The simplest form of nuclear battery is the Burke Cell (
US Patent # 3,939,366, Ref. 4). [This patent for a betavoltaic type of nuclear power device was issued to Yasuro Ato and Soji Miyagawa of the Agency of Industrial Science & Technology of Japan, so I not sure why he referred to it as Burke Cell. If a Burke Cell is a device, I haven't seen anything about it. A
Holmes and Burke Cell is apparently a type of zinc-acid battery, but that's probably unrelated.] This method consists of a conventional battery and a conventional load connected by means of a radioactive conductor. If we inspect this arrangement we find that all of the power dissipated in the load is not drawn from the battery. And upon closer examination we find that a current amplification occurs within the radioactive conductor (Ref. 3).
This phenomenon is known as the Beta Voltaic Effect, and it may be explained by referring to Figure 6. For the simple case of this example, we will set the radioactive source (any alpha or beta emitter) external and separate from a silver wire. Now the battery from Figure 5 provides an electromotive force (emf) across the wire and consequently, conduction electrons within the wire are set in uniform motion. By definition, electricity is measured in terms of the number of charged particles (electrons) moving past a point in a unit of time and we call this amperes.
The process by which a beta particle is absorbed, is such that the beta particle collides with the molecular structure of the copper, knocking electrons free. This electron avalanche occurs until the beta particle (electron) effectively comes to rest. A single beta particle emitted from strontium-90 that is absorbed in copper will generate 80,000 ions in a distance of 0.030 inches. Now, as soon as these electrons are knocked loose, they effectively become free electrons in the wire, and as such these additional electrons are acted upon by the emf applied across the wire to give the avalanche electrons a uniform direction of flow, regardless of their incident angle. This increase in the number of moving charged carriers is measured in the real world as increased current. We also measure a reduction in the resistance of the wire (Ref. 6), an increase in its conductivity (Ref. 7), while the current is directly proportional to the voltage (Ref. 8). In other words, the current goes up with an increase in voltage (Ref. 5). This is basically attributed to the increased emf acting on a greater number of avalanche electrons.
Additionally, flux cutting also occurs as the beta particle approaches the current carrying wire which yields an emf to help drive electrons (Ref. 9).
Now we will look at how we apply this phenomenon to our device. Figure 7 depicts a basic LC tank circuit comprised of an inductor and a capacitor. Theoretically, if this LC circuit were superconductive, then an externally applied electric impulse would yield an LC oscillation that would continue to oscillate forever due to no losses in the system.
However, our LC circuit is not superconductive, and the oscillation damps out due to the losses inherent to the LC tank. To minimize these inherent losses, we tune the circuit into resonance at the self-resonant frequency of the inductor. This causes the inductive and capacitive reactances to cancel, leaving only ohmic losses (resistance).
If we apply a radioactive source as part of the LC tank, then through every cycle of the oscillation of which current is flowing, that current gets amplified by an amount proportional to the activity of the source. All we need is an input of an amount of energy equal to the system losses to achieve a sustained oscillation. At this point, we have a self-driven oscillator that we call a Nuclear Powered Oscillator.
Any energy contributed to this oscillating LC tank must be removed and we accomplish this by simply impedance-matching a transformer which yields high-frequency AC current to drive a load. In a nutshell, that is the principle of operation for the Resonant Nuclear Power Supply: an LC tank circuit oscillating at its self-resonant frequency, driven by natural radioactive decay energy. Energy in excess of the operational requirements is removed through a transformer to yield electrical energy in usable form to drive a load.
Figure 10 depicts the starting method which involves the use of a high voltage source to charge the capacitor of the tank circuit, which is then discharged to ground through a Class C amplifier at a rate equal to the resonant frequency of the tank circuit. A spectrum analyzer is used to monitor the activity within the tank and once a clean oscillation is started, the high voltage power supply and Class C amplifier are removed, a process that takes a few seconds. Then the power removed from the tank circuit is determined by measuring the voltage drop across a resistor of known value and double-checked by directly measuring the current delivered to the load.
In 1985, a feasibility study was performed including a search of the published literature. This revealed a significant amount of supportive data. Experiments followed on the effects of alpha and beta radiation absorbed in a current-carrying inductor. The results demonstrated (1) a reduction in the resistance of the coil, (2) an increase of the quality factor (Q) of the circuit, and (3) an increased conductivity of the inductor.
A proof of feasibility prototype was built in early 1987, which yielded 75 watts of power. Although the device generated electricity, it also demonstrated a frequency stability problem and showed signs of material degradation.
In mid-1988 a co-development venture was initiated with Atomic Energy of Canada's Radiochemical Company for the purpose of exploring source configuration possibilities in regard to performance and safety parameters.
Our efforts in 1989 primarily centered around optimization of the oscillator, which must be of a design with a high Q, tight coupling, and low loss.