Optoelectric nuclear battery
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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.
- High price of the radionuclides.
- High-pressure (up to 10 MPa (100 bar)) heavy containment vessel.
- A failure of containment in this form of device would release high-pressure jets of finely divided radioisotopes, forming an effective Dirty Bomb.
The inherent risk of failure is likely to limit this device to space-based applications, where the finely divided radioisotope source is only removed from a safe transport medium, and placed in the high-pressure gas, after the device has left Earth orbit.
- Atomic battery
- Radioisotopic Thermoelectric Generator
- Radioisotope piezoelectric generator
Polymers, Phosphors, and Voltaics for Radioisotope Microbatteries, by Kenneth E. Bower (Editor), et al. US Patent 7,482,533-Nuclear-cored battery