1st quarter 2001 The Actinide Research Los Alamos National ...deep-freeze of space. The Light Weight...

1Nuclear Materials Technology/Los Alamos National Laboratory

Los Alamos National LaboratoryThe Actinide Research

In This Issue

4Pit Manufacturing

Project Presents ManyChallenges

6Can Los Alamos

Meet Its Future NuclearChallenges?

9Detecting and

Predicting PlutoniumAging are Crucial to

StockpileStewardship

12Pit Disassembly and

Conversion Address a‘Clear and Present

Danger’

14Publications and

Invited Talks

Newsmakers

15Energy SecretarySpencer Abraham

Addresses Employees

1st quarter 2001

N u c l e a r M a t e r i a l s R e s e a r c h a n d T e c h n o l o g y

Researcher Provides a HistoricalPerspective for Plutonium Heat Sources

continued on page 2

Quarterly

artist rendering of RoverPathfinder on Mars fromNASA/JPL

For more than 30 years,Los Alamos has designed,developed, manufactured,and tested heat sources forradioisotope thermoelectricgenerators (RTGs). Thesepowerful little “nuclearbatteries” produce heatfrom the decay of radioac-tive isotopes—usuallyplutonium-238—and canprovide electrical powerand heat for years insatellites, instruments,and computers.

We begin the seventhyear of ActinideResearch Quarterlyby focusing onmajor programs inNMT Division. Thepublication teamalso welcomes itsnew editor, Meredith“Suki” Coonley, who isassuming the positionwhile Ann Mauzytakes on actingmanagementduties in IM-1.

K.C. Kim

Actinide Research Quarterly

2 Nuclear Materials Technology/Los Alamos National Laboratory

Los Alamos developeda General PurposeHeat Source (GPHS) inthe late 1970s to meetthe larger powerrequirements of theGalileo, Ulysses,and Cassinispace missions.

Early development efforts from themid-1960s through the early 1970s focusedon fuel forms for space applications. The first,plutonia-molybdenum-cermet (PMC), wasused on the Pioneer 10 and 11 missions toJupiter and Saturn and the Viking Landermissions. PMC was fabricated by hot-pressingmicrospheres of molybdenum-coated plutoniainto hockey-puck-shaped discs, which werethen stacked and encapsulated in arefractory alloy.

During the same period, Los Alamosdeveloped a medical-grade fuel for use incardiac pacemakers and early artificial hearts.The fuel in the artificial hearts was made of 90percent enriched plutonium-238 and providedup to 50 watts of power. Some of the earlypacemakers are still in use; some have beenreturned to Los Alamos’ Plutonium Facilityfor recovery.

As electrical power requirements forspacecraft increased during the 1970s, so didthe need to increase the power density of theheat source. Using “inert” materials such asmolybdenum proved unattractive. Los Alamosbegan investigating fuel forms that used pureplutonia, which can generate more power ina smaller, lighter package.

The first pure plutonia fuel formdeveloped at Los Alamos was theMultihundred Watt (MHW) for the RTGs usedon the Voyager 1 and 2 missions to Jupiter,Saturn, Uranus, and Neptune. The heat sourcewas a 100-watt hot-pressed sphere of plutoniaencapsulated in iridium. Twenty-four heatsources were contained within the RTG. Heatwas converted to electrical power by 312silicon-germanium thermoelectric couples.

Each Multihundred Watt RTG provided about 157watts of power at the beginning of the mission.

To meet the larger power requirements ofthe Galileo, Ulysses, and Cassini missions inthe late 1970s, Los Alamos developed theGeneral Purpose Heat Source (GPHS). ThisRTG contained 572 silicon germanium ther-moelectric couplesinside a thermoelectricconverter and pro-vided 285 watts ofelectrical power atthe beginning.

The heat sourcefor these RTGs con-sisted of 18 GPHSmodules. Each modulehad four fueled cladsand each cylindricalfueled clad containeda hot-pressed 150-gram pellet ofplutonium-238 dioxideencapsulated in an iridium-tungsten container.

Los Alamos fabricated the 216 GPHSfueled clads used on the Cassini mission.Each iridium clad contained a sintered iridiumpowder frit vent designed to release thehelium generated by the alpha particle decayof the fuel. The iridium is compatible withplutonium dioxide at temperatures greaterthan 1,773 K and melts at 2,698 K.

In addition to developing RTGs to provideelectrical power to operate instruments, LosAlamos also designed and fabricated heaterunits to keep equipment operating in thedeep-freeze of space. The Light WeightRadioisotope Heater Unit (LWRHU) providedone thermal watt of heat and was used on theGalileo and Cassini spacecraft and MarsPathfinder Rover. At the heart of this heaterunit was a platinum-30 percent rhodiumfueled clad containing a hot-pressed2.67-gram pellet of plutonium-238 dioxide.

Los Alamos has also fabricated a largenumber of heat sources for the weaponsprogram. From 1981 to 1990 more than 3,000Milliwatt Generator (MWG) heat sources were

This article wascontributed byGary Rinehart(NMT-9)

A General Purpose HeatSource (GPHS) fueledclad.

1st quarter 2001

Nuclear Materials Technology/Los Alamos National Laboratory 3

fabricated and shipped to the Pinellas, Fla.,plant for assembly into the MWG-RTG. TheseRTGs were used in devices that reduce thepossibility of accidental detonation from anuclear warhead. Each of the MilliwattGenerator heat sources had a nominal powerof 4.0 to 4.5 watts. Los Alamos is currentlyrecovering fuel from excess MWG-RTGs andperforming shelf-life and stockpile surveil-lance on both the MWG heat source and theMWG-RTG. See Actinide Research Quarterly,Winter 1994, “Milliwatt Surveillance ProgramEnsures RTG Safety and Reliability.”

