Tem Study of Radiation Damage and Annealing of Neutron Irradiated Zirconolite

1995 ◽  
Vol 412 ◽  
Author(s):  
Gregory R. Lumpkin ◽  
Katherine L. Smith ◽  
Ron G. Blake
Keyword(s):  
Radiation Damage ◽  
Heavy Ions ◽  
Initial Level ◽  
Amorphous State ◽  
Alpha Decay ◽  
Fluorite Phase ◽  
Main Stage ◽  
Structural Recovery ◽  
Dose Levels ◽  
Electron Beam Heating

AbstractNeutron irradiation was used to simulate alpha-decay damage in zirconolite, resulting in a transformation from the crystalline to the amorphous state at doses of 4–25 × 1019 n/cm2 (E ≥ 1 MeV). With increasing dose, the radiation damage microstructures resemble damage caused by: 1) alpha-decay of 232Th and 238U in natural zirconolites, 2) alpha-decay of 238Pu or 244Cm in synthetic samples, and 3) collision cascades in samples irradiated with heavy ions. Heavily damaged zirconolite recovers to a defect fluorite phase on annealing at temperatures up to 1000 °C. The main stage of structural recovery was found to occur at temperatures of 600–800 °C. The microstructures after heating depend on the initial level of damage: zirconolite grains with low to moderate levels of damage anneal to imperfect single crystals, whereas heavily damaged grains recrystallize to a polycrystalline microstructure. Complications encountered in this work include the production of fission tracks (due to trace amounts of U) and a non-uniform distribution of damage at higher dose levels (possibly due to electron beam heating).

Self-Radiation Damage in Actinide Host Phases of Nuclear Waste Forms

1984 ◽  
Vol 44 ◽  
Author(s):  
W. J. Weber ◽  
J. W. Wald ◽  
Hi. Matzke
Keyword(s):  
Radiation Damage ◽  
Nuclear Waste ◽  
Amorphous State ◽  
Alpha Decay ◽  
Ceramic Materials ◽  
Thermal Recovery ◽  
Radiation Induced ◽  
Crystalline Ceramic ◽  
Higher Doses ◽  
Nuclear Waste Forms

AbstractThree crystalline ceramic materials, which occur as host phases for the long-lived actinides in many nuclear waste formulations, were doped with Cm-244, and the effects of self-radiation damage from alpha decay on microstructure and physical properties were investigated. The irradiation-induced microstructure consisted of individual amorphous tracks from both the alpha-recoil particles and the spontaneous fission fragments. The eventual overlap of the tracks at higher doses leads to a completely amorphous state. This radiation-induced amorphization process results in measured increases in volume, leachability, and stored energy. Thermal recovery of the radiation-induced swelling and amorphization occurs with full recrystallization to the initial structures.

Specimen Preparation of Near Surface Ion Irradiated Samples

1985 ◽  
Vol 43 ◽  
pp. 170-171
Author(s):  
K. F. Russell ◽  
L. L. Horton
Keyword(s):  
Radiation Damage ◽  
Heavy Ions ◽  
Target Material ◽  
Metal Alloys ◽  
Specimen Surface ◽  
Specimen Preparation ◽  
Particle Accelerators ◽  
Near Surface ◽  
Graaff Accelerator ◽  
Van De Graaff

Beams of heavy ions from particle accelerators are used to produce radiation damage in metal alloys. The damaged layer extends several microns below the surface of the specimen with the maximum damage and depth dependent upon the energy of the ions, type of ions, and target material. Using 4 MeV heavy ions from a Van de Graaff accelerator causes peak damage approximately 1 μm below the specimen surface. To study this area, it is necessary to remove a thickness of approximately 1 μm of damaged metal from the surface (referred to as “sectioning“) and to electropolish this region to electron transparency from the unirradiated surface (referred to as “backthinning“). We have developed electropolishing techniques to obtain electron transparent regions at any depth below the surface of a standard TEM disk. These techniques may be applied wherever TEM information is needed at a specific subsurface position.

Characterization of Radiation Damage at the Nb Site in Natural Pyrochlores and Samarskites by X-Ray Absorption Spectroscopy

1988 ◽  
Vol 127 ◽  
Author(s):  
R. B. Greegor ◽  
F. W. Lytle ◽  
B. C. Chakoumakos ◽  
G. R. Lumpkin ◽  
J. K. Warner ◽  
...  
Keyword(s):  
Radiation Damage ◽  
Long Range ◽  
Absorption Spectroscopy ◽  
Alpha Decay ◽  
Long Range Order ◽  
Static Disorder ◽  
Annealed Condition ◽  
X Ray ◽  
X Ray Absorption

ABSTRACTX-ray absorption spectroscopy has been used to investigate the Nb B-site in pyrochlores (A1.2B2O6Y0–1, Fd3m, Z=8) and samarskites (A3B5O16) in both metamict and annealed condition. The XANES and EXAFS measurements indicate significant changes in pyrochlore and smaller changes in samarskite as a result of radiation damage. In the metamict state the Nb site in both pyrochlores and samarskites is similar to Nb in Nb2O5. Short Nb-O (1.65Å) bonds are not disrupted by alpha-decay/recoil-nuclei events as much as longer bonds (2.00Å). This increases the asymmetry and static disorder at the local Nb site while long range order is greatly diminished resulting in considerable distribution in Nb-M distances and bond angles.

