1st quarter 1999 TheLos Actinide Alamos National Research Laboratory N u c l e a r M aQuarterly 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 a U.S. Department of Energy Laboratory
Photoemission Studies at the Advanced Light Source Shed Light on Plutonium Phase Characteristics
In This Issue The physical characteristics of any given material are largely derived from the behavior of its valence electrons. Valence 1 electrons are the lowest-energy electrons in a material and Photoemission are responsible for the formation of chemical bonds. Typi- Studies at the cally, in a metal, electrons are either localized around a particu- Advanced Light lar atom or are delocalized (i.e., shared by all the atoms in the crystal) Source Shed Light on throughout the entire metal. The actinide series is interesting because as Plutonium Phase the atomic number increases across the series, the electrons in the Characteristics actinide metals transit from delocalized 5f electrons 4 (Ac–Pu) to localized 5f electrons (Pu–No). Plutonium (element 94) is located right at this transition. O2F in FOOF Holds Promise for Pu This placement in the series leads to pluto- Decontamination nium metal being one of the most com- plex materials known. Metallic 6 plutonium displays six allotropic Nuclear Materials phases (α, β, γ, δ, δ′, and ε) at stan- Including “Orphans” dard pressure. A 20% volume Require a Comprehen- expansion occurs during the sive Management change from the α phase to the Strategy δ phase. These physical properties 8 have been attributed to the 5f valence Wing 9 Hot Cells electrons changing from delocalized states to Support Work localized states as the crystal structure changes from Involving Highly the α to the δ phase. XBD9811-03028.tif photo courtesy Radioactive Materials Soft x-ray techniques (photonof University energyof California, in Berkeley the range of 10–1000 eV) such as photoelectron; x-ray emission; and near-edge resonant photoemission spectrum 11 x-ray absorption spectroscopies have been used to determine the Publications and electronic structure of many (in fact most) materials. However, these Invited Talks techniques have not been fully utilized on the actinides. The safety is- sues involved in handling the actinides make it necessary to minimize 12 NewsMakers the amount of radioactive materials used in the measurements. To our knowledge, the only synchrotron radiation source in the world where soft x-ray measurements have been performed on plutonium is the Spectromicroscopy Facility at Beam Line 7.0.1 at the Advanced Light Source (ALS). The ALS is the premier synchrotron radiation facil- ity in the world for the study of the electronic structure of materi- als using soft x-ray photons. The Spectromicroscopy Facility was first used for resonant photoemission measurements on plutonium oxide in 1993. Our first measurements on plutonium were conducted in the fall of 1998. continued on page 2
Nuclear Materials Research and Technology/Los Alamos National Laboratory 1 Actinide Research Quarterly
Photoemission Studies at the Advanced Light Source Shed Light on Plutonium Phase Characteristics (continued) The Spectromicroscopy Facility is de- Figure 2 shows the Pu 4f core-level photo- This article was signed so that measurements can be made on emission spectra from the α- and δ-plutonium contributed by small quantities of hazardous material. This samples. The spectrum arising from core-level Jeff Terry and facility has a photon flux of 1013 photon/sec at photoemission is sensitive to energy differ- Roland Schulze a photon energy of 100 eV with 0.01 eV resolu- ences in the initial state (no core hole) and the (both NMT-11). tion. The high photon flux allows one to focus final state (core hole and free photoelectron). Others contributing the beam down to a size of 50 microns and still The two core-level spectra in Figure 2 are simi- to the research were Jason have enough light intensity at the sample for lar in that they both show two features, a sharp Lashley (MST measurements to be conducted in a reasonable feature at low binding energy and a broad Division), Tom time frame, 1–10 minutes per spectrum. There- feature at higher binding energy. The low- Zocco (NMT-11), fore, the sample size can be on the order of 100 binding-energy feature can be ascribed to a J. Doug Farr microns in diameter. This greatly minimizes metallic initial state with a delocalized final (NMT-11), Eli the amount of plutonium on site during the state. As the 5f electrons are more delocalized Rotenberg, Keith experiment. The microfocussing capability in the α- than in the δ-plutonium, the greater Heinzelman, and also allowed us to focus onto a single δ- number of delocalized electrons in the α- David Shuh plutonium microcrystallite grown by Jason plutonium leads to greater intensity in this (Lawrence Lashley (MST Division). peak than the δ-plutonium. Berkeley We performed core-level photoemission, Presently, the higher-binding-energy fea- Laboratory), and Mike Blau and valence band photoemission, and near-edge ture is not completely understood. It is likely Jim Tobin x-ray absorption spectroscopy on both poly- that this feature has two states contributing to α δ (Lawrence crystalline -plutonium and -plutonium it. We believe that, in simplistic forms, one Livermore National microcrystals. Only the photoemission possible component contributing to the feature Laboratory). experiments will be described here. Photo- is made up of emission to an electronic final electron spectroscopy is predicated upon the state with localized 5f electrons. If this is the photoelectric effect first described by Einstein case, it suggests that both localized and delo- in 1905. The experimental photoemission calized 5f electrons are present in the α- and setup at the δ-plutonium phases. The second possible com- Spectromicroscopy ponent of this feature is from an initial state Facility is shown in that has been oxidized. Figure 1. An incident Valence band spectra show that a small photon is absorbed amount of oxygen remains on the surface after by an atom in the the sample preparation. The binding energy of
