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1.
I. Han L. Demir 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(1):3-8
The total mass attenuation coefficients (μm), for Cr, Fe, Ni and FexNi1−x (x = 0.8, 0.7, 0.6, 0.5, 0.4, 0.3 and 0.2), FexCryNi1−(x+y) (x = 0.7, y = 0.1; x = 0.5, y = 0.2; x = 0.4, y = 0.3; x = 0.3, y = 0.3; x = 0.2, y = 0.2 and x = 0.1, y = 0.2) and NixCr1−x (x = 0.8, 0.6, 0.5, 0.4 and 0.2) alloys were measured at 22.1, 25.0, 59.5 and 88.0 keV photon energies. The samples were irradiated with 10 mCi Cd-109 and 100 mCi Am-241 radioactive point source using transmission arrangement. The γ- and X-rays were counted by a Si(Li) detector with a resolution of 160 eV at 5.9 keV. Total atomic and electronic cross-sections (σt and σe), effective atomic and electron numbers (Zeff and Neff) were determined experimentally and theoretically using the obtained mass attenuation coefficients for investigated 3d alloys. The theoretical mass attenuation coefficients of each alloy were estimated using mixture rule. The experimental values were compared with the calculated values for all samples. 相似文献
2.
Solubility of ThO2 in gadolinium zirconate pyrochlore, a potential host for radioactive materials, has been investigated. The phase relations in Gd2−xThxZr2O7+x/2 (0.0 ? x ? 2.0) systems have been established under the slow-cooled conditions from 1400 °C. XRD studies reveal that the compositions corresponding to x = 0.0-0.075 are single phasic in nature and beyond x ? 0.1 the biphasic region starts. The first biphasic region comprising of pyrochlore and thoria exist from x = 0.1-0.8, and from x = 1.2 another biphasic region consisting of gadolinia stabilized zirconia (GSZ) and thoria appears which persists till x = 1.6. The end member (i.e. x = 2.0) of the series is found to be a mixture of monoclinic ZrO2 and thoria. Interestingly, gadolinia which has wide solubility in thoria, did not show any miscibility in thoria in the presence of zirconia. Irregular grains of Gd1.8Th0.2Zr2O7.1 as shown in SEM supports its biphasic nature. Raman spectra of heavily thoria doped (x = 0.1 and 0.2) samples, indicates the presence of Zr-O7 mode which implies the samples are highly disordered in nature. 相似文献
3.
Solid state reactions of UO2 and ZrO2 in mild oxidizing condition followed by reduction at 1673 K showed enhanced solubility up to 35 mol% of zirconium in UO2 forming cubic fluorite type ZryU1−yO2 solid solution. The lattice parameters and O/M (M = U + Zr) ratios of the solid solutions, ZryU1−yO2+x, prepared in different gas streams were investigated. The lattice parameters of these solid solutions were expressed as a linear equation of x and y: a0 (nm) = 0.54704 − 0.021x - 0.030y. The oxidation of these solid solutions for 0.1 ? y ? 0.2 resulted in cubic phase MO2+x up to700 K and single orthorhombic zirconium substituted α-U3O8 phase at 1000 K. The kinetics of oxidation of ZryU1−yO2 in air for y = 0-0.35 were also studied using thermogravimetry. The specific heat capacities of ZryU1−yO2 (y = 0-0.35) were measured using heat flux differential scanning calorimetry in the temperature range of 334-860 K. 相似文献
4.
