns after carrying the sources on their backs. The units were eventually recovered and isolated. There are approximately 1,000 such RTGs in Russia. All of them have long exhausted their 10-year engineered life spans. They are likely no longer functional, and may be in need of dismantling. Some of them have become the prey of metal hunters, who strip the RTGs' metal casings, regardless of the risk of radioactive contamination. Fig. 2 RADIOISOTOPE THERMOELECTRIC GENERATOR
  • 9. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 9 3. THERMOPHOTOVOLTAIC CELLS Thermo photovoltaic (TPV) energy conversion is a direct conversion process from heat differentials to electricity via photons. A basic thermophotovoltaic system consists of a thermal emitter and a photovoltaic diode cell. The temperature of the thermal emitter varies between different systems from about 900 °C to about 1300 °C, although in principle TPV devices can extract energy from any emitter with temperature elevated above that of the photovoltaic device (forming an optical heat engine). The emitter can be a piece of solid material or a specially engineered structure. A conventional solar cell is effectively a TPV device in which the Sun functions as the emitter. Thermal emission is the spontaneous emission of photons due to thermal motion of charges in the material. For normal TPV temperatures, this radiation is mostly at near infrared and infrared frequencies. The photovoltaic diodes can absorb some of these radiated photons and convert them into free charge carriers, that is electricity. Thermophotovoltaic systems have few, if any, moving parts and are therefore very quiet and require low maintenance. These properties make thermophotovoltaic systems suitable for remote-site and portable electricity-generating applications. Their efficiency-cost properties, however, are often rather poor compared to other electricity-generating technologies. Current research in the area aims at increasing the system efficiencies while keeping the system cost low. In the design of a TPV system, it is usually desired to match the optical properties of thermal emission (wavelength, polarization, direction) with the most efficient conversion characteristics of the photovoltaic cell, since unconverted thermal emission is a major source of inefficiency. Most groups focus on gallium antimonide (GaSb) cells. Germanium (Ge) is also suitable.[1] Much research and development in TPVs therefore concerns methods for controlling the emitter's properties. TPV cells have often been proposed as auxiliary power conversion devices for regeneration of lost heat in other power generation systems, such as steam turbine systems or solar cells.A prototype TPV hybrid car was even built. TPV research is a very active area. Among others, the University of Houston TPV Radioisotope Power Conversion Technology development effort is aiming at combining thermophotovoltaic cell concurrently with thermocouples to provide a 3 to 4-fold improvement in system efficiency over current radioisotope thermoelectric generators. TPVs have significant promise for efficient and economically viable power systems for both military and commercial applications. Compared to traditional nonrenewable energy sources, burner TPVs have little NOx emissions and are virtually silent. Solar TPVs, on the other hand, are a source of entirely renewable energy with no emissions. Compared to photovoltaics, TPVs can be more efficient owing to recycling of unabsorbed photons. However, the structure of TPVs is more complex, and losses at each energy conversion step can result in a lower efficiency than that of photovoltaics. Further developments must be made to the absorber/emitter and PV cell to realize its full potential as a renewable energy source. Unlike PVs, however, when TPVs are
  • 10. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 10 used with a burner source, they provide on-demand energy. As a result, no form of energy storage is needed. In addition, owing to the PV‟s proximity to the radiative source, TPVs can generate current densities 300 times that of conventional PVs. Fig. 3 THERMOPHOTOVOLTAIC CELLS 4. ALKALI-METAL THERMAL TO ELECTRIC CONVERTER The alkali metal thermal to electric converter (AMTEC), originally called the sodium heat engine (SHE) was invented by Joseph T. Kummer and Neill Weber at Ford in 1966. This device accepts a heat input in a range from about 900 K–1300 K and produces direct current with predicted device efficiencies of 15-40%. In the AMTEC sodium is driven around a closed thermodynamic cycle between a high temperature heat reservoir and a cooler reservoir at the heat rejection temperature. The unique feature of the AMTEC cycle is that sodium ion conduction between a high pressure or activity region and a low pressure or activity region on either side of a highly ionically conducting refractory solid electrolyte, is thermodynamically nearly equivalent to an isothermal expansion of sodium vapor between the same high and low pressure. Electrochemical oxidation of neutral sodium at the anode leads to sodium ions which traverse the solid electrolyte and electrons which travel from the anode through an external circuit where they
