The U.S. Military Is Working on Nuclear Batteries
But atomic power packs could be a toxic problem
For most of us, recharging a phone is simply a matter of finding a standard electrical outlet.
But war zones aren’t so conveniently wired. As the military learned during more than a decade at war, supplying immense quantities of diesel fuel for generators at forward operating bases proved costly in money and lives.
To keep their radios and sensors powered up, some soldiers in Afghanistan lug almost 30 pounds of batteries during long patrols. During the summer heat, the added weight can contribute to potentially lethal heat exhaustion.
Faced with its staggering power demands, the Pentagon is turning to the most potent and portable energy source there is—nuclear energy—to keep its soldiers supplied with juice.
A 2013 report by the Defense Science Board identified “nuclear batteries” as an essential technology for the U.S. military in the 21st century. Though the technology sounds like science fiction, nuclear batteries have long served space exploration and medicine.
The technology exists. The problem is how to dispose of the batteries without contaminating the environment.
From the space program … to pacemakers
Let’s get one thing out of the way. Nuclear batteries are not nuclear reactors that just happen to be really small.
Nuclear reactors generate power through the controlled splitting of heavy elements. Nuclear batteries, on the other hand, rely on the radioactive decay of isotopes, or flavors, of various natural and artificial elements.
Nuclear batteries have existed almost as long as nuclear reactors. The first experimental units appeared in the 1950s. Then and now, the batteries employ one of two methods of generating electricity—heat and radioactivity.
One such nuclear battery is the radioisotope thermoelectric generator—which converts heat into electricity—and has flown on dozens of space missions. The Voyager, Galileo and Cassini deep-space probes all run on RTGs.
The generators power the Curiosity and Opportunity rovers on Mars. Apollo astronauts even deployed them on the Moon to power scientific instruments.
Voyager II transmits data today—almost 40 years after its launch date—due to the long life of its plutonium-powered RTG.
The reason is because the non-fissile, plutonium-238 isotope pumps out a lot of heat as it slowly decays into a uranium isotope.
Closer to home, plutonium-238 powered the first nuclear pacemakers in the 1970s. The tiny generators allowed heart patients to go for a lifetime without ever replacing the pacemakers’ batteries.
But the problem with plutonium-238 is its toxicity. Plutonium is one of the most toxic substances known to humanity. As little as a microgram can kill you. That’s why it gradually lost out in favor of promethium, a less-toxic element.
With the development of lithium-ion batteries, the nuclear-powered pacemakers disappeared from the market. But the technology works. Deemed safe enough even for pregnant women, some 40-year-old nuclear pacemakers are still ticking today.
There’s more than one way to build a nuclear battery. RTGs rely on heat. But betavoltaic devices rely on beta radiation—in the form of electrons—emitted from decaying isotopes.
Electricity is simply the flow of electrons through a conducting material. This means betavoltaic devices generate electricity directly from radioactivity. It’s similar to a solar cell, except that the radioactive isotope provides the power, instead of sunlight.
Beta radiation doesn’t travel far. A thin sheet of aluminum is enough to block it. This makes them relatively safe. The batteries that replaced plutonium pacemakers were betavoltaic devices safe enough to put inside a person’s chest.
The most promising candidates today for betavoltaic batteries include strontium-90, nickel-63 and tritium—a super-heavy form of hydrogen. All three emit beta radiation, and almost no penetrating, deadly gamma radiation. And they last a long time.
Strontium-90 has a half-life of more than 28 years, tritium for more than 12 years and nickel-63 for more than a century.
While strontium and nickel-based batteries are still mostly experimental, tritium-based batteries are already on the market. One Florida-based battery manufacturer markets a tritium-powered battery to military and industrial customers—those who need a small amount of power for a long time.
Nuclear micro and nano-batteries also hold promise for powering “smart dust” sensors—or dust-sized, electronic spies—which require tiny amounts of power.
But what about troops humping heavy batteries in the field? Or larger sensors implanted deep in hostile territory? You need more than nanowatts.
The Army Research Laboratory has developed prototype nuclear batteries powered by tritium. Matching the Army’s existing BA-5590 battery pack in size and using the same connector, the Army’s nuclear battery can last for 13 years.
Tritium’s advantages are many—it’s already widely used in emergency exit signs, gun sights and even watches. As a beta radiation source, it’s not very difficult to physically handle.
Because it’s an essential fuel for hydrogen bombs, the Pentagon will always have a ready supply of it.
But as any owner of modern gizmos is surely aware, there’s a pile of dead batteries at the end of the tech rainbow. And that poses a real waste problem—especially when the dead batteries are nuclear.
The heavy, non-radioactive metals in chemical batteries makes up a huge proportion of the hazardous waste in American landfills. While the decades-long service lives of nuclear batteries will mean fewer dead batteries end up in the garbage, widespread military use could create an even more toxic disposal issue.
Nuclear batteries are unlikely sources of proliferation or terrorism. The isotopes are unable to undergo nuclear fission, which makes them useless as bomb fuel. But they are long-lived—and radioactive.
Tritium doesn’t produce the gamma radiation that cobalt-60 does, but it is a gas. That makes it dangerous if released into the atmosphere, and deadly if inhaled. Strontium-90 also has its problems. The isotope binds to the same places in the human body as calcium.
Nickel-63 might seem less frightening. It’s a heavy metal, like the fuel inside today’s consumer batteries. But throwing the metal into a burn pit—a common and hazardous practice in war zones—would emit metal vapor into the atmosphere.
Metal vapor that’s also radioactive.
Nuclear batteries are going to war—and sooner rather than later. And as the wars in Iraq and Afghanistan have demonstrated, the waste of conflict can be as deadly as the fighting.
Let’s hope the planning for nuclear batteries goes as far as their shelf lives.