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#1 2003-05-18 21:07:50

Bill White
Member
Registered: 2001-09-09
Posts: 2,114

Re: Nuclear Space - specifics please

Can anyone point me towards detailed information concerning David Poston and the SAFE-400 nuclear reactor?

Are there published articles with technical details? Google leads me to some tantalizing stuff but then dead ends. . .

For example, February 2002 article from Christian Science Monitor. An extensive quote from the above link:

A reactor built in their 'spare time'

Is it possible to design a nuclear reactor for space exploration that isn't too hot to handle?

Seven years ago, David Poston decided to find out.

With a bit of discretionary money from his lab director's budget, the Los Alamos National Laboratory physicist and colleagues have pulled together a mini nuclear-power plant that they say could keep a craft humming long after it reached the outer solar system.

Although the reactor has not been fully activated, or taken "critical," it has passed several key tests during the past four years, highlighting its potential, says Dr. Poston, leader of the lab's space-fission power team.

Dubbed the SAFE-400 reactor, the project came together "pretty much in our spare time," Poston says.

The reactor's core, about the size of a small trash can, consists of uranium fuel surrounding a set of pipes that circulate gas through the core. Energy released in nuclear chain reactions would heat the gas, which can be fed into one of several types of systems to produce electricity.

That electricity would power a spacecraft's instruments as well as run advanced units such as ion-drive motors, which build momentum by constantly expelling electrically charged particles from its exhaust nozzle.

The core's small size contributes to what Poston calls its "passively safe" design. Standing on its own, the reactor can't go critical because neutrons from the decaying uranium are more likely to escape the core than they are to strike another nucleus and start a chain reaction. Indeed, the reactor requires special shields to keep the neutrons corralled for use.

The system could be engineered, he says, to move those shields into place only after command from the ground. Thus the likelihood of a launch accident activating the reactor would be vanishingly small.

Moreover, he adds, the inactive core emits so little radiation that a person would have to hug it for 84 days to receive a dose of radiation as large as a typical chest X-ray.

So far, Poston says, his team has tested the 400-kilowatt reactor at NASA's Marshall Space Flight Center and at CalTech's Jet Propulsion Laboratory. In lieu of chain reactions to generate heat, the team substituted electrical heating elements to achieve the operating temperatures the reactor is designed to reach. Tests included connecting the reactor to an ion-drive motor at JPL.

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#2 2003-05-18 21:24:18

Bill White
Member
Registered: 2001-09-09
Posts: 2,114

Re: Nuclear Space - specifics please

Nevermind the question - here is a good link to a fascinating technical discussion.

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