Historically, reactors at Savannah Riverproduced all of the United States’ plutonium-238 until the late 1980s. With the shutdown ofthe Savannah River reactors, the United Stateshas had to purchase plutonium-238 dioxidefrom Russia to supplement U.S. inventoriesfor future NASA space missions. Recently, theDOE has proposed that plutonium-238 be pro-duced at the Advanced Test Reactor (ATR) inIdaho and the High Flux Isotope Reactor(HFIR) at Oak Ridge National Laboratory.

The Mars Pathfinder Rover contained three LightWeight Radioisotope Heater Units (LWRHUs).

A Light WeightRadioisotope HeaterUnit (LWRHU) beforefinal assembly. The heatsource consists of agraphite aeroshell,pyrolytic graphitethermal insulators, anda platinum-rhodiumfueled clad. A sinteredplatinum powder frit ventis electron-beam-weldedinto the end cap of thefueled clad to releasehelium generated by thealpha decay of the fuel.

A significant amount of the heat sourcefuel in the Los Alamos inventory, including theRussian material and fuel from disassembledterrestrial heat sources, must be purifiedbefore it can be fabricated into new heatsources. Heat source fuel was previouslyrecycled and purified at Savannah River.Los Alamos is qualifying a plutonium-238aqueous recoveryprocess in its pluto-nium facility toprovide feed for theheat-source fabrica-tion process.

A new glove-boxline is being installedfor this work and thefull-scale aqueousrecovery process isexpected to becomeoperational this fiscalyear, which will have the capacity to purify5 kilograms of plutonium-238 per year. Inaddition, Los Alamos has the capability offabricating more than 5 kilograms ofplutonium-238 into heat sources per year.

These improvements to the plutoniumfacility will ensure that Los Alamos can fullysupport future NASA requirements. TheEuropa Orbiter mission, scheduled for launchin 2006, and the Solar Probe mission, scheduledfor launch in 2007, will each require approxi-mately 3 kilograms of plutonium-238 if aStirling radioisotope power system wereused. If RTGs are used, approximately8 kilograms of plutonium-238 will berequired for each mission.

Over the next decade, several Marsexploration missions will carry LWRHUs,which will require approximately 0.3 kilogramof plutonium-238 per mission. In the longterm—the next 20 to 35 years—NASA isexpected to need 2 to 5 kilograms ofplutonium-238 per year for itsspace missions.■



Pit Manufacturing Project Presents Many ChallengesThis article wascontributed byDavid Mann andSean McDonald,NMT-5

Central to the function of a thermonuclearweapon is a plutonium pit, the trigger that ini-tiates the sustained nuclear reaction. LosAlamos’ experience in making pits dates backmore than 50 years, to the Manhattan Project.Since that time, the Lab has produced a smallnumber of pits—about a dozen a year—forresearch purposes and underground testingin Nevada. By comparison, the number of pitsproduced yearly at the now-closed RockyFlats defense plant near Denver was inthe thousands.

In 1993, the Department of Energy (DOE)requested that Los Alamos develop the manu-facturing capabilities to produce war-reservepits as part of the stockpile stewardship pro-gram. The designation “war reserve” meansthat the components meet the specificationsrequired for use in a stockpiled nuclearweapon. Los Alamos was chosen in partbecause it has the nation’s only full-capabilityplutonium facility. DOE plans call for LosAlamos to develop the capability to make20 to 50 pits a year eventually.

Los Alamosestablished the PitManufacturingProject to coordinatethe activities of themany divisions acrossthe Laboratoryinvolved in pitmanufacturing. Withsupport from manyLab divisions—Engi-neering Sciences andApplications (ESA),Materials Science andTechnology (MST),Chemistry (C), andDecision Applications(D—the NuclearMaterials Technology(NMT) Division isdeveloping andimplementingprocesses thatrange from castingthe plutonium to the

final assembly of the nuclear and nonnuclearcomponents. Complicating matters are thechanges that have had to be made in a substan-tial number of these processes because of theunavailability of the original equipment,the need to comply with new environmentalregulations, or the ability to take advantageof improved equipment.

NMT has faced a number of challengesin setting up these capabilities. The first andprobably most significant challenge has beento set up a formal manufacturing operation—with all its controls, infrastructure, andrestrictions—in an existing research anddevelopment facility, and to do so withoutcompletely disrupting the existing programs.

To manufacture pits to the same specificationsas Rocky Flats, each of the more than 100 pro-cesses involved has had to be installed, tested,and proven to function as it did at Rocky Flats.Currently, more than 98 percent of these pro-cesses have been installed and used in thedevelopment program designed to prove theeffectiveness of either new procedures or sig-nificant modifications to procedures used atRocky Flats.

With the suspension of underground testingfollowing the advent of the Nuclear Test BanTreaty, scientists currently have no way toprove absolutely that any production changesdo not affect the pits. Because of this, each pro-cess that has undergone any significant changemust go through a formal process qualificationplan, which consists of a series of experimentsdesigned to capture the possible variables ofthe new system. The process qualification planis followed by an independent statistical analy-sis of the data by D Division before the processis fully approved.

The development program consists of 10development pits, each of which tests one ormore areas of concern to physicists or designengineers. As part of the development pro-gram, researchers will test the fabrication andassembly processes to identify and solvepotential problems that may occur in the sub-sequent qualification and production lots. Thedevelopment program also includes trainingpersonnel in nuclear manufacturing processes,

A casting furnace inoperation.

1st quarter 2001


providing destructive evaluation results forprocess feedback where this information can’tbe obtained nondestructively, and establishingan assembly information database for LosAlamos manufacturing methods suitable forpredicting process yields for actualproduction runs.

The development pits will be followed by aseries of qualification pits, which will be madecompletely to war-reserve specifications. Thesepits will be used in the certification program.