solid, and an electron PuOx is higher than that of the metal and is ejected. An electron would be expected to be seen around the posi- energy analyzer is tion of the unknown high-binding-energy fea- used to measure the ture. A final determination of the exact nature direction and kinetic of this high-binding-energy feature will shed energy of the emitted light on the poorly understood valence elec- electron. The kinetic tronic structure of plutonium, as well as on the energy of the photo- presence of localized and delocalized 5f elec- electron is directly trons in the different plutonium phases. related to its binding Our initial goal of the valence electronic energy in the solid. structure measurements was to determine the density-of-state of the 5f valence electrons in Figure 1. The photoemission setup at the α- and δ-plutonium. This experiment can be Spectromicroscopy Facility at ALS. The position of the directly compared with electronic structure analyzer is fixed with respect to the incoming photons. calculations performed by theoreticians. Fig- Angle-resolved photoemission is performed by rotating the ures 3(a and b) show the resonant photoemis- sample. sion spectra of the valence band from δ- and
2 Nuclear Materials Research and Technology/Los Alamos National Laboratory 1st quarter 1999
α 2.0 -plutonium, respec- Pu 4f Core Level Sharp Figure 2. Core-level photoemission Broad Manifold hν = 850 eV Metallic tively. In a resonant of States spectra from a large crystallite δ- Pass Energy 6 eV State photoemission experi- Alpha plutonium sample and a polycrystalline 1.5 ment, valence band Delta α-plutonium sample are shown. These photoemission spectra spectra were collected with a photon are collected as the pho- 1.0 energy of 850 eV and an analyzer pass energy of 6 eV. Note that two large
ton energy is scanned Intensity through a core-level components are visible in each spec- absorption edge. This 0.5 trum, a sharp feature at low binding can result in an en- energy and a broad feature at higher hancement of the emis- binding energy. sion from specific 0 -450 -440 -430 -420 -410 valence levels. In the Binding Energy (eV) case of plutonium, scanning the photon energy through the 5d A large theoretical Figure 3. The 5d–5f resonant photo- absorption edge results in a resonant enhance- effort has been under- emission spectrum with analyzer ment of the 5f valence emission. The 5d–5f taken to understand pass energy of 1 eV showing the 5f resonant photoemission measurements in plu- the plutonium data density of states in the valence band tonium are a measurement of the 5f contribu- that we have collected. from (a) a large crystallite δ-plutonium tion to the valence density of states. The next phase of the sample, and (b) a polycrystalline α- Two types of information are obtained in valence-band, elec- plutonium sample. the resonant photoemission measurements tronic structure mea- that can greatly enhance the understanding of surements will involve measuring the electron plutonium metal. Two-dimensional data slices dispersion relation (band structure) of the va- can be taken in either the constant-photon- lence electrons in δ-plutonium, and the energy direction or the constant-binding- data will be compared with theoreti- energy direction. Slices taken with a constant cal calculations. The band struc- photon energy are the equivalent to standard ture can only be measured on photoemission spectra with the exception that a single crystal of a material, specific valence states are emphasized. Differ- and it is imperative to have excellent crystals for the ent states turn on or become enhanced at dif- Binding Energy (eV) ferent photon energies. measurement. Future investi- The data in Figures 3(a and b) show clear gations will be based upon spin- differences in the resonant photoemission resolving and photon-dichroic α δ spectra from the - and -plutonium. This is photoelectron spectroscopy. The Photon Energy(a) (eV) most evident in the state at binding energy photon-dichroic measurements include the 0 eV. If this peak is followed as the photon variant magnetic x-ray linear dichroism. energy is varied, one notices that in the δ- The unique 5f valence electronic prop- plutonium (Figure 3a), after 100 eV, the peak erties of plutonium metal cannot be smoothly increased to a maximum and then explained by the typical one- smoothly decreased after the maximum was electron calculations used to reached. In direct contrast, the α-plutonium describe prototypical met- (Figure 3b) showed oscillatory behavior after als. Calculations on pluto- the initial maximum was reached. Theoretical nium metal incorporate calculations of the resonant photoemission are these properties into calcula- Binding Energy (eV) currently ongoing to try to understand these tions in an ad hoc manner. We can differences. measure these effects directly to fur- ther our understanding of one of the most (b) complex materials known. Photon Energy (eV)
Nuclear Materials Research and Technology/Los Alamos National Laboratory 3 Actinide Research Quarterly
O2F in FOOF Holds Promise for Pu Decontamination
