Nuclear / Atomic Pacemakers

Nuclear batteries were introduced in the pacing industry around 1973 to prolong the longevity of the implanted device. Several pacemaker manufacturers of the time introduced nuclear models to their product lines. These devices offered young patients the possibility of having a single pacemaker implant last their whole life.

However, by the mid-1970s, nuclear pacemakers were displaced by devices powered by lithium cells. The lithium-powered units had a calculated longevity of approximately 10 years far shorter than the nuclear type. Why replace the battery with a less superior battery. The U.S is controlled by oil men and they seek to maintain a global oil paradigm, decentralized and safe nuclear energy escapes that paradigm.

The implant of nuclear-powered pacemakers stopped in the mid-1980s [Parsonnet et al.,1990]. Lithium-powered batteries are now the norm, and just a handful of patients remain implanted with nuclear pacemakers.

In the late 1960s Medtronic – today the largest manufacturer of implantable medical devices in the world - teamed up with Alcatel, a French company, to design a nuclear-powered pacemaker. The first human implant of the device took place in Paris in 1970. The nuclear battery (Figure 1) in the Medtronic device used a tiny 2.5 Ci slug of metallic Plutonium 238 (Pu-238). The radiation produced by the Pu-238 bombarded the walls of its container, producing heat that a thermopile then converted to an electrical current. A thermopile is a stack of thermocouples, which are devices that convert thermal energy directly into electrical energy using Seebeck effect. As shown in Figure 2, a thermocouple is made of two kinds of metal (or semiconductors) connected to each other in a closed loop. If the two junctions are at different temperatures, an electric current will flow in the loop.

Plutonium-238 decays with a half-life of approximately 85 years. As such, the radioisotope thermal generator (RTG) using this material will lose a factor of 0.81% of its capacity per year. Although the thermocouples used to convert thermal energy into electrical energy degrade as well, the electrical output of the complete assembly degrades by only 11% in 10 years. The pacemaker shown in Figure 3 still works well 35 years after it was manufactured.

Figure 1 – The nuclear battery developed by Alcatel for Medtronic used a tiny slug of metallic Plutonium 238. The heat produced by the decay of the Pu-238 was converted to electricity by a thermopile.

It's a heat source for a thermo-electric effect, Peltier effect

Figure 2 – In a thermocouple, a voltage - the thermoelectric EMF - is created in the presence of a temperature difference between two different metals or semiconductors. In the isotopic thermoelectric generator, many thermocouples are arranged in series/parallel to form a thermopile which produces useful power levels. One of the junctions of each thermocouple (e.g. T1) is exposed to the heat generated by the decay of the Pu-238, the other junction (e.g. T2) is at body temperature.

Amazing battery technology

One of the main problems of these isotopic generators is the extremely high toxicity of plutonium. Just 1μg in the blood stream could be fatal. Indeed, plutonium is among the sixth most toxic material ever discovered. It spontaneously bursts into flame upon contact with air, and then burns to give off a fine, highly-radioactive dust.

The various shields designed to prevent accidental escape of the plutonium fuel were responsible for most of the battery’s volume and weight. Multiple encapsulation layers were designed to protect the core against incineration, air-plane accidents and direct gunshot wounds.

Radiation was not a major concern. 1 mR/hr could be measured 2 cm away from the capsule.

Most of the pacemakers included some additional shielding, so wearing a plutonium-powered pacemaker delivered a dose of approximately 100 mrem per year to the patient. To put this in perspective, a healthy U.S. adult receives an average of 360 mrem every year from natural and medical sources, where between 26 and 96 mrem come from solar radiation, and about 40 mrem come from natural radioactivity in our food. A single transatlantic flight contributes about 2 mrem. Parsonnet et al. reported that the frequency of malignancy in his 155 nuclear-pacemaker patients was similar to that of the population at large and primary tumor sites were randomly distributed.

In fact, the radiation from plutonium-based pacemakers was so low that it was deemed harmless even for a pregnant woman. A pacemaker implanted in the abdomen was calculated to deliver a dose of 57 mrem during the full term, which is approximately 20 times less than the maximum allowable dose (1,125 mrem).

For alternative applications the thermal-generators rely on a heat element that requires additional attention, such as cooling. The thermal-electric effect is inefficient and a heat engine requires moving parts. Maintenance is high, what would be more better would be a source that doesn't have the thermal runaway issue. Maybe we can use the emitted electrons ballistically or directly.

