[cdn-nucl-l] Personal Nuclear Power: New Battery Lasts 12 Years

["Adam Mclean" <adam.mclean@utoronto.ca>]

Posted on Yahoo LiveScience on May 13, 2005 and at:
http://story.news.yahoo.com/news?tmpl=story&cid=96&e=2&u=/space/20050513/sc_
space/personalnuclearpowernewbatterylasts12years
Local connection to the UofT electrical engineering department of photonics.

Adam

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Personal Nuclear Power: New Battery Lasts 12 Years Robert Roy Britt
LiveScience Senior Writer
Fri May 13, 5:13 PM ET
 
A new type of battery based on the radioactive decay of nuclear material is
10 times more powerful than similar prototypes and should last a decade or
more without a charge, scientists announced this week.

The longevity would make the battery ideal for use in pacemakers or other
surgically implanted devices, developers say, or it might power spacecraft
or deep-sea probes. 

You might also find these nuclear batteries running sensors and other small
devices in your home in a few years. Such devices "don't consume much
power," said University of Rochester electrical engineer Philippe Fauchet,
"and yet having to replace the battery every so often is a real pain in the
neck."

Fauchet told LiveScience the batteries could last a dozen years. They're
being developed at Rochester and the technology has been licensed by
BetaBatt Inc.

How it works

The technology is called betavoltaics. It uses a silicon wafer to capture
electrons emitted by a radioactive gas, such as tritium. It is similar to
the mechanics of converting sunlight into electricity in a solar panel. 

Until now, betavoltaics has been unable to match solar-cell efficiency. The
reason is simple: When the gas decays, its electrons shoot out in all
directions. Many of them are lost.

"For 50 years, people have been investigating converting simple nuclear
decay into usable energy, but the yields were always too low," Fauchet
explained. "We've found a way to make the interaction much more efficient,
and we hope these findings will lead to a new kind of battery that can pump
out energy for years."

Fauchet's team took the flat silicon surface, where the electrons are
captured and converted to a current, and turned it into a three-dimensional
surface by adding deep pits.

Each pit is about one micron wide. That's four ten-thousandths of an inch.
They're more than 40 microns deep. 

Tritium is a radioactive form of hydrogen. Mixed with chemicals that emit
light, it is used to illuminate exit signs without electricity -- the sort
commonly found in schools and other public buildings.

"It is safe and can be implanted in the body," Fauchet said. "The energetic
particles emitted by tritium do not penetrate inside the skin."

Tritium emits only low energy particles "that can be shielded by very thin
materials, such as a sheet of paper," said Gadeken of BetaBatt. "The
hermetically-sealed, metallic BetaBattery cases will encapsulate the entire
radioactive energy source, just like a normal battery contains its chemical
source so it cannot escape."

The device is detailed in today's issue of Advanced Materials.

Improvements needed

The manufacturing process is standard to the semiconductor industry, so no
other technology breakthroughs are needed to bring the batteries to market.
Still, don't expect anything on the store shelves for at least two years,
Fauchet said. His team is now working to improve the manufacturing process,
aiming for batteries many times more efficient than those announced today. 

"If we are as successful as we think we may be, it will take less than five
years before this technology is adopted," he said.

Graduate student Wei Sun of the University of Toronto was lead author on the
paper describing the work, which was supported by the     National Science
Foundation.