The traditional method of recovering ura- Plutonium hexafluoride is the only known nium and plutonium from process streams is stable gaseous molecule at room temperature, to dissolve actinide-containing residues and so it is not surprising that several isotope sepa- wastes in strong acidic media and put them ration schemes were devised in the early years through a series of separation processes such using this molecule. as precipitation, filtration, and ion exchange. Once produced, plutonium hexafluoride is Over the half century of nuclear materials pro- fairly stable under process conditions such as cessing activities, this method has produced circulation, compression, and expansion, in- voluminous nuclear wastes stored at various side the process pipes. However, it is not so nuclear sites. The search for safe disposal easy to make plutonium hexafluoride under methods continues to this day. From a pro- mild chemical conditions. This problem is fur- This article was cessing efficiency standpoint, a better way of ther complicated when the MLIS end product contributed by separating actinides from their major constitu- is solid particles, and plutonium hexafluoride Kyu C. Kim, ents is to act upon only the minor components also decomposes slowly to a solid product that NMT Chief without dissolving the entire matrices. It coats the inside wall of the process pipes as the Scientist. would be ideal if a gaseous reactant could be process continues. So we needed a way or flowed through the residue matrices, and only ways to recover the solid product from the the volatile actinides recovered as gaseous process line. The only way to accomplish this products, leaving behind the actinide-depleted recovery was then to turn the solid product residues. This article describes identification back to gaseous product in situ. We were and analysis of an exotic chemical that holds searching for chemicals to accomplish the a great promise in actinide recovery, decon- product recovery and cleanup of the tamination of process equipment, and waste process line. reduction in actinide processing. By the early to mid 1980s we had identi- In the early 1980s the Los Alamos laser fied a few chemicals that could be used for the
isotope separation program for plutonium had purpose. Krypton difluoride (KrF2), dioxygen completed the scientific concept demonstra- difluoride (FOOF), and the fluorine atom were tion and moved toward a small-scale process the most promising among all we investigated. demonstration. This program was called Krypton and oxygen in these molecules are molecular laser isotope separation (MLIS) and merely carriers of F atoms. In the case of FOOF code-named Lippizan. Before this we had an we discovered subsequently that the active uranium isotope separation program code- species involved in the actual fluorination re-
named Jumper. Our sister laboratory at action was a radical species—O2F—derivable Livermore had two similar programs; their from FOOF. This story is about the discovery
process was called atomic vapor laser isotope of O2F and characterization of some of its separation. properties. A radical has unpaired electrons An MLIS process uses stable molecules unlike a stable molecular electronic configura- that bear the isotope of interest in their mo- tion so that it is usually very reactive with lecular structures. Both uranium and pluto- neighboring species, and it does not hang nium form stable gaseous molecules called around long (less than several seconds at hexafluorides. Six fluorine atoms occupy the most) for us to detect readily in its isolated six apexes in an octahedral geometry with a state. uranium or plutonium atom in the center. The structure of FOOF had been studied This particular soccer-ball-like geometry ac- previously by microwave spectroscopy by counts for the chemical stability as a gaseous other researchers. This compound is also very molecule. Most of the world’s supply of sepa- unstable. It can be stored indefinitely only at rated uranium isotope 235U comes largely from very low temperature, such as that of liquid a gaseous diffusion process employing ura- nitrogen. The infrared spectrum of solid (fro-
nium hexafluoride as the workingRN97377002.eps medium. zen) FOOF at 77 K had been recorded, and all
4 Nuclear Materials Research and Technology/Los Alamos National Laboratory 1st quarter 1999
1.20 fundamental vibrations assigned also. But the O F directly and O2F 2 0.29 spectral quality was very poor because these record its spectrum FOOF 0.21 measurements had been made on a minute in the absence of 0.85 FOOF. Now, this 0.14 quantity of impure samples. A serious obstacle Absorbance to the study of FOOF in the gas phase had experimental design 0.07 0 1560 1528 1496 1464 1432 been the difficulty in obtaining sufficient is based on the Wave number (cm-1) 0.50
amounts of the pure compound and preserv- assumption that the Absorbance C40-1.eps ing it for a sufficient length of time for spectro- half-life of O2F is suf- scopic investigation. ficiently long (for ex- In late 1984 we recorded for the first time a ample, seconds) so 0.15 complete infrared spectrum of gaseous FOOF that we could probe 3275 2425 1788 1363 938 513 obtained under well-defined conditions using continually while we Wave numbers (cm-1) a special spectrometer that we had developed produced this short- at Los Alamos. For the first time we were able lived species in an to make accurate vibrational frequency assign- experimental design, described below. Figure 1. The first ments and determine their intensities. The experimental design thus conceived is complete infrared Immediately after recording the first com- laser flash photolysis combined with coaxial spectrum of plete spectrum of FOOF, we noticed an unex- probing. A strong laser beam produces F at- gaseous FOOF. plainable spectral feature centered at 1490 cm-1 oms along its beam path, the F atoms react The laser pro- (See Figure 1.) This spectral feature did not with an oxygen molecule to form the transient duced O2F spec- trum is shown in vary in its relative intensity with the rest of the radical O2F, and its presence is detected simul- peaks. Furthermore, it is the