A team of researchersÌýfrom NASA and Los Alamos National LaboratoryÌýhave demonstrated a new reactor conceptÌýthat combines a Stirling engine with modern heat pipe cooling technologyÌýto provideÌýa powerÌýsource for future space missions.
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| LANL's new reactor concept (Image: LANL) |
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TheÌýdesign is a remarkably simple combination of old andÌýmodern technology that isÌýflexible, lightweight and does not require complex controls. According to the developers it could be used on exploration missions to supplement existing Pu-238 power systems, and therefore help preserve stocks of the valuable radioisotope, which is currently in short supply.
A full-scale reactor would consists of just six sections: aÌý23 kgÌýenriched uraniumÌýcore, a core reflector,Ìýa single control rod fully capable of turning the reactor on and off, radiation shielding and eight heat pipes connected to eight Stirling enginesÌýthat wouldÌýgenerate electricity. The entire unit would be compact andÌýpassively safe - relying on principles of nuclear physics to adjust reactivityÌýand power output rather than any additional equipment.
Technology old and new
TheÌýStirling engineÌýwas originally designed in the 19th century but only now with improved efficiency is it finding small niche applications.ÌýIt is a simple closed loop design which contains a cylinder of pressurized gas that expands as it heats up and contracts as it does work. This can be used to generate electricity on a small scale, although it is not suitable for power stations. Requiring neither pumps or fans, heat pipes are a form of passive cooling technology now commonlyÌýincluded in laptops and other electronics. They consist ofÌýa sealed tube containing an internal liquid whichÌýcirculates to transport heat. TheyÌýwere invented in Los AlamosÌýin 1963.
Being modular with an intended capacity of 500 We, it would be straightforward to add units as required and future scaled-up designsÌýcouldÌýeven beÌýusedÌýfor both surface and space propulsion.ÌýTheÌýsimplicity of the designÌýmakes it easy to assemble and should make it comparatively easy toÌýlicense.
The Demonstration Using Flattop Fission (DUFF)ÌýexperimentÌýwas carried out at theÌýNevada National Security Site’s Device Assembly Facility.ÌýThe scaled-downÌýprototype -Ìýdubbed KRUSTY (KilowattÌýReactor Using Stirling TechnologY) -producedÌýonly 24 We, butÌýconfirmed theÌýbasic principle of the design. "The nuclear characteristics and thermal power level of the experiment are remarkably similar to our space reactor flight concept," noted Los Alamos engineer David Poston. "The biggest difference between DUFF and a possible flight system is that the Stirling input temperature would need to be hotter to attain the required efficiency and power output needed for space missions."
DUFFÌýis noteworthy in beingÌýthe first demonstration of a new space reactor systemÌýto take place in the USA since 1965. Its designersÌýhope that it will open up "new frontiers" for space exploration and research.ÌýThe demonstration arguably alsoÌýholds lessons for the verification and testing of new nuclear powerÌýreactors. "Perhaps one of the more important aspects of this experiment is that it was taken from concept to completion in 6 months for less than a million dollars," said Los Alamos engineer David Dixon. "We wanted to show that with a tightly-knit and focused team, it is possible to successfully perform practical reactor testing."ÌýÌýÌý
Researched and written
by ¶¶Òõ´«Ã½ÔÚÏß Nuclear News
