Quantitative X-Ray Diffraction Analysis of Titanate Waste Forms and its Application to Damage Ingrowth

1992 ◽  
Vol 294 ◽  
Author(s):  
T.J. White ◽  
H. Mitamura
Keyword(s):  
Ionizing Radiation ◽  
Diffraction Analysis ◽  
Nuclear Waste ◽  
Alpha Decay ◽  
X Ray Diffraction ◽  
Structural Degradation ◽  
X Ray ◽  
Waste Forms ◽  
Radiation Induced

ABSTRACTQuantitative powder X-ray diffraction was used to analyse the phase assemblages of titanate nuclear waste ceramics doped with 244Cm and accumulating a-decay doses up to 1.24 × 1018 alpha-decay-events g−1. Among the Cm-bearing phases, perovskite is more susceptible to damage than zirconolite. Phases devoid of curium (hollandite and freudenbergite) experience a flux of ionizing radiation, and may also undergo radiation-induced structural degradation. The analysis demonstrated that at a dose of 1.24 × 1018 alpha-decay-events g−1 approximately 20 wt% of the waste phases remain aperiodic after annealing for 2 hours at 800°C.

Rietveld Analysis of Phase Separation in Annealed and Leach Tested Cm-Doped Perovskite

1994 ◽  
Vol 353 ◽  
Author(s):  
T. J. White ◽  
H. Mitamura ◽  
T. Tsuboi
Keyword(s):  
Nuclear Waste ◽  
Bulk Composition ◽  
Alpha Decay ◽  
Weight Percent ◽  
Rietveld Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Reducing Conditions ◽  
Structural Recovery ◽  
Fluorite Type

AbstractA quantitative powder X-ray diffraction study was made of actinide doped perovskite of bulk composition Ca0.98919An0.01081Ti0.98919Al0.01081O3 where An corresponded to approximately equimolar proportions of Cm-244 and Pu-240. Sections of this sample accumulated irradiation doses up to 7.51 × 1017 alpha decay events per gram (± g−1). The damaged samples were treated in two ways. First, to establish the critical temperature for structural recovery under the reducing conditions of geological repositories, isochronal annealing was carried out at 600, 800, 1000 and 1100˚C for 12 hours in graphite crucibles. Two groups of perovskites that had previously sustained doses of 4.5 × 1017 and 7.4 × 1017 ± g−1 were tested in this way. For the former group, these conditions resulted in up to 9 weight percent (wt%) of available actinide separating as a fluorite-type dioxide near the perovskite surface. In the latter group, calcium was reduced to the metal which vaporised, leaving an excess of refractory titanium that crystalised as rutile. Second, material which had sustained doses of 1.6–4.0 × 1017 alpha decays per gram was subjected to an MCC-1 leach test for two months at 90˚C using a pH ∼ 2 solution. Under these conditions surficial perovskite dissolved congruently to release calcium into solution while the titanium reprecipitated as anatase. The implications of these results for the ultimate disposal of perovskite-bearing polyphase nuclear waste ceramics are considered.

The Metamict State

MRS Bulletin ◽  
1987 ◽  
Vol 12 (4) ◽  
pp. 58-66 ◽  
Author(s):  
R.C. Ewing ◽  
B.C. Chakoumakos ◽  
G.R. Lumpkin ◽  
T. Murakami
Keyword(s):  
Ion Beam ◽  
Alpha Decay ◽  
Alpha Particles ◽  
X Ray Diffraction ◽  
X Ray ◽  
Conchoidal Fracture ◽  
Decay Series ◽  
Radiation Induced ◽  
Metamict Minerals ◽  
Amorphous Substances

Recently, the words “metamict” or “metamictization” have been increasingly used instead of “amorphous” or “amorphization” in acknowledgment of the fact that the first recognized example of the transition from the crystalline to the aperiodic state was in natural materials—minerals. The term (originally “metamikte” from Greek for “mix otherwise” because of their complex compositions) was first defined by Broegger in a Danish encyclopedia as one of three classes of amorphous substances: porodine (= colloidal), hyaline, and metamikte. Minerals considered to be metamict were judged amorphous because of their conchoidal fracture and isotropic optical properties; however, well-developed crystal faces evidenced the prior crystalline state.Hamberg was the first to suggest that metamictization is a radiation-induced, periodic-to-aperiodic phase transition caused by alpha particles which originate from constituent radionuclides in the uranium and thorium decay series. Rinne and Vegard confirmed by x-ray diffraction studies that metamict minerals were either amorphous or finely crystalline. Later work supported the idea of a radiation-induced transformation. The work of Stackelberg and Rottenbach established that the decrease in density, refractive indices, and birefringence correlated with the breakdown of the structure with increasing alpha-decay dose. Stackelberg and Rottenback tried to test this hypothesis directly by bombarding a thin slab of zircon with alpha particles. The results were inconclusive because the slab fractured, but this must have been one of the first experiments in which an “ion beam” was used to “modify” a material.