only feature in the taneously by probing the sample volume the inset. entire fundamental infrared region apart from within the laser beam path. Although easily those of FOOF. The molecular vibrational described, this arrangement requires that the theory tells us that whatever species is respon- laser beam and the probe beam should be sible for this feature must be a compound sim- made co-linear, and the probe beam should be pler than FOOF or a heteronuclear, diatomic inside the laser beam volume for maximum molecule. We did not consider the idea of a sensitivity. We would make a mixture of two radical because of the attributes of radicals dis- basic ingredients, fluorine and oxygen, which cussed above. The half-life of a radical species we considered as the starting materials. An is typically so short that one cannot record its intense ultraviolet laser beam at 248 nm was spectrum over many minutes as required for a injected into the sample chamber that con- spectral scan. And yet this unexplained feature tained the mixture. The laser beam was pulsed persisted in all samples of FOOF. We also at less than 10 Hz. The probe infrared beam eliminated early on the possibility that it might from the spectrometer was combined using a be the diatomic radical OF because molecules dichroic mirror and made co-linear along the such as FOOF do not break apart at their entire beam path. Our hope was that as the stronger O-O bonds spontaneously under laser beam produced the expected radical these experimental conditions. species at some low-frequency interval, a
Within the first week of successfully re- steady-state concentration of O2F would be cording the FOOF spectrum, we had to specu- established between the production and disap- late that we might have an unusual radical pearance, and the probe infrared beam would species—O2F—coexisting with FOOF in our be monitoring this steady-state concentration sample. How then could we prove our hy- continually. (A dichroic optical material pothesis that a reactive radical species like O2F reflects and transmits different wavelength coexists with another unstable molecule— lights so that two beams of different wave- FOOF? To answer this question unambigu- lengths can be combined coaxially and propa- ously we devised an experiment to produce gated together along the same beam path.) continued on page 11
Nuclear Materials Research and Technology/Los Alamos National Laboratory 5 Actinide Research Quarterly
Editorial Nuclear Materials Including “Orphans” Require a Comprehensive Management Strategy
“Nuclear materials” is a generic term Our ability to achieve the goals of our excess meaning materials of interest to the nuclear fissile material disposition programs is depen- K. K. S. Pillay industry, sometimes synonymous with dent on complex international agreements and is the Project “source” and “special materials,” as listed in is likely to take many decades. Leader for Waste the Atomic Energy Commission Manual. A vast A large inventory of nuclear materials Management, knowledge base has been generated over the originating within and outside of national se- NMT-DO. past six decades to safely manage all nuclear curity programs exists in addition to those materials to maximize their benefits and mini- necessary for national security or declared ex- mize their hazards. However, it should be rec- cess. These may be properly described as “or- ognized that the knowledge base was not phan nuclear materials.” The disposition of always adequate nor effectively used in the orphan nuclear materials is still awaiting rec- preservation and use of these materials. As a ognition and resource allocations. A prelimi- result, many environments have been im- nary but incomplete estimate made last year pacted by nuclear materials, and the potential identified over 30,000 records of 72 million for impacting more still exists. Therefore, it is curies of miscellaneous radioactive materials. important to develop a comprehensive strategy The actual numbers may be many times those to better manage these valuable resources for identified last year. the future. A unique example of orphan nuclear ma- A recent estimate by the Brookings Institu- terials is the man-made neutron sources that tion points out that the United States spent are used extensively in defense projects, in- over $5.5 trillion during the past five decades dustries, universities, and research organiza- to build and maintain nuclear defense capabili- tions. Most of these neutron sources consist of ties, almost $1 trillion of this in nuclear materi- homogeneous mixtures of an alpha- or als production and related activities. Under a gamma-emitting radionuclide and a low- series of Congressional initiatives, the DOE has atomic-number element or its compound. It is the major responsibilities for long-term man- estimated that there are several hundred thou- agement of all nuclear materials from the de- sand such sources now in use within the U.S., fense sector and a major portion of those and about 3,000 are being produced and dis- originating from the civilian sector. Currently, tributed annually (Figure 1) . A 1985 Congres- numerous programs address the long-term sional mandate makes the DOE responsible Figure 1. Scott management of materials for national security for receiving abandoned, damaged, and re- Allen and George (including those re- Powell (BUS-4) sulting from weapons may be called dismantlement, upon to recover nuclear wastes, spent and transport nuclear fuels, and neutron sources contaminated sites widely used in and facilities). These oil and gas well programs are at vari- logging. Nuclear ous stages of develop- material "or- ment, demonstration, phans" such as and implementation. these sources pose a problem for the managed disposal of excess nuclear materials.