Alternatively…

Unlike using a thermal effect, a transistor is used to sort the positive and negative particles, as they built up this causes an arc across the junction. Similar to the way lightning works.

At more or less the same time that implantable-grade plutonium cells made their appearance, McDonnell-Douglas Astronautics developed a different kind of nuclear cell for pacemakers. The Betacel 400 had promethium-147 sandwiched between semiconductor wafers (Figure 6). Promethium-147 is a soft β emitter with no γ lines. It has a half life of 2.6 years. As the radioactive promethium isotope decays, it emits β-particles (electrons). Internally, and as shown in Figure 7, the impact of the β-particles on a p-n junction causes a forward bias in the semiconductor similar to what happens in a photovoltaic cell (a solar cell). Electrons scatter out of their normal orbits in the semiconductor and into the circuit creating a usable electric current. The Betacel 400 had an open-circuit voltage of 4.7V and a short circuit current of 115μA. The maximum power output was 370μW. A pacemaker of the time (the current consumption of which could be modelled by a 200kΩ resistor) was expected to last for 10 years when powered by this nuclear battery.

A Betacel-powered nuclear pacemaker was implanted by Dr. Orestes Fiandra1 in Uruguay. The device, shown in Figure 8, was constructed by Dr. Fiandra’s factory in South America. This pacemaker stimulated the heart at a constant rate of 68 ppm. The first successful long-term human implant of a pacemaker was achieved in Uruguay on February 2, 1960 by Dr. Orestes Fiandra and Dr. Roberto Rubio. The pacemaker was manufactured by Elmqvist and was implanted in Uruguay in a 34-year-old patient with AV block. In 1969, Dr. Fiandra started manufacturing pacemakers at the “Centro de Construccion de Cardioestimuladores del Uruguay” (CCC for short).

A battery stores electricity while these generate electricity, their is no harmful radiation and no recharging. Simple versions of beta emitters may be incorporated with capacitors or batteries constantly charging an electrical device such as a phone. Ramped up versions cells and banks may not be able to power a house or electric car directly but can provide constant charging to a capacitor or battery bank in a decentralized electrical network where electricity is just another home appliance. While lithium exists there is no indications for the figures in the below chart.

City Labs is the first company in the betavoltaic battery industry to be granted a Product Regulatory General License to manufacture, sell, and distribute betavoltaic batteries. NanoTritium batteries are the first betavoltaic Tritium batteries to achieve such a classification.

• Nano-Tritium chips are stackable in series and parallel
• 0.8 Volts 50-350 nanoAmps
• 1.6 Volts 50-350 nanoAmps
• 2.4 Volts 50-350 nanoAmps
• Has defense contracts to research and produce

• Wicker Seminar Beta Voltaics Mike Spencer Cornell University PDF
• Jake Blanchard University of Wisconsin PDF
• Review Of Betavoltaic Energy Conversion by Larry C. Olsen PDF

• Strontium-90 is a commonly used beta emitter used in industrial sources. It is also been used as a thermal power source in radioisotope thermoelectric generator power packs. Strontium-90 based RTGs have been used to power remote lighthouses.
• Tritium is a low-energy beta emitter commonly used as a radiotracer in research and in tracer self-powered lightings and some “glow-in-the-dark” paints. The half-life of tritium is 12.3 years. The electrons from beta emission from tritium are so low in energy that a Geiger counter can not be used to detect them.
• Carbon-14 is also commonly used as a beta source in research, it is commonly used as a radiotracer in organic compounds. While the energy of the beta particles is higher than those of tritium they are still quite low in energy.
• Phosphorus-32 is a short-lived high energy beta emitter, which is used in research in radiotracers. It can be used in DNA research. Phosphorus-32 can be made by the neutron irradiation (np reaction) of sulphur-32 or from Phosphorus-31 by neutron capture.
• Nickel-63 is a special isotope of nickel that can be used as an energy source in Radioisotope Piezoelectric Generators. It has a half-life of 100.1 years. It can be created by irradiating Nickel-62 with neutrons in a nuclear reactor. Nickel 63 Production & Prospects

• Emergency power for beacons that can transmit location co-ordinates to GPS satellite for years if required. Smartphone, watches, planes, cars.
• Real-time systems that need to remain in a standby mode.
• Baseline emergency power, for example electric vehicle can have an emergency inexhaustible baseline power supply allowing 10km per hour inexhaustible, eliminating out of gas and just enough to get you to a charging station.