  • 11. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 11 perform electrical work, to the low pressure cathode, where they recombine with the ions to produce low pressure sodium gas. The sodium gas generated at the cathode then travels to a condenser at the heat rejection temperature of perhaps 400–700 K where liquid sodium reforms. The AMTEC thus is an electrochemical concentration cell which converts the work generated by expansion of sodium vapor directly into electric power. The converter is based on the electrolyte used in the sodium-sulfur battery, sodium beta"- alumina, a crystalline phase of somewhat variable composition containing aluminum oxide, Al2O3, and sodium oxide, Na2O, in a nominal ratio of 5:1, and a small amount of the oxide of a small cation metal, usually lithium or magnesium, which stabilizes the beta" crystal structure. The sodium beta"-alumina solid electrolyte (BASE) [ceramic] is nearly insulating with respect to transport of electrons, and is a thermodynamically stable phase in contact with both liquid sodium and sodium at low pressure. Single cell AMTECs with open voltages as high as > 1.55 V and maximum power density as high as > 0.50 W/cm² at temperature of 1173K (900°C) have been obtained with long term stable refractory metal electrodes. Efficiency of AMTEC cells has reached 16% in the laboratory. High voltage multi-tube modules are predicted to be 20% to 25% efficient, and power densities up to 0.2 kilowatts per liter appear to be achievable in the near future. Calculations show that replacing sodium with a potassium working fluid increases the peak efficiency from 28% to 31% at 1100 K with a 1 mm thick BASE tube. AMTEC requires energy input at modest elevated temperatures, and not at a specific wavelength, it is easily adapted to any heat source, including radioisotope, concentrated solar, external combustion, or nuclear reactor. A solar thermal power conversion system based on an AMTEC has advantages over other technologies (including photovoltaic systems) in terms of the total power that can be achieved with such a system and the simplicity of the system (which includes the collector, energy storage (thermal storage with phase change material) and power conversion in a compact unit). The overall system could achieve as high as 14 W/kg with present collector technology and future AMTEC conversion efficiencies. The energy storage system outperforms batteries, and the temperatures at which the system operates allows long life and reduced radiator size (heat reject temperature of 600 K). Deep-space applications would use radioisotope thermoelectric generators; hybrid systems are in design. While space power systems are of intrinsic interest, terrestrial applications will offer large scale applications for AMTEC systems. At the +25% efficiency projected for the device and projected costs of $350/kW, AMTEC is expected to prove useful for a very wide variety of distributed generation applications including self-powered fans for high efficiency furnaces and water heaters and recreational vehicle power supplies cathodic protection of pipelines, remote telemetry from oil well sites are other areas where this type of electrical generation might be
  • 12. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 12 used. The potential to scavenge waste heat may allow for integration of this technology into general residential and commercial cogeneration schemes although costs per kilowatt-hour would have to drop substantially from current projections. Fig. 4
  • 13. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 13 II. NON-THERMAL CONVERTERS Non-thermal converters extract a fraction of the nuclear energy as it is being degraded into heat. Their outputs are not functions of temperature differences as are thermoelectric and thermionic converters. Non-thermal generators can be grouped into five classes. 1. DIRECT CHARGING GENERATORS In the first type, the primary generators consists of a capacitor which is charged by the current of charged particles from a radioactive layer deposited on one of the electrodes. Spacing can be either vacuum or dielectric. Negatively charged beta particles or positively charged alpha particles, positrons or fission fragments may be utilized. Although this form of nuclear-electric generator dates back to 1913, few applications have been found in the past for the extremely low currents and inconveniently high voltages provided by direct charging generators. Oscillator/transformer systems are employed to reduce the voltages, then rectifiers are used to transform the AC power back to Direct Current. English physicist H.G.J. Moseley constructed the first of these. Moseley‟s apparatus consisted of a glass globe silvered on the inside with a radium emitter mounted on the tip of a wire at the center. The charged particles from the radium created a flow of electricity as they moved quickly from the radium to the inside surface of the sphere. As late as 1945 the Moseley model guided other efforts to build experimental batteries generating electricity from the emissions of radioactive elements. 2. BETAVOLTAICS Betavoltaics are generators of electrical current, in effect a form of battery, which use energy from a radioactive source emitting beta particles (electrons). A common source used is the hydrogen isotope, tritium. Unlike most nuclear power sources, which use nuclear radiation to generate heat, which then is used to generate electricity (thermoelectric and thermionic sources), betavoltaics use a non-thermal conversion process; converting the electron-hole pairs produced by the ionization trail of beta particles traversing a semiconductor. Betavoltaic power sources are particularly well-suited to low-power electrical applications where long life of the energy source is needed, such as implantable medical devices or military and space applications. The primary use for betavoltaics is for remote and long-term use, such as spacecraft requiring electrical power for a decade or two. Recent progress has prompted some to suggest using betavoltaics to trickle-charge conventional batteries in consumer devices, such as cell phones and laptop computers. As early as 1973, betavoltaics were suggested for use in long-term medical devices such as pacemakers.