6 Nuclear Materials Research and Technology/Los Alamos National Laboratory 1st quarter 1999
turned neutron sources and disposing of them country participated in developing data and in an environmentally benign fashion. Inap- strategies for the management of all the propriate disposition of these sources has the “excess” nuclear materials within the DOE potential to cause extreme hazard to human complex and those that are likely to become beings and irreparable harm to the environ- DOE’s responsibility in the future. The three ment (Figure 2). Los Alamos National Labora- teams prepared a total of twelve independent tory spent many years to develop a simple, reports (nuclear material management plans) elegant method (chemical separation flow and submitted them to DOE/EM in 1998. sheet) to separate the two components of the Separate materials management plans were neutron sources. This technology was success- prepared for depleted uranium, high-enriched fully demonstrated in dismantling over a uranium, low-enriched uranium, natural ura- thousand neutron sources and making them nium, nonactinide isotopes, 241Am, 237NP and innocuous and environmentally benign. 238Pu, 239Pu, 242Pu, thorium, transuranic heavy Unfortunately, the implementation of this elements, and 233U. These reports are presently elegant technology to address large-scale dis- considered “predecisional draft documents” Figure 2. A dam- position of neutron sources is now in doubt. and are not yet available for general aged americium- Present challenges to nuclear materials distribution. beryllium neutron management are too numerous for extensive While many such studies have developed source recovered discussion here. There is, however, a tacit rec- valuable data, heretofore, follow-up actions from a private ognition that a common strategic framework have been disappointing. Missing in previous company by Los is necessary to avoid the environmental blun- follow-up actions is the desire to address the Alamos. ders of the past. During the past decade, a se- problem as a national or societal issue. Instead ries of studies and assessments have been it is always addressed as the issue relevant to performed to identify and quantify the needs a particular agency of the government or a of nuclear materials management. subordinate bureaucracy interested only in On January 20, 1998, the DOE Office of the simplistic solutions. It is this approach that Deputy Assistant Secretary for Nuclear Mate- ought to change to achieve the goals of a rial and Facility Stabilization initiated the comprehensive strategy to manage all nuclear Nuclear Material Integration (NMI) Project. materials for the benefit of mankind and to The goals of the NMI were to inventory and instill public confidence in associated tech- The opinions analyze the nuclear materials in the DOE nologies and institutions. in this editorial Complex. The scope of this project included In the best traditions of U.S. science, an are mine; they not only materials owned by the Office of En- objective evaluation of the recommendations do not neces- vironmental Management (EM) but also those made by the NMI teams has been requested by sarily represent owned by other programs and stored in EM an independent organization, the National the opinions facilities. The ultimate goal of this effort was Academy of Sciences. DOE/EM is champion- of Los Alamos to develop a comprehensive nuclear material ing the cause for an Academy study to review National management plan for the nation. the 12 reports. However, this study is still Laboratory, Three material management teams were waiting because of limited DOE resources. the University responsible for the different groups of materi- It is to be hoped that the Academy will evalu- of California, als in the DOE Complex: the Transuranic ate the reports, and that their recommenda- the Department Team, responsible for most transuranic ele- tions will include comprehensive management of Energy, or ments; the Uranium/Thorium Team, respon- and preservation of nuclear materials, includ- the U.S. sible for most uranium and thorium materials; ing neutron sources and other “orphans,” that Government. and the Nonactinide Isotope and Sealed are generated by both the defense and civilian Sources Team, responsible for all radioactive sectors. It is also to be hoped that such recom- isotopes with an atomic number less than 90, mendations will be implemented in a timely and all sealed sources, irrespective of atomic manner. number. About 250 people from across the
Nuclear Materials Research and Technology/Los Alamos National Laboratory 7 Actinide Research Quarterly
Wing 9 Hot Cells Support Work Involving Highly Radioactive Materials
The Wing 9 hot cells in the CMR Facility The current authorization basis allows a total were designed and constructed in 1960 to pro- inventory in the16 hot cells of up to 77 kg of vide shielding and remote handling capabili- 239Pu equivalent. ties for work on highly radioactive materials. Technical and programmatic objectives Commissioned in 1961 by President John F. require the Hot Cell Team in Group NMT-11 Kennedy, the hot cells supported the Rover to work on programs that encompass state-of- Project and the postmortem of irradiated fuels the-art remote handling of highly irradiated for breeder reactors. Even as the hot cells be- materials, components, and systems. A key gan decommissioning for closure in the late component of this program includes effective 1980s, they were used successfully to demon- facility management practices to maintain re- strate the characterization and packaging of mote handling operations that are compliant with DOE regulations. The Wing 9 staff exper- tise is the key to success with capabilities such as design engineering, process analysis, project management, welding, fabrication, robotic operations, and handing and shipping of high-activity components. Additionally, the staff has experience with the fabrication of parts made from special nuclear materials and disassembly and analysis of highly irradiated components and materials. Currently, the Wing 9 team is providing expertise to other laboratories and universities for a variety of special remote handling problems. Following are descriptions of some current Wing 9 projects.
