Self-irradiation Effects Research Articles

Systematics of ovidic actinide compounds

This paper gives an updated review of recent developments in the field of ovidic actinide compounds, especially with respect to evisting systematics. It is shown that there is some success in evtending the number of evisting ovidation states, e.g. of curium to curium(V), as well as the hope of clarifying open vuestions on the possible evistence of octavalent plutonium in Li v PuO 6 mived ovides or of divalent americium fluoride, stabilived by incorporation in the fluorite structure of BaF 2 (SrF 2). The fluorite lattice in ovidic systems of An(Ac — Cm) can undergo a lot of changes, both in anionic and cationic sublattices. E.m.f. measurements in such systems as well as heat of solution data on actinide sesvuiovides and ordered perovskites give a good picture of the thermodynamic stabilities. Magnetic measurements of 5f 1 and 5f 3 ovidic compounds demonstrate a clear relationship between the transition temperature of magnetic ordering and the shortest An-An distance in the compound. No ordering evists if it is larger than about 450 pm. Despite a lot of new data being available many vuestions still remain open, e.g. those on the stability regions for actinide sesvuiovides, the influence on self-irradiation effects of high ovidation states or of phase evuilibria in most AnO 1.5-AnO 2+ v fluorite phases, e.g. for the AmO 1.5-UO 2 + v system.

Self-irradiation effects in plutonium compounds and the role of thermal spikes: EPR studies

The self-irradiation effects caused by α-radiation in a number of plutonium compounds have been studied using EPR technique. The radical species formed have been identified and the spin concentration measurements have been made. The efficiency parameter η, and the radiation-chemical G-value have been determined. The observed η and G-values are interpreted on the basis of thermal spike phenomena associated with α-paricles and recoil nuclei in the solid phase.

Self-irradiation effects in 238Pu-substituted zirconolite: II. Effect of damage microstructure on recovery

Samples of 238Pu-substituted zirconolite (CaPuTi 2O 7) were stored near room temperature to allow accumulation of alpha recoil damage. Differential thermal analysis was employed to measure release of stored energy accompanying recrystallization, after damage had proceeded for times from 35 days ( 4.7 × 10 24 alpha decays/m 3 ) to 1198 days ( 1.6 × 10 26 α/m 3 ). It was found that three parameters related to energy release (amount of stored energy, transformation temperature, and abruptness of transformation) were dependent on damage dose. Results are interpreted in terms of the quantity and distribution of remanent crystallinity, and of the consequences of redamage to once-damaged material.

Self-irradiation effects in 238Pu-substituted zirconolite : I. Temperature dependence of damage

238Pu-substituted cubic zirconolite (CaPuTi 2O 7) was stored near ambient temperature, at 575 K, and at 875 K until alpha decay doses as high as 6.1 × 10 25 α/m 3 were attained. Self-damage at the lowest temperature proceeded by accumulation of alpha-recoil tracks, but this was partly or wholly suppressed at the higher temperatures. Full conversion to the metamict condition near ambient temperature was accompanied by bulk swelling of 5.4 vol%. Self-damage at 575 K and 875 K was characterized by lesser amounts of swelling (4.3 vol% and 0.4 vol%); however, subsequent reduction of the storage temperature to ambient resulted in further swelling. Details of this swelling response imply structural differences between metamict states formed at 575 K and ambient temperature. Implications for self-irradiation effects in nuclear waste forms under variable temperature conditions are discussed.

