SUPERCOMPACT RADIO NUCLIDE BATTERY

Abstract: A light weight nuclide battery, being supercompact, relatively low cost, and relatively low maintenance. Dust particles are made of radioactive isotopes where very little if any gamma radiation is emitted. Nuclides from low cost radioactive waste of nuclear power reactors are used. The dust particles have small diameters so beta decay leaves nearly without loss. Surrounding weakly ionized plasma has gases with excimer lines and surrounding walls contain photovoltaic layers with wide forbidden zones so much of the energy of beta electrons are converted into electric energy. Power density is increased by increasing the battery pressure above atmospheric pressure.

Description: SUPERCOMPACT RADIO NUCIJDE BATTERY TECHNICAL FIELD The present invention relates to nuclide batteries and, more particularly, to light weight nuclide batteries. BACKGROUND OF THE INVENTION As elaborated before in the patent application DE 196 38 066.2, the topic is the following. Radio nuclide batteries usually are very inefficient, heavy and expensive, but nevertheless are needed in space crafts and similar important applications. A remarkable reduction in weight and increase in efficiency is possible when the beta active nuclides {e.g., krytpon-85 or argon-39) are exciting their own electrons in the narrow excimer band at a minimum of thermal losses and this radiation is converted in a high band gap photovoltaic layer {e.g., in p-n diamond) very efficiently into electricity (German Patent disclosure 196 02 875 Al). The electric power per weight compared with existing radio nuclide batteries can then be increased by a factor 10 to 50 and more. The disadvantage consists in the yet high price of the mentioned radio nuclides and in the high pressure of up to 100 bar and more for the gas that requires an expensive and heavy container. What is well known are the dust plasmas. The dust plasmas were predicted by Izeki (Phys. Fluids 29, 1764 (1986) and realized since 1994 (V. E. Fortov, et al, Pisma ZhETP 1994 reported about dust plasmas at atmospheric pressure, see also V. E. Fortov, et al., ionization rate is produced, e.g., by a microwave or RF discharge or by electron beam irradiation (120 keV, 0.02 mA/cm 2 , if solid or liquid (dust) particles of diameters between 1 and 100 μm are dispersed in this plasma, the double layer between plasma and particle causes a charging of the particles by 1000 to 1 million electron charges. The Coulomb forces between the particles lead to their repulsion such that crystalline orders are being produced (plasma or dust crystals) depending on a very high plasma parameter. The mechanisms of the Debye length and the charging by double layers is well known (S. Eliezer and H. Hora, Physics Reports (172, 339 (1989)). SUMMARY OF THE INVENTION The present invention resides in a radio nuclide battery such that the nuclide is located on dust particles which are suspended in a gas or plasma where the radioactivity generated radiation is converted into electricity by photovoltaic layers in the boundary surface of the plasma. The plasma state of the gas in an aspect of the invention is produced by an external dc discharge. In another aspect of the invention, the plasma state of the gas is produced by an ac discharge including the high frequency of microwave range. In a further aspect of the invention, the plasma state of the gas is produced by irradiation of electron beams of at least keV energy. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates a supercompact radio nuclide battery of the present invention. Figure 2 is a cross-sectional view of the supercompact radio nuclide battery of Figure 1. Figure 3 is a detailed view of a portion of the cross-sectional view of Figure 3. DETaAILED DESCRIPTION OF THE INVENTION An additional detailed description and an addition of the claims are given to the Patent Application DE 196 38 066.2: "Solid or liquid state emitters of the size around 0.1 to 50 μm diameter suspended in gas or plasma containing luminescent gas particles, e.g., of the excimer type, consisting in a dust plasma. This permits a nearly lossless emission of beta electrons from the emitting dust particles for excitation of the gases whose excimer line is adjusted for the conversion of the radioactivity into a surrounding photovoltaic layer such that a comparably light weight low pressure battery of high efficiency can be produced. The mentioned disadvantages of the krypton-excimer battery (DE 196 02 875 Al) are despite of the reached hitherto most compact radio nuclide battery (highest electric power per weight): high costs of the beta active nuclides, a residual (for krypton-85) vert kiw rest gamma emission, the problem of removal of the generated alkali metals after the beta decay: all these disadvantages can be avoided and an essential increase of the compactness of the battery can be reached, if - according to the invention - with solid beta emitters without -and gamma emission is being worked which are a component of a dust plasma, beta electrons are emitted with a minimum o losses into an excimer active gas where the energy (of the beta electrons) is highly efficiently converted into a narrow band excimer radiation, which provides electric-energy in wide band gap photovoltaic layers. According to the invention, the dust particles are made of radioactive isotopes, e.g., little particles of elementary strontium-90 or chemical compounds of strontium-90, or of technetium 99 (=Masurium-99) where not any or very little gamma radiation is emitted. These nuclides are low cost radioactive waste of nuclear power reactors. The diameter of the dust particles is so small (few micrometers), such that the electrons from the beta decay leave