The Molybdenum-99 Project Figure 1. The hot resident, remote-handled transuranic waste for In response to the U.S. medical cells in Wing 9 of eventual shipment to the Waste Isolation Pilot community’s concern that the nation must rely the CMR Building Plant (WIPP). This expertise continues to be a on a single, limited, foreign source for the ra- can remotely Wing 9 capability available to the industry and dioisotope molybdenum-99 (99Mo), Congress handle and the DOE complex. Since 1989, a variety of has tasked the DOE to develop a domestic process all types projects have been identified that have ex- source of 99Mo, which is essential for conduct- of radioactive tended the life of the facility and are discussed ing thousands of life-saving medical diagnos- materials that are later in this article. tic procedures each day. The 99Mo program Each of the 16 6’x6’x11’ hot cells and the alpha, beta, or involves five primary activities: (1) target fab- corridor that connects them are designed to rication, (2) target irradiation, (3) extraction neutron emitters. provide adequate shielding to the worker from Capabilities in- and purification, (4) transportation, and a 100,000 Ci source of 1-MeV gamma radiation (5) waste management. The Isotope Produc- clude character- (Figure 1). Also contained in the hot cells are ization and pack- tion and Distribution branch of the DOE in-cell remote machining and handling capa- conducted assessments that identified the best aging of WIPP bilities that allow operations on highly irradi- 99 waste as well as Mo production option currently available: ated components. The inner-cell door design the fabrication of uranium targets at Los tasks that may also provides a means of connecting two hot Alamos National Laboratory and target irra- require a room- cells for installation of large pieces of equip- diation, and extraction and purification pro- sized, heavily ment. The facility can handle all types of radio- cessing at Sandia National Laboratories. shielded remote- active materials that are alpha, beta, gamma, A target fabrication demonstration handling facility and neutron emitters. An array of 364 heavily program has successfully been completed in for highly radioac- shielded storage wells and a crane capacity up Wing 9. A target is a 304 stainless steel tube tive materials. to 25 tons support the hot cell capability.
8 Nuclear Materials Research and Technology/Los Alamos National Laboratory 1st quarter 1999
approximately 18 inches long and 1.25 inches in outer diameter. Inside the tubing, 235U is electroplated onto the steel surface to provide a very thin layer of uranium to interact with neutrons. The process takes 36 to 48 hours to deposit approximately 20 grams of uranium coating per target. The target tubes have caps welded at each end and are qualified as “reactor-ready” before transfer to Sandia for irradiation. The fabrication and electroplating process is shown in the glovebox enclosures in Figure 2.
Neptunium Project The NMT-11 staff of Wing 9 has been 237 asked to fabricate a clad, solid ~7 kg Np C377-4 metal sphere for criticality measurements at TA-18. The 237Np first-daughter product, 233Pa, is highly radioactive so the entire process must be performed within a shielded hot cell. Figure 2. The The necessary equipment to melt and cast other weapons-related activities. The system the 237Np metal remotely will be installed in a designed for accomplishing this activity con- Wing 9 fabrication hot cell “alpha box” to process the alpha- sists of an induction furnace for melting me- line produces emitting materials and to contain potentially tallic components and a jaw crusher for uranium targets high levels of contamination. The alpha box pulverizing brittle, nonmetallic items. This that will be used will be purged with nitrogen gas, which pro- system is tentatively planned for installation for production vides a low-oxygen-concentration atmosphere in Wing 9 of the CMR Building and consists of of 99Mo. to allow work with the neptunium metal, a several glove boxes containing the processing pyrophoric material. equipment and a HEPA-filtered environmen- The 237Np sphere will be cast in a vacuum tal housing surrounding the glove box system. within a graphite mold designed by MST-6 to Discussions with DOE sponsors are currently eliminate voids in the sphere volume. The underway to establish the funding and scope mold design (shown in Figure 3) has been suc- of the operation. cessfully tested by MST-6 using depleted ura- nium to cast a sphere to within about 0.010" on ULISSES Program the diameter and very near theoretical density. To achieve the next generation of uranium MST-7 personnel encapsulate the 237Np sphere processing technology, Los Alamos has devel- first within tungsten hemispheres and then oped the Uranium Line for Special Separation within two pure, welded Ni spheres for Science (ULISSES), a modular test-bed for cladding. This project provides a tool to the chemical process optimization. This new pro- Los Alamos Critical Experiments Facility staff cessing line will include state-of-the-art disso- Figure 3. Mold for experiments for fundamental research. lution chemistry and separation science, design test cast- on-line sensors coupled to automated instru- Sanitization Project mentation, and recycling with waste minimi- ing using depleted zation based on environmentally benign uranium. Eventu- Plans are being formulated to initiate a 237 sanitization project at Los Alamos to remove chemicals. This technology base will be used ally a clad Np classified aspects from actinide-contaminated, to develop, design, and demonstrate advanced sphere will be nonnuclear weapon components generated chemical processing technology that mini- used for criticality from disassembly of nuclear weapons and mizes hazardous wastes. measurements. continued on page 10