Irradiation Effects in the Storage and Disposal of Radioactive Ion-Exchange Resins

ABSTRACTResearch is under way to characterize the effects of self-irradiation on radwastes which may be generated when organic ion-exchange media are used in water demineralization or decontamination operations at nuclear facilities. External factors affecting the relation between laboratory evaluations and field performance are emphasized. Initial experiments do not yet indicate substantial radiation dose-rate effects on radiolytic gas yields or acid product formation, when (fully swollen) sulfonic acid resins are irradiated in a sealed air environment. At the same time, oxygen gas is removed from the environment of irradiated resins. Interaction between mild steel coupons and acidic species produced in the irradiation induced decomposition of sulfonic acid resin results in irradiation enhanced corrosion. Corrosion rates depend on radiation dose rate, moisture content and resin chemical loading. In some cases, corrosion rates decrease with time, suggesting depletion of acidic species within the resin bed, or a synergistic interaction between resin and corrosion coupon. Implications of these and other results on evaluating field behavior of radwaste containing ion-exchange media are discussed.

Radiolysis and synthests of [N-methylene-3H]thiamine 1-adamantyl trisulfide hydrochloride

[N-methylene-3H]Thiamine 1-adamantyl trisulfide hydrochloride (VII) was synthesized. Both the γ-radiolysis of thiamine 1-adamantyl trisulfide hydrochloride (VIII) in ethanol and the self-radiolysis of VII in the crystalline state containing 17 molepercent of ethanol have been studied. G(-VII) in the crystalline state by the gross effects of self-irradiation was 3.4, and the four decomposition products were found. The self-radiolysis products yielded from VII in the crystalline state were the same as those products isolated from the γ-radiolysis of VIII in ethanolic solution and determined the structures as di-(1-adamantyl)tetrasulfide, 2-dihydro-3-(4-amino-2-methyl-5-pyrimidinylmethyl)-5-(1-adamantyl dithio)-3a-methylperhydrofuro[2,3-d]thiazole, 2-(1-hydroxyethyl)-3-(4-amino-2-methyl-5-pyrimidinyl-methyl)-5-(1-adamantyl dithio)-3a-methylperhydrofuro-[2,3-d]thiazole and thiamine chloride hydrochloride respectively.

Lattice parameters of 244Cm(OH) 3 and the effect of self-irradiation on crystalline 241Am(OH) 3 and 244Cm(OH) 3

Precipitation of 241Am or 244Cm (55% 244Cm) trihydroxides from an aqueous solution yields very small (10–20 Å in diameter) amorphous particles. Aging of these amorphous particles in water results in the formation of crystalline, rod-like structures of the trihydroxide, which are isomorphous with the hexagonal lanthanide trihydroxides. The lattice parameters and the above crystallization behavior has been reported for 241Am(OH) 3[1]. Reported here are similar studies for 244Cm(OH) 3 and the effects of self-irradiation on the crystalline structures of 241Am(OH) 3 and 244Cm(OH) 3. The crystallinity of these trihydroxides is destroyed by the alpha particles and/or atom recoil; with 244Cm(OH) 3, the destruction was complete in less than 1 day, while a period of several months was required to observe the same effect for 241Am(OH) 3. Lattice parameters for 244Cm(OH) 3 were determined from both X-ray and electron diffraction data. Parameters derived from the X-ray were generally larger than values obtained by electron diffraction are believed to be the better parameters for the 244Cm(OH) 3 preparation and are as follows: a 0 = 6.391 ± 0.002 Å and c 0 = 3.712 ± 0.002 Å.

The effects of aging and self-irradiation on crystalline 147promethium trihydroxide

Precipitation of 147promethium trihydroxide from aqueous solutions yields amorphous particles 10–15 Å, in diameter. Aging of these particles in water results in the formation of crystalline, rod-like structures of the trihydroxide, which are isomorphous with the other known hexagonal lanthanide trihydroxides. The lattice constants for the pure 147promethium compound were determined to be: a o = 6.396 ± 0.003 A ̊ and c o = 3.707 ± 0.003 A ̊ . These values are in excellent agreement with lattice constants for promethium trihydroxide predicted from a linear relationship of several lanthanide isomorphs but differ slightly from previously reported values by Weigel and Scherrer of a o = 6.39 A ̊ and c o = 3.68 A ̊ . The 147promethium trihydroxide crystals were periodically examined over one half-life of 147Pm to determine the effects of self-irradiation by β particles and the transmutation of the Pm to Sm. The data show that the self-irradiation damage to the crystals is minor as compared to extensive effects by high energy α particles previously observed in 244curium trihydroxide. Analysis of the 147promethium trihydroxide crystals by electron and X-ray diffraction after one half-life of the 147Pm had passed gave lattice parameters which were approximately equal to the averages of values for promethium and samarium trihydroxides; the measured values were a o = 6.382 ± 0.003 A ̊ and c o = 3.690 ± 0.002 A ̊ .