Yin Zhong Shen Sung Ho Kim Hai Dong Cho Chang Hee Han Woo Seog Ryu 《Nuclear Engineering and Design》2009,239(4):648-68
One of the reasons that ferritic/martenstic steels have been considered as candidate materials for nuclear power reactors is their superior creep resistance at elevated temperature. The creep rupture strength of 9% chromium steel could be improved by a fine dispersion of secondary precipitate phase. The precipitate phases in extra-low carbon 9% chromium steel with tempered conditions were investigated by transmission electron microscope and energy-dispersive X-ray analysis. The steel specimens were normalized and then tempered at different temperatures. Niobium-rich MN nitrides (Nb0.6V0.3Cr0.1)N, and two kinds of vanadium nitrides, (V0.6Nb0.2Cr0.2)N and (V0.45Nb0.45Cr0.1)N having a f.c.c. crystal structure, were identified in the steel specimens tempered at 600-780 °C, and 750 or 780 °C respectively. Hexagonal chromium-rich M2N precipitate phases with different lattice parameters, a = 2.80 Å/c = 4.45 Å and a = 7.76 Å/c = 4.438 Å, were determined in the tempered steel specimens. The M2N phase showed a decrease/an increase in its chromium/vanadium content as the tempering temperature was increased. The influence of precipitates and heat treatment conditions on the high temperature properties of 9% Cr steel was discussed. 相似文献
5.
The corrosion behavior and oxide structure of 9CrODS steel in supercritical water has been studied. Samples were exposed to supercritical water at 500 and 600 °C for times of 2, 4 and 6 weeks. The oxide structure was studied using microbeam synchrotron X-ray diffraction and fluorescence analysis. The 600 °C samples exhibited a three-layer structure with Fe3O4 in the outer layer, a mixture of FeCr2O4 and Fe3O4 in the inner layer, and a mixture of metal and oxide grains (FeCr2O4 and Cr2O3) in the diffusion layer. Between the 2 and 4-week samples exposed to 600 °C supercritical water, a Cr2O3 film appeared at the diffusion layer-metal interface which appears to be associated with slower oxidation of the metal. The 500 °C samples also showed a three-layer structure, but both the outer and inner oxide layers contained mainly Fe3O4, and the diffusion layer contained much fewer oxide precipitates and was a solid solution of oxygen ahead of the oxide front. 相似文献
6.
L. Vernon 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2010,268(19):2942-2946
Low energy (10-40 eV) interaction of small TixOy clusters with a rutile (1 1 0) substrate was investigated using molecular dynamics with the aim of determining the influence of various parameters on surface growth and defect formation. Rutile growth was simulated through depositing randomly selected clusters with energies in the tens of eV range. Long time scale evolution was approximated through heating the substrate. A modified second-moment-Buckingham-QEq (SMB-Q) empirical potential was developed for the purpose. Crystal growth on amorphous and anatase TiO2 substrates was also considered. Grown lattice layers were compared by visual inspection along with radial distribution function (RDF) plots. Bombardment at an energy of around 20 eV in an oxygen rich atmosphere with a high proportion of bombarding clusters, TiO, TiO2, as opposed to single atoms, was found to produce rutile growth with the best crystallinity. 相似文献
7.
The dependence of the oxygen potentials on oxygen non-stoichiometry and temperature of Am0.5Pu0.5O2−x has been obtained by the electromotive force (EMF) method with the cell: (Pt) air |Zr(Ca)O2−x| Am0.5Pu0.5O2−x (Pt). The x value of Am0.5Pu0.5O2−x was changed at 1333 K over 0.02 < x ? 0.25 by the coulomb titration method. The temperature dependence of the oxygen potential was also measured over the range of 1173-1333 K. It was found that the oxygen potential decreased from −80 to −360 kJ mol−1 with increasing x from 0.021 to 0.22 at 1333 K and that it remained almost constant at −360 kJmol−1 around x = 0.23. It was concluded that Am0.5Pu0.5O2−x should be composed of the single fluorite-type phase over 0.02 < x ? 0.22 and the mixed phases of fluorite-type and (Am, Pu)9O16 at around x = 0.23. 相似文献
8.
Ken Kurosaki Kosuke Tanaka Hiroaki Muta Shinsuke Yamanaka 《Journal of Nuclear Materials》2009,389(1):85-88
The thermal conductivity, Young’s modulus, and hardness of (U0.65−xCe0.3Pr0.05Ndx)O2 (x = 0.01, 0.08, 0.12) were evaluated and the effect of Pr and Nd addition on the properties of (U, Ce)O2 were studied. The polycrystalline high-density pellets were prepared with solid state reactions of UO2, CeO2, Pr2O3, and Nd2O3. We confirmed that all Ce, Pr, and Nd dissolved in UO2 and formed solid solutions of (U, Ce, Pr, Nd)O2. We revealed that the thermal conductivity of (U0.65−xCe0.3Pr0.05Ndx)O2 (x = 0.12) was up to 25% lower than that of x = 0.01 at room temperature. The Young’s modulus of (U0.65−xCe0.3Pr0.05Ndx)O2 decreased with x, whereas the hardness values were constant in the investigated x range. 相似文献
9.