Nuclear Materials Research and Technology/Los Alamos National Laboratory 9 Actinide Research Quarterly
Wing 9 Hot Cells Support Work Involving Highly Radioactive Materials (continued)
Remote-Handled Transuranic Waste have an activity of up to approximately 20 Ci. (RH-TRU) Radioisotopes of interest to be separated are 82Sr/85Sr, 32P/33P, 184Re/186Re, 168Tm, 170Tm/ The RH-TRU Program involved character- 171 173 174m 174g 88 93 95 190 izing and packaging remote-handled TRU Tm, Lu/ Lu/ Lu, Zr/ Zr/ Zr, Ir/ This article was 192 waste for ultimate WIPP disposal. Because Ir, and possibly others. These radioisotopes contributed by many of the waste cans packaged thus far are limited to nonactinide materials. Stan have typical radiation readings between 400 Bodenstein, and 1000 R/hr at contact, a unique drum- Accelerator Production of Tritium Suzanne loading and canister-handling system was (APT) Program Helfinstine, designed and constructed for loading, weld- This Wing 9 capability has been developed Robert Romero, ing, packaging, and transportation of the to support the APT Program by evaluating and and Jim RH-TRU Waste (see Figure 4). To date, sixteen testing candidate materials that have been Ledbetter, WIPP-approved canisters have been character- irradiated (Alloy 718, 316L and 304L stainless ized, packaged, and placed into retrievable all of NMT-11. steel, modified Fe9Cr1Mo(T91), Al6061-T6, underground storage at Los Alamos (Area G) Al5052-0) for use in the APT target and awaiting shipment to WIPP. This capability in blanket. The specimens have been irradiated the hot cell facility is operational to support for fewer than 3,600 hours to a maximum the eventual disposition of RH-TRU waste at proton fluence of 4 x 1021 p/cm2 in the center of WIPP. The technology will also serve to re- the proton beam. Specimens are then carefully solve RH-TRU packaging problems at other sites within the DOE complex. removed from the packages in the hot cells in Wing 9 to begin mechanical testing, which Figure 4. Drum- Magnetic Isotope Separation (MIS) includes tensile, bend and compact tension loading, canister- tests, metallographic examination, and handling system Program transmission electron microscopy. Specimens for loading, weld- The MIS process is designed to separate will yield data on the effects of proton ing, packaging, isotopes for medical applications and the irradiation under a number of test conditions. and transportation stockpile stewardship program. The process is of waste destined performed in a separator system with the po- Actinide Source-Term Waste Test for WIPP. tential to process many different elements. The isotopes being separated are radioactive and Program (STTP) The Actinide STTP is designed to measure time-dependent concentrations of actinide ele- ments from actual, contact-handled TRU waste immersed in brines that are chemically similar to those typically found in the underground formations of WIPP. The STTP will determine the effect of TRU waste matrices and brine chemistry on the concentrations and behavior of actinides under WIPP bounding conditions. Several actual TRU waste types typical of DOE waste inventories have been character- ized and loaded into specially designed test containers filled with brine containing addi- tives to enhance the action of each influencing variable. The test containers are then placed in environmental chambers in Wing 9 to simulate in-situ conditions found at WIPP. Analysis is then performed on the brine leachate and headspace gas in the test containers.
10 Nuclear Materials Research and Technology/Los Alamos National Laboratory 1st quarter 1999
Publications and Invited Talks (December 1998–February 1999)
Editor’s note: We get information from the library when P. A. Leonard, E. A. Strietelmeier, M. E. Pansoy-Hjelvik, and R. T. Villarreal, papers have received LA numbers. However, it may be “Microbial Characterization for the Source-Term Waste Test Program (STTP) at many months before the papers are published. Since ARQ Los Alamos,” in WM ’99 Proceedings, HLW, LLW, Mixed Waste and lists only those papers that are published or have been Environmental Restoration - Working Towards a Cleaner Environment, accepted for publication, we have no way to track them WM Symposia, Inc., Tucson, AZ, in press. from the time they first receive numbers. We must rely on authors to tell us when their papers are accepted for R. Marshall, A. S. Wong, and D. Thronas, “Lawrence Livermore National publication in journals or proceedings. So when your Laboratory Working Reference Material Production Plan,” Los Alamos paper is accepted, we’ll tell your colleagues: please let us National Laboratory report LA-13552-MS (December 1998). know! Ann Mauzy, 