Self-irradiation effects in americium oxides

Using X-ray powder diffraction techniques we have followed as a function of time the effects of self-irradiation damage at room temperature in the americium-241 oxides. The radiation induced lattice expansion of the dioxide is slightly different wether the samples are kept in a vacuum or under an oxygen atmosphere: differential oxygen losses under the effect of self-irradiation would satisfactorily account for this effect. The influence of the irradiation of the sesquioxide is shown to be markedly dependent upon the crystalline form under investigation. Evidence is presented for the spontaneous transformation over a period of several years of the room-temperature cubic form of the sesquioxide into the hexagonal high-temperature form.

Actinide(lanthanide)-noble metal alloy phases, preparation and properties

Actinide (AThCm)-noble metal phases with platinum, palladium, rhodium, and iridium (B)- and lanthanide-noble metal phases with platinum and palladium have been prepared by reduction of corresponding oxides or fluorides in the presence of noble metals by extremely purified hydrogen. Alloy phases of composition AB 2, AB 3, and/or AB 5 have been identified, most of which crystallize in the Cu 2Mg, Cu 3Au, Ni 3Ti, Cd 3Mg, Ni 5U, and Pt 5Sm types of structure. The lattice constants of isostructural series show a trend which also is known for the radii of the actinide elements. Analytical data, self-irradiation effects, magnetic data, nuclear γ resonance spectra, and thermal behaviour of selected alloy phases as well as the preparation of alloy phases of some other transition and main group elements, e.g., Zr, Hf, Nb, Ta, MgBa, are reported.

The Effects of Self-Irradiation on the Lattice of 238 (80%)PuO2.III

AbstractThe results of the fourth year of observations on the effects of self-irradiation on the lattice of 238(80%)PuO2 confirm the predictions derived from previous observations. Namely, the lattice constant continues to decrease with time but at a slower rate indicating an approach to equilibrium. Very small reductions are also noted in the half-width of the diffraction lines.

The Effect Of Self-Irradiation on the Lattice of 238(80%)PuO2. II

AbstractThe results of the third year of observations on the effects of self-irradiation on the lattice of 238(80%)PuO2 indicate a small but definite trend toward a reduction in the lattice parameter of this material. The lattice parameter increased from 5.41408±6 Å at 5 weeks to 5.41636±38 at 114 weeks and then decreased to 5.41364±23 at 157 weeks after the start of the experiment. A similar trend is noted in the half-widths of the diffraction lines. For the 622 reflection the half-width increased from 0.283±14°20 at 5 weeks to 0.711±90 at 114 weeks and then decreased to 0.660±89 at 157 weeks.

Radiation damage by soft β-particles self-irradiation of β-tritiated polystyrene

Abstract The effect of self-irradiation of β-tritiated polystyrene under high vacuum at 25°C was studied, and simultaneous random chain scission and cross-linking were observed. Analyses of the gaseous products and the colored polymer residue showed that hydrogen was the only volatile product, while spectroscopic measurements indicated that the coloration was associated with the presence of main-chain double bonds. G values for hydrogen formation GH2, cross-linking, G XL and chain scission, G CS were obtained as follows: GH2=0.031; G CS=0.044; G XL=0.061. Possible mechanisms of radiation damage are discussed.

