Nuclear Batteries

Since the 1950s, numerous designs have been developed for Nuclear Batteries as a long lived, compact, portable source of electrical power.

Nuclear Thermal Battery
In the Nuclear Thermal Battery, the heat generated by radioactive decay of a radioactive substance is converted into electricity by a thermoelectric generator (e.g. a Peltier element). This uses the Peltier/Seebeck Effect to convert a temperature gradient directly into electricity. This technology is used on space probes but its efficiency is low.

Betavoltaic Battery
In the Betavoltaic battery, which has been known for over 50 years, a semiconductor PN junction is exposed to beta particles (electrons) emitted by a radioactive substance. This in turn then generates electricity.

In May 2005, the University of Rochester announced the development of a 3D Silicon Diode fabricated in porous silicon. This greatly increases the PN junction surface area exposed to beta radiation from a tritium radioactive source. The tritium is incorporated into a plastic to prevent its accidental loss. The technology has been licensed to BetaBatt Inc, who call it the Direct Energy Conversion Cell or DEC Cell.

Betabatt state that the power developed by this technology is between 50 and 125 microWatts per cc of active material. It is therefore a very low power source, suitable for long life applications where battery replacement is difficult or inconvenient.

For an example of an earlier version of this technology, see US Patent 3,094,634 issued in 1963. This used a PN junction formed by Silicon doped with Boron on one side and Silicon doped with Antimony on the other.

Resonant Nuclear Battery
Not only PN junctions but any dipole or potential barrier - such as the electric field between the plates of a capacitor, a metal-semiconductor junction, a metal to dissimilar metal contact potential - exposed to radiation will give rise to an electric current flow. Radiation that is absorbed in the vicinity of any potential barrier will generate separated electron-hole pairs which in turn flow as electric current under the influence of the electric potential field.

In the 1980s, researcher Dr Paul Brown used the Betavoltaic effect to develop what he called the Resonant Nuclear Battery. The beta particles from a radioactive source (Sr90 or Kr85) are absorbed by a Beryllium-Copper resistor linked to an LC tank circuit with a coil made of Silver. Each beta particle absorbed by a copper wire releases 80,000 free electrons within a distance of 0.762mm. With a potential applied to the wire, these free electrons will flow, creating a current.

An earlier version of this concept was patented in 1970 by Burke (US 3,530,316). The basic principle is shown on the right.

A copper canister was filled with Strontium 90 and connected in series with a battery and load. The free electrons generated in the copper canister by the radioactive decay of the Sr90 then amplify the current supplied by the battery and power the load.

It can be seen that a High Impedance Battery (a battery with a high internal resistance) that supplies voltage but little current would be ideally suited for this system. The battery supplies very little current and so will have a very long life; current is supplied instead by the radioactive source. This combines with the voltage source (the battery) to provide a Combined High Power Source of long life.

Paul Brown's Resonant Nuclear Power Supply is effectively an LC tank circuit oscillating at its self resonant frequency driven by radioactive decay energy.

A small prototype the size of a soup can produced a continuous 75W.

This technology used waste Strontium 90 or Krypton 85 from spent nuclear fuel rods.

 

References

1. "Resonant Nuclear Battery May Aid in Mitigating the Greenhouse Effect", PM Brown, Trans. Am. Nucl. Soc., 60, 491, (1989).

2."Electric Power Methods and Apparatus", JO Burke, US 3,530,316

Battery Motors Atmospheric Remediation

 
 
 

Copyright 2005 Meridian International Research
Last updated 22/09/05