667-5387, [email protected]. H. Nakotte, L. Laughlin, H. Kawanaka, Dimitri N. Argyriou, R. I. Sheldon, and Y. Nishihara, “Magnetic Properties of Single-Crystalline Mott Insulator YV0 ,” Invited Talks 3 Applied Physics, in press. E. A. Blum, “Inorganic Membranes for Metal Ion Separations: Surface Effects on Cation Transport L. L. Romero, J. M. Hoffman, E. May Foltyn, and T. E. Buhl, “Operational across Porous Alumina Membranes,” IE&C Comparison of Bubble (Super Heated Drop) Dosimetry with Routine Albedo Division, American Chemical Society, Anaheim, CA, TLD for a Selected Group of Pu-238 Workers,” accepted for publication in March 21–25, 1999. Operational Radiation Safety supplement to Health Physics Journal, in press. A. C. Lawson, B. Cort, J. A. Roberts, and S. B. Schreiber, S. L. Yarbro, E. M. Ortiz, F. Coriz, and S. Balkey, “Disposition of B. I. Bennett, “Neutron Diffraction and the Mixed Waste Organics at the Los Alamos Plutonium Facility,” Los Alamos Physical Properties of the Light Actinides,” National Laboratory report LA-13558-MS (January 1999). American Nuclear Society, Washington, D.C., November 16, 1998. S. M. Wander, I. R. Triay, P. S. Z. Rogers, S. T. Kosiewicz, D. R. Yeamans, A. R. Barr, J. D. Farr, J. Foxx, A. J. Montoya, M. A. Gavett, D. P. Taggart, S. E. Publications Betts, G. R. Allen, H. D. Poths, D. R. Janecky , C. P. Leibman, G. I. Vigil, and J. J. D. K. Dennison, D. Gallant, D. C. Nelson, Vigil, “Preparation of the First Shipment of Transuranic Waste by the Los L. A. Stovall, and D. E. Wedman, “Automated Alamos National Laboratory. A Rest Stop on the Road to WIPP,” in Nuclear Material Recovery and Decontamination Proceedings of the Waste Management ’99 Symposium, Laser Options, Inc., of Large Steel Dynamic Experiment Containers,” Tucson, AZ, in press. in “Proceedings of the 8th International Topical Meeting on Robotics and Remote Systems,” American Nuclear Society (ANS), ANS Pittsburgh Section, Monroeville, PA, in press.
O2F in FOOF Holds Promise for Pu Decontamination (continued)
Success was immediate. The spectrum of helped to meet some of the important isotope This article was based
O2F was recorded without the interference of separation program goals. The discovery of on the author’s work
FOOF and analyzed. With this discovery we O2F in FOOF found other applications in later and papers published in were able to study the properties of O2F and years for recovery of plutonium from pluto- the mid 1980’s. its chemical relationship with FOOF, another nium-containing residues and waste. In the Los Alamos first in laser photochemistry. future it may be a preferable alternative to It was one of the most wonderful detective acid dissolution of radioactive waste and can stories of an exotic chemical species and it be used to recover plutonium from glove box systems and process lines in reactor vessels.
Nuclear Materials Research and Technology/Los Alamos National Laboratory 11 Actinide Research Quarterly
NewsMakers ■ LBL Director Eulogizes Nobel Laureate Glen Seaborg, Who Died February 25, 1999. Following are excerpts from Lawrence Berkeley Laboratory Charles V. Shank’s memo to LBL employees: Dr. Seaborg was a true giant of the 20th Century, a legend in the annals of scientific discovery. His daily commitment to matters of the laboratory, even in retirement as associate director-at-large and as an active researcher, was an inspiration to us all…For his service to science, to education, and to our nation, we honor Dr. Seaborg’s distinguished lifetime and will forever treasure his contributions to our institu- tions and to our lives. We who have been touched by his wisdom, his energy, and his tireless devotion to our profession will miss him… I encourage you to reflect on Dr. Seaborg’s extraor- dinary life, much of it chronicled by him on an Internet Website accessible through our home page. Our thoughts and prayers are with the Seaborg family…
Dr. Seaborg’s Life and Contributions are on-line at
■ Division Awards Gordon Jarvinen has garnered the Division’s 1999 R. D. Baker Award in Science and Technology; Diedra Yearwood will receive the 1999 William J. Maraman Award for Excellence in Facility Operations at an award ceremony to be held Thursday, May 13, during the Division Review.
Nuclear Materials Technology Division Los Alamos Mail Stop E500 NATIONAL LABORATORY Los Alamos National Laboratory Los Alamos, New Mexico 87545 Los Alamos, New Mexico 87545 505/667-2556 FAX 505/667-7966 LALP-99-74 Director of NMT: Bruce Matthews Deputy Directors: Dana C. Christensen and David S. Post Chief Scientist: Kyu C. Kim Writer/Editor: Ann Mauzy Design and Production: Susan L. Carlson Printing Coordination: Lupe Archuleta
The Actinide Research Quarterly is published quarterly to highlight recent achievements and ongoing programs of the Nuclear Materials Technology Division. We welcome your suggestions and contributions. If you have any comments, suggestions, or contributions, you may contact us by phone, by mail, or on e-mail ([email protected]). ARQ is now on the Web also. See this issue as well as back issues on-line (http://www.lanl.gov/ Internal/divisions/NMT/nmtdo/AQarchive/AQhome/AQhome.html).
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12 Nuclear Materials Research and Technology/Los Alamos National Laboratory