the dust particles nearly without loss. The surrounding weakly ionized plasma consists at least partially of gases or gas mixtures {e.g., krypton, argon, xenon) with excimer lines, such that a considerable amount of the energy of the beta electrons is being converted into this radiation. The surrounding walls contain photovoltaic layers with wide forbidden zones as, e.g., diamond, which convert the optical energy generated from the energy of the beta electrons into electric energy. An especially high power density (electric power per weight) much higher than from before mentioned radio nuclide batteries without dust plasmas are being reached, e.g., a 500 Watts battery of 5 kg weight where not any radiation screening is necessary. This high power density can be further increased if, e.g., instead of working at atmospheric pressure a higher one is used. E.g., at 10 atmospheres working pressure a battery to 1 kW is being produced with a weight of 1.5 kg. Thus these batteries accordmg to the invention are called supercompact. At initial operation, the non-equilibrium plasma needs an excitation between the dust particles where the needed energy is remarkably left than the gain of the battery. An improvement of the battery according to the invention the following described design I possible without additional electrical discharge. For this purpose (apart from the initiation of the performance) instead of using a plasma generating electron beam current J. of 120 keN electrons of about 0.02 mA/cm, current density, the emission of the beta electrons form the particles is being chosen of at least the same electron density which generate the equilibrium of the dust plasma with its negative charging of the dust particles as well of the wall in order to produce the mutual repulsion of the particles an their repulsion form the wall. One problem appeared with the question of three-dimensional crystal structure of the dust particles. It is well known that one dimensional crystals can be produced (a chain of dust particles) of two dimensional dust crystals within the gravitation field (A. Hosemann, A. Meizer, S. Peters, R. Madani and A. Piel, Physics Letters, A242, 173 (1998) what is not possible with three dimensions because of the gravitation. According to the inventions, however, three-dimensional crystals can be produced if the gravitation is compensated by an electric field. These fields are in the range of 10 N/cm and produce a loss current through the plasma, which on the other hand can be used for exciting the plasma. In the case according to the invention that no external discharge current or an external electron beam excitation is being performed, the current J. for the gravitation compensating electric field is then a loss factor. The electric field E (in N/cm) for compensation of gravitational forces for a mechanical accelerating in m/5 2 within the reaction chamber is given by the following working parameters according to the invention. Where Pd is the density (in kg/m 3 ) of the particles and the direction of E is the same as the gravitational field eo is the electrical (influence) constant l^ is the average diameter of the dust particles and 0 tangling potential which is large than 1.5 Volts. Using the battery in space crafts at zero gravitation, the compensation current Id can be dropped and has to be used only for the stages before the gravitation free flight are reached. In Figure 1 is an example of a supercompact radio nuclide battery described, the left hand part of the figure consists in a rectangularly drawn container with xenon gas (dotted area) which is being excited containing dust particles of strontium-90 (as element or as compound). Furthermore there are the black drawn electrodes to produce the electric field in an antiparallel way to the gravitation field. Between the dust plasma there are cylindrical or plane parts which are separately drawn at the right hand side of the figure in the inner part is a metal cylinder or plate covered by a photovoltaic layer. Preferably of CVP-or VCE-produced diamond {see Hora and Prelas, Diamond and Related Materials, 4, 1376 (1995) or of aluminiumnitrid layers (H. Hora, R. HopfL M.A. Prelas. "Theoretical Aspects of AIN and Diamond In View of Laser and Photovoltaic Action," NATO Advanced Workshop on Wide Band Electronic Material, Minsk, 1944, p. 487-502) having a p-n junction. These diamond (or AIN) layers are covered by an optically semitransparent conduction layer (a for the minus pulse and the inner metal as a plus pole of the photovoltaic cell). The beta electrons e from the strontium-90 in the dust particles produce photons of energy E pt = hv in the xenon gas which primarily are in the small excimer band. Photons from these ranges are adjusted in an optimum way to the semiconductor bands width of diamond or AIN, such that at least 60% of the photon energy is converted into electrical energy. The photovoltaic elements are linked - as seen in Figure 1 in series producing the output power. If lower voltages are desired, the linking is being done partially or completely in parallel way. The dimensioning of the container, is pressure properties and properties of the emission of thermal radiation due to the still remaining, but highly reduced thermal losses in the battery, follows similarly as in Patent Application DE 196 02 875A1). For operation in space without gravitation, the electrical field can be reduced or completely switched off. The strontium-90 in the dust particles is converted by the beta emission without gamma emission into indium which had properties of solids and is being contained within the dust Particles contrary to the rubidium, e.g., in the Kr-85 battery where a special procedure is necessary for its removing.

