University of Missouri researchers are developing a nuclear energy source that is smaller, lighter and more efficient. Before you freak out, Jae Kwon, assistant professor of electrical and computer engineering at MU says, “People hear the word ‘nuclear’ and think of something very dangerous. However, nuclear power sources have already been safely powering a variety of devices, such as human heart pace-makers, space satellites and underwater systems.”

This likely will be quite important.  Professor Kwon’s recent paper submitted to the 15th International Conference on Solid-State Sensors, Actuators and Microsystems (also known this year by its snappier name, Transducers 2009) was awarded the honor of being selected as “outstanding paper” out of the 599 papers admitted out of 1,306 accepted for review to the June conference in Denver, Colo.

Brian Wang at has dug into this and says with another quote from Kwon, “The radioisotope battery can provide power density that is six orders of magnitude higher than chemical batteries.” The nuclear batteries are providing power for a decade or more. There are various radiation sources for energy levels of watts to kilowatts. Higher power levels would tend to need radiation shielding. The smaller devices would provide a fraction of a watt, but again last for a decade.  Brian has also learned The Navy thinks it is feasible to scale liquid nuclear batteries to the 100 kw to 1 MW levels. For that kind of application you could have a need for the radiation shielding.  That’s major power.

Kwon explains, “To provide enough power, we need certain methods with high energy density. The radioisotope battery can provide power density that is six orders of magnitude higher than chemical batteries.”  So Kwon and his research team have been working on building a small nuclear battery, currently the size and thickness of a penny, intended to power various micro/nanoelectromechanical systems (M/NEMS).

The problem until Kwon’s breakthrough is that nuclear batteries with their local radiation tear up the semiconductors inside the battery module.  Kwon’s innovation is not only in the battery’s size, but also in its semiconductor. Kwon’s battery uses a liquid semiconductor rather than a solid semiconductor.  “The critical part of using a radioactive battery is that when you harvest the energy, part of the radiation energy can damage the lattice structure of the solid semiconductor,” Kwon said. “By using a liquid semiconductor, we believe we can minimize that problem.”

In collaboration with J. David Robertson, chemistry professor and associate director of the MU Research Reactor, the pair is working to build and test the battery at the MU facility. In the future, they hope to increase the battery’s power, shrink its size and try various other materials. Kwon said that the battery could be thinner than the thickness of human hair. They’ve also applied for a provisional patent.

Nuclear Battery with Liquid Semiconductors

Nuclear Battery with Liquid Semiconductors

Kwon says that there is “a long way to go” before his battery is ready for commercial marketing, “Not necessarily in terms of a long time, but we have a lot of work before it is ready for industry. At this moment, we’re still at the fundamental research level.”  Kwon, Robertson and their team are currently focused on increasing the power output and shrinking the size of the battery even further – among other things, they are exploring using other materials besides the sulfur-35 isotope they are currently using.  That is good news; sulfur-35 isn’t a heavy metal or rare.

Meanwhile, U.S. Defense Advanced Research Projects Agency gave Francis Tsang, and colleagues at Global Technologies, in Idaho Falls, Idaho, funds to support their Liquid Electronics Advanced Power System (LEAPS) program: first, $1.4 million to prove the concept by producing current in a test cell, with a provision that would have allowed for additional funding of up to $26.6 million for over four and a half years. With submarine power plants in mind, DARPA wanted GTI to run full speed toward proving that a reactor of the 100- to 1000-kilowatt scale could be built.  Now that’s serious money.  It also would be a seriously large battery.

Tsang’s group is also working towards the liquid semiconductor and explains the problem with a good metaphor, ”Shoot a bullet into a block of ice, and the ice will shatter and can’t go back into its original form. But if you shoot a bullet into water, the water repairs itself.”

Tsang’s take on this is much like the MU effort.  The U.S. Patent and Trademark Office posted GTI’s key patent application this past November. Tsang has not published data in a peer-reviewed journal (though some of the experiments were replicated at Lawrence Berkeley National Laboratory.  That might open up some patent issues between the researchers.

This is not at all an overlooked area.  “Nuclear batteries” have been dreams since the early 1950s.  University of Wisconsin’s Jake Blanchard is reserving final judgment until he sees published data and thinks the concept of a liquid nuclear battery is a good one. ”It’s a clever idea,” he says. ”It’s not totally crazy.”  Blanchard develops MEMS-based radioisotope batteries so he knows alpha particles and other high-energy radiation will trash the semiconductor by displacing the atoms. That has kept this class of nuclear battery from housing enough radioactive material to produce more than mere milliwatts of power.

Tsang’s research has gotten to not having quite reached 1 percent efficiency.  So there is much room for improvement.

Kwon and Robertson aren’t saying anywhere how efficient they are today. But one thing is very likely – solving the radiation damage issue will put the efficiency matter up front.  If they can get a good portion of the decay energy back into electrical current the million times more idea could be an order of magnitude too low.


1 Comment so far

  1. donb on October 13, 2009 9:03 AM

    The original posting states:
    Brian Wang at has dug into this and says with another quote from Kwon, “The radioisotope battery can provide power density that is six orders of magnitude higher than chemical batteries.”

    It should really state that the radioisotope battery can provide ENERGY density that is six orders of magnitude higher than chamical batteries.

    Energy and power are related, but are not the same thing. Energy is how much work is done. Power is how fast you do that work. For example, you can drive a car up a hill. It takes a given amount of energy to do that. To drive it up the hill quickly takes a lot of power. Driving up the hill slowly takes less power. But in both cases, getting the car up the hill represents the same amount of energy.

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