One of the manufacturing challenges isthe selection of process materials to be usedduring fabrication, many of which havechanged over the years. To remedy this, theWar Reserve Materials Compatibility Board(WRMCB) has been established to evaluateprocess materials for use in war-reserve manu-facturing. The WRMCB reviews historical dataobtained from Rocky Flats to make a determi-nation on whether or not a process material iscompatible for use with plutonium or otherwar-reserve metals. If there isn’t enough his-torical information to make a determination,the WRMCB commissions a compatibilitystudy to be performed by the MaterialsTesting Laboratory in C-ACT.

Another challenge for project researchershas been the changing environmental regula-tions controlling the use of organic solvents.At Rocky Flats, plutonium components werecleaned with trichloroethane, which is nowbanned by the Montreal Protocols. Anothersolvent, trichloroethylene (TCE), is currentlybeing used, but it is a suspected carcinogen.Besides its potential health risk, TCE isextremely costly to dispose of when it’s con-taminated with plutonium.

NMT Division is resolving these issueswith a multilevel approach. NMT-11, inconjunction with C-PCS, has developed ahydrothermal technique for destroying TCEby reducing it to water, carbon dioxide, andhydrochloric acid. To reduce the amount ofTCE produced while this system is beinginstalled, NMT-5 and C-ACT have developeda cleaning system that reduces by 75 percentthe amount of solvent used. The groups arealso developing a method to recycle the TCE

when it becomes too contaminated toeffectively clean the components.

As a long-term solution, a new methodusing carbon dioxide as the cleaning agent isbeing developed to completely replace thesolvent cleaning system. This will allow theplutonium components to be cleaned in anenvironmentally benign method, producingnegligible waste.

In addition to a multitude of manufacturingchallenges, NMT faces two challenges in thequality arena. A technical challenge is to pro-vide a more formal method than what wasused at Rocky Flats for qualifying processesand documenting the qualification.

A regulatory challenge is to institute aquality-assurance system that meets the DOE’sstrenuous requirements for war-reserve com-ponents, and to do so without the substantialresources that were devoted to the qualitydepartment at Rocky Flats. To meet the regula-tory challenge, small, specialized teams havebeen formed to qualify processes and write adocumented manufacturing manual.

Despite the large number of challengesfacing the pit manufacturing process, theproject has had many successes and is onschedule to meet all of the major milestonesfor producing a certifiable pit by 2003 and afully certified pit by 2007.

This is a significant achievement,particularly in light of last spring’s CerroGrande Fire, during which the plutoniumfacility was completely shut down for severalweeks. The first pit produced following thefire was made on schedule just weeks after thefacility reopened. A second pit was producedseveral weeks later to test the quality- andproduction-control systems.

The next stage of development is tocomplete the process qualification plans andimplement formalized work instructions foreach process. These will be completed by theApril 2002 milestone, along with all of the sup-port and quality systems necessary to satisfywar-reserve requirements for documentationand quality.■



Can Los Alamos Meet Its Future Nuclear Challenges?Balancing the Need to Expand Capabilities While Reducing Capacity

Editorial

The CMR Building,which opened in 1952and consists of sevenwings that house twobanks of hot cells,laboratories designedfor actinide materialsscience and analyticalchemistry, and uniquecapabilities for workingactinide metals.

Editor’s note: Tim George is head of the NuclearMaterials Technology (NMT) Division. In this, hisfirst editorial for Actinide Research Quarterly, hediscusses some of the challenges facing the division.

Since the early 1980s, the vast array ofDepartment of Energy (DOE) facilities oncedevoted to the study and use of actinide mate-rials has undergone a dramatic restructuring.Sites such as Mound, Ohio; Pinellas, Fla.;Hanford, Wash.; and Rocky Flats, Colo., whichonce formed the backbone of the nation’sweapons complex, have either closed outrightor exchanged well-defined production andsupport missions for goals of decontaminationand decommissioning.

DOE’s remaining active sites are handicappedin the near term by deteriorating nuclear andhigh-hazard facilities, and infrastructure bud-gets that in most cases are inadequate toaddress a half-century of accumulated liabilities.

Although also burdened with its share ofaging facilities, Los Alamos is unique in that itcontinues to operate the nation’s only full-serviceplutonium facility. Building PF-4, which islocated at TA-55, is both the newest (it opened in1978) and only remaining facility in the DOEcomplex with the capability to conduct opera-tions with all isotopes and chemical forms ofplutonium, as well as other actinides. Thesediverse capabilities are packed into approxi-mately 80,000 square feet of nuclearlaboratory space.

Los Alamos also maintains significantcapabilities for actinide research and processingin a much older facility, the Chemistry andMetallurgy Research (CMR) Building, whichopened in 1952. The CMR Building consists ofseven wings that house two banks of hot cells,laboratories designed for actinide materialsscience and analytical chemistry, and uniquecapabilities for working with actinide metals.

The seven wings of the CMR Buildingoriginally contained more than 50,000 squarefeet of nuclear laboratory space. By 2001, how-ever, degradation of critical support systemsresulted in a suspension of activities in onewing, increasingly stringent requirements foroperational safety resulted in suspension ofoperations in a second, and planned decommis-sioning of a third wing reduced the amount ofusable nuclear laboratory space to approxi-mately 28,000 square feet.

In the 1990s, Los Alamos embarked on anaggressive program of upgrades to ensure con-tinued safe operation of the CMR Buildingthrough 2010. By early 2001, approximately$76 million had been spent on the CMRupgrades, of which about one-half consistedof urgent maintenance items, with the balancedirected toward upgrading building systemsto meet regulatory requirements and to ensurecontinued safe operations.