The Effects of Self-Irradiation on the Laitice of 238(80%)Puo2

As a function of self-irradiation, the crystalline lattice of 238(80%) PuO2 is gradually altered. The technique of x-ray line broadening was used to search for changes in the crystallite size and strain in the lattice following an initial annealing treatment. She integral breadth, Fourier coefficient, and variance methods were used to analyze the broadening of the x-ray powder pattern lines. The mechanism of alteration appears to be one of retained strain as no evidence was forthcoming from these techniques to indicate that the material undergoes significant crystallite size change. The strain in the lattice increased from zero at time zero to approximately 0.2% during a 2-year period.

Self-irradiation effects in a cerium alloy containing 15 at.% plutonium

Four samples of an α-phase cerium alloy (85 at.% Ce-15 at.% Pu) were stored at 2O°K for 1076 h. The plutonium used in making the samples was variably enriched with the Pu 238 isotope to provide four different levels of irradiation. Accumulation of lattice damage due to the alpha activity of plutonium was followed by periodically measuring the electrical resistivities of the samples during storage at low temperature. Annealing of damage was then followed from 20° to 35o°K, by the isochronal method. Results are discussed in terms of the nature of the lattice damage.

Comparison of Self-Irradiation Effects in Alpha Plutonium Enriched and Unenriched in 238Pu

Self-damage accumulation at 22.5°K has been studied in alpha plutonium enriched and unenriched in 238Pu. The enriched specimen was held at this low temperature for a period equivalent to about 14 000 h in terms of damage accumulated in the unenriched specimen. The resistivity of the enriched specimen increased to a maximum of 141.5 μΩ-cm and then decreased gradually with additional time. The increase has been attributed to self-irradiation damage consisting of interstitials and vacancies, and the decrease is discussed in terms of possible effects due to phase transformation, internal stresses, magnetic ordering, impurities, and clustering of defects. Annealing behavior differed widely in the two plutonium specimens studied and this is also discussed.

The effect of self-irradiation on the lattice constants of alloys of plutonium in alpha-uranium

The effect of self-irradiation on the lattice constants of alloys of plutonium in alpha-uranium

Effects of impurities and self-irradiation on the electrical resistivity of alpha-phase plutonium below 300°K

Electrical resistivities were measured as a function of temperature below 300°K on six α-phase plutonium specimens, each made from a different purity of plutonium metal. The observed resistivity behaviors are discussed and correlated with impurity contents and with other physical properties of plutonium. Possible electrical conduction mechanisms in α-phase plutonium are discussed. In addition, measurements were made showing that self-irradiation from the α-activity in plutonium produces damage at low temperatures. The resistivity was found to increase linearly with time at constant temperatures and annealing of stored damage was also studied. The radiation damage behavior of α-phase plutonium is discussed.

Effect of self-irradiation on the resistivity of plutonium

Continuous observations were made on alpha -Pu kept below 20 deg K for more than 3.5 x 10/sup 3/ hours. The specimen was kept in liquid He (~5 deg K) for most of the time and was occasionally temporarily transferred into a bath of liquid H (~20 deg K). Changes in conductivity were plotted in relation to temperature and time, and features aiding in understanding the mechanism of the electric conductivity anomaly were noted. (L.N.N.)

The effect of radioactivity of substances on their physicochemical properties

Radioactive substances have a number of features which can be explained by the effect of selfirradiation. Systems containing radioactive elements are in a nonequilibrium state. The fraction of particles (molecules, atoms, ions) having increased energy exceeds the equilibrium value in these systems. The regions of the substance in which there is retardation of the ex- and s-particles and the recoil atoms have a higher concentration than the equilibrium value of structure defects and increased free energy. These factors should affect the vapor pressure, solubility, dissociation pressure, equilibrium constants of chemical reactions, reactivity, specific heat, density, electrical conductivity, thermal conductivity and other properties of radioactive substances and also the character of their phase transformations. From this point of view a study is made of literature data on some properties of various radioactive substances.