  • 14. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 14 Although betavoltaics use a radioactive material as a power source, the beta particles used are low energy and easily stopped by shielding, as compared to the gamma rays generated by more dangerous radioactive materials. With proper device construction (that is, proper containment), a betavoltaic device would not emit dangerous radiation. Leakage of the enclosed material would engender health risks, just as leakage of the materials in other types of batteries leads to significant health and environmental concerns. As radioactive material emits, it slowly decreases in activity. Thus, over time a betavoltaic device will provide less power. For practical devices, this decrease occurs over a period of many years. For tritium devices, the half-life is 12.32 years. In device design, one must account for what battery characteristics are required at end-of-life, and ensure that the beginning-of-life properties take into account the desired usable lifetime. Liability connected with environmental laws and human exposure to tritium and its beta decay must also be taken into consideration during risk assessment and product development. Naturally, this increases both time-to-market and the already high cost associated with tritium. A 2007 report by the UK government's Health Protection Agency Advisory Group on Ionizing Radiation declared the health risks of tritium exposure to be double those previously set by the International Commission on Radiological Protection located in Sweden. Fig. 5 BETAVOLTAIC CELL
  • 15. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 15 3. ALPHAVOLTAICS Alpha voltaic power sources are devices that use a semiconductor junction to produce electrical particle from energetic alpha particles. 4. OPTOELECTRIC An opto-electric nuclear battery is a device that converts nuclear energy into light, which it then uses to generate electrical energy. A beta-emitter such as technetium-99 or strontium-90 is suspended in a gas or liquid containing luminescent gas molecules of the excimer type, constituting a "dust plasma." This permits a nearly lossless emission of beta electrons from the emitting dust particles. The electrons then excite the gases whose excimer line is selected for the conversion of the radioactivity into a surrounding photovoltaic layer such that a lightweight, low- pressure, high-efficiency battery can be realised. These nuclides are relatively low-cost radioactive waste from nuclear power reactors. The diameter of the dust particles is so small (a 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 (such as krypton, argon, and xenon) with excimer 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 e.g. diamond which convert the optical energy generated from the radiation into electrical energy. The battery would consist of an excimer of argon, xenon, or krypton (or a mixture of two or three of them) in a pressure vessel with an internal mirrored surface, finely-ground radioisotope, and an intermittent ultrasonic stirrer, illuminating a photocell with a bandgap tuned for the excimer. When the beta active nuclides (e.g., krypton-85 or argon-39) emit beta particles, they excite their own electrons in the narrow excimer band at a minimum of thermal losses that this radiation is converted in a high band gap photovoltaic layer (e.g. in p-n diamond) very efficiently into electricity. The electric power per weight compared with existing radionuclide batteries can then be increased by a factor 10 to 50 and more. If the pressure-vessel is carbon fiber/epoxy the weight-to-power ratio is said to be comparable to an air-breathing engine with fuel tanks. The advantage of this design is that precision electrode assemblies are not needed, and most beta particles escape the finely-divided bulk material to contribute to the battery's net power.