Shuhei Miwa Isamu Sato Kosuke Tanaka Takashi Hirosawa Masahiko Osaka 《Journal of Nuclear Materials》2010,400(1):32-421
The melting behavior of MgO-based inert matrix fuels containing (Pu,Am)O2−x ((Pu,Am)O2−x-MgO fuels) was experimentally investigated. Heat-treatment tests were carried out at 2173 K, 2373 K and 2573 K each. The fuel melted at about 2573 K in the eutectic reaction of the Pu-Am-Mg-O system. The (Pu,Am)O2−x grains, MgO grains and pores grew with increasing temperature. In addition, Am-rich oxide phases were formed in the (Pu,Am)O2−x phase by heat-treatment at high temperatures. The melting behavior was compared with behaviors of PuO2−x-MgO and AmO2−x-MgO fuels. 相似文献
10.
Alfons Weisenburger Kazumi Aoto Annette Heinzel Tomohiro Furukawa 《Journal of Nuclear Materials》2006,358(1):69-76
The behaviour of protective oxide layers on P122 steel and its welds and of ODS steel in liquid Pb44.5Bi55.5 (LBE) is examined under conditions of changing temperatures and oxygen concentrations. P122 (12Cr) and its welded joints are exposed to LBE at 550 °C for 4000 h with oxygen concentrations of 10−6 and 10−8 wt% (p(O2) = 8.1 × 10−23 bar and 5.2 × 10−27 bar) which change every 800 h. It is found that like in case of constant oxygen concentration of 10−6 wt% a protective spinel layer (Fe(Fe1−xCrx)2O4) was maintained on P122 and also on its welded joint. Two experiments with exposure times of 4800 h are conducted on ODS steel, both with temperatures changing from 550 to 650 °C and back every 800 h, one experiment with 10−6 the other with 10−8 wt% oxygen in LBE. Both experiments show strong local dissolution attack after 4800 h which is in agreement with the behaviour of ODS in LBE at a constant temperature of 650 °C. However, dissolution attack is less in LBE with 10−8 wt% oxygen (p(O2) = 3.0 × 10−25 bar). 相似文献
11.
G. Sattonnay S. Moll V. Menvie Bekale L. Thomé 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2010,268(19):3040-3043
The modifications of the mechanical properties of related-fluorite oxides (cubic zirconia [c-ZrO2] and pyrochlores [Gd2(Ti1−xZrx)2O7 with x = 0.5 and x = 1]) induced by swift heavy ion irradiation are investigated. Polycrystalline pellets of both materials were irradiated at room temperature with 940 MeV Pb or 870 MeV Xe ions at the GANIL accelerator in Caen at fluences ranging from 2 × 1011 to 1013 cm−2. Residual macroscopic stresses induced by irradiation were determined using X-ray diffraction and the sin2ψ method. The microhardness and the fracture toughness of irradiated samples were studied by Vickers micro-indentation. Amorphization occurs in Gd2TiZrO7 and not in Gd2Zr2O7 and c-ZrO2. The mechanical behavior of materials is found to be closely related to the residual stresses induced in the surface layer by irradiation. Compressive stresses are generated in c-ZrO2 and Gd2TiZrO7 (leading to an increase of fracture toughness), whereas tensile stresses (inducing a large decrease of fracture toughness) are observed in Gd2Zr2O7 due to the lattice contraction related to a pyrochlore fluorite→transition. 相似文献
12.
Alloy 617 has been selected for the intermediate heat exchanger (IHX) of the very high temperature gas-cooled reactor (VHTR) for the economic production of electricity and hydrogen. In this work, the strengthening effects of Cr2O3 thermally grown on alloy 617 foils at 800 and 900 °C were investigated. A micro-tensile test system was used for in situ measurement of tensile strain in the foils and superficial thermally-grown Cr2O3. Each foil was heated until the thermally-grown Cr2O3 reached a predetermined thickness; then, a load was applied to measure the tensile response. As the Cr2O3 layer thickened on the surface of the metal foils, the strengths and stiffnesses of the foils were enhanced. We assumed that there was no interaction between the substrate and the superficial chromia, and the strength of Cr2O3 itself was measured. At 800 °C, the Cr2O3 was brittle and the strength was governed by crack initiation. At 900 °C, the Cr2O3 was much more ductile, and strain hardening was observed for even the smallest thickness. The strength was maintained even after crack initiation was observed on the surface. 相似文献
13.
Yang-Soon Park Yeong-Keong Ha Sun-Ho Han Kwang-Yong Jee Won-Ho Kim 《Journal of Nuclear Materials》2008,372(1):59-65
A micro X-ray diffractometer with a micrometer sized beam concentrator was developed to investigate the changes in the chemical structures of oxide layers for Zr-based alloys (Zircaloy-4) and Ti metal from the center of the cross section to the surface. Zircaloy-4 and Ti metal were chosen because of their use as a fuel cladding and a heat exchange tubing in a nuclear reactor, respectively. The diffraction patterns were obtained from the cross sectional specimens of the oxidized Zircaloy-4 and Ti metal at 50 μm intervals. For the cross section of Zircaloy-4, Zr metal (hexagonal) was identified in the center, ZrO2−x (hexagonal, about 200 μm in thickness) inside the edge and ZrO2 (monoclinic, about 400 μm in thickness) at the edge. In the case of Ti metal, Ti metal (hexagonal) was identified in the center, TiO (cubic, about 200 μm in thickness) inside the edge and rutile-TiO2 (tetragonal, about 230 μm in thickness) at the edge. From this study, it was concluded that the intermediate phase formed between the fuel and the cladding can be identified by the micro-XRD system. 相似文献
14.
The radiation shielding and optical properties of xBi2O3:(100-x)SiO2, xPbO:(100-x)SiO2 and xBaO:(100-x)SiO2 glass systems (where 30 ? x ? 70 is the composition by weight%) have been investigated. Total mass attenuation coefficients (μm) of glasses at 662 keV were improved by increasing their Bi2O3 and PbO content, which raised the photoelectric absorption in glass matrices. Raising the BaO content to the same fraction range, however, brought no significant change to μm. These results indicate that photon is strongly attenuated in Bi2O3 and PbO containing glasses, and but not in BaO containing glass. The results from the optical absorption spectra show an edge that was not sharply defined; clearly indicating the amorphous nature of glass samples. It is observed that the cutoff wavelength for Bi2O3 containing glass was longer than PbO and BaO containing glasses. 相似文献
15.
S.K. Sharma 《Journal of Nuclear Materials》2008,378(2):144-152
The microstructure of thermally grown oxides (TGO) and the creep properties of alloy 617 were investigated. Oxidation and creep tests were performed on 100 μm thick foils at 800-1000 °C in air environment, while the thickness of TGO was monitored in situ. According to energy dispersive X-ray (EDX) mapping micrographs observation, superficial dense oxides, chromia (Cr2O3), which was thermodynamically unstable at 1000 °C, and discrete internal oxides, alumina (α-Al2O3), were found. Consequently, the weight of the foil specimen decreased due to the spalling and volatilization of the Cr2O3 oxide layer after an initial weight-gaining. Secondary and tertiary creeps were observed at 800 °C, while the primary, secondary and tertiary creeps were observed at 1000 °C. Dynamic recrystallization occurred at 800 °C and 900 °C, while partial dynamic recrystallization at 1000 °C. The apparent activation energy, Qapp, for the creep deformation was 271 kJ/mol, which was independent of the applied stress. 相似文献
16.
Y.H. Li Y.Q. WangM. Zhou C.P. XuJ.A. Valdez K.E. Sickafus 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2011,269(18):2001-2005
We have recently synthesized “stuffed” (i.e., excess Lu) Lu2(Ti2−xLux)O7−x/2 (x = 0, 0.4 and 0.67) compounds using conventional ceramic processing. X-ray diffraction measurements indicate that stuffing more Lu3+ cations into the oxide structure leads eventually to an order-to-disorder (O-D) transition, from an ordered pyrochlore to a disordered fluorite crystal structure. At the maximum deviation in stoichiometry (x = 0.67), the Lu3+ and Ti4+ ions become completely randomized on the cation sublattices, and the oxygen “vacancies” are randomized on the anion sublattice. Samples were irradiated with 400 keV Ne2+ ions to fluences ranging from 1 × 1015 to 1 × 1016 ions/cm2 at cryogenic temperatures (∼77 K). Ion irradiation effects in these samples were examined by using grazing incident X-ray diffraction. The results show that the ion irradiation tolerance increases with disordering extent in the non-stoichiometric Lu2(Ti2−xLux)O7−x/2. 相似文献
17.
Two monazite glass-ceramic wasteforms were sintered by mixing the lanthanum metaphosphate glass powder with the oxide powder of the components in simulated α-HLWs. The co-existence of components Al and Mo in an iron phosphate melt separated the melt into two immiscible glass melts, namely aluminum iron phosphate glass (Gb) and molybdenum iron phosphate glass (Gg). 24 wt% of ZrO2, together with P2O5 and proper amounts of Fe and Mo formed a zirconium pyrophosphate glass (Gg1), which was immiscible with the phase Gg. The iron ions in the wasteforms were all in Fe3+, 1/3 of which was in 4-fold coordination. The O/P and O/(P + 1/3Fe3+) ratios for the glass phases were Gg1 3.70, Gb 3.89-3.98, Gg 4.23-4.25, and Gg1 3.58, Gb 3.47-3.42, Gg 3.74-3.69, respectively. The dissolution rates of two wasteforms were 0.3008 and 0.2598 g/m2d, respectively. 相似文献
18.
The redox behavior of Eu2+ and Eu3+ in the LiCl-KCl eutectic at 773 K was investigated. Since the equilibrium potential of the melt is very close to the redox potential of the Eu3+|Eu2+ couple, the Eu2+ and Eu3+ species coexist. Quantitative analysis of Eu2+ and Eu3+ was performed by spectrophotometry and by potentiometry. Under the coexistence of Eu2+ and Eu3+, potentiometric titration of Eu ion using a yttria-stabilized zirconia membrane electrode (YSZME) was performed by changing the concentration of O2−. The formation of the europium oxychloride, EuOCl, was confirmed by X-ray diffraction analysis, whiles no precipitation of the oxides, EuO and Eu2O3, was found. The equivalent point of the EuOCl formation (x = [O2−]added/[Eu]total) was shifted to a smaller value from the theoretical value (x = 1) due to the coexisting Eu2+. The contribution of the coexisting Eu2+ to the formation of EuOCl was estimated by using [Eu2+]/[Eu3+] as determined by potentiometry and this was subtracted from the titration data. The solubility product of EuOCl was determined to be pks(EuOCl) = 7.81 ± 0.10. 相似文献
19.
The thermal conductivities of (U0.68Pu0.30Am0.02)O2.00−x solid solutions (x = 0.00-0.08) were studied at temperatures from 900 to 1773 K. The thermal conductivities were obtained from the thermal diffusivities measured by the laser flash method. The thermal conductivities obtained experimentally up to about 1400 K could be expressed by a classical phonon transport model, λ = (A + BT)−1, A(x) = 3.31 × x + 9.92 × 10−3 (mK/W) and B(x) = (−6.68 × x + 2.46) × 10−4 (m/W). The experimental A values showed a good agreement with theoretical predictions, but the experimental B values showed not so good agreement with the theoretical ones in the low O/M ratio region. From the comparison of A and B values obtained in this study with the ones of (U,Pu)O2−x obtained by Duriez et al. [C. Duriez, J.P. Alessandri, T. Gervais, Y. Philipponneau, J. Nucl. Mater. 277 (2000) 143], the addition of Am into (U, Pu)O2−x gave no significant effect on the O/M dependency of A and B values. 相似文献