Alpha-Decay Damage and Annealing Effects in Natural Pyrochlores: Analogues for Long-Term Radiation Damage Effects in Actinide, Pyrochlore, Structure Types

1988 ◽  
Vol 127 ◽  
Author(s):  
G. R. Lumpkin ◽  
R. C. Ewing
Keyword(s):  
Pyrochlore Structure ◽  
Alpha Decay ◽  
X Ray Diffraction ◽  
Final State ◽  
X Ray ◽  
Waste Forms ◽  
Annealing Effects ◽  
Long Term Performance ◽  
Term Performance

ABSTRACTCubic pyrochlore structure types, A2-mB2O6(O, OH, F) i-n*pH2O, and their derivatives (e.g., monoclinic zirconolite) are important actinide-bearing phases in polyphase, ceramic waste forms (e.g., SYNROC). These waste form phases may typically accumulate alpha-decay doses of 1025 alpha-events/m3 in 1, 000 years or 1026alpha-events/m3 in one million years (i.e., for SYNROC with 20 wt. % HLW). Natural pyrochlores have calculated doses ranging from 1024 to 1027 alpha-events/m3 (= 0.02 to 50 dpa) which have accumulated over ten to a thousand million years. Actinide doping experiments typically reach doses of 1025 alpha-events/m3over periods of several years. Detailed x-ray diffraction analysis of natural samples reveals that the alpha-decay dose at which there is an initial loss of crystallinity (i.e., transition from crystalline to the aperiodic, metamict state as a result of alpha-decay damage) increases as a function of the geologic age of the sample. The increase in the calculated alpha-decay dose which is associated with a specific degree of damage (e.g., loss of x-ray diffraction intensity) is attributed to annealing of isolated alpha-recoil tracks back to the original, crystalline structure. Based on a model of gradual track fading, the alpha-recoil tracks in natural pyrochlores have mean lives on the order of 108 years. In contrast, minerals which remain crystalline (e.g., uraninite, UO2) despite doses of over 1027 alpha-events/m3 have mean alpha-recoil track lives of approximately 104 years. This demonstrates that the microstructure of alpha-decay damaged materials depends not only on the total alpha-event dose, but also on the annealing kinetics of alpha-recoil track fading. Therefore, the prediction of the long-term performance and final state of crystalline phases in ceramic nuclear waste forms requires the determination of alpha-recoil damage annealing as a function of time and temperature.

Ten-Vertex Polyhedral Monocarbaborane Chemistry. The Novel High-Yield Formation of the Ten-Vertex closo Compound [6-(PMe2Ph)-closo-1-CB9H9] from the Thermolysis of [8,8-(PMe2Ph)2-nido-8,7-PtCB9H11]

1993 ◽  
Vol 58 (12) ◽  
pp. 2924-2935 ◽  
Author(s):  
Jane H. Jones ◽  
Bohumil Štíbr ◽  
John D. Kennedy ◽  
Mark Thornton-Pett
Keyword(s):  
Nmr Spectroscopy ◽  
Diffraction Analysis ◽  
High Yield ◽  
Monoclinic Space Group ◽  
The Novel ◽  
X Ray Diffraction ◽  
Metal Centre ◽  
X Ray ◽  
Yield Formation ◽  
Boiling Toluene

Thermolysis of [8,8-(PMe2Ph)2-nido-8,7-PtCB9H11] in boiling toluene solution results in an elimination of the platinum centre and cluster closure to give the ten-vertex closo species [6-(PMe2Ph)-closo-1-CB9H9] in 85% yield as a colourles air stable solid. The product is characterized by NMR spectroscopy and single-crystal X-ray diffraction analysis. Crystals (from hexane-dichloromethane) are monoclinic, space group P21/c, with a = 903.20(9), b = 1 481.86(11), c = 2 320.0(2) pm, β = 97.860(7)° and Z = 8, and the structure has been refined to R(Rw) = 0.045(0.051) for 3 281 observed reflections with Fo > 2.0σ(Fo). The clean high-yield elimination of a metal centre from a polyhedral metallaborane or metallaheteroborane species is very rare.

Bis(μ-carboxylato)dienerhodium(I) Complexes - Synthesis, Characterization and Catalytic Activity

2008 ◽  
Vol 73 (8-9) ◽  
pp. 1205-1221 ◽  
Author(s):  
Jiří Zedník ◽  
Jan Sedláček ◽  
Jan Svoboda ◽  
Jiří Vohlídal ◽  
Dmitrij Bondarev ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Diffraction Analysis ◽  
Spectroscopic Methods ◽  
X Ray Diffraction ◽  
X Ray

Dinuclear rhodium(I) η2:η2-cycloocta-1,5-diene (series a) and η2:η2-norborna-2,5-diene (series b) complexes with μ-RCOO- ligands, where R is linear C21H43 (complexes 1a, 1b), CH2CMe3 (2a, 2b), 1-adamantyl (3a, 3b) and benzyl (4a, 4b), have been prepared and characterized by spectroscopic methods. Structures of complexes 2b, 3a and 4a were determined by X-ray diffraction analysis. Complexes prepared show low to moderate catalytic activity in polymerization of phenylacetylene in THF giving high-cis-transoid polymers, but they show only oligomerization activity in dichloromethane.

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