Radiation damage in β-Ga2O3 induced by swift heavy ions

2019 ◽  
Vol 58 (12) ◽  
pp. 120914 ◽  
Author(s):  
Wensi Ai ◽  
Lijun Xu ◽  
Shuai Nan ◽  
Pengfei Zhai ◽  
Weixing Li ◽  
...  
Keyword(s):  
Radiation Damage ◽  
Heavy Ions ◽  
Swift Heavy Ions

Self-Irradiation of Monazite Ceramics: Contrasting Behavior of PuPO4 and (La,Pu)PO4 Doped with Pu-238

2004 ◽  
Vol 824 ◽  
Author(s):  
Boris E. Burakov ◽  
Maria A. Yagovkina ◽  
Vladimir M. Garbuzov ◽  
Alexander A. Kitsay ◽  
Vladimir A. Zirlin
Keyword(s):  
Radiation Damage ◽  
Crack Formation ◽  
Alpha Decay ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
Deep Blue ◽  
Long Term Storage ◽  
First Time ◽  
Term Storage

AbstractTo investigate the behavior of monazite during accelerated radiation damage, which simulates effects of long term storage, 238Pu-doped polycrystalline samples of (La,Pu)PO4 and PuPO4 were synthesized for the first time ever and studied using powder X-ray diffraction (XRD) analysis and optical microscopy. The starting precursor materials were obtained by precipitation of La and (or) Pu from their aqueous nitrate solutions followed by calcination in air at 700°C for 1 hour, cold pressing, and sintering in air at 1200-1250°C for 2 hours. The 238Pu contents in ceramic samples measured using gamma spectrometry were (in wt.% el.): 8.1 for (La,Pu)PO4 and 7.2 for PuPO4. The (La,Pu)PO4 monazite remained crystalline at ambient temperature up to a cumulative dose of 1.19 × 1025 alpha decays/m3. In contrast, the PuPO4 monazite became nearly completely amorphous at a relatively low dose of 4.2 × 1024 alpha decays/m3. Swelling and crack formation due to the alpha decay damage was observed in the PuPO4 ceramic. Also, under self-irradiation this sample completely changed color from initial deep blue to black. The (La,Pu)PO4 monazite was characterized by a similar change in color from initial light blue to gray, however, no swelling or crack formation have so far been observed. The results of this study allow us to conclude that the radiation damage behavior of monazite strictly depends on the chemical composition. The justification of monazite-based ceramics as actinide waste forms requires additional investigation.

Self-Irradiation of Ceramics and Single Crystals Doped With Pu-238: Summary of 5 Years of Research of the V. G. Khlopin Radium Institute

2008 ◽  
Vol 1107 ◽  
Author(s):  
Boris E. Burakov ◽  
Maria A. Yagovkina ◽  
Maria V. Zamoryanskaya ◽  
Vladimir M. Garbuzov ◽  
Vladimir A. Zirlin ◽  
...  
Keyword(s):  
Single Crystal ◽  
Radiation Damage ◽  
Single Crystals ◽  
Cumulative Dose ◽  
Crack Formation ◽  
Tetragonal Zirconia ◽  
Alpha Decay ◽  
Chemical Durability ◽  
Radium Institute ◽  
Cubic Zirconia

AbstractTo investigate the resistance of actinide host phases to accelerated radiation damage, which simulates radiation induced effects of long term storage, the following samples doped with plutonium-238 (from 2 to 10 wt. %) have been repeatedly studied using XRD and other methods: cubic zirconia, Zr0.79Gd0.14Pu0.07O1.99; monazite, (La,Pu)PO4; ceramic based on Pu-phosphate of monazite structure, PuPO4; ceramic based on zircon, (Zr,Pu)SiO4, and minor phase tetragonal zirconia, (Zr,Pu)O2; single crystal zircon, (Zr,Pu)SiO4; single crystal monazite, (Eu,Pu)PO4; ceramic based on Ti-pyrochlore, (Ca,Gd,Hf,Pu,U)2Ti2O7. No change of phase composition, matrix swelling, or cracking in cubic zirconia were observed after cumulative dose 2.77×1025 alpha decay/m3. The La-monazite remained crystalline at cumulative dose 1.19×1025 alpha decay/m3, although Pu-phosphate of monazite structure became nearly amorphous at relatively low dose 4.2×1024 alpha decay/m3. Zircon has lost crystalline structures under self-irradiation at dose (1.3-1.5)×1025 alpha decay/m3, however, amorphous zircon characterized with high chemical durability. The Ti-pyrochlore after cumulative dose (1.1-1.3)×1025 alpha decay/m3 became amorphous and lost chemical durability. Radiation damage caused crack formation in zircon single crystals but not in the matrix of polycrystalline zircon. Essential swelling and crack formation as a result of radiation damage were observed in ceramics based on Ti-pyrochlore and Pu-phosphate of monazite structure, but not so far in La-monazite doped with 238Pu.