Claims: CLAIMS Radio nuclide battery, such that the nuclide is located in dust particles which are 2. suspended in a gas or plasma where the radioactivity generated radiation is converted into electricity by photovoltaic layers in the boundary surface of the plasma, 3. Radio nuclide battery according to claim 1, such that the plasma state of the gas is produced by an external dc discharge. 3. Radio nuclide battery according to claim 1, such that the plasma state of the gas is produced by an ac discharge including the high frequency of microwave range. 4. Radio nuclide battery according to claim 1, such that the plasma state of the gas is produced by irradiation of electron beams of at least keV energy. 5. Radio nuclide battery according to claims 1 to 4, such that the dust particles are solid or liquid of a diameter between 0.01 and 100 u 6. Radio nuclide battery according to claim 1, such that no external energy source for the discharge is applied. 7. Radio nuclide battery according to claim 1 and 6, such that the dust is a stable aerosol. 8. Radio nuclide battery according to claims 1 and 5, such that the partially plasmatized gas between the dust particles is stationary produced by the radioactive emission from the radio nuclide contained in the dust particles. 9. Radio nuclide battery according to claims 1 to 8, such that the inner wall of the container is made of an insulator optically partially transparent to the radiation from the plasma. 10. Radio nuclide battery according to claims 1 to 9, such that the radio nuclide is a beta emitter. 11. Radio nuclide battery according to claims 1 to 10, such that the radio nuclide is a beta emitter without gamma emission. 12. Radio nuclide battery according to claims 1 to 9, such that the radio nuclide is an alpha emitter. 13. Radio nuclide battery according to claims 1 to 12, such that the photovoltaic converter is a wide band gap material. 14. Radio nuclide battery according to claims 1 to 13, such that the gas between the dust particles contain atoms of molecules which have narrow excimer lines.

Inventors: BARNOV WLADIMIR JUREWITSCH, BOODY FREDERICK P, FORTOV WLADIMIR EUGENOWITSCH, HOPFL REINHARD, HORA HEINRICH, PAL ALEKSANDR FRIEDRICHOWITSCH, PRELAS MARK ANTONY, STAROSTIN ANDREY NIKONOWITSCH, BARNOV, WLADIMIR JUREWITSCH, BOODY, FREDERICK, P., FORTOV, WLADIMIR EUGENOWITSCH, HOPFL, REINHARD, HORA, HEINRICH, PAL, ALEKSANDR FRIEDRICHOWITSCH, PRELAS, MARK, ANTONY, STAROSTIN, ANDREY NIKONOWITSCH
Applicants: BARNOV WLADIMIR JUREWITSCH, BOODY FREDERICK P, FORTOV WLADIMIR EUGENOWITSCH, HOPFL REINHARD, HORA HEINRICH, PAL ALEKSANDR FRIEDRICHOWITSCH, PRELAS MARK ANTONY, RHOMBIC CORP, STAROSTIN ANDREY NIKONOWITSCH, BARNOV, WLADIMIR JUREWITSCH, BOODY, FREDERICK, P., FORTOV, WLADIMIR EUGENOWITSCH, HOPFL, REINHARD, HORA, HEINRICH, PAL, ALEKSANDR FRIEDRICHOWITSCH, PRELAS, MARK, ANTONY, RHOMBIC CORPORATION, STAROSTIN, ANDREY NIKONOWITSCH
Application year: 1998
Main classification: H01L31
IPC codes: G21H3