Aside from p-n junction betacell, by replacing the electrodes in a traditional battery with radioactive ones to create a nuclear battery, more specifically electrodes based on an Americium 231 anode and a Nickel 63 cathode, these are very clean emitters, non penetrating. Further shielding or cell design may be required so that the electrodes do not pull equality from the surrounding air or surrounding materials. The second type is using a common battery chemistry and using an additional circuit to restore the electrode state of the common battery so as to be a “self recharging battery”.

This practical method, uses a beta emitter such as tritium to excite phosphor to activate a solar panel to produce current. Tritium emits electrons through beta decay, and, when they interact with a phosphor material, fluorescent light is created, a process called radioluminescence. Identical to the way common fluorescent house lights work. We use an optimal beta source Sr90 to activate an optimal phosphorescent material and enclose that in a solar panel to create a cell.

Below is an example of how ambient electricity from the air is replaced by a constant source, a transmitter to a collector plate in order to raise reliability instead of reliance on a source that may or may not be there. Tritium is a weak beta emitter and expensive in small quantity. Baseline above zero is a philosophy that at full depletion auxiliary power is inexhaustible but modestly useful for getting back to a base station for instance electric vehicles.

Utilizing the Alpha radiation has not been as preferable as beta emitters. An alpha voltaic battery utilizes a radioactive substance that emits energetic alpha particles and is coupled to a semiconductor p/n junction diode. Alpha voltaics have not been technologically successful to date primarily because the alpha particles damage the semiconductor material, thus degrading the electrical output of the solar cell in just a matter of hours.

However the use of an alpha emitter with a piezoelectric effect may be better suited, alpha is the safest radiation, these micro or nano devices would lock a safe alpha emitting isotope into a piezoelectric chamber so that the force of the radiation travelling at close to the speed of light strikes to piezo material and registers some voltage. Required banks of these units would create a cell. Alpha emitting isotope candidates are Cm-243, Cf-250, Am-241 found in smoke detectors. The method is similar to the way atomic clocks work in that Caesium radiation strikes a quartz crystal registering a voltage, instead of registering the voltage as a tick of the atomic clock, ample alpha radiation through quartz crystal produces power.

Cassini’s electrical power source — Radio-isotope Thermoelectric Generators (RTGs)— have provided electrical power for some of the U.S. space program’s greatest successes, including the Apollo lunar landings and the Viking landers that searched for life on Mars. RTGs made possible NASA’s celebrated Voyager explorations of Jupiter, Saturn, Uranus and Neptune, as well as the Pioneer missions to Jupiter and Saturn. RTG power sources are enabling the Galileo mission to Jupiter, the international Ulysses mission studying the Sun’s polar regions, and the Cassini mission to Saturn. Extensive studies conducted by NASA’s Jet Propulsion Laboratory (JPL) showed that NASA’s Cassini mission, given its science objectives, available launch systems, travel time to its destination and Saturn’s extreme distance from the Sun, requires RTGs.

What Are RTGs?

RTGs are lightweight, compact spacecraft power systems that are extraordinarily reliable. RTGs are not nuclear reactors and have no moving parts. They use neither fission nor fusion processes to produce energy. Instead, they provide power through the natural radioactive decay of plutonium (mostly Pu-238, a non-weapons-grade isotope). The heat generated by this natural process is changed into electricity by solid-state thermoelectric converters. (Seebeck effect)

An ideal thermal source would be safe rather than efficient, two proven materials used in RTG's are Pu-238 and Sr-90. Sr90 is safe and a waste product of the nuclear industry. The costs involved in this waste product make Sr-90 viable. They are used in some air-craft ice detection systems as well as medical uses, Soviet ocean bottom and Artic devices used Sr-90 heat sources.

The Cassini NASA mission utilized a radioisotope thermoelectric generator.

Radio-isotopes are produced using a cyclotron. An electron is released and accelerated until it reaches sufficient speed, then it is collided with an atom causing it to become unstable. Their are also naturally occurring radio-isotopes and manufactured radio-isotopes that are in our everyday lives such Americium 241 in common smoke detectors.

• Summary of Radioactivity: Properties and Uses
• Also see Hyperion Power Generation & Accumulators
• This nuclear battery could power your smartphone forever