Radiation damage of UO2 by high-energy heavy ions

1997 ◽  
Vol 248 ◽  
pp. 191-195 ◽  
Author(s):  
Kimio Hayashi ◽  
Hironobu Kikuchi ◽  
Kousaku Fukuda
Keyword(s):  
Radiation Damage ◽  
Heavy Ions ◽  
High Energy

An Overview of the Crystal Chemistry, Durability, and Radiation Damage Effects of Natural Pyrochlore

2000 ◽  
Vol 663 ◽  
Author(s):  
G.R. Lumpkin ◽  
R.C. Ewing ◽  
C.T. Williams ◽  
A.N. Mariano
Keyword(s):  
Radiation Damage ◽  
Large Body ◽  
Amorphous State ◽  
X Ray Diffraction ◽  
Natural Systems ◽  
Pyrochlore Group ◽  
Thermal Histories ◽  
Host Rocks ◽  
Long Term Behavior

ABSTRACTNumerous studies of pyrochlore group minerals have been completed over the previous 15 years, providing researchers in the field of nuclear waste disposal with a large body of data relevant to the behavior of these minerals in natural systems. The information obtained from studies of natural pyrochlore is applicable to the formulation of diverse waste form compositions and provides data for the assessment of the long-term behavior. Although resistant to dissolution, pyrochlore is subject to chemical alteration by ion exchange with hydrothermal fluids and low temperature ground water; however, Th and U are generally immobile and are retained in the structure. X-ray diffraction, TEM, EXAFS-XANES, and other techniques have been employed in studies of radiation damage. These studies reveal the classic sequence of damage microstructures with increasing dose and provide details about the structure of the amorphous state. Furthermore, the radiation damage studies are now complemented by data relating to the thermal histories of some of the host rocks.

The structure of aperiodic, metamict (Ca, Th)ZrTi2O7 (zirconolite): An EXAFS study of the Zr, Th, and U sites

1993 ◽  
Vol 8 (8) ◽  
pp. 1983-1995 ◽  
Author(s):  
François Farges ◽  
Rodney C. Ewing ◽  
Gordon E. Brown
Keyword(s):  
Radiation Damage ◽  
Nearest Neighbor ◽  
Alpha Decay ◽  
Range Order ◽  
Medium Range Order ◽  
Ambient Temperatures ◽  
Major Cations ◽  
Medium Range ◽  
Radiation Induced ◽  
Decay Event

The structural environments of Zr, Th, and U in aperiodic (metamict) (Ca, Th)ZrTi2O7 were examined using Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. Samples are aperiodic due to a radiation-induced transformation caused by alpha-decay event damage. In the aperiodic samples, Zr is mainly 7-coordinated [d(Zr−O) ≍ 2.14–2.17 ≍ 0.02 Å]; whereas, Th is mainly 8-coordinated [d(Th–O) ≍ 2.40−2.41 ≍ 0.03 Å]. Nearly identical bond lengths and coordination numbers for these elements were determined for an annealed, crystalline sample. The radiation-induced transition from the periodic to the aperiodic state is characterized by a significant broadening of the distribution of (Zr, Th)–O distances. In one metamict sample with ≍1.9 wt.% U3O8, U is essentially tetravalent. The absence of higher oxidation states (U6+) is consistent with the lack of evidence for alteration (samples are over 500 million years old). The reduced medium-range order around Zr, Th, and U is related to the increase of alpha-decay event damage and precludes decomposition of zirconolite into simple oxides of Zr, Th, or U. Comparison with other metamict (Zr, Th, U)-bearing phases (e.g., ZrSiO4 and ThSiO4) suggests that Zr4+, Th4+, and U4+ prefer 7-, 8-, and 6-coordinated sites, respectively, in aperiodic phases at ambient temperatures and pressures. Examination of the structure of crystalline (Ca, Th)ZrTi2O7 demonstrates that M–O–M angles (M = Ca, Ti, Zr, and Th) are relatively small (≍100–120° for edge-sharing polyhedra). A limited relaxation of the constraints of periodicity around M cations caused by radiation damage (e.g., tilting of polyhedra) dramatically affects the distribution of these angles. This type of structural relaxation may be the mechanism by which long-range periodicity is lost and medium-range order is reduced with increasing radiation damage, while the major cations retain their nearest-neighbor environments. This relaxation may also help explain the lattice expansion observed in zirkelites when they undergo radiation damage.

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