Atomic battery

An atomic battery, also called a radioisotope generator, produces electricity from radioactive decay. This process involves a radioactive isotope, which is a type of unstable matter. As these isotopes decay, they release energy. Unlike a nuclear reactor, an atomic battery does not use a chain reaction to work. It is also different from common electrochemical batteries. You cannot charge or recharge an atomic battery. While they are very expensive, they have high energy density. This means they pack a lot of power into a small space. They also have extremely long lives.

Scientists classify these batteries by how they convert energy. The first group is thermal converters. These devices turn the heat from nuclear decay into electricity. One common example is the radioisotope thermoelectric generator, or RTG. Another thermal type is the thermionic converter, or TEC. A TEC uses a hot electrode to emit electrons across a barrier to a cooler electrode. Some researchers also study thermophotovoltaic cells. These convert infrared light from hot surfaces into power. There are also Stirling generators. These use a Stirling engine driven by temperature differences.

Thermal conversion relies heavily on temperature gradients. In an RTG, electricity is produced through the Seebeck effect. This process uses thermocouples, which are pairs of different metal wires. When one end of the wire is heated and the other is cooled, a voltage is created. To get more power, many thermocouples are connected in series or parallel. Scientists often use semiconductor materials like bismuth telluride for better efficiency. These materials have higher charge densities than simple metals. However, thermal conversion is often inefficient. Most atomic batteries have an efficiency between 0.1% and 5%.

Non-thermal converters work differently. They extract energy directly from radiation before it turns into heat. This makes them easier to miniaturize for small machines. One method is electrostatic conversion. This happens when charged particles build up in a conductor. This creates an electrostatic potential, or voltage. This voltage can be very high. It might reach several kilovolts for beta radiation. It can even reach megavolts for alpha radiation. One way to use this is a direct-charging generator. This uses a capacitor to collect the current from a radioactive layer.

Another non-thermal method is radiovoltaic conversion. These devices use a semiconductor junction to create electricity. This is similar to how a solar cell works. Depending on the radiation used, they have different names. Alphavoltaic devices use alpha particles. Betavoltaic devices use beta particles, which are electrons. Gammavoltaic devices use gamma particles, which are high-energy photons. Betavoltaics are very popular for research. This is because beta emitters cause less radiative damage. This allows the battery to last longer with less shielding. High-efficiency betavoltaic devices can reach 6% to 8% efficiency.

The history of atomic batteries began with early discoveries in radioactivity. Henri Becquerel discovered natural radioactivity in 1896. Marie Curie discovered the elements polonium and radium in 1898. Later, Ernest Rutherford identified alpha and beta particles. He and Frederick Soddy discovered radioactive decay between 1902 and 1903. In 1913, Henry Moseley demonstrated a current from radium decay. He showed a high voltage of 150kV with a tiny current of 0.01nA. In 1954, RCA created a prototype for hearing aids. In 1961, NASA used an RTG in space. That mission used the isotope Plutonium 238 as fuel.

Today, these batteries are vital for extreme environments. They power spacecraft that travel far into the solar system. They also power medical devices like pacemakers. They are used in underwater systems and remote scientific stations. A company called Betavolt is currently testing a miniature device. It uses the isotope nickel-63 inside a module the size of a small coin. It is designed to produce 100 microwatts of power at 3V. This device could potentially last for 50 years without maintenance. As the nickel-63 decays, it turns into stable copper. This makes it safe for the environment.