⚛️ Diamond Betavoltaics: Power from Nuclear Waste
Arkenlight, a spinout from the University of Bristol's interface analysis centre, has achieved a significant advance in betavoltaic nuclear battery technology, demonstrating a diamond-based cell that produces 100 microwatts of continuous electrical power with a projected operational lifetime exceeding 5,000 years. The technology works by incorporating carbon-14, a radioactive isotope with a half-life of 5,730 years, into a synthetic diamond lattice.
The diamond matrix acts simultaneously as the radioactive source, the semiconductor, and the radiation shield. As carbon-14 undergoes beta decay, it emits low-energy electrons (average 49 keV) that generate electron-hole pairs within the diamond semiconductor, producing a small but steady electric current.
The carbon-14 feedstock is extracted from irradiated graphite moderator blocks removed from decommissioned nuclear reactors in the UK. The UK alone has approximately 95,000 metric tons of such graphite waste, containing an estimated 55 petabecquerels of carbon-14, currently stored as intermediate-level radioactive waste at a cost of billions of pounds. Arkenlight's process reduces the volume of graphite waste by separating the carbon-14 as carbon dioxide, then converting it to methane for diamond synthesis via chemical vapor deposition.
The diamond encapsulation prevents any radiation leakage; beta particles from carbon-14 cannot penetrate human skin, and the diamond crystal absorbs them entirely.
At 100 microwatts, Arkenlight's cell is not suitable for consumer electronics, which require milliwatts to watts, but is highly relevant for niche applications where battery replacement is impossible or prohibitively expensive: implantable medical sensors (cardiac monitors, intracranial pressure sensors, continuous glucose monitors), structural health monitoring sensors embedded in bridges and buildings, subsea and downhole monitoring equipment, and environmental sensors in remote locations.
Arkenlight is working with Medtronic on a feasibility study for a betavoltaic-powered implantable cardiac monitor that would never require battery replacement surgery, a potentially transformative improvement in patient quality of life.
🚀 Europe's Americium RTG for Deep Space
The European Space Agency has completed environmental testing of the world's first radioisotope thermoelectric generator (RTG) powered by americium-241 rather than plutonium-238. Plutonium-238, the standard RTG fuel used by NASA since the 1960s, is in critically short supply; US production at Oak Ridge National Laboratory, restarted in 2015, amounts to only 400 grams per year, and NASA's remaining stockpile after the Perseverance rover RTG is approximately 22 kilograms.
Americium-241, extracted from reprocessed civil nuclear fuel (specifically from aged plutonium containing americium from beta decay of plutonium-241), offers a European supply chain independent of US plutonium-238 production. The isotope has a half-life of 432 years, longer than plutonium-238's 88 years, and while its power density is lower (0.1 watts thermal per gram versus 0.57 for Pu-238), it is far more available.
The ESA americium RTG will provide approximately 10 watts of electrical power and will fly on a 2028 deep space mission. A parallel NASA project is developing the Next-Generation RTG using Stirling cycle dynamic conversion to achieve approximately 500 watts of electrical power at 25% conversion efficiency, roughly four times the efficiency of the thermoelectric converters used in the current Multi-Mission RTG powering Perseverance and the New Horizons spacecraft.
📋 Chinese and Other International Developments
The Chinese startup Betavolt, based in Beijing, announced in early 2024 its BV100 betavoltaic device using nickel-63 (half-life 100 years) rather than carbon-14. The device measures 15 by 15 by 5 millimeters and produces 1 microwatt at 3 volts and has triggered a wave of commercial interest in miniature nuclear batteries for low-power IoT sensors, medical implants, and military applications where battery replacement is logistically impossible.
Betavolt has announced plans to scale to 1 watt by 2028 by increasing the nickel-63 loading and stacking multiple layers. However, independent analysts note that nickel-63 must be produced in specialized reactors or accelerators at considerable expense, unlike carbon-14 which is an existing waste product.
The international regulatory landscape for these devices is evolving. Both the UK Office for Nuclear Regulation and the US Nuclear Regulatory Commission have issued guidance classifying betavoltaic cells of sufficiently low activity as exempt from licensing requirements similar to the exemption applied to americium-241 in smoke detectors, a regulatory precedent critical for commercial adoption. The global market for ultra-long-life power sources is projected to reach $4.7 billion by 2035 according to market research, driven primarily by medical devices (where surgical battery replacement adds risk and cost) and industrial IoT (where accessing sensors for battery changes is expensive or physically impossible).