  • 16. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 16 5. RECIPROCATING ELECTROMECHANICAL ATOMIC BATTERIES A Radioisotope piezoelectric generator converts energy stored in the radioactive material directly into motion to generate electricity by the repeated deformation of a piezoelectric material. This approach creates a high-impedance source and, unlike chemical batteries, the devices will work in a very wide range of temperatures. A piezoelectric cantilever is mounted directly above a base of the radioactive isotope nickel-63. All of the radiation emitted as the millicurie-level nickel-63 thin film decays is in the form of beta radiation, which consists of electrons. As the cantilever accumulates the emitted electrons, it builds up a negative charge at the same time that the isotope film becomes positively charged. The beta particles essentially transfer electronic charge from the thin film to the cantilever. The opposite charges cause the cantilever to bend toward the isotope film. Just as the cantilever touches the thin-film isotope, the charge jumps the gap. That permits current to flow back onto the isotope, equalizing the charge and resetting the cantilever. As long as the isotope is decaying - a process that can last for decades - the tiny cantilever will continue its up-and-down motion. As the cantilever directly generates electricity when deformed, a charge pulse is released each time the cantilever cycles. Radioactive isotopes can continue to release energy over periods ranging from weeks to decades. The half-life of nickel-63, for example, is over 100 years. Thus, a battery using this isotope might continue to supply useful energy for at least half that time. Researchers have demonstrated devices with about 7% efficiency with high frequencies of 120 Hz to low-frequency (every three hours) self-reciprocating actuators. Fig. 6 Radioisotope piezoelectric generator
  • 17. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 17 CHAPTER 4 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. Strontium-90 gives off no gamma radiation so it does not necessitate the use of thick lead shielding for safety.strrrontium-90 does not exist in nature, but it is one of the several radioactive waste products resulting from nuclear fission. The utilizable energy from strontium-90 substantially exceeds the energy derived from the nuclear fission which gave rise to this isotope.
  • 18. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 18 Once the present stores of nuclear wastes have been mined, the future supplies of strontium-90 will depend on the amount of nuclear electricity generated hence strontium-90 decay may ultimately become a premium fuel for such special uses as for perpetually powered wheel chairs and portable computers. Plutonium-238 dioxide is used for space application. Half life of tantalum-180m is about 1015 years. In its ground state, tantalum-180 (180Ta) is very unstable and decays to other nuclei in about 8 hours but its isomeric state, 180m Ta, is found in natural samples. Tantalum 180m hence can be used for switchable nuclear batteries.
  • 19. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 19 Fig. 7
  • 20. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 20 CHAPTER 5 ADVANTAGES The most important feat of nuclear cells is the life span they offer, a minimum of 10years! This is whopping when considered that it provides non stop electric energy for the seconds spanning these 10long years, which may simply mean that we keep our laptop or any hand held devices switched-on for 10 years nonstop. Contrary to fears associated with conventional batteries nuclear cells offers reliable electricity, without any drop in the yield or potential during its entire operational period. Thus the longevity and reliability coupled together would suffice the small factored energy needs for at least a couple of decades. The largest concern of nuclear batteries comes from the fact that it involves the use of radioactive materials. This means throughout the process of making a nuclear battery to final disposal, all radiation protection standards must be met. Balancing the safety measures such as shielding and regulation while still keeping the size and power advantages will determine the economic feasibility of nuclear batteries. Safeties with respect to the containers are also adequately taken care as the battery cases are hermetically sealed. Thus the risk of safety hazards involving radioactive material stands reduced. As the energy associated with fissile material is several times higher than conventional sources, the cells are comparatively much lighter and thus facilitates high energy densities to be achieved. Similarly, the efficiency of such cells is much higher simply because radioactive materials in little waste generation. Thus substituting the future energy needs with nuclear cells and replacing the already existing ones with these, the world can be seen transformed by reducing the green house effects and associated risks. This should come as a handy savior for almost all developed and developing nations. Moreover the nuclear produced therein are substances that don‟t occur naturally. For example strontium does not exist in nature but it is one of the several radioactive waste products resulting from nuclear fission.
  • 21. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 21 CHAPTER 6 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. Above all, to gain social acceptance, a new technology must be beneficial and demonstrate enough trouble free operation that people begin to see it as a “normal” phenomenon. Nuclear energy began to loose this status following a series of major accidents in its formative years. Acceptance accorded to nuclear power should be trust-based rather than technology based. In other words acceptance might be related to public trust of the organizations and individuals utilizing the technology as opposed to based on understanding of the available evidence regarding the technology.
  • 22. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 22 CHAPTER 7 APPLICATIONS Nuclear batteries find many fold applications due to its long life time and improved reliability. In the ensuing era, the replacing of conventional chemical batteries will be of enormous advantages. This innovative technology will surely bring break-through in the current technology which was muddled up in the power limitations. Space applications In space applications, nuclear power units offer advantages over solar cells, fuel cells and ordinary batteries because of the following circumstances: 1. When the satellite orbits pass through radiation belts such as the van-Allen belts around the Earth that could destroy the solar cells 2. Operations on the Moon or Mars where long periods of darkness require heavy batteries to supply power when solar cells would not have access to sunlight 3. Space missions in the opaque atmospheres such as Jupiter, where solar cells would be useless because of lack of light. 4. At a distance far from the sun for long duration missions where fuel cells, batteries and solar arrays would be too large and heavy. 5. Heating the electronics and storage batteries in the deep cold of space at minus 245° F is a necessity. So in the future it is ensured that these nuclear batteries will replace all the existing power supplies due to its incredible advantages over the other. The applications which require a high power, a high life time, a compact design over the density, an atmospheric conditions- independent it is quite a sure shot that future will be of „Nuclear Batteries‟. NASA is on the hot pursuit of harnessing this technology in space applications.
  • 23. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 23 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. The first implanted cardiac pacemaker used nickel-cadmium rechargeable battery, later on zinc-mercury battery was developed and used which lasted for over two years. Lithium iodide battery, developed in 1972 made the real impact to implantable cardiac pacemakers and is on the way. But it draws the serious threat lasts for about ten years and this is a serious problem. The life time solution is nuclear battery. Nuclear batteries are the best reliable and it lasts lifetime. The definitions for some of the important parts of the battery and its performances are parameters like voltage, duty cycle, temperature, shelf life, service life, safety and reliability, internal resistance, specific energy (watt-hour/ kg), specific power (watts/kg), and in all that means nuclear batteries stands out. The technical advantages of nuclear batteries are in terms of its longevity, adaptable shapes and sizes, corrosion resistance, minimum weight, excellent current drain that suits to cardiac pacemakers.
  • 24. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 24 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. Automobiles Although it is on the initial stages of development, it is highly promised that the nuclear batteries will find a sure niche in the automobiles replacing the weary conventional iconic fuels there will be no case such as running out of fuel and running short of time. „Fox valley auto association, USA‟ already conducted many seminars on the scopes and they are on the way of implementing this. Although the risks associated the usage of nuclear battery, even concerned with legal restrictions are of many, but its advantages over the usual gasoline fuels are overcoming all the obstacles. Military applications The army is undertaking a transformation into a more responsive, deployable, and sustainable force, while maintaining high levels of lethality, survivability and versatility. In unveiling this strategy, the final resource that fit quite beneficial is „nuclear battery‟. “TRACE photonics, U.S. Army Armaments Research, Development and Engineering Centre” has harnessed radioisotope power sources to provide very high energy density battery power to
  • 25. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 25 the men in action. Nuclear batteries are much lighter than chemical batteries and will last years, even decades. No power cords or transformers will be needed for the next generation of micro electronics in which voltage-matched supplies are built into components. Safe, long-life, reliable and stable temperature is available from the direct conversion of radioactive decay energy to electricity. This distributed energy source is well suited to active radio frequency equipment tags, sensors and ultra wide-band communication chips used on the modern battlefield. Underwater sea probes and sea sensors The recent flare up of Tsunami, Earthquakes and other underwater destructive phenomenon has increased the demand for sensors that keeps working for a long time and able to withstand any crude situations. Since these batteries are geared towards applications where power is needed in inaccessible places or under extreme conditions, the researchers envision its use as deep-sea probes and sensors, sub-surface, coal mines and polar sensor application s, with a focus on the oil industry. And the next step is to adapt the technology for use in very tiny batteries that could power micro- electro-mechanical-systems (MEMS) devices, such as those used in the optical switches or the free floating “smart-dust” sensors being developed by the military.
  • 26. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 26 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 throughout 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.
  • 27. Nuclear Batteries Department of Electrical Engineering_AGI_Jaipur_2013-2014 Page 27 REFERENCES # “Power from radioisotopes,” USAEC, Division of Technical Information # Powerstream.com # Powerpaper.com # Technologyreview.com # Wikipedia.com/atomic_battery