Planned and completed upgrades includedHEPA filter replacement in operational wings,upgrades to the fire protection system,improvements to exhaust stack monitoringsystems, major upgrades of facility electricalsystems, and safety-driven improvements tothe building personnel accountability system.

NMT Division DirectorTim George.

The opinions in this editorial are theauthor’s. They do not necessarilyrepresent the opinions ofLos Alamos National Laboratory,the University of California, theDepartment of Energy, or theU.S. government.

1st quarter 2001


Recent experience has demonstrated thatsubstantial additional maintenance will berequired to reduce the probability ofunplanned outages resulting from the failureof aging and obsolete building systems.

Together, the Plutonium Facility and theCMR Building represent a lifeboat for preservingthe nation’s most critical nuclear technologiesuntil they can be transitioned to the facilitiesof the future. In the near term, an increasingworkload in support of production and sup-port missions is competing for limited CMRand PF-4 floor space.

These missions currently include pilotproduction of nuclear defense components;surveillance of defense components; fabricationof components used in subcritical experi-ments; small-scale production of plutoniumheat sources, analytical standards, andadvanced nuclear fuels; materials surveillance;development and implementation of tech-nologies for materials disposition; andinvestigative research.

Of these missions, the most difficult toprioritize is investigative research. However,history has repeatedly demonstrated thataggressive programs to understand today’sbench-top curiosities are the only certainmeans to avoid being on the wrong end oftomorrow’s technological surprises.

The challenge then, for the NuclearMaterials Technology (NMT) Division, whichoperates both PF-4 and the CMR Building, istwofold: to ensure continued success in cur-rent and future programmatic missions, andto preserve and expand technical capabilitieswhile reducing the space and resourcesdevoted to excess capacities.

The most critical factors to ensuringNMT’s success in completing programmaticassignments are adequate and sustained bud-gets for facility operations and maintenance.Although the CMR upgrades project hasaddressed the most critical deficiencies in thefacility, additional investment will be requiredto address the failure of aging and obsoletenonsafety-related systems.

In the case of the Plutonium Facility, theoutlook is for increased facility maintenanceand operational costs as the facility ages.Because PF-4 has operated for nearly 25 yearswith no comprehensive plan for capitalreinvestment and with limited budgets forfacility maintenance and operation, unplannedoutages will become increasingly common ascomponents in key facility systems reach theend of their design lifetimes.

In addition, facility resources are stretchedeven further by requirements to meet regula-tory and operational standards that were notin place, or even envisioned, at the time thefacility was constructed.

The goal of reducing excess capacitieswhile preserving and expanding technicalcapabilities will be much more difficult toachieve than completion of well-definedprogrammatic assignments.

The key factors to success in this area areby nature subjective. Assumptions must bemade on the probabilities of increased ordecreased program requirements for theoutputs of various processes. Predictions mustalso be made on the significance and opera-tional requirements of emergent technologies,such as room-temperature ionic liquids, thatoffer the promise of reducing the need for, oreven replacing, current separations processes.

The entrance to theTA-55 PlutoniumFacility.



Both sets of assumptions and predictionsmust then be compared with existing facilityconfigurations to identify specific laboratoriesand glove boxes (currently devoted to excessprocess capacities) that may be suitable forreconfiguration. Finally, funds must beidentified to reconfigure these laboratoriesfor other uses.

With sufficient budget, there aresignificant opportunities to reclaim thespace occupied by excess process capacities.In PF-4, for example, which was originallydesigned as the nation’s premier actinideresearch and development facility, a portionof the facility remains configured to separateand purify relatively large quantities ofplutonium and other actinides.

Although these capabilities madesignificant contributions to the nation’sdefense in the early 1980s, it is unlikely thatthey will ever again be required to operate onthat scale. Consolidation of the separationsprocesses into a smaller footprint offers thepotential to free up space that can then beused to support increasing programmaticworkloads, emergent technologies, or wastereduction and treatment processes required tomeet new regulatory standards.

Significant questions remain as to howlong PF-4 and the CMR Building can beexpected to remain operational given currentand expected facility budgets and when newfacilities will be available to house trans-itioned operations. Questions also remainabout the long-term effects of compromisesnecessary to maintain production, program-matic support, research, and developmentwithin the limited space available in thesetwo facilities.

Given the long lead time needed forconstruction of nuclear facilities and the lim-ited remaining lifetime of the CMR Building,decisions must be made soon on the size,location, and capabilities of the DOE’sreconfigured nuclear complex.

At Los Alamos, work needs to accelerateon replacing the CMR Building with a newfacility (or a set of smaller, cheaper facilities),and on development and implementation ofthe Integrated Nuclear Park (INP) conceptproposed by Gen. John Gordon, head of theNational Nuclear Security Administration(NNSA). The INP, if implemented, wouldconsolidate all Los Alamos nuclear opera-tions into one area.■

1st quarter 2001


Detecting and Predicting Plutonium AgingAre Crucial to Stockpile Stewardship This article was

contributed byDavid Clark andJoseph Martz,G. T. SeaborgInstitute, NMTDivision

During the past decade we have seenunprecedented changes in the world’s politicalclimate. The end of the Cold War, the breakupof the former Soviet Union, strategic armsreduction treaties—all have contributed toa decrease in nuclear arms buildup. Thesechanges notwithstanding, nuclear weaponstechnology continues to play a key role inreducing the global nuclear danger.

However, the configuration of theweapons complex is far from static. The sizeand number of nuclear weapons within theU.S. arsenal have been dramatically reduced,nuclear testing has been curtailed, the weap-ons in the stockpile are aging, and downsizedfabrication facilities are being tightly inte-grated and focused as much on maintainingcapability as on delivering small numbers ofnew components.

Within this new environment, theDepartment of Energy (DOE) has implementedthe Science-Based Stockpile StewardshipProgram, which relies on the use of methodsother than nuclear testing to ensure the safety,security, and reliability of the stockpile. Thesemethods include advanced diagnostic equip-ment, data from critical new experiments,enhanced computational power, and retainingthe very best scientists and engineers at thenation’s nuclear research facilities.

Several new missions are growing inimportance, including the analysis and surveil-lance of weapon systems and the associatedmeasurement of the effects of aging on theweapons in the stockpile.

A qualitativerepresentation of theconnection betweenchanges in atomicstructure, microstruc-ture, materialproperties, andcomponent perfor-mance. The onset ofpotential aging effectsin plutonium isincluded along thetime axis. The goal isto identify thesignatures of aging atthe earliest possibletime. This require-ment has driven theprogram to atomicand nanoscalescientificinvestigations.

Time

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He ingrowthsurface corrosion

He bubble formation?

phase stability

ComponentPerformance

Microstructure

AtomicStructure

MaterialProperties

Understanding Materials Agingis Key for Early Warning ofStockpile Issues

void swelling

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Stockpile SurveillanceThe Stockpile Surveillance Program

ensures that the stockpile is free of defects thatmay affect performance, safety, or reliability.The surveillance program has two elements:the Stockpile Evaluation Program and theEnhanced Surveillance Campaign.

The first element, stockpile evaluation,provides examinations and assessments ofwar-reserve stockpile weapons and components.The second element, enhanced surveillance,provides the means to strengthen theStockpile Evaluation Program to meet thechallenges of maintaining an aging stockpilein an era of no nuclear testing. Enhancedsurveillance also provides lifetime assessmentsand predictions for Stockpile Life ExtensionProgram (SLEP) planning.

The goal of the Enhanced SurveillanceCampaign is to protect the health of thestockpile by screening weapons systems formanufacturing and aging defects to identifyunits that need to be refurbished. It also will beused to predict material and component agingrates as a basis for annual certification, refur-bishment scope and timing, and nuclearweapon complex planning. Results of thework will be used to make improvements tothe basic surveillance program.

Because nuclear weapons will be retainedin the stockpile for lifetimes beyond our expe-rience, the DOE needs to be able to determinewhen stockpile systems must be refurbished orreconditioned. If new refurbishment capabilityis needed, the DOE needs to know when thesecapabilities must be operational and what therequired capacity should be, if the capacity forexisting facilities is adequate, and when poten-tial refurbishment for the various stockpile systems must be scheduled.

The DOE also needs to have a basis onwhich to characterize the functional reliabilityof aged components, which is part of theannual assessment process.

Plutonium AgingDetecting and predicting age-induced

changes in nuclear materials are perhaps themost challenging and technically engagingaspects of Science-Based StockpileStewardship. Indeed, “science-based” arisesprincipally from this need, as opposed to a“production-based” alternative or the“test-based” strategy used in years past. Analy-sis, prediction, and mitigation of aging effectsare key to ensuring long-term functionality.

However, changes in weapon performanceas a result of aging represent the end in a seriesof events that began years or decades earlier.Changes occur first in the fundamental (oratomic-scale) properties of the materials withinthe weapon—properties such as composition,crystal structure, and chemical potential.Changes are later found in the applied behav-ior of these materials—behaviors such asdensity, compressibility, strength, and chemicalreaction rates.

Only when the applied properties havesufficiently changed can we anticipate theirimpact on weapon performance. Therefore, theneeds of the stewardship program have drivenour studies toward nanoscale scientific investi-gations. The essence of this approach can beseen in the illustration on page 9, wherechanges at the atomic scale precede changes atthe microscopic or macroscopic scale, whichlead to changes in material properties, andultimately, in device performance.

Analyzing, predicting, and mitigatingaging effects in pits, specifically plutoniumpits, are key to ensuring long-term safety andreliability in the primary stage of nuclearweapons. We are studying the many changesthat result from aging, including engineeringand physics performance characteristics suchas equation of state, spall and ejecta formation,strength, density, geometry, corrosion resis-tance, and nuclear reactivity.

1st quarter 2001


Our understanding of plutonium aging iscomplicated by the fact that plutonium dis-plays some of the most complex physical andchemical properties of any element in the peri-odic table. Aging mechanisms that can causechanges in fundamental plutonium materialand mechanical properties include thein-growth of decay products, uranium recoildamage and associated void formation, voidswelling, changes in density, phase stabilityconcerns, changes in surface chemistry, and avariety of environmental changes, includingthermal cycling.

Developing advanced characterizationtools to measure changes in these propertieswill expand our nuclear materials knowledgebase and form the basis for computationalmodels necessary for predictive assessment.

We have adopted a dual strategy of usingdata obtained from the oldest available pitsand validated accelerated aging experimentsusing plutonium-238-spiked alloys to charac-terize the physics, engineering, and materialsproperties of plutonium.

Accelerated aging alloys can be qualifiedby comparing them with normal alloys andthe oldest pits. Changes in key properties canbe predicted by modeling anticipated agingeffects, especially radiation damage within theplutonium lattice. Measurement of these keypit properties will be used to determine age-related changes and to validate models.

The Enhanced Surveillance Campaignand the needs of the Science-Based StockpileStewardship Program have supported thedevelopment of new science and technology,including resonant ultrasound measurementsof the plutonium modulus, X-ray absorptionspectroscopy and neutron-scattering measure-ments of plutonium structure, microstructureand surface characterization, positron annihi-lation spectroscopy, isochronal annealingstudies of radiation damage, dynamic prop-erty measurements, and new theoreticalmodels of radiation damage effects.

These tools will be useful in makingstockpile life-extension decisions,determining when or if a Modern PitManufacturing Facility will be built, and forthe weapon systems’ annual certification tothe president.■



Pit Disassembly and Conversion Addressa ‘Clear and Present Danger’

Pit Disassembly

Hydride-DehydrideFurnace

OxideConversion

IncomingPit Assay

PlutoniumOxide Canning and

Decontamination

Plutonium Removal and Conversion

O2

PlutoniumMetal

ProductAssay

For five decades, the world’s superpowerssought to increase the number of weapons intheir nuclear stockpiles. With the end of theCold War and the advent of strategic armsreduction treaties and agreements, the UnitedStates and Russia are committed to retiringthousands of weapons from their stockpiles.But peace poses a dilemma: What should bedone with the hundreds of tons of weapons-grade plutonium removed from thesedismantled weapons?

In 1994, the National Academy of Sciences,in the report “Management and Disposition ofExcess Weapons Plutonium,” called the exist-ence of this excess material “a clear andpresent danger to national and internationalsecurity.” The safe disposal of surplus plutoniumis key to the U.S./Russia arms-reduction effort.

The heart of the disposition program is pitdisassembly and conversion, which is led byLos Alamos. The technology includes disman-tling pits, the core of nuclear weapons;converting the plutonium from pits into aform suitable for use as an actinide ceramicmaterials, mixed-oxide fuel; providingtechnical support for the design of the PitDisassembly and Conversion Facility (PDCF)at Savannah River, slated to open before 2010;managing the Russian Federation pit disas-sembly and conversion; and supporting theRussian Federation nuclear fuel activities.

A major part of the Laboratory’s pitdisassembly and conversion responsibilitiesis the Advanced Recovery and IntegratedExtraction System (ARIES), a state-of-the artprototype glove-box line operated at theTA-55 Plutonium Facility by NMT-15.

The ARIES line converts plutonium intoan unclassified form that can be stored insealed containers and examined by interna-tional nuclear material inspectors. Thetechnology has been demonstrated to mini-mize waste and reduce worker exposure. Datacollected from ARIES is being used to helpdesign the PDCF at Savannah River.

ARIES incorporates a variety of basicand applied research, and development anddemonstration activities, including gas-solidkinetics, materials corrosion, glove-box andcontainer decontamination, pit machiningoperations, plutonium-conversion processes,tritium removal from contaminated plutonium,actinide electrochemistry, and long-termstorage packaging.

Evaluation techniques used at ARIESinclude nondestructive assay, classified-partsanitization, and advanced separation.The work requires expertise in a variety ofdisciplines, including materials science, engi-neering, chemistry, physics, robotics andautomation, and software development.

Housed in a sequential series of gloveboxes, ARIES consists of five modules, eachdesigned to carry out a specific function. Eachmodule incorporates advanced technologiesthat increase operational efficiency.

The process begins when a pit is introducedinto the system. The pit enters the pit bisectionmodule, where it is bisected by a tool thatworks like a pipe cutter. The pit may also bedisassembled using a lathe. However, unliketraditional lathes, the pit bisection tool and theadvanced lathe operations produce minimalwaste chips. From here, the pit undergoes aplutonium removal and conversion process.

Contributors to thisproject are:Timothy Nelson(NMT-15 groupleader), StevenMcKee (NMT-15deputy group leader),Chris James (U.S.Pit Disassembly andConversion projectleader), StanZygmunt (U.S./Russian Conversionproject leader),Douglas Wedman(ARIES projectleader), andDavid Kolman(Pit Disassembly andConversion Researchand Developmentproject leader)

A flow chart of theARIES glove-box line.

1st quarter 2001


To convert plutonium into an oxideform—the preferred product form for mixed-oxide fuel (MOX)—the plutonium from the pitis oxidized in the direct metal oxidation(DMO) furnace. In some pits, the plutoniummay be removed by a reaction with hydrogen,which forms plutonium hydride powder. Thepowder is thermally treated to form a metalpuck that releases the small amount of hydro-gen for reaction with more plutonium. To con-vert plutonium metal to oxide, the puck alsocan be processed through the DMO furnace.Researchers currently are investigating otheroxide conversion processes, including onethat involves a hydride/nitride processand oxidation.

Once the plutonium has been convertedinto either an oxide or a metal, it is packagedto meet Department of Energy (DOE) long-term storage criteria. This packaging involvesthree containers, two of which are hermeticallysealed and leak-checked. Before the first her-metically sealed container can be removedfrom the glove-box line, researchers electrolyti-cally clean the surface using a process similarto electropolishing.

An electrolyte that consists of a sodiumsulfate and water solution uses electricity toinduce a chemical reaction that removes a uni-form layer of material and any contaminantson the cans. This module minimizes waste byrecycling the electrolyte.

After the metal or oxide is packaged, aseries of robotically operated nondestructiveassay instruments confirms the quantity ofplutonium in each package. These measure-ments are important for nuclear security andsafeguards; similar techniques will be used byinternational inspectors to confirm the pack-age contents without having to open them.

The pit bisector and hydride/nitrideprocesses were collaborative efforts betweenLos Alamos and Lawrence Livermore NationalLaboratory. Currently, NMT-15 and NIS-5 areworking with the Russian Federation todevelop a similar nondestructive assaysystem for use in Russia.

ARIES has beensupported since 1995by the DOE Office ofFissile MaterialsDisposition, nowknown as NN-60 inthe National NuclearSecurity Administra-tion. It was dedicatedin September 1998.The ARIES line thenwent through a seriesof “hot” tests andcompleted its firstintegrated demonstra-tion, a three-month production-typerun that included seven pit types, inSeptember 1999.

Since its first integrated demonstration, theARIES line has been upgraded to allow for anincrease in the size of the container. Thischange required adjustments to the nonde-structive assay instruments and robot, electro-lytic decontamination fixture, and inner andouter container welding station.

Other upgrades performed since 1999include the development of a pit disassemblylathe, a process control system for the lathe,and a process-control system for thehydride/dehydride process.

ARIES is being readied for a secondintegrated demonstration later this year. Afterthis demonstration, researchers will install asecond set of upgrades that includes a fullyautomated packaging line, developed withSandia National Laboratories; a part sanitiza-tion process; a uranium cleaning and burningglove-box line; two new direct-metal oxidationfurnaces; a laser-ablation inductively coupledplasma mass spectrometer for elementalanalysis; and uranium nondestructiveassay equipment.

The upgrades also will includemodifications to the special recovery linethat removes tritium contamination fromplutonium and adapting robotics forpit handling in conjunction withlathe operations. ■

A Fanuc robotpositions a weldedARIES material canfor leak testing beforedecontamination. Thisfully automated systemreduces workerexposure during thepackaging of plutoniumoxide. The system isundergoing extensivepreinstallation testing atTA-46 and should beoperational within theTA-55 PlutoniumFacility by the end ofDecember.



Bailey, G., E.A. Bluhm, J.L. Lyman, R.E. Mason,M.T. Paffett, G.P. Polansky, G.D. Roberson,M.P. Sherman, K. Veirs, and L.A. Worl, “GasGeneration from Actinide Oxide Materials,”Los Alamos National Laboratory report LA-13781-MS (December 2000).

Balkey, J.J., and R.E. Wieneke, “Transuranic WasteManagement at Los Alamos National Laboratory,”Nuclear Energy—Journal of the British Nuclear EnergySociety 40 (1), 53-58 (2001).

Jordan, H., “Analysis of Aircraft Crash Accident ofWETF,” Los Alamos National Laboratory reportLA-13799-MS (January 2001).

Jordan, H., “Seismic Performance Requirements onWETF,” Los Alamos National Laboratory reportLA-13798-MS (January 2001).

Martinez, B.T., “WITS — Waste Data Collection withOur Palms at Our Fingertips,” Los Alamos NationalLaboratory document LA-UR-00-4028, in Proceedingsof Spectrum 2000, International Conference onNuclear and Hazardous Waste Managment,CD-ROM (August 2000).

Miller, D.A., W.R. Thissell, D. MacDougall, andJ.J. Balkey, “Effect of Repeated CompressiveDynamic Loading on the Stress-Induced MartensiticTransformation in Niti Shape Memory Alloys,” LosAlamos National Laboratory document LA-UR-00-384 (June 2000).

Mitchell, J.N., R.A. Pereyra, W.B. Hutchinson,L.A. Morales, T.G. Zocco, and J.E. Vorthman,“Microstructural and Phase Characterization ofCimmaron Test Material,” Los Alamos NationalLaboratory report LA-13779-MS (January 2001).

Reimus, M.A.H., and G.L. Silver, “Metals for theContainment of Nitric Acid Solutions of Plutonium-238,” J. Radioanal. Nucl. Chem. 242, 265-277 (1999).

Ronquillo, R., “Preparation of a Glovebox for Cast-ing Plutonium Enriched with 238Pu,” in Abstracts ofPapers of the American Chemical Society 220, Pt.1,p. U210 (August 2000).

Scoates, J.S., and J.N. Mitchell, “The Evolution ofTroctolitic and High Al Basaltic Magmas in Protero-zoic Anorthosite Plutonic Suites and Implications forthe Voisey’s Bay Massive Ni-Cu Sulfide Deposit,Econ. Geol. 95, 677-701 (2000).

Sheldon, R.I., G.H. Rinehart, S. Krishnan, andP.C. Nordine, “The Optical Properties of LiquidCerium at 632.8 nm,” Mater. Sci. Eng. B 79, 113-122(2001).

Silver, G.L., “Pu(IV) Polymer Formation,” LosAlamos National Laboratory document LA-UR-00-2506 (to be published in J. Radioanal. Nucl. Chem.).

Wong, A.S., “Chemical Analysis of Plutonium-238for Space Applications,” in Space Technology andApplications International Forum 2001 552,(February 2001).

PublicationsandInvited Talks

Attention, authors:Have you published apaper, book or bookchapter, or givenaninvited talk? Pleasesend the particulars [email protected] andwe’ll publish your cita-tion in a future issueof ARQ.

Newsmakers

■ Fellows Prize: David Clark (NMT-DO) is one of three technical staff members named 2000 LabFellows Prize winners. The Fellows Prize recognizes high-quality published research in science andengineering having a significant impact on a particular field or discipline. Clark was recognized for hisoutstanding contributions to the understanding of the molecular behavior and solution chemistry ofactinide ions. Recipients of the award received a $3,000 check and a certificate from Director John Browne.

■ High school talk: As part of NMT’s outreach activities, Derek Gordon (NMT-14) recently gave a talkon nuclear energy to juniors at St. Michael’s High School in Santa Fe. His talk covered the Los AlamosARIES program and the current U.S.–Russia collaborations on weapons dismantlement and the use ofmixed-oxide fuels.

■ Pollution Prevention Award: A team from NMT-9 has earned a 2000 Pollution Prevention Awardfrom the Lab’s Environmental Stewardship office for its development of an improved process to isolateplutonium oxide from scraped fuel. Plutonium-238 is used in heat sources and heat units for NASAdeep-space missions. The innovation has cut the recovery waste stream by more than 75 percent and ishelping the Lab move closer to meeting the DOE’s 2005 pollution prevention goals. Team members include.Gerald Allethauser, Jason Brock, Amy Ecclesine, Paul Moniz, Jonetta Nixon, Maria Pansoy-Hjelvik,Kevin Ramsey, Mary Ann Reimus, Mary Remerowski, and Gary Silver.

1st quarter 2001


Editor's note: The following excerpts are fromEnergy Secretary Spencer Abraham's April 19all-hands meeting at Los Alamos.

… Los Alamos has a history that is aspecial one and, perhaps, can best be describedas humbling to all of us. I’m sure when youthink about the people in whose footsteps youhave followed—the Oppenheimers, the Tellers,and others, it’s on one hand inspiring and onthe other hand kind of overwhelming. I sus-pect that’s a daunting challenge, but I believethat the people working here today are everybit as able and talented as those who precededyou, and we look forward to accomplishinggreat things together.

You look at what has happened and whatLos Alamos has been able to contribute tomankind, and in my judgment those benefitsare incalculable, whether it was victory for theAllies in the second world war or it was vic-tory for the West in the Cold War. But for you,breakthrough science would take place inanother country. But for you, supercomputingwould be a technology for us to purchaseabroad, not develop and refine here at home.And, but for the people who’ve worked at thisfacility, we would now be living in the 55th

year of the Cold War, instead of enjoying theeleventh year of the peace dividend.

… But we don’t live in a totally peacefulworld, even though the Cold War may be over.It’s still a dangerous place. Our stockpile, theweapons that are built and maintained, is aresult of no small measure of the work that’shere, remain the vital factor that ensures thestability of America’s national security in achanging and dangerous world. As much aswe admire the work of the scientists whobrought us the first weapons—Fat Man andLittle Boy—it is clear that your scientific con-tributions are no less important than theirs.

… Gen. Gordon has pointed out to me thatour labs are today again exploring territorythat is virtually as uncharted and complex asthat which was opened up by the scientists ofthe Manhattan Project. No one in history, asfar as I know, has ever tried to confirm the

reliability of weapons without testing them,and yet, that’s precisely what we are doingnow. It’s really an astonishing technical andscientific enterprise, and it calls for the samequalities of genius that this facility has un-leashed throughout its history.

At the same time, our missiontoday is broader and more difficultbecause we have added counter-proliferation and nonproliferation toour traditional missions of deterrentsas we attempt to reduce a host ofthreats to our nation. I can’t think ofanything more compelling in termsof a mission or one that calls upon agreater degree of technical excellencethan those that we confront today.

… I consider nothing that I havein terms of responsibility moreimportant then the duty that I sharewith the secretary of defense to cer-tify to the president, along with ourLab directors, the fitness of ourstockpile. … What I’ve tried to con-vey to the White House and to theother policymakers is the significantimportance of the stockpile stewardship pro-cess that we are so integrally tied up with herein the department and the NNSA. In an erawhere we don’t test, as you know better thananybody does, the work that we do to certifyis the most critical component in manyrespects of America’s national securitythat we have.

Our deterrent capability is only premisedon the belief on the part of the rest of theworld that the weapons we have will work ina reliable fashion. If we don’t test thoseweapons, but in fact work through the science-based stockpile program to try to ensure thatreliability, then the work you’re doing is prob-ably as central as anything could possibly beto the long-range security of this country.

It is my hope and my plan to worktogether with John Gordon to make sure thatsufficient resources are provided to be able todo that work in the fullest sense. …

New Energy Secretary Addresses Los Alamos Employees

photo by LeRoy N. Sanchez

Energy SecretarySpencer Abraham.



The Actinide Research Quarterly highlights recent achievements and ongoing programs of the NuclearMaterials Technology (NMT) Division. We welcome your suggestions and contributions. If you have comments,suggestions, or contributions, you may contact us by phone, mail, or e-mail ([email protected]). ARQ also can be readon the World Wide Web at: http://www.lanl.gov/Internal/divisions/NMT/nmtdo/AQarchive/AQindex/AQindex.html.

Nuclear Materials Technology DivisionMail Stop E500Los Alamos National LaboratoryLos Alamos, New Mexico 87545Phone (505) 667-2556/Fax (505) 667-7966

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NMT Division Director: Timothy GeorgeChief Scientist: Kyu C. KimWriter/Editor: Meredith S. CoonleyDesign and Production: Susan L. CarlsonPrinting Coordination: Lupe Archuleta

Los Alamos National Laboratory, an affirmative action/equal opportunity employer, is operated by the University of California for the U.S. Department of Energy under contract W-7405-ENG-36.All company names, logos, and products mentioned herein are trademarks of their respective companies. Reference to any specific company or product is not to be construed as an endorsementof said company or product by the Regents of the University of California, the United States Government, the U.S. Department of Energy, nor any of their employees. Los Alamos NationalLaboratory strongly supports academic freedom and a researcher’s right to publish; as an institution, however, the Laboratory does not endorse the viewpoint of a publication or guarantee itstechnical correctness.

Newsmakers ■ Department of Energy Secretary Spencer Abraham recently made his first visit to LosAlamos since becoming energy secretary. One of his stops was TA-55, where he was given a les-son on how to work in a glove box and an overview of the Laboratory’s plutonium pit fabrica-tion program. He also was trained and performed a step in the pit fabrication and certificationprocess. “What the trip today has so far done is reinforce my pride in and confidence in thepeople who work in our labs,” Abraham said. “I wanted to come here early to just reinforce myalready-held opinion of the quality of work done here and to try to assess some of the needs soI could be a more effective participant in the [national security] reviews.” Abraham later toldreporters he is working closely with NNSA Administrator Gen. John Gordon to identify chal-lenges the DOE faces and how it can work with the National Security Council, Department ofDefense, and otheragencies. One of thosechallenges, he said, islong-range strategicdecisions as to theU.S.’s nuclear forces,the nation’s stockpileof nuclear weapons inrelation to nonprolif-eration, and counter-proliferation programs.Gen. Gordon accom-panied Abraham onhis April 19 visit.

See page 15 forexcerpts fromAbraham’sall-hands meeting. photo by